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  • Evolution  (274)
  • Springer  (274)
  • American Chemical Society
  • Springer Nature
  • 1995-1999  (207)
  • 1980-1984  (67)
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  • 101
    Electronic Resource
    Electronic Resource
    Structure and regulation of the fushi tarazu gene from Drosophila hydei (1995)
    Springer
    Development genes and evolution 205 (1995), S. 160-170 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Evolution ; fz ; Homeodomain ; Plasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Drosophila melanogaster segmentation gene fushi tarazu (ftz) encodes a homeodomain-type transcription factor involved in the control of larval pattern formation. Loss of function mutations cause an embryonic lethal, pair-rule phenotype. The segmentation defects, but not the lethality, can be partially rescued by the ftz orthologue from Drosophila hydei. In this work, the primary structure, expression and regulation of the D. hydei ftz gene was characterized. Sequence comparisons classify ftz as a rather fast evolving gene. However, since the homeodomain of the D. hydei FTZ protein is highly similar to that of D. melanogaster, proper regulation of D. melanogaster ftz downstream genes would be expected. In D. melanogaster embryos, a D. hydei ftz transgene is expressed normally, independent of endogenous ftz gene activity, suggesting that D. hydei ftz regulatory sequences are correctly recognized by D. melanogaster transcription factors. Accordingly, lacZ fusion constructs driven by the D. hydei ftz upstream element are expressed normally in D. melanogaster embryos. Altogether, the similarities between the two ftz orthologues by far outweigh the differences. The limited success of the trans-species rescue might be, therefore, a consequence of the accumulation of too many subtle changes in gene function, exceeding the limits of developmental plasticity during fly embryogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357762
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  • 102
    Electronic Resource
    Electronic Resource
    Identification and genetic mapping of Xenopus TAP2 genes (1999)
    Springer
    Immunogenetics 49 (1999), S. 171-182 
    Details
    ISSN: 1432-1211
    Keywords: Key words MHC ; Transporter ; Evolution ; PCR cloning ; Allelic lineage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The amphibian Xenopus laevis is one non-mammalian vertebrate in which the major histocompatibility complex (MHC) has been analyzed extensively. Class IIβ, class Ia, LMP2, LMP7, HSP70, C4, Factor B, and Ring3 genes have been identified and mapped to the MHC. Here, we report the isolation of a transporter associated with antigen processing (TAP) gene, TAP2, and demonstrate its linkage to the MHC. While the ATP-binding region of Xenopus TAP2 is highly conserved in evolution, amino acid identity to other vertebrate TAP proteins was not detected in the N-terminal region. Segregation analysis of 34 individuals from two families showed exact restriction fragment length polymorphism matching between the MHC class Ia gene and the one TAP2 gene demonstrating linkage conservation since the mammalian/amphibian divergence ∼350 million years ago. In addition, one non-MHC-linked TAP2–hybridizing fragment was detected in approximately half of the individuals tested. Interestingly, TAP2 allelic lineages appear to match those of LMP7 and classical class I, which previously were categorized into two highly divergent groups that emerged at least 60 million years ago. Similar to LMP7 and class Ia,TAP2 is expressed ubiquitously with highest levels in intestine and spleen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050478
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  • 103
    Electronic Resource
    Electronic Resource
    Organization of the genes encoding the human proteasome activators PA28α and β (1999)
    Springer
    Immunogenetics 49 (1999), S. 438-445 
    Details
    ISSN: 1432-1211
    Keywords: Key words PA28 ; Proteasome ; Gene structure ; Evolution ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Two proteasome activators PA28α and β, which have been implicated in antigen processing for loading class I MHC molecules, are synthesized in response to Ifn-γ. The human genes encoding these activators (PSME1 and PSME2, respectively) were analyzed by sequencing. Each gene comprised 11 exons, consistent with gene duplication during vertebrate evolution. The intron/exon organization of both genes was highly conserved, the major difference being the absence of the exon encoding the lysine and glutamic acid-rich 'KEKE' motif in PA28β. Two other genes of relevance to the immune system were located close to those for PA28 at 14q11.2 including ISGF3G, a protein involved in transcription after IFNα signalling. These sequences were also characterized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050517
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  • 104
    Electronic Resource
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    β 2 -microglobulin in neotropical primates (Platyrrhini) (1998)
    Springer
    Immunogenetics 48 (1998), S. 133-140 
    Details
    ISSN: 1432-1211
    Keywords: Key words β2-microglobulin ; Primates ; Evolution ; Diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Nucleotide sequences for the three exons of the β2-microglobulin (β2m) gene (B2m) were determined for 135 animals representing 37 species and all 16 genera of neotropical primates (Platyrrhini). Twenty-eight different nucleotide sequences, encoding for 26 different proteins, were obtained. In comparison with those of other primate species, the β2-microglobulins of the Platyrrhini form a distinct clade. Individual genera of neotropical primates have distinctive B2m sequences, but within a genera species can have either the same or different B2m sequences. B2m polymorphism was found within three of the species sampled: Callicebus personatus, Saguinus midas, and Aotus azarae. Of these only the polymorphism in A. azarae has an effect upon the mature, functional β2m protein: residue 4 being either alanine or threonine. The A. azarae B2m allele encoding alanine at position 4 is shared with another species of Aotus (A. infulatus). In pairwise comparison the mature β2m proteins of neotropical primates differ by 1–9 amino acid substitutions which can occur at 18 positions within the sequence. The substitutions are distributed throughout the primary structure but are more commonly found in loops rather than β strands of the tertiary structure. Of 17 residues of β2m which hydrogen-bond with the class I heavy chain in human MHC class I molecules, 13 are conserved in the neotropical primates. The overall pattern of sequence variation in the B2m genes of the Platyrrhini is consistent with an evolution by successive selectively neutral events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050413
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  • 105
    Electronic Resource
    Electronic Resource
    Variation in the number of expressed MHC genes in different cattle class I haplotypes (1999)
    Springer
    Immunogenetics 50 (1999), S. 319-328 
    Details
    ISSN: 1432-1211
    Keywords: Key words Cattle ; MHC class I ; Haplotypes ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Analysis of cattle major histocompatibility complex (MHC) (BoLA) class I gene expression using serological and biochemical methods has demonstrated a high level of polymorphism. However, analysis of class I cDNA sequences has failed to produce conclusive evidence concerning the number and nature of expressed genes. Such information is essential for detailed studies of cattle immune responses, and to increase our understanding of the mechanisms of MHC evolution. In this study a selective breeding programme has been used to generate a number of MHC homozygous cattle expressing common serologically defined class I specificities. Detailed analysis of five class I haplotypes was carried out, with transcribed class I genes identified and characterized by cDNA cloning, sequence analysis, and transfection/expression studies. Surface expression of the gene products (on lymphocytes) was confirmed using monoclonal antibodies of defined BoLA specificity. Phylogenetic analysis of available transcribed cattle MHC class I sequences revealed complex evolutionary relationships including possible evidence for recombination. The study of individual haplotypes suggests that certain groupings of related sequences may correlate with loci, but overall it was not possible to define the origin of individual alleles using this approach. The most striking finding of this study is that none of the cattle class I genes is consistently expressed, and that in contrast to human, haplotypes differ from one another in both the number and composition of expressed classical class I genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050608
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  • 106
    Electronic Resource
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    A divergent non-classical class I gene conserved in salmonids (1999)
    Springer
    Immunogenetics 49 (1999), S. 479-490 
    Details
    ISSN: 1432-1211
    Keywords: Key words Comparative immunology ; Evolution ; MHC class I ; Molecular biology ; Salmonids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Complementary DNA for two class I genes of the rainbow trout, Oncorhynchus mykiss, were characterized. MhcOnmy-UBA*01 is similar to Onmy-UA-C32 and the classical major histocompatibility complex class I genes of other fish species, whereas Onmy-UAA*01 is divergent from all class I genes so far characterized. Onmy-UAA*01 is expressed at lower levels than Onmy-UBA*01. Although Onmy-UAA*01 exhibits restriction fragment length polymorphism on Southern blotting, the encoded protein is highly conserved. Two allotypes, which differ only by substitution at amino acid position 223 of the α3 domain, have been defined. Onmy-UAA*01 has an exon-intron organization like other class I genes and contains a Tc1-like transposon element in intron III. Orthologues of Onmy-UAA*01 have been characterized in four other species of salmonid. Between four species of Oncorhynchus, UAA*01 proteins differ by only 2–6 amino acids, whereas comparison of Oncorhynchus with Salmo trutta (brown trout) reveals 14–16 amino acid differences. The Onmy-UAA*01 gene has properties indicative of a particularly divergent non-classical class I gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050524
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  • 107
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    Evolution of the Mhc class I region: the framework hypothesis (1999)
    Springer
    Immunogenetics 49 (1999), S. 362-367 
    Details
    ISSN: 1432-1211
    Keywords: Key words Major histocompatibility complex ; Class I region ; Evolution ; Orthology ; Olfactory receptor genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  A comparison of the major histocompatibility complex (Mhc) region between human and mouse highlights both stability and differences. The class II and class III regions are orthologous; they probably existed in the ancestor in a similar organization and were not subjected to major rearrangement. The class I genes, by contrast, are definitely paralogous, having been reorganized several times. As long as only class I genes were identified, the class I regions of human and mouse were difficult to compare directly. The identification of non-class I genes has allowed a comparative map to be drawn, which shows that the class I region is orthologous between human and mouse as well. The lack of orthology specifically applies to the class I sequences. However, the comparative map shows that the non-orthologous class I sequences occupy homologous locations with regard to the conserved genes. I propose a model to explain this paradox. The conserved genes may represent samples of a dense "framework" of genes whose alterations are deleterious. The homologous positions occupied by class I genes would thus represent the few permissive places allowing major perturbations. The evolution of the class I sequences, by duplication and deletion, independently in the two species, has taken place within the scope defined by the framework: insertion at the permissive places, and expansion by creation of class I-related DNA by duplication, thus pushing back the boundaries of the framework.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050507
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  • 108
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    Gene organization of the quail major histocompatibility complex (MhcCoja) class I gene region (1999)
    Springer
    Immunogenetics 49 (1999), S. 384-394 
    Details
    ISSN: 1432-1211
    Keywords: Key words Antigen processing ; Evolution ; Cell surface ; molecules ; Mhc ; Transporters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Class I genomic clones of the quail (Coturnix japonica) major histocompatibility complex (MhcCoja) were isolated and characterized. Two clusters spanning the 90.8 kilobase (kb) and 78.2 kb class I gene regions were defined by overlapping cosmid clones and found to contain at least twelve class I loci. However, unlike in the chicken Mhc, no evidence for the existence of any Coja class II gene was obtained in these two clusters. Based on comparative analysis of the genomic sequences with those of the cDNA clones, Coja-A, Coja-B, Coja-C, and Coja-D (Shiina et al. 1999), these twelve loci were assigned to represent one Coja-A gene, two Coja-B genes (Coja-B1 and -B2), four Coja-C genes (Coja-C1-C4), four Coja-D genes (Coja-D1-D4), and one new Coja-E gene. A class I gene-rich segment of 24.6 kb in which five of these genes (Coja-B1, -B2, -D1, -D2 and -E) are densely packed were sequenced by the shotgun strategy. All of these five class I genes are very compact in size [2089 base pairs (bp)–2732 bp] and contain no apparent genetic defect for functional expression. A transporter associated with the antigen processing (TAP) gene was identified in this class I gene-rich segment. These results suggest that the quail class I region is physically separated from the class II region and characterized by a large number of the expressible class I loci (at least seven) in contrast to the chicken Mhc, where the class I and class II regions are not clearly differentiated and only at most three expressed class I loci so far have been recognized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050511
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  • 109
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    Distinct patterns of IgH structure and organization in a divergent lineage of chrondrichthyan fishes (1998)
    Springer
    Immunogenetics 47 (1998), S. 234-245 
    Details
    ISSN: 1432-1211
    Keywords: Key words MHC class I ; Chimpanzee ; Inter-species allele ; Intron ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Immunoglobulin heavy chain (IgH) genes in representative chondrichthyan fishes (sharks and skates) consist of independently functioning clusters, containing separate variable (V H ), diversity (D H ), and joining (J H ) region elements and constant (C H ) region exons. IgH loci have been characterized in Hydrolagus colliei (spotted ratfish), a modern representative of a major independent chondrichthyan lineage. Three distinct families of IgH gene clusters were identified. The most numerous genes consist of unjoined V H -D 1 -D 2 -J H segments that correspond to the most abundant Hydrolagus spleen (cDNA) transcripts which apparently arise from a diversified gene family. In the second cluster type, V H , D H , and J H segments are germline-joined, whereas the C H exons exhibit typical organization. This gene type is found in only a few copies per haploid genome and both transmembrane and secretory transcripts have been identified. A third cluster type has been identified that consists of unjoined V H elements but lacks a typical C H 1 exon, which is substituted with a second C H 2-like exon. Transcripts from this third cluster type also appear to derive from a diversified gene family. Genomic D regions of the two unjoined clone types exhibit structural differences that are consistent with incorporation of recombination machinery-mediated events. Genomic library screening indicates that 90% of V H + clones are truncated, nearly identical pseudogenes (lacking J H and C H ). These studies demonstrate an early phylogenetic origin for the cluster type of gene organization and document extensive organizational diversification within an apparent single class of IgH genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050353
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  • 110
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    Evolutionary stability of the immunoglobulin heavy chain variable region gene families in teleost (1998)
    Springer
    Immunogenetics 47 (1998), S. 272-277 
    Details
    ISSN: 1432-1211
    Keywords: Key words Immunoglobulin ; Evolution ; Arctic charr ; Rainbow trout ; VH gene familiy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  A comparison between related species would allow us to study the evolutionary changes in complex gene families. To investigate the evolution of immunoglobulin VH gene families in lower vertebrates, we compared cDNA VH clones from two related teleost fish species, Arctic charr (Salvelinus alpinus) and rainbow trout (Oncorhynchus mykiss), which are separated from their common ancestor by 12–20 million years (MY). The results showed that randomly isolated charr VH genes could be closely grouped to known VH genes of rainbow trout, suggesting that the VH family structure is stable during 12–20 MY and that the total number of VH families changes only gradually over a longer period. This finding also led us to define eight VH gene families of Arctic charr, designated Salalp VH I, VH II, and so on. The presence of species-specific amino acids suggests that non-reciprocal genetic exchanges (e.g., gene duplication) play an important role in shaping the evolution of the V gene family.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050357
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  • 111
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    Structural differences between the repertoires of mouse and human germline genes and their evolutionary implications (1998)
    Springer
    Immunogenetics 47 (1998), S. 355-363 
    Details
    ISSN: 1432-1211
    Keywords: Key words Mice ; Immunoglobulins ; Canonical ; structures Igk-V ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Although human and mouse antibodies are similar when one considers their diversification strategies, they differ in the extent to which kappa and lambda light chains are present in their respective variable light chain repertoires. While the Igk-V germline genes are preponderant in mice (95% or more), they comprise only 60% in humans. This may account for differences in the structural repertoire encoded in the Igk-V germline genes of these species. However, this subject has not been properly investigated, partially because a systematic structural characterization of the mouse Igk-V germline genes has not been undertaken. In the present study we compiled all available information on mouse Igk-V germline genes to characterize their structural repertoire. As expected, comparison with the structural repertoire of human Igk-V germline genes indicates differences. The most interesting is that the mouse Igk-V germline gene repertoire is more diverse in structural terms than its human counterpart: the mouse encodes seven canonical structure classes (combination of canonical structures in L1 and L3). In contrast, the human encodes only four. Analysis of the evolutionary relationships of human and mouse Igk-V germline genes led us to propose that the difference reflects a strategy of mice to compensate for the small lambda chain contribution to the repertoire of their variable light chains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050370
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  • 112
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    BAC/YAC contigs from the H2-M region of mouse Chr 17 define gene order as Znf173-Tctex5-Mog-D17Tu42-M3-M2 (1998)
    Springer
    Immunogenetics 47 (1998), S. 371-380 
    Details
    ISSN: 1432-1211
    Keywords: Key words Major histocompatibility complex (MHC) ; Sequence tagged sites (STS) ; Physical mapping ; Evolution ; HLA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  A yeast artificial chromosome (YAC) contig from the C57BL/6 (H2 b ) mouse was created from the major histocompatibility complex (Mhc, H2 in mouse) class Ib subregion, H2-M. It spans approximately 1.2 megabase (Mb) pairs and unites the previous 〉1.5-Mb YAC contigs (Jones et al. 1995) into a single contig, which includes 21 Mhc class I genes distal to H2-T1. A bacterial artificial chromosome (BAC) contig from the 129 (H2 bc ) mouse, spanning approximately 600 kilobases, was also built from Znf173 (Afp, a gene for acid finger protein), through Tctex5 (t-complex testis expressed-5) and Mog (myelin oligodendrocyte glycoprotein), to H2-M2. Twenty-four sequence-tagged site (STS) markers were newly developed, and 35 markers were mapped in the YAC/BAC contigs, which define the marker order as Cen –Znf173–Tctex5 – Mog–D17Tu42–D17Mit232–H2-M3–D17Leh525–H2-M2– Tel. The gene order of Znf173 – Tctex5 – Mog – D17Tu42 is conserved between mouse and human, showing that the middle H2-M region corresponds to the subregion of the human Mhc surrounding HLA-A.
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    URL: http://dx.doi.org/10.1007/s002510050372
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  • 113
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    Isolation and molecular characterization of the rat MR1 homologue, a non-MHC-linked class I-related gene (1998)
    Springer
    Immunogenetics 47 (1998), S. 477-482 
    Details
    ISSN: 1432-1211
    Keywords: Key words Rat ; Major histocompatibility complex class I ; Mr1 ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  We isolated and analyzed a new rat gene which is homologous to the recently described human major histocompatibility complex class I-related gene MR1. The deduced amino acid sequence of the rat Mr1 gene shows conserved cysteine residues typical of class I genes as well as conserved β2-microglobulin and CD8 contact sites. Analysis of partial DNA sequences and restriction fragment length polymorphism patterns of several inbred rat strains indicate that Mr1 is not polymorphic. Mr1 is a single-copy gene, which could be mapped to rat chromosome 13 by co-segregation analysis of Mr1 and a microsatellite marker in the renin (Ren) gene in double-backcross hybrids. The recombination frequency between both genes was determined to be 14.7% (4.9–31.1, 95% confidence limits). Expression analysis revealed various Mr1 transcripts in each organ tested and occurrence of alternative splicing.
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    URL: http://dx.doi.org/10.1007/s002510050385
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  • 114
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    DNA sequence and structure of the mouse RING3 gene: identification of variant RING3 transcripts (1998)
    Springer
    Immunogenetics 48 (1998), S. 82-86 
    Details
    ISSN: 1432-1211
    Keywords: Key words MHC ; H2 ; Kinases ; Alternative splicing ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050406
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  • 115
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    Linkage of RXRB-like genes to class I and not to class II Mhc genes in the zebrafish (1998)
    Springer
    Immunogenetics 48 (1998), S. 141-143 
    Details
    ISSN: 1432-1211
    Keywords: Key words Major histocompatibility complex (Uhc) ; Retinoid receptor genes ; Evolution ; Linkage ; Zebrafish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050414
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  • 116
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    MHC class I genes in a New World primate, the cotton-top tamarin (Saguinus oedipus), have evolved by an active process of loci turnover (1999)
    Springer
    Immunogenetics 49 (1999), S. 196-205 
    Details
    ISSN: 1432-1211
    Keywords: Key words New world primates ; MHC ; Evolution ; Gene duplication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Lymphocytes of a New World primate, the cotton-top tamarin (Saguinus oedipus), express classical G–related major histocompatibility complex (MHC) class I molecules with unusually limited polymorphism and variability. Three G-related loci, an F locus, an E locus, and two pseudogenes (So-N1 and So-N3) have been identified by cDNA library screening and extensive PCR analysis of both cDNA and genomic DNA from the cotton-top tamarin. Furthermore, each genus of the subfamily Callitrichinae (tamarins and marmosets) appears to express its own unique set of MHC class I genes, likely due to a rapid turnover of loci. The rapid emergence of unique MHC class I genes in the Callitrichinae genera, resulting from an active process of duplication and inactivation of loci, may account for the limited diversity of the MHC class I genes in the cotton-top tamarin. To determine the nature of the entire complement of MHC class I genes in the cotton-top tamarin, we synthesized a genomic DNA library and screened it with MHC class I-specific probes. We isolated nine new MHC class I pseudogenes from this library. These newly isolated tamarin G–related MHC class I pseudogenes are not closely related to any of their functional counterparts in the tamarin, suggesting that they do not share a recent common ancestral gene with the tamarin's currently expressed MHC class I loci. In addition, these tamarin sequences display a high rate of nonsynonymous substitutions in their putative peptide binding region. This indicates that the genes from which they have derived were likely subject to positive selection and, therefore, were once functional. Our data support the notion that an extremely high rate of loci turnover is largely responsible for the limited diversity of the MHC class I genes in the cotton-top tamarin.
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    URL: http://dx.doi.org/10.1007/s002510050480
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  • 117
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    Evolution of a new nonclassical MHC class I locus in two Old World primate species (1999)
    Springer
    Immunogenetics 49 (1999), S. 86-98 
    Details
    ISSN: 1432-1211
    Keywords: Key words MHC ; Primates ; Reproduction ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  HLA-G is a nonclassical major histocompatibility complex (MHC) class I molecule that is expressed only in the human placenta, suggesting that it plays an important role at the fetal-maternal interface. In rhesus monkeys, which have similar placentation to humans, the HLA-G orthologue is a pseudogene. However, rhesus monkeys express a novel placental MHC class I molecule, Mamu-AG, which has HLA-G-like characteristics. Phylogenetic analysis of AG alleles in two Old World primate species, the baboon and the rhesus macaque, revealed limited diversity characteristic of a nonclassical MHC class I locus. Gene trees constructed using classical and nonclassical primate MHC class I alleles demonstrated that the AG locus was most closely related to the classical A locus. Interestingly, gene tree analyses suggested that the AG alleles were most closely related to a subset of A alleles which are the products of an ancestral interlocus recombination event between the A and B loci. Calculation of the rates of synonymous and nonsynonymous substitution at the AG locus revealed that positive selection was not acting on the codons encoding the peptide binding region. In exon 4, however, the rate of nonsynonymous substitution was significantly lower than the rate of synonymous substitution, suggesting that negative selection was acting on these codons.
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    URL: http://dx.doi.org/10.1007/s002510050467
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  • 118
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    Opposite orientation of the α- and υ-chain constant region genes in the immunoglobulin heavy chain locus of the duck (1999)
    Springer
    Immunogenetics 49 (1999), S. 692-695 
    Details
    ISSN: 1432-1211
    Keywords: Key words Duck ; Immunoglobulin genes ; IgH locus ; Class switching ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050666
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  • 119
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    Multi-level evolution in population games (1998)
    Springer
    International journal of game theory 27 (1998), S. 21-35 
    Details
    ISSN: 1432-1270
    Keywords: Evolution ; games ; multilevel ; group selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract In this paper, we analyze a generalization of the evolutionary model of Kandori, Mailath, & Rob (1993) where the population is partitioned into groups and evolution takes place “in parallel” at the following two levels: (i) within groups, at the lower level; among groups, at the higher one. Unlike in their context, efficiency considerations always overcome those of risk-dominance in the process of selecting the long-run equilibrium. This provides an explicitly dynamic basis for a conclusion reminiscent of those put forward in the biological literature by the so-called theories group selection. From a normative viewpoint, it suggests the potential importance of “decentralization”, here understood as local and independent interaction.
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    URL: http://dx.doi.org/10.1007/BF01243192
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    Ig heavy chain of the sturgeon Acipenser baeri : cDNA sequence and diversity (1998)
    Springer
    Immunogenetics 48 (1998), S. 372-382 
    Details
    ISSN: 1432-1211
    Keywords: Key words Immunoglobulin ; Heavy chain ; VH gene ; Diversity ; Evolution ; Sturgeon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  To investigate the gene organization of the IGH locus, and the VH diversity of the Siberian sturgeon, a cDNA library was constructed and screened with VH-specific probes from two holostean fish. Isolated clones were analyzed and domain-specific probes used in rescreening of the library, Southern blot analysis, and northern blots. It was concluded that the Siberian sturgeon has one IGH locus with a translocon type of organization. Two allelic variants of the mu gene were found, with identities ranging from 80 to 100% for the different domains (highest for CH4 and lowest for CH2). Sturgeon CH sequences are most closely related to those of holostean fish. There are three distinct VH families, VHI grouping with mammalian clan III, VHII grouping with the teleost clan, and VHIII grouping with the archaic clan. The variability of the CDR 3 region is substantial, and we identified a number of conserved motifs in the D segment. Further, we deduced that there are at least nine different JH segments in the locus, contributing to the antibody repertoire of the sturgeon. The variable segments of the three families can be associated with any of the D or JH segments in the rearrangement. Sturgeon, in addition to the random rearrangement of VH, D, and JH segments, have exonuclease activity, and an introduction of N and probably P nucleotides at the site of rearrangement.
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    URL: http://dx.doi.org/10.1007/s002510050448
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    Sequences and evolution of mammalian RH gene transcripts and proteins (1999)
    Springer
    Immunogenetics 49 (1999), S. 15-25 
    Details
    ISSN: 1432-1211
    Keywords: Key words Rh blood group system ; Phylogenesis ; RH genes ; Evolution ; Nonhuman primates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The presence of Rh30-like polypeptides with an apparent relative molecular mass of 33 000 in the erythrocyte membranes from nonhuman primates and nonprimate mammals (mouse, rat, and dog) was demonstrated by immunoblotting. Nonhuman primates (orangutan, baboon, New World monkeys, lemur) and mouse Rh-like transcripts were amplified and sequenced. Analysis of the deduced amino acids sequences allowed us to determine the amino acid variability of Rh-like polypeptides which correlated with the hydrophylicity indexes. Hence, the putative transmembrane domains exhibited low indexes of variability, while the highest indexes were observed on extramembrane loops with a maximum on the sixth external loop. The cDNA sequences were compared with those previously reported in human, nonhuman primates, and cattle. The time of coalescence of mammalian Rh cDNA sequences was estimated by phylogenetic analysis to be 100 million years.
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    URL: http://dx.doi.org/10.1007/s002510050459
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    TNFB polymorphisms characterize three lineages of TNF region microsatellite haplotypes (1997)
    Springer
    Immunogenetics 47 (1997), S. 6-16 
    Details
    ISSN: 1432-1211
    Keywords: Key words TNF ; Microsatellites ; Haplotype ; Evolution ; Response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The human major histocompatibility complex (MHC) contains a variety of genes, many of which are highly polymorphic and of immunological importance. A database of MHC extended haplotypes was used to integrate experimental, cell line, and population data. Three alleles of the human TNF-beta (lymphotoxin-alpha) gene were identified, named TNFB *1SL, TNFB *2LL, and TNFB *1LS, each representing a different lineage in the evolution of TNF region haplotypes. Lower variability in the length of the associated microsatellite alleles indicates that *1SL characterizes the youngest of the three haplotype lineages. Microsatellite haplotypes in the two older lineages show evidence for a coevolution of alleles through concerted expansions. Genetic predispositions to high and low TNF-alpha (cachectin) responses seem to have evolved independently in more than one lineage. The literature data suggest different, or even opposite, associations concerning the regulation of TNF-alpha in macrophages and lymphoid cells. Microsatellite ud may be the most informative marker for studies of the associations of individual TNF region markers with secretion levels, immunity, and disease.
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    URL: http://dx.doi.org/10.1007/s002510050320
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    A hypothesis on the evolution of isoprenoid emission by oaks based on the correlation between emission type and Quercus taxonomy (1998)
    Springer
    Oecologia 115 (1998), S. 302-305 
    Details
    ISSN: 1432-1939
    Keywords: Key words Chemo-taxonomy ; Isoprenoid emission ; Evolution ; Quercus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We show that Mediterranean oaks that emit isoprene, monoterpenes or no isoprenoids belong to different subgenera as indicated by morpho-taxonomy and molecular genetics. On the other hand, oaks from North America and Asia that are taxonomically similar to the Mediterranean monoterpene emitter Q. ilex emit isoprene only. We surmise that isoprene emission is a genetic character which evolved ancestrally in the oak genus since this is the prevalent emission type in oaks widespread around the world and adapted to different environments. This ancestral character may have been either lost or modified in more recent clades such as those originating the Mediterranean oaks. If our hypothesis is correct then the taxonomy of European oaks is validated by this independent trait. Isoprenoid emission could serve as a chemo-taxonomical marker and could be used to reconstruct the phylogeny of oaks in association with molecular markers.
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    URL: http://dx.doi.org/10.1007/s004420050520
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    Evidence on the nature and origins of endosperm dosage requirements in Solanum and other angiosperm genera (1995)
    Springer
    Sexual plant reproduction 8 (1995), S. 189-196 
    Details
    ISSN: 1432-2145
    Keywords: Endosperm balance number ; Congruity ; Imprinting ; Evolution ; Lycopersicon ; Triploid block
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Success of seed development following sexual crosses is primarily dependent on proper endosperm function and development. The failure to produce triploids, or “triploid block” in 4x×2x crosses served as the impetus for numerous studies of embryo and endosperm to attempt to explain cross failure. Early explanations were based upon a concept of a 2∶3∶2 ploidy balance between maternal tissue, endosperm, and embryo. Subsequent studies done with maize demonstrated that normal endosperm development in intraspecific maize crosses is dependent solely on having a 2∶1 maternal to paternal genome dosage in the endosperm. These results have been modified and extended to solanaceous species in the form of an endosperm dosage system in which empirically determined factors must bear the same 2∶1 relationship for crosses to succeed. Crossing behavior of these species suggest that the system is polygenically controlled and regulates both interspecific and intraspecific crosses. Endosperm dosage systems explain many aspects of species evolution, but the system appears to have originated as an ancient means of ensuring diploid fidelity.
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    URL: http://dx.doi.org/10.1007/BF00228936
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    The evolution of self-incompatibility: a molecular voyeur's perspective (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 357-361 
    Details
    ISSN: 1432-2145
    Keywords: Self-incompatibility ; Evolution ; S-RNases ; Solanaceae ; Rosaceae ; Scrophulariaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This review summarises current understanding of the evolution of self-incompatibility inferred from DNA sequence analysis. Self-incompatibility in many plant families is controlled by a single, highly polymorphicS-locus which, in the Solanaceae, encodes an allelic series of stylar ribonucleases known as the S-RNases. PCR approaches are a convenient way to examine the diversity of S-RNase sequences within and between wild populations of a self-incompatible species and provide a unique view into the species' current and historic population structure. Similar molecular appoaches have also been used to show that S-RNases are involved in self-incompatibility in families other than the Solanaceae. A model for the evolution of ribonuclease-based self-incompatibility systems is discussed.
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    URL: http://dx.doi.org/10.1007/BF02441956
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    The catalytic group-I introns of the psbA gene of Chlamydomonas reinhardtii : core structures, ORFs and evolutionary implications (1999)
    Springer
    Current genetics 36 (1999), S. 69-78 
    Details
    ISSN: 1432-0983
    Keywords: Key wordsChlamydomonas ; Chloroplast ; Evolution ; Group-I introns ; psbA gene ; Self-splicing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sequences and predicted secondary structures of the four catalytic group-I introns in the psbA gene of Chlamydomonas reinhardtii, Cr.psbA-1–Cr.psbA-4, have been determined. Cr.psbA-1 and Cr.psbA-4 are subgroup-IA1 introns and have similar secondary structures, except at the 3′ end where Cr.psbA-1 contains a large inverted-repeat domain. Cr.psbA-4 is closely related to intron 1 of the Chlamydomonas moewusii psbA gene, with which it shares the same location, high nucleotide identity in the core, and an identically placed ORF that shows 58% amino-acid identity. Cr.psbA-2 is a subgroup-IA3 intron, and shows similarities to the Chlamydomonas eugametos rRNA intron, Ce.LSU-1. Cr.psbA-3 is a subgroup-IA2 intron, and is remarkably similar to the T4 phage intron, sunY. Interestingly, a degenerate version of Cr.psbA-3 is located in the intergenic region between the chloroplast petA and petD genes. All four introns contain ORFs, which potentially code for basic proteins of 11–38 kDa. The ORFs in introns 2 and 3 contain variants of the GIY-YIG motif; however, the Cr.psbA-2 ORF is free-standing, whereas the Cr.psbA-3 ORF is contiguous and in-frame with the upstream exon. The Cr.psbA-4 ORF contains an H-N-H motif, and possibly a GIY-YIG motif. These data indicate that the C. reinhardtiipsbA introns have multiple origins, and illustrate some of the evolutionary DNA dynamics associated with group-I introns in Chlamydomonas.
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    Sequence similarities of glyceraldehyde-3-phosphate dehydrogenases, phosphoglycerate kinases, and pyruvate kinases are species optimal temperature-dependent (1998)
    Springer
    European biophysics journal 27 (1998), S. 409-410 
    Details
    ISSN: 1432-1017
    Keywords: Key words Sequence similarity ; Glyceraldehyde-3-phosphate dehydrogenase ; Phosphoglycerate kinase ; Pyruvate kinase ; Evolution ; Phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Data are presented that suggest enzyme sequence similarities among species are not solely a function of their evolutionary relationship. It is demonstrated that sequence similarities of glyceraldehyde-3-phosphate dehydrogenases, phosphoglycerate kinases, and pyruvate kinases from yeast, bacteria, mammals and a bird possess a significant species optimal thriving temperature dependence that crosses through conventional phylogenetic divisions. It is therefore suggested that species which are distantly related evolutionarily may possess some degree of enzyme sequence similarity if they happen to thrive at near the same optimal temperature; conversely, organisms which are closely related evolutionarily but function at radically different temperatures will possess a sequence dissimilarity that may mask the close relatedness.
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    URL: http://dx.doi.org/10.1007/s002490050148
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    The organization structure and regulatory elements of Chlamydomonas histone genes reveal features linking plant and animal genes (1995)
    Springer
    Current genetics 28 (1995), S. 333-345 
    Details
    ISSN: 1432-0983
    Keywords: Green algae ; Volvox ; Transcription signals ; Gene expression ; Intron ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genome of the green alga Chlamydomonas reinhardtii contains approximately 15 gene clusters of the nucleosomal (or core) histone H2A, H2B, H3 and H4 genes and at least one histone H1 gene. Seven non-allelic histone gene loci were isolated from a genomic library, physically mapped, and the nucleotide sequences of three isotypes of each core histone gene species and one linked H1 gene determined. The core histone genes are organized in clusters of H2A–H2B and H3–H4 pairs, in which each gene pair shows outwardly divergent transcription from a short (300 bp) intercistronic region. These intercistronic regions contain typically conserved promoter elements, namely a TATA-box and the three motifs TGGCCAG-G(G/C)-CGAG, CGTTGACC and CGGTTG. Different from the genes of higher plants, but like those of animals and the related alga Volvox the 3′ untranslated regions contain no poly A signal, but a palindromic sequence (3′ palindrome) essential for mRNA processing is present. One single H1 gene was found in close linkage to a H2A–H2B pair. The H1 upstream region contains the octameric promoter element GGTTGA-CC (also found upstream of the core histone genes) and two specific sequence motifs that are shared only with the Volvox H1 promoters. This suggests differential transcription of the H1 and the core histone genes. The H1 gene is interrupted by two introns. Unlike Volvox H3 genes, the three sequenced H3 isoforms are intronfree. Primer-directed PCR of genomic DNA demonstrated, however, that at least 8 of the about 15 H3 genes do contain one intron at a conserved position. In synchronized C. reinhardtii cells, H4 mRNA levels (representative of all core histone mRNAs) peak during cell division, suggesting strict replication-dependent gene control. The derived peptide sequences place C. reinhardtii core histones closer to plants than to animals, except that the H2A histones are more animal-like. The peptide sequence of histone H1 is closely related to the V. carteri VH1-II (66% identity). Organization of the core histone gene in pairs, and non-polyadenylation of mRNAs are features shared with animals, whereas peptide sequences and enhancer elements are shared with higher plants, assigning the volvocalean histone genes a position intermediate between animals and plants.
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    Analysis of a transketolase gene from Kluyveromyces lactis reveals that the yeast enzymes are more related to transketolases of prokaryotic origins than to those of higher eukaryotes (1997)
    Springer
    Current genetics 31 (1997), S. 15-21 
    Details
    ISSN: 1432-0983
    Keywords: Key wordsKluyveromyces lactis ; Transketolase ; Evolution ; Carbohydrate metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of the pentose-phosphate pathway in carbohydrate metabolism of the yeast Kluyveromyces lactis, and the evolutionary relationships between the encoding genes, was investigated. For this purpose, we isolated the gene encoding transketolase (KlTKL1) and determined its nucleotide sequence. Surprisingly, comparisons of the deduced amino-acid sequence with those from other organisms revealed that the yeast enzymes are more related to those from prokaryotic sources than to those from higher eukaryotes. Functional analyses showed that KlTKL1 also complemented a Saccharomyces cerevisiae tkl1 tkl2 double mutant for growth in the absence of aromatic amino acids and restored transketolase activity in this mutant. A band detected in these transformants by Western-blot analysis corresponded to a band detected in K. lactis both in a wild-type strain and in a multicopy transformant with elevated transketolase activity.
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    URL: http://dx.doi.org/10.1007/s002940050171
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    Origin and evolution of mitochondria: what have we learnt from red algae? (1997)
    Springer
    Current genetics 31 (1997), S. 193-207 
    Details
    ISSN: 1432-0983
    Keywords: Key words Mitochondrial genome ; Red algae ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The purpose of this review is to present an account of our current understanding of the structure, organization and evolution of mitochondrial genomes, and to discuss the origin and evolution of mitochondria from the perspective recently provided by the extensive sequenc-ing of various mitochondrial genomes. Mitochondrial-en-coded protein phylogenies are congruent with nuclear phylogenies and strongly support a monophyletic origin of mitochondria. The newly available data from red-algal mitochondrial genomes, in particular, show that the structural and functional diversity of mitochondrial genomes can be accounted for by paralogous evolution. We also discuss the influence of other constraints, such as uniparental inheritance, on the evolution of genome organization in mitochondria.
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    URL: http://dx.doi.org/10.1007/s002940050196
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    Plasticity of the mitochondrial genome in Podospora. Polymorphism for 15 optional sequences: group-I, group-II introns, intronic ORFs and an intergenic region (1997)
    Springer
    Current genetics 31 (1997), S. 308-317 
    Details
    ISSN: 1432-0983
    Keywords: Key words Mitochondria ; Introns ; Evolution ; Fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mitochondrial chromosome of 15 Podo-spora anserina and one Podospora comata wild-type strains have been extensively examined for the presence of optional elements and for sequence divergence. Among the P. anserina strains, nine optional sequences were found. By comparing P. anserina with the closely related and weakly interfertile P. comata species, six additional optional sequences were detected. These optional elements correspond to mitochondrial introns belonging to different groups and subgroups (11 cases), intronic open reading frames (two cases), a complex insert and an intergenic region. Although difficult to explain, the distribution of optional mitochondrial sequences among the 15 wild-type isolates of P. anserina is far from random.
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    The evolution of the Calvin cycle from prokaryotic to eukaryotic chromosomes: a case study of functional redundancy in ancient pathways through endosymbiosis (1997)
    Springer
    Current genetics 32 (1997), S. 1-18 
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    ISSN: 1432-0983
    Keywords: Key words Chloroplast ; Mitochondria ; Endosymbiosis ; Endosymbiotic gene transfer ; Calvin cycle ; Glycolysis ; Evolution ; Amitochondriate ; Metabolism ; Compartmentation ; Hydrogenosome ; Eukaryote ; Origin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The evolutionary histories of the 12 enzymes that catalyze the reactions of the Calvin cycle in higher-plant chloroplasts are summarized. They are shown to be encoded by a mixture of nuclear genes of cyanobacterial and proteobacterial origin. Moreover, where cytosolic isoforms of these enzymes are found they are almost invariably encoded by genes of clearly endosymbiont origin. We infer that endosymbiosis resulted in functional redundancy that was eliminated through differential gene loss, with intruding eubacterial genes repeatedly replacing pre-existing nuclear counterparts to which they were either functionally or structurally homologous. Our findings fail to support the `product-specificity corollary', which predicts re-targeting of nuclear-encoded gene products to the organelle from whose genome they originated. Rather it would appear that the enzymes of central carbohydrate metabolism have evolved novel targeting possibilities regardless of their origins. Our findings suggest a new hypothesis to explain organelle genome persistence, based on the testable idea that some organelle-encoded gene products might be toxic when present in the cytosol or other inappropriate cellular compartments.
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    URL: http://dx.doi.org/10.1007/s002940050241
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    The gene for ribosomal protein S10 is present in mitochondria of pea and potato but absent from those of Arabidopsis and Oenothera (1995)
    Springer
    Current genetics 27 (1995), S. 559-564 
    Details
    ISSN: 1432-0983
    Keywords: RNA editing ; Group-II intron ; Gene transfer ; Evolution ; tRNA genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A novel group II intron has been identified in the pea (Pisum sativum) mitochondrial genome. The gene harbouring this intron is identified as rps10 (encoding protein S10 of the small ribosomal subunit) by similarity to its known homologues in bacteria and in the mitochondrion of the liverwort Marchantia polymorpha. The rps10 gene is transcribed in pea, the intron is removed, and RNA editing in the rps10 reading frame increases similarity to its homologue in the M. polymorpha mitochondrion. Contrary to the situation in bacteria and Marchantia, rps10 is not part of a ribosomal-protein gene cluster in pea. It is flanked upstream by the genes trnF and trnP, encoding phenylalanine-and proline-accepting tRNAs, and downstream by cox1, encoding subunit 1 of the cytochrome-c-oxidase. Southern hybridization shows that sequences homologous to rps10 exist in potato mitochondria but not in mitochondria of Oenothera berteriana and Arabidopsis thaliana. The pea rps10 intron is homologous to introns in rrn26 and cox3 in the Marchantia mitochondrial genome, while the Marchantia rps10 gene lacks an intron.
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    Multi-copy nuclear pseudogenes of mitochondrial DNA reveal recent acute genetic changes in the human genome (1995)
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    Current genetics 28 (1995), S. 410-414 
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    ISSN: 1432-0983
    Keywords: Mitochondrial DNA ; Multi-copy ; Pseudogene ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four nuclear pseudogenes homologous to the 10031–10195-bp region of the human mitochondrial genome were detected by constant denaturant capillary electrophoresis. Among them, one pseudogene is present as at least five copies in each cell, in accordance with our previous observations of multi-copy mitochondrial DNA pseudogenes. The presence of multiple identical copies of pseudogenes suggests that the human genome underwent a series of genetic changes, including gene amplifications, very recently in evolutionary history, i.e., within the last 390000 years.
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    The cox1 gene from Euglena gracilis: a protist mitochondrial gene without introns and genetic code modifications Received: 10 October / 22 November 1996 (1997)
    Springer
    Current genetics 31 (1997), S. 208-213 
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    ISSN: 1432-0983
    Keywords: Key wordsEuglena ; Mitochondria ; cox1 ; Evolution ; RNA editing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present the nucleotide sequence of the cox 1 gene encoding subunit 1 of cytochrome c oxidase in Euglena gracilis, the first report on a mitochondrial gene from this protist. Its study reveals that the Euglena mitochondrial genome does not appear as a compact and homogeneous structure and that its A+T content is high (about 76%) whereas this value is less than 50% in nuclear DNA. The Euglena cox1 gene does not exhibit any intron, and an amino-acid alignment of Euglena COX1 with homologous proteins shows that the universal genetic code is used. Comparisons of the genomic and cDNA sequences of Euglena cox1 indicate that the transcript does not undergo RNA editing as found in trypanosomes and in higher plants. The phylogeny obtained with COX1 protein sequences is in agreement with that obtained with nuclear rRNA sequences and places Euglena and Trypanosoma far apart from other eukaryotes. This result strengthens the hypothesis that these protists represent the earliest mitochondrion-containing organisms.
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    URL: http://dx.doi.org/10.1007/s002940050197
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    Intron-encoded open reading frame of the GIY-YIG subclass in a plastid gene (1995)
    Springer
    Current genetics 28 (1995), S. 97-99 
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    ISSN: 1432-0983
    Keywords: GIY-YIG ORF ; Endonuclease ; Plastid ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Group-I introns, containing open reading frames (ORFs) that code for homing endonucleases, are widely distributed amongst eukaryotic organellar genomes. However, endonucleases of the GIY-YIG subclass have a restricted distribution in mitochondria and bacteriophages, and have never been observed in plastids. We have found the GIY-YIG motif in an intronic ORF within the previously published psbA gene sequence from Chlamydomonas reinhardtii chloroplasts. Based on phylogenetic analysis and an evaluation of amino-acid substitutions, this ORF is not closely related to any of the other GIY-YIG ORFs. These results suggest that GIY-YIG ORFs have a longer evolutionary history than previously assumed.
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    Nucleotide sequence of the clustered genes for apocytochrome b6 and subunit 4 of the cytochrome b/f complex in the spinach plastid chromosome (1984)
    Springer
    Current genetics 8 (1984), S. 543-549 
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    ISSN: 1432-0983
    Keywords: Plastid DNA ; Cytochrome b6 gene ; Amino acid sequence ; Hydropathy ; Thylakoid membrane ; Transcript modification ; Evolution ; Spinach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A 2.4 kilobase-pair segment of the spinach plastid chromosome carrying the genes for apocytochrome b6 and subunit 4 of the thylakoid membrane cytochrome b/f complex has been analysed by DNA sequencing and Northern blot analysis. The nucleotide sequence reveals two uninterrupted open reading frames of 211 and 139 triplets coding for two hydrophobic proteins of 23.7 kd (cytochrome b6) and 15.2 kd (subunit 4). The genes are located on the same strand and are separated from each other by 1018 untranslated base pairs. They map adjacent to the gene for the P680 chlorophyll α apoprotein of the photosystem II reaction center. The three genes appear to be under common transcriptional control and the transcripts post-transcriptionally modified. The deduced amino acid sequences of cytochrome b6 and subunit 4 both exhibit significant homology with published sequences from mitochondrial b cytochromes (42 kd) suggesting that these functionally equivalent polypeptides in photosynthetic and respiratory electron transport chains arose monophyletically.
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    Detection of multiple stimulus features forces a trade-off in the pyramidal cell network of a gymnotiform electric fish's electrosensory lateral line lobe (1997)
    Springer
    Journal of comparative physiology 182 (1997), S. 103-113 
    Details
    ISSN: 1432-1351
    Keywords: Key words Constraint ; Electroreception ; Evolution ; Sensory system ; Neural network
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Modification of an existing neural structure to support a second function will produce a trade-off between the two functions if they are in some way incompatible. The trade-off between two such sensory functions is modeled here in pyramidal neurons of the gymnotiform electric fish's medullar electrosensory lateral line lobe (ELL). These neurons detect two electric stimulus features produced when a nearby object interferes with the fish's autogenous electric field: (1) amplitude modulation across a cell's entire receptive field and (2) amplitude variation within a cell's receptive field produced by an object's edge. A model of sensory integration shows that detection of amplitude modulation and enhancement of spatial contrast involve an inherent mechanistic trade-off and that the severity of the trade-off depends on the particular algorithm of sensory integration. Electrophysiology data indicate that of the two algorithms for sensory integration modeled here for the gymnotiform fish Brachyhypopomus pinnicaudatus, the algorithm with the better trade-off function is used. Further, the intrinsic trade-off within single cells has been surmounted by the replication of ELL into multiple electrosensory map segments, each specialized to emphasize different sensory features.
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    URL: http://dx.doi.org/10.1007/s003590050162
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    Correlation between auditory sensitivity and vocalization in anabantoid fishes (1998)
    Springer
    Journal of comparative physiology 182 (1998), S. 737-746 
    Details
    ISSN: 1432-1351
    Keywords: Key words Auditory sensitivity ; Sound spectra ; ABR ; Evolution ; Communication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Several anabantoid species produce broad-band sounds with high-pitched dominant frequencies (0.8–2.5 kHz), which contrast with generally low-frequency hearing abilities in (perciform) fishes. Utilizing a recently developed auditory brainstem response recording-technique, auditory sensitivities of the gouramis Trichopsis vittata, T. pumila, Colisa lalia, Macropodus opercularis and Trichogaster trichopterus were investigated and compared with the sound characteristics of the respective species. All five species exhibited enhanced sound-detecting abilities and perceived tone bursts up to 5 kHz, which qualifies this group as hearing specialists. All fishes possessed a high-frequency sensitivity maximum between 800 Hz and 1500 Hz. Lowest hearing thresholds were found in T. trichopterus (76 dB re 1 μPa at 800 Hz). Dominant frequencies of sounds correspond with the best hearing bandwidth in T. vittata (1–2 kHz) and C. lalia (0.8–1 kHz). In the smallest species, T. pumila, dominant frequencies of acoustic signals (1.5–2.5 kHz) do not match lowest thresholds, which were below 1.5 kHz. However, of all species studied, T. pumila had best hearing sensitivity at frequencies above 2 kHz. The association between high-pitched sounds and hearing may be caused by the suprabranchial air-breathing chamber, which, lying close to the hearing and sonic organs, enhances both sound perception and emission at its resonant frequency.
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    URL: http://dx.doi.org/10.1007/s003590050218
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    Differential regulation of a homologous peptidergic neuron in grasshoppers: evolution of a neural circuit (1998)
    Springer
    Journal of comparative physiology 182 (1998), S. 755-765 
    Details
    ISSN: 1432-1351
    Keywords: Key words Acetylcholine ; Evolution ; Histamine ; Homology ; Insect ; Vasopressin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The vasopressin-like immunoreactive (VPLI) neurons of grasshoppers have paired cell bodies in the suboesophageal ganglion and both anterior and posterior running axons. In non-oedipodine grasshopper species (e.g. Schistocerca gregaria), most of their arborisations are distributed in dorsal and lateral neuropil, while in oedipodine species (e.g. Locusta migratoria), the neurons have additional extensive axonal projections in both the optic lobes and proximal portions of the ganglionic peripheral nerves. This study demonstrates that these morphological differences correlate with their physiology. In L. migratoria, VPLI neuron activity is regulated primarily via a spontaneously active interneuron which descends from the brain. This descending interneuron is inhibited by a light-activated brain extraocular photoreceptor. Regulation of VPLI neuron activity by an extraocular photoreceptor is also seen in the other oedipodine grasshopper investigated. In the four non-oedipodines examined (from two subfamilies), we find no extraocular photoreceptor regulation of VPLI neuron activity. Despite this, VPLI neuron in S.␣gregaria does appear to be driven by a descending interneuron homologous to that in L. migratoria. The descending interneuron in both species receives similar mechanosensory input and excites the VPLI neuron via cholinergic synapses. Histamine injection into the medial protocerebrum of both species causes strong inhibition of the descending interneuron. The evolution of the neural circuitry, by which an extraocular photoreceptor comes to regulate the descending interneuron in oedipodine species, is discussed.
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    URL: http://dx.doi.org/10.1007/s003590050220
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  • 141
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    Purification, primary structure, and evolution of cytochrome c-550 from the magnetic bacterium, Magnetospirillum magnetotacticum (1995)
    Springer
    Archives of microbiology 163 (1995), S. 400-406 
    Details
    ISSN: 1432-072X
    Keywords: Magnetospirillum magnetotacticum ; Cytochrome c ; Amino acid sequence ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytochrome c-550 was purified from Magnetospirillum magnetotacticum to an electrophoretically homogeneous state, and some of its properties were determined. The cytochrome showed absorption peaks at 528 and 409 nm in the oxidized form, and at 550, 521, and 414 nm in the reduced form. Its midpoint redox potential at pH 7.0 was determined to be +289 mV. The primary structure of cytochrome c-550 was determined. Cytochrome c is composed of 97 amino acid residues, and its molecular weight was calculated to be 10,873, including heme c. Its primary structure is very similar to those of Rhodospirillum fulvum and Rhodospirillum molischianum cytochromes c 2, suggesting that M. magnetotacticum is phylogenetically related to photosynthetic bacteria.
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    Glycogen in thermoacidophilic archaebacteria of the genera Sulfolobus, Thermoproteus, Desulfurococcus and Thermococcus (1982)
    Springer
    Archives of microbiology 132 (1982), S. 297-303 
    Details
    ISSN: 1432-072X
    Keywords: Glycogen ; Archaebacteria ; Thermoacidophiles ; Sulfolobus ; Thermoproteales ; Glucosyl transferase ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glycogen has been found in thermoacidophilic archaebacteria of the genera Sulfolobus, Thermoproteus, Desulfurococcus and Thermococcus. Thermoplasma acidophilum yielded a related, though less defined compound. Glycogen was identified by elementary analysis, infrared spectroscopy, the nature of the hydrolysis products, the iodine reaction, and the nature of the products of periodate oxydation and reduction. The average chain length was 7. From crude extracts of Sulfolobus and Thermoproteus complexes of glycogen with 4 respectively 2 proteins have been isolated by CsCl density gradient centrifugation. In either case, one of the proteins was identified as glucosyl transferase. The glucosyl transferase of Sulfolobus acidocaldarius strain B 12 utilizes UDP-glucose as well as ADP-glucose as substrates, with K m values of 0.42 and 0.2 mM respectively and turnover numbers of 4.6 and 5.2 per second respectively. In electron micrographs the isolated glycogen protein complex appears as scale like aggregates, whereas in cell sections amorphous bodies fill large portions of the cells.
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    Evolutionary relationships of superoxide dismutases and glutamine synthetases from marine species of Alteromonas, Oceanospirillum, Pseudomonas and Deleya (1984)
    Springer
    Archives of microbiology 138 (1984), S. 170-178 
    Details
    ISSN: 1432-072X
    Keywords: Superoxide dismutase ; Glutamine synthetase ; Evolution ; Marine bacteria ; Alcaligenes ; Alteromonas ; Deleya ; Oceanospirillum ; Pseudomonas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Evolutionary relationships among marine species assigned to the genera Alteromonas, Oceanospirillum, Pseudomonas, and Alcaligenes were determined by an immunological study of their Fe-containing superoxide dismutases (FeSOD) and glutamine synthetases (GS), two enzymes with differentially conserved amino acid sequences which are useful for determining intermediate and distant relationships, respectively. Five reference antisera were prepared against the FeSODs from Alteromonas macleodii, A. haloplanktis, Oceanospirillum commune, Pseudomonas stanieri, and Deleya pacifica. For GS, a previously prepared antiserum to the enzyme from Escherichia coli was employed. Amino acid sequence similarities for both enzymes were determined by the quantitative microcomplement fixation technique and the Ouchterlony double diffusion procedure. Six evolutionary groups were detected by FeSOD sequence similarities: three subgroups within the genus Alteromonas, the genera Oceanospirillum and Pseudomonas, and a new genus, Deleya (to accommodate marine Alcaligenes). Only four groupings were delineated by the GS data: the latter three genera and one group composed of all the species of Alteromonas. Evidence that all of these subgroups are derived from the evolutionary lineage defined by the purple sulfur photosynthetic bacteria is presented.
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    Pentalenolactone-insensitive glyceraldehyde-3-phosphate dehydrogenase fromStreptomyces arenae is closely related to GAPDH from thermostable eubacteria and plant chloroplasts (1996)
    Springer
    Archives of microbiology 165 (1996), S. 179-186 
    Details
    ISSN: 1432-072X
    Keywords: Glyceraldehyde-3-phosphate dehydrogenase ; Streptomyces arenae ; Antibiotic resistance ; Sequence comparison ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Streptomyces arenae produces the antibiotic pentalenolactone, a highly specific inhibitor of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). During the phase of pentalenolactone production,S. arenae expresses a pentalenolactone-insensitive GAPDH isoform; otherwise, a pentalenolactone-sensitive form is expressed. The gene of the pentalenolactone-insensitive GAPDH was cloned and sequenced. Regulatory elements typical for genes encoding antibiotic resistance and production are localized upstream and downstream of the open reading frame. No expression of pentalenolactone-insensitive GAPDH was detected inStreptomyces lividans transformed with the gene. InEscherichia coli, the gene was expressed from an inducedlac promoter. Amino-terminal sequencing of the heterologously expressed GAPDH proved its identity with pentalenolactone-insensitive GAPDH fromS. arenae. Sequence comparisons with GAPDH from other organisms showed a close relationship to GAPDH of plant chloroplasts, of other gram-positive bacteria, and of thermophilic gram-negative bacteria. Pentalenolactone-insensitive GAPDH differs from all closely related GAPDHs only in a few residues, none of which are directly involved in catalysis or substrate binding. The total amino acid composition is more similar to GAPDH of thermophilic species than to that of mesophilic species. The purified enzyme was moderately thermotolerant, which could be a side effect of the structural changes causing pentalenolactone-resistance.
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    Evolutionary relationships in Vibrio and Photobacterium as determined by immunological studies of superoxide dismutase (1981)
    Springer
    Archives of microbiology 130 (1981), S. 111-120 
    Details
    ISSN: 1432-072X
    Keywords: Evolution ; Vibrio ; Photobacterium ; Alteromonas ; Aeromonas ; Marine bacteria ; Superoxide dismutase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The amino acid sequence divergence of superoxide dismutases (SODs) from 22 species and five groups of Vibrio, Photobacterium, and a number of related organisms was determined by means of the microcomplement fixation technique and the Ouchterlony double diffusion procedure. Five reference antisera were used which had been prepared against the purified SODs from V. alginolyticus, V. splendidus II, V. fischeri, V. cholerae, and P. leiognathi. With a few exceptions the results were in agreement with past studies of other informational molecules and provided a comprehensive overview of evolutionary relationships in Vibrio and Photobacterium. The genus Vibrio was found to consist of a major group of primarily marine species which included V. fischeri, V. logei, V. splendidus, V. pelagius, V. nereis, V. campbellii, V. harveyi, V. natriegens, V. alginolyticus, V. parahaemolyticus, V. proteolyticus, V. fluvialis, V. vulnificus, V. nigripulchritudo, and V. anguillarum. On the outskirts of this large and relatively heterogeneous group were the fresh water and estuarine species V. cholerae and V. metschnikovii as well as the marine species V. gazogenes. A considerable distance from Vibrio were the related species of Photobacterium: P. phosphoreum, P. leiognathi, and P. angustum. Both genera were distant from species of Aeromonas as well as from Plesiomonas shigelloides, Escherichia coli, and Alteromonas hanedai, a luminous strict aerobe. The agreement between these and previous studies of evolution of informational molecules in Vibrio and Photobacterium is best explained by vertical evolution (involving no genetic exchange between species) rather than by its opposite — horizontal evolution.
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    Purification, primary structure, and evolution of cytochrome c-550 from the magnetic bacterium, Magnetospirillum magnetotacticum (1995)
    Springer
    Archives of microbiology 163 (1995), S. 400-406 
    Details
    ISSN: 1432-072X
    Keywords: Key wordsMagnetospirillum magnetotacticum ; Cytochrome c ; Amino acid sequence ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytochrome c-550 was purified from Magnetospirillum magnetotacticum to an electrophoretically homogeneous state, and some of its properties were determined. The cytochrome showed absorption peaks at 528 and 409 nm in the oxidized form, and at 550, 521, and 414 nm in the reduced form. Its midpoint redox potential at pH 7.0 was determined to be +289 mV. The primary structure of cytochrome c-550 was determined. Cytochrome c is composed of 97 amino acid residues, and its molecular weight was calculated to be 10,873, including heme c. Its primary structure is very similar to those of Rhodospirillum fulvum and Rhodospirillum molischianum cytochromes c 2, suggesting that M. magnetotacticum is phylogenetically related to photosynthetic bacteria.
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    Pentalenolactone-insensitive glyceraldehyde-3-phosphate dehydrogenase from Streptomyces arenae is closely related to GAPDH from thermostable eubacteria and plant chloroplasts (1996)
    Springer
    Archives of microbiology 165 (1996), S. 179-186 
    Details
    ISSN: 1432-072X
    Keywords: Key words Glyceraldehyde-3-phosphate dehydrogenase ; Streptomyces arenae ; Antibiotic resistance ; Sequence comparison ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Streptomyces arenae produces the antibiotic pentalenolactone, a highly specific inhibitor of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). During the phase of pentalenolactone production, S. arenae expresses a pentalenolactone-insensitive GAPDH isoform; otherwise, a pentalenolactone-sensitive form is expressed. The gene of the pentalenolactone-insensitive GAPDH was cloned and sequenced. Regulatory elements typical for genes encoding antibiotic resistance and production are localized upstream and downstream of the open reading frame. No expression of pentalenolactone-insensitive GAPDH was detected in Streptomyces lividans transformed with the gene. In Escherichia coli, the gene was expressed from an induced lac promoter. Amino-terminal sequencing of the heterologously expressed GAPDH proved its identity with pentalenolactone-insensitive GAPDH from S. arenae. Sequence comparisons with GAPDH from other organisms showed a close relationship to GAPDH of plant chloroplasts, of other gram-positive bacteria, and of thermophilic gram-negative bacteria. Pentalenolactone-insensitive GAPDH differs from all closely related GAPDHs only in a few residues, none of which are directly involved in catalysis or substrate binding. The total amino acid composition is more similar to GAPDH of thermophilic species than to that of mesophilic species. The purified enzyme was moderately thermotolerant, which could be a side effect of the structural changes causing pentalenolactone-resistance.
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    Evidence for recombination as a mechanism for KIR diversification (1998)
    Springer
    Immunogenetics 48 (1998), S. 413-416 
    Details
    ISSN: 1432-1211
    Keywords: Key words KIR ; Natural killer cell ; Recombination ; Gene conversion ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/s002510050453
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    The [2Fe-2S] protein I (Shetna protein I) from Azotobacter vinelandii is homologous to the [2Fe-2S] ferredoxin from Clostridium pasteurianum (1999)
    Springer
    JBIC 4 (1999), S. 311-317 
    Details
    ISSN: 1432-1327
    Keywords: Key words Iron-sulfur ; Nitrogen fixation ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The [2Fe-2S] protein from Azotobacter vinelandii that was previously known as iron-sulfur protein I, or Shethna protein I, has been shown to be encoded by a gene belonging to the major nif gene cluster. Overexpression of this gene in Escherichia coli yielded a dimeric protein of which each subunit comprises 106 residues and contains one [2Fe-2S] cluster. The sequence of this protein is very similar to that of the [2Fe-2S] ferredoxin from Clostridium pasteurianum (2FeCpFd), and the four cysteine ligands of the [2Fe-2S] cluster occur in the same positions. The A. vinelandii protein differs from the C. pasteurianum one by the absence of the N-terminal methionine, the presence of a five-residue C-terminal extension, and a lesser number of acidic and polar residues. The UV-visible absorption and EPR spectra, as well as the redox potentials of the two proteins, are nearly identical. These data show that the A. vinelandii FeS protein I, which is therefore proposed to be designated 2FeAvFdI, is the counterpart of the [2Fe-2S] ferredoxin from C. pasteurianum. The occurrence of the 2FeAvFdI-encoding gene in the nif gene cluster, together with the previous demonstration of a specific interaction between the 2FeCpFd and the nitrogenase MoFe protein, suggest that both proteins might be involved in nitrogen fixation, with possibly similar roles.
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    The evolution of self-incompatibility: a molecular voyeur’s perspective (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 357-361 
    Details
    ISSN: 1432-2145
    Keywords: Key words Self-incompatibility ; Evolution ; S-RNases ; Solanaceae ; Rosaceae ; Scrophulariaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  This review summarises current understanding of the evolution of self-incompatibility inferred from DNA sequence analysis. Self-incompatibility in many plant families is controlled by a single, highly polymorphic S-locus which, in the Solanaceae, encodes an allelic series of stylar ribonucleases known as the S-RNases. PCR approaches are a convenient way to examine the diversity of S-RNase sequences within and between wild populations of a self-incompatible species and provide a unique view into the species’ current and historic population structure. Similar molecular appoaches have also been used to show that S-RNases are involved in self-incompatibility in families other than the Solanaceae. A model for the evolution of ribonuclease-based self-incompatibility systems is discussed.
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    Stellar evolution and late type stars (1995)
    Springer
    Astrophysics and space science 230 (1995), S. 169-176 
    Details
    ISSN: 1572-946X
    Keywords: Late-type Stars ; Evolution ; Carbon Stars ; RV Tauri Stars
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The M, S and C stars may be placed in an evolutionary sequence on the basis of direct observation of the spectroscopic transitions on the AGB of rich intermediate-age clusters in the Magellanic Clouds, but some S and C stars cannot be accounted for in this way. The S stars inω Centauri owe their peculiarity to a primordial enrichment in s-process elements. The J-type (13C-rich) carbon stars originate in a different way to the ordinary cool N-type carbon stars. Some of them have silicate-rich circumstellar dust, contrary to expectation. Some of the carbon-rich RV Tauri stars also have silicate-rich dust and in both cases it may be organised in a disc. Observational evidence for gas and dust ejection by ordinary N-type carbon stars has been found and may be inferred for some RV Tauri stars.
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    Low-mass protostars and protostellar stages (1995)
    Springer
    Astrophysics and space science 224 (1995), S. 29-42 
    Details
    ISSN: 1572-946X
    Keywords: Protostars ; Evolution ; Infall ; Jets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The use of sensitive receivers on large ground-based radiotelescopes such as the JCMT, the IRAM 30 m MRT, and the VLA has recently yielded significant progress in our observational understanding of low-mass protostars. Submillimeter continuum observations suggest that the youngest stellar objects detected in the near-/mid-IR range -the so-called Class I sources or “infrared protostars” - have only residual amounts of circumstellar material and are thus relatively evolved. At the same time, a smaller number of colder and more obscured YSOs - designated “Class 0” - characterized by virtually no emission below 10µm but strong submillimeter emission have been identified. These Class 0 or “submillimeter protostars” have not yet assembled the bulk of their final stellar mass, and correspond to the youngest protostar stage known to date (probable age ≲ 104 yr). Direct evidence for gravitational infall has been found in some of these sources confirming their protostellar nature. However, most (if not all) Class 0 protostars already drive highly collimated CO outflows.
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    A genetic algorithm for the automated generation of molecules within constraints (1995)
    Springer
    Journal of computer aided molecular design 9 (1995), S. 181-202 
    Details
    ISSN: 1573-4951
    Keywords: De novo drug design ; Evolution ; Automated structure generation ; 3D database ; Expert system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A genetic algorithm has been designed which generates molecular structures within constraints. The constraints may be any useful function, for example an enzyme active site, a pharmacophore or molecular properties from pattern recognition or rule-induction analyses. The starting point may be random or may utilise known molecules. These are modified to ‘grow’ into families of structures which, using the evolutionary operators of selection, crossover and mutation evolve to better fit the constraints. The basis of the algorithm is described together with some applications in lead generation, 3D database construction and drug design. Genetic algorithms of this type may have wider applications in chemistry, for example in the design and optimisation of new polymers, materials (e.g. superconducting materials) or synthetic enzymes.
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    The economy as an evolving network (1997)
    Springer
    Journal of evolutionary economics 7 (1997), S. 339-353 
    Details
    ISSN: 1432-1386
    Keywords: Key words: Market organisation ; Network ; Communication ; Evolution ; Learning ; JEL-classification: C70; D23; D40; L11
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract. The purpose of this paper is to suggest a view of the economy as a network of links between the individuals involved. One approach is to consider the structure of links as fixed as is the case with spatial models in which agents are situated on a lattice, another is to regard all links as possible but stochastic. If the probability of any of the links existing is uniform we have the situation familiar from the “population games” of evolutionary game theory. The basic idea here is to allow the network to evolve and to make the probability of each of the links dependent on the experience of the agents involved. Such analysis can give rise to interesting behaviour on the aggregate level which is very different from that which might have been predicted by looking at the individuals in isolation.
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    Detecting self-organisational change in economic processes exhibiting logistic growth (1999)
    Springer
    Journal of evolutionary economics 9 (1999), S. 109-133 
    Details
    ISSN: 1432-1386
    Keywords: Key words: Discontinuity ; Evolution ; Logistic diffusion ; Non-linearity ; Non-stationarity ; Self-organisation ; Spectral methods ; JEL-classification: C4; C5; N1; N2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract. This paper offers an econometric methodology for the detection of self-organisational change (defined in terms of the presence of time irreversibility, structural change and fundamental uncertainty) in economic processes that follow logistic diffusion growth paths in historical time. The approach we adopted is built upon recent developments in `moving window' spectral methods which are applied to the scaled residuals generated by estimated logistic diffusion models. We illustrate the use of such methods by examining the case of a financial instrument, namely, the Australian Building Society Deposit, which experienced logistic growth in its market share until bank deregulation was enacted in the 1980s. We show that there is clear evidence that self-organisational change is present over the historical period considered.
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    Polymorphism with selection and genotype-dependent migration (1981)
    Springer
    Journal of mathematical biology 11 (1981), S. 245-267 
    Details
    ISSN: 1432-1416
    Keywords: Population genetics ; Evolution ; Migration ; Geographical variation ; Habitat choice ; Polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract For a single autosomal locus with multiple alleles both an island and a multiple-niche model with discrete nonoverlapping generations are formulated for the maintenance of genetic variability. Both models incorporate viability selection in an arbitrary way and allow for genotypic differences in the pertinent migration structure. Random drift is ignored, and mating is at random. A global analysis is given for the island model in the neutral case. For a subdivided population, conditions are derived for the existence of a protected polymorphism, and the model is examined in some special two-niche cases. Of particular consideration is the loss of neutral alleles due solely to population regulation and genotype-dependent migration, and the possible existence of equilibrium clines without selection.
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    A mathematical model of biological evolution (1982)
    Springer
    Journal of mathematical biology 14 (1982), S. 327-353 
    Details
    ISSN: 1432-1416
    Keywords: Evolution ; Molecular evolution ; Dynamical system ; Neo-Darwinian evolution ; Non-Darwinian evolution ; Neutral theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In order to understand generally how the biological evolution rate depends on relevant parameters such as mutation rate, intensity of selection pressure and its persistence time, the following mathematical model is proposed: dN n (t)/dt=(m n (t-μ)N n (t)+μN n-1(t) (n=0,1,2,3...), where N n (t) and m n (t) are respectively the number and Malthusian parameter of replicons with step number n in a population at time t and μ is the mutation rate, assumed to be a positive constant. The step number of each replicon is defined as either equal to or larger by one than that of its parent, the latter case occurring when and only when mutation has taken place. The average evolution rate defined by $$\upsilon _\infty \equiv {\text{ lim}}_{t \to \infty } \sum _{n = 0}^\infty nN_n (t)/t\sum _{n = 0}^\infty N_n (t)$$ is rigorously obtained for the case (i) m n (t)=m n is independent of t (constant fitness model), where m n is essentially periodic with respect to n, and for the case (ii) $$m_n (t) = {\text{ }}s( - 1)^{n + [1/\tau ]} $$ (periodic fitness model), together with the long time average m ∞ of the average Malthusian parameter $$\bar m \equiv \sum _{n = 0}^\infty m_n (t)N_n (t)/\sum _{n = 0}^\infty N_n (t)$$ . The biological meaning of the results is discussed, comparing them with the features of actual molecular evolution and with some results of computer simulation of the model for finite populations.
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    URL: http://dx.doi.org/10.1007/BF00275397
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    Evolutionary stable strategies and game dynamics for n-person games (1984)
    Springer
    Journal of mathematical biology 19 (1984), S. 329-334 
    Details
    ISSN: 1432-1416
    Keywords: Evolution ; ESS ; games ; game dynamics ; n-person games ; strategies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract This note contains a generalization of the definition of an evolutionary stable strategy and of the corresponding game dynamics from 2-person to n-person games. This broader framework also allows modelling of several interacting populations or of populations containing different “types” of individuals, for example males and females.
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    URL: http://dx.doi.org/10.1007/BF00277103
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    Evolutionary dynamics of predator–prey systems: an ecological perspective (1996)
    Springer
    Journal of mathematical biology 34 (1996), S. 556-578 
    Details
    ISSN: 1432-1416
    Keywords: Key words: Dynamical systems ; Evolution ; Game theory ; Asymptotic stability ; Population dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract.  Evolution takes place in an ecological setting that typically involves interactions with other organisms. To describe such evolution, a structure is needed which incorporates the simultaneous evolution of interacting species. Here a formal framework for this purpose is suggested, extending from the microscopic interactions between individuals – the immediate cause of natural selection, through the mesoscopic population dynamics responsible for driving the replacement of one mutant phenotype by another, to the macroscopic process of phenotypic evolution arising from many such substitutions. The process of coevolution that results from this is illustrated in the context of predator–prey systems. With no more than qualitative information about the evolutionary dynamics, some basic properties of predator–prey coevolution become evident. More detailed understanding requires specification of an evolutionary dynamic; two models for this purpose are outlined, one from our own research on a stochastic process of mutation and selection and the other from quantitative genetics. Much of the interest in coevolution has been to characterize the properties of fixed points at which there is no further phenotypic evolution. Stability analysis of the fixed points of evolutionary dynamical systems is reviewed and leads to conclusions about the asymptotic states of evolution rather different from those of game-theoretic methods. These differences become especially important when evolution involves more than one species.
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    URL: http://dx.doi.org/10.1007/s002850050021
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    A model of evolutionary appearance of dissipative structure in ecosystems (1983)
    Springer
    Journal of mathematical biology 18 (1983), S. 13-23 
    Details
    ISSN: 1432-1416
    Keywords: Ecosystem ; Evolution ; Autonomous oscillations ; issipative structure ; Bifurcation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The interrelation between autonomous oscillations in local systems and stable dissipative structures in spatially distributed systems is analyzed. Darwinian evolution in populations comprising the ecosystem is shown to be able to cause the qualitative rearrangements of dynamic modes and smooth appearance of oscillations in local systems. The same evolutionary mechanisms analyzed within bilocal systems, may lead to appearance of dissipative structures (both smooth and sharp).
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    URL: http://dx.doi.org/10.1007/BF00275907
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    On the eigenvalue distribution of genetic and phenotypic dispersion matrices: Evidence for a nonrandom organization of quantitative character variation (1984)
    Springer
    Journal of mathematical biology 21 (1984), S. 77-95 
    Details
    ISSN: 1432-1416
    Keywords: Evolution ; quantitative inheritance ; random matrix theory ; morphological integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A quantitative genetic model of “random pleiotropy” is introduced as reference model for detecting the kind and degree of organization in quantitative genetic variation. In this model the genetic dispersion matrix takes the form of G = BB T, where B is a general, real, Gaussian random matrix. The eigenvalue density of the corresponding ensemble of random matrices (ℰG) is considered. The first two moments are derived for variance-covariance matrices G as well as for correlation matrices R, and an approximate expression of the density function is given. The eigenvalue distribution of all empirical correlation matrices deviates from that of a random pleiotropy model by a very large leading eigenvalue associated with a “size factor”. However the frequency-distribution of the remaining eigenvalues shows only minor deviations in mammalian skeletal data. A prevalence of intermediate eigenvalues in insect data may be caused by the inclusion of many functionally unrelated characters. Hence two kinds of deviations from random organization have been found: a “mammal like” and an “insect like” organization. It is concluded that functionally related characters are on the average more tightly correlated than by chance (= “mammal like” organization), while functionally unrelated characters appear to be less correlated than by random pleiotropy (“insect like” organization).
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    URL: http://dx.doi.org/10.1007/BF00275224
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    Evolutionary dynamics of predator-prey systems: an ecological perspective (1996)
    Springer
    Journal of mathematical biology 34 (1996), S. 556-578 
    Details
    ISSN: 1432-1416
    Keywords: Dynamical systems ; Evolution ; Game theory ; Asymptotic stability ; Population dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Evolution takes place in an ecological setting that typically involves interactions with other organisms. To describe such evolution, a structure is needed which incorporates the simultaneous evolution of interacting species. Here a formal framework for this purpose is suggested, extending from the microscopic interactions between individuals — the immediate cause of natural selection, through the mesoscopic population dynamics responsible for driving the replacement of one mutant phenotype by another, to the macroscopic process of phenotypic evolution arising from many such substitutions. The process of coevolution that results from this is illustrated in the context of predator-prey systems. With no more than qualitative information about the evolutionary dynamics, some basic properties of predator-prey coevolution become evident. More detailed understanding requires specification of an evolutionary dynamics; two models for this purpose are outlined, one from our own research on a stochastic process of mutation and selection and the other from quantitative genetics. Much of the interest in coevolution has been to characterize the properties of fixed points at which there is no further phenotypic evolution. Stability analysis of the fixed points of evolutionary dynamical systems is reviewed and leads to conclusions about the asymptotic states of evolution rather different from those of game-theoretic methods. These differences become especially important when evolution involves more than one species.
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    URL: http://dx.doi.org/10.1007/BF02409750
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    Nonlinear stochastic effects of substitution — an evolutionary approach (1996)
    Springer
    Journal of evolutionary economics 6 (1996), S. 1-30 
    Details
    ISSN: 1432-1386
    Keywords: Innovation ; Technology ; Master equation ; Survival probability ; Evolution ; O3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract Technological innovations have been investigated by means of substitution and diffusion as well as evolution models, each of them dealing with different aspects of the innovation problem. In this paper we follow the well known research traditions on self-organisation models of complex systems. For the first time in the literature we show the existence of a specific niche effect, which may occur in the first stage of establishment of a new technology. Using a stochastic Master equation approach, we obtain analytical expressions for the survival probabilities of a new technology in smaller or larger ensembles. As a main result we demonstrate how a hyperselection situation might be removed in a stochastic picture and thresholds against the prevailing of a new technology in a step-by-step process can be overcome.
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    URL: http://dx.doi.org/10.1007/BF01202370
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    Economic evolution and the science of synergetics (1996)
    Springer
    Journal of evolutionary economics 6 (1996), S. 239-260 
    Details
    ISSN: 1432-1386
    Keywords: Synergetics ; Self-organisation ; Time-irreversibility ; Evolution ; Structural change ; O30 ; O31 ; C60 ; C63
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper deals with synergetic methods, which have developed as a sub-field of the self-organisation approach in the natural sciences. Such methods have been used successfully to model structural transitions in physio-chemical contexts. The synergetic approach is explained in a non-technical way and the main elements of the synergetic methodology are introduced. The extent to which such methods can be applied in the presence of historical time series data, which are subject to underlying processes of evolutionary economic change, is assessed. Proposals, concerning more appropriate synergetic methods for evolutionary economic application, are considered.
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    URL: http://dx.doi.org/10.1007/BF01193632
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    A spectrum of equilibration processes in game theory (1998)
    Springer
    Journal of evolutionary economics 8 (1998), S. 67-87 
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    ISSN: 1432-1386
    Keywords: Key words: Bounded rationality ; Cognitive rationality ; Game equilibrium ; Evolution ; Learning ; JEL-classification: B 41; C 73; D 83; D 84
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract. In game theory, four dynamic processes converging towards an equilibrium are distinguished and ordered by way of agents' decreasing cognitive capacities. In the eductive process, each player has enough information to simulate perfectly the others' behavior and gets immediately to the equilibrium. In epistemic learning, each player updates his beliefs about others' future strategies, with regard to their sequentially observed actions. In behavioral learning, each player modifies his own strategies according to the observed payoffs obtained from his past actions. In the evolutionary process, each agent has a fixed strategy and reproduces in proportion to the utilities obtained through stochastic interactions. All along the spectrum, longer term dynamics makes up for weaker rationality, and physical relations substitute for mental interactions. Convergence, if any, is towards an always stronger equilibrium notion and selection of an equilibrium state becomes more sensitive to context and history. The processes can be mixed if associated to different periods, agents or mechanisms and deepened if obtained by formal reasoning principles.
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    URL: http://dx.doi.org/10.1007/s001910050056
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    A note on evolutionary stability of Bertrand equilibrium (1999)
    Springer
    Journal of evolutionary economics 9 (1999), S. 367-371 
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    ISSN: 1432-1386
    Keywords: Key words: Bertrand ; Oligopoly ; Evolution ; Evolutionary stability ; JEL-classification: D43 ; L13 ; C72
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract. It is shown that the equilibrium notion of an evolutionary stable strategy (ESS) does have predictive power for standard models of Bertrand competition. This is in contrast to a recent claim by Qin and Stuart (1997). The claim is based on the observation that the solution concept ESS behaves discontinuously when finite (discrete) action games approach an infinite (continuous) action game in the limit. Furthermore, it is argued that from a model-theoretic point of view evolutionary stability in prices (i.e. in the Bertrand model) is quite different from evolutionary stability in quantities (i.e. in the Cournot model).
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    Changes in DNA composition in the evolution of Vicia species (1984)
    Springer
    Theoretical and applied genetics 68 (1984), S. 187-192 
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    ISSN: 1432-2242
    Keywords: Vicia ; nuclear DNA ; Evolution ; Base sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The composition of nuclear DNA in 3 Vicia species are compared. The species V. eriocarpa, V. johannis and V. melanops are from three separate subgeneric sections of Vicia and show a fourfold variation in their amounts of nuclear DNA. DNA melting experiments, buoyant density gradient analysis and Cot reassociation experiments show that the quantitiative change in nuclear DNA between the three species is achieved by changes in the amounts of both repetitive and nonrepetitive DNA sequences. It is suggested that while the increase in the repetitive fraction is achieved by the proliferation of repetitive base sequences the increase in the nonrepetitive fraction is due to the steady accretion of highly diverged base sequences resulting from mutations, deletions, insertions and base sequence rearrangements among families of repetitive sequences.
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    URL: http://dx.doi.org/10.1007/BF00252337
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    A specific oligonucleotide of the 5S rDNA spacer and species-specific elements identify symmetric somatic hybrids between Solanum tuberosum and S. pinnatisectum (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 720-726 
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    ISSN: 1432-2242
    Keywords: 5S rDNA ; Evolution ; Protoplast fusion ; Somatic hybrids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nucleotide sequences of the 5S rRNA genes (5S rDNA) of two Solanum tuberosum breeding lines (R1 and B15) and of the Mexican wild species S. pinnatisectum were determined and compared with each other and to the 5S rDNA of other Solanaceae species (Lycopersicon esculentum, Nicotiana rustica and Petunia hybrida). The 5S rDNA repeats of the Solanum species are 324–329 bp in length, and they exhibit 91–95% sequence identity. Sequence variability is mainly located in a short region of the spacer separating the 5S rRNA coding regions. A synthetic 28-mer oligonucleotide constructed according to this region can be used as a specific hybridization probe to distinguish symmetric somatic hybrids between S. tubersosum breeding line B15 and S. pinnatisectum produced by protoplast fusion. Interestingly, the two Solanum breeding lines R1 and B15 differ also in this spacer region.
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    URL: http://dx.doi.org/10.1007/BF00222139
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    Species-specific evolution of telomeric and rDNA repeats in the tobacco composite genome (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 1108-1111 
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    ISSN: 1432-2242
    Keywords: Evolution ; Tobacco ; Telomeres ; Ribosomal genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to investigate possible interactions between parental genomes in the composite genome of Nicotiana tabacum we have analyzed the organization of telomeric (TTTAGGG)n and ribosomal gene (rDNA) repeats in the progenitor genomes Nicotiana sylvestris and Nicotiana tomentosiformis or Nicotiana otophora. Telomeric arrays in the Nicotiana species tested are heterogeneous in length ranging from 20 to 200 kb in N. sylvestris, from 20 to 50 kb in N. tomentosiformis, from 15 to 100kb in N. otophora, and from 40 to 160kb in N. tabacum. The patterns of rDNA repeats (18S, 5.8S, 25S RNA) appeared to be highly homogeneous and speciesspecific; no parental rDNA units corresponding to N. sylvestris, N. tomentosiformis or N. otophora were found in the genome of N. tabacum by Southern hybridization. The results provide evidence for a species-specific evolution of telomeric and ribosomal repeats in the tobacco composite genome.
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    Analysis of a set of homoeologous group 1 wheat-Aegilops umbellulata recombinant chromosome lines using genetic markers (1997)
    Springer
    Theoretical and applied genetics 94 (1997), S. 293-297 
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    ISSN: 1432-2242
    Keywords: Key words Glutenin loci ; Mapping ; Evolution ; Genome organization ; Wheat ; Aegilops umbellulata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eleven wheat-Ae. umbellulata recombinant lines involving chromosome 1U, including an important high-molecular-weight glutenin locus, were characterized by protein and RFLP markers. Four 1U-1A recombinants, one 1U-1B recombinant, two 1U deletions with either nullisomy for chromosome 1A or 1B and a 1U ditelosomic addition line were detected, while 3 recombinant lines involved 1U and non-homoeologous wheat chromosomes. Similar recombination events were found in independent lines, and no small segmental translocations of Ae. umbellulata chromatin were detected. Correlation of the markers with physical maps of the wheat-Ae. umbellulata breakpoints obtained using in situ hybridization enabled the marker order to be established on chromosomes 1A, 1B and 1U. The short arm of chromosome 1A probably differs from both 1U and 1B by one inversion. As now being found to be universal in the Triticeae, clustering of the genetical map in the distal physical regions of the group 1 chromosomes was found.
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    Phylogenetic classification and molecular evolution of knotted1 homeobox genes (1999)
    Springer
    Theoretical and applied genetics 99 (1999), S. 203-209 
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    ISSN: 1432-2242
    Keywords: Key words Homeobox gene ; KNOTTED1 ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Homeobox genes encode a family of DNA-binding regulatory proteins which are crucial for development. The first plant homeobox gene identified was knotted1 which plays a major role in leaf development. The knotted1 gene has a homeobox which encodes a homeodomain (HD) and HD proteins have been shown to function as transcription factors. A phylogenetic classification of the KNOTTED1 HD is presented. Here, we report six kn1 HDs from the cereals oat, barley, wheat, rye and rice. The KN1 class-I and -II genes can be divided into two distinct clades. Further, we hypothesize that KN1 and BELL1/MEIS HDs, (the closest non-KN1 class HDs) evolved from a common ancestor after divergence from the common precursor of all the homeobox genes. Our analysis clearly shows the presence of an ancestral KN1 HD from which all the known plant kn1 class of genes evolved.
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    URL: http://dx.doi.org/10.1007/s001220051226
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    Contrasting patterns of genetic diversity in two tropical pines: Pinus kesiya (Royle ex Gordon) and P. merkusii (Jungh et De Vriese) (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 436-441 
    Details
    ISSN: 1432-2242
    Keywords: Pinus ; Allozymes ; Chloroplast DNA ; Genetic variation ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied allozyme and chloroplast (cp) DNA variation in natural populations of Pinus kesiya and P. merkusii from Thailand and Vietnam. The results showed striking differences between the two species in the amount and distribution of allozyme variation. P. kesiya harboured considerable allozyme variation and showed weak interpopulational differentiation. In contrast, P. merkmii had very low intrapopulational variability but a high level of interpopulational differentiation. The average Nei's genetic distance separating the two species was exceptionally high (0.701) taking into account their close taxonomic placement in the same subsection Sylvestres. The constructed phylogenetic trees revealed very early divergence of P. kesiya and P. merkusii. The present analysis of cpDNA variation also confirmed the dissimilar character of these two species and was compatible with other evidence indicating the outstanding position of P. merkusii as compared to other Asian members of the subsection Sylvestres. Analysis of cpDNA variation in sympatric populations of P. kesiya and P. merkusii revealed that they are pure representatives of the species in question. This result indicates that despite an overlapping distribution P. kesiya and P. merkusii do not hybridise in nature. We suggest that the distinctive character of P. merkusii is a result of an early separation from other Eurasian pines. Despite spatial proximity, P. kesiya and P. merkusii are kept apart by strong reproductive barriers. The low genetic variability of P. merkusii may be explained by previous bottlenecks, reduced gene flow among populations, and an inbreeding due to small population size and asynchronous flowering.
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    Development of a set of oligonucleotide primers specific for genes at the Glu-1 complex loci of wheat (1995)
    Springer
    Theoretical and applied genetics 91 (1995), S. 189-194 
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    ISSN: 1432-2242
    Keywords: Wheat ; HMW glutenin genes ; Polymerase chain reaction (PCR) ; Multigene families ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Specific amplification of the complete coding region of all six high-molecular-weight (HMW) glutenin genes present in hexaploid wheat was obtained by the polyerase chain reaction (PCR). Primers specific for the N-terminal region of the 1Dx gene and for the repetitive domain of the y-type HMW glutenin genes were also developed. Although the primers were constructed on the basis of the nucleotide sequences of HMW glutenin genes present in T. aestivum L. cv ‘Cheyenne’, they were very efficient in amplifying HMW glutenin genes of diploid and tetraploid wheat species. PCR analysis of HMW glutenin genes of T. urartu Tuman., T. longissimum (Schweinf. & Muschl.) Bowden and T. speltoides (Tausch) Gren. ex Richt, showed a high degree of length polymorphism, whereas a low degree of length variation was found in accessions of T. tauschii (Coss.) Schmal. Furthermore, using primers specific for the repetitive regions of HMW genes, we could demonstrate that the size variation observed was due to a different length of the central repetitive domain. The usefulness of the PCR-based approach to analyze the genetic polymorphism of HMW glutenin genes, to isolate new allelic variants, to estimate their molecular size and to verify the number of cysteine residues is discussed.
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    Classification of African plantain landraces and banana cultivars using a phenotypic distance index of quantitative descriptors (1998)
    Springer
    Theoretical and applied genetics 96 (1998), S. 904-911 
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    ISSN: 1432-2242
    Keywords: Key words Musa ; Core collection ; Duplicates ; Evolution ; Variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Proper classification and establishment of relationships between and within Musa taxonomic clusters will be important tools for the genetic improvement of plantain and banana. This paper assesses the value of a phenotypic diversity index, based on 16 quantitative descriptors, for germplasm clustering and for identification of duplicates among 92 triploid plantain and banana accessions. Data were recorded during the plant and ratoon crops at Onne, a humid forest location in southeastern Nigeria. The phenotypic distance matrix was developed by calculating the average difference between each pair of accessions for all quantitative descriptors. Significant differences were observed for this phenotypic distance index between Musa taxonomic clusters. The between-cluster variance was larger (0.001779) than the within-cluster variance (0.001380). Wright’s φFS, which measures the overall diversity, was 0.5663. This value suggested little gene flow among triploid taxonomic clusters via pollen, which explains the higher population differentiation exhibited by this vegetatively propagated crop with very low male fertility. The results also suggested that variation observed within each Musa taxonomic cluster arose from mutations accumulated throughout the history of cultivation of this crop. Some putative duplicates based on qualitative descriptors were not regarded as the same accession according to the phenotypic diversity index based on quantitative descriptors. Hence, gene-bank curators should assess quantitative descriptors for the identification of duplicate accessions in Musa.
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    URL: http://dx.doi.org/10.1007/s001220050818
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    Investigations on the relations within the family papilionaceae on the basis of electrophoretic banding patterns (1980)
    Springer
    Theoretical and applied genetics 57 (1980), S. 225-232 
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    ISSN: 1432-2242
    Keywords: Electrophoresis ; Proteins ; Leguminosae ; Taxonomy ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Gel electrophoretic investigations were made on the seed albumins of several members of the family Papilionaceae. Relationships were found with taxa of a lower order i.e. between mutants, varieties and subspecies. More distantly related ones, for example species of the same genus or species of different genera, did not show similarities. Thus, it was concluded that the albumin banding pattern is only suitable for studying phylogenetic and taxonomic problems if the material under investigation is not too distantly related.
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    Cross-incompatibility between two sympatric polyploid Solanum species (1981)
    Springer
    Theoretical and applied genetics 60 (1981), S. 65-70 
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    ISSN: 1432-2242
    Keywords: Cross-incompatibility ; Solanum ; Reproductive barriers ; Introgression ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Preliminary results from a large number of reciprocal crosses between the closely related sympatric species S. gourlayi Hawkes (2n=4x=48) and S. oplocense Hawkes (2n=6x=72) indicated that they are difficult to hybridize. Pollen-pistil incompatibility barriers were detected via fluorescent microscopy. The cross incompatibility reaction occurred at three sites in 6x×4x crosses; on the stigma, in the first one-third of the style, and in the first two-thirds of the style. In the reciprocal 4x×6x crosses the incompatibility reaction invariably occurred in the ovary. Backcrosses of interspecific pentaploid hybrids (that were occasionally formed) to both parental populations were fully compatible, partially compatible, and fully incompatible with three sites of cross-incompatibility reaction similar to those observed in 6x×4x crosses, respectively. Both polyploid species were found to be selfcompatible, whereas their F1 hybrids were found to be self-incompatible. An hypothesis based on interactions of dominant cross-incompatibility (CI) genes in pistils and dominant specific complementary genes in pollen grains is postulated to explain these observations. The cross-incompatibility system that appears to be operating in nature between 4x S. gourlayi and 6x S. oplocense provides a way for gene exchange between sympatric populations without threatening the identity of either species.
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    URL: http://dx.doi.org/10.1007/BF00282417
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    Nicotiana chloroplast genome III. Chloroplast DNA evolution (1982)
    Springer
    Theoretical and applied genetics 61 (1982), S. 73-79 
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    ISSN: 1432-2242
    Keywords: Nicotiana ; Chloroplast DNA ; Restriction fragments ; Deletion ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nicotiana chloroplast genomes exhibit a high degree of diversity and a general similarity as revealed by restriction enzyme analysis. This property can be measured accurately by restriction enzymes which generate over 20 fragments. However, the restriction enzymes which generate a small number (about 10) of fragments are extremely useful not only in constructing the restriction maps but also in establishing the sequence of ct-DNA evolution. By using a single enzyme, Sma I, a elimination and sequential gain of its recognition sites during the course of ct-DNA evolution is clearly demonstrated. Thus, a sequence of ct-DNA evolution for many Nicotiana species is formulated. The observed changes are all clustered in one region to form a “hot spot” in the circular molecule of ct-DNA. The mechanisms involved for such alterations are mostly point mutations but inversion and deficiency are also indicated. Since there is a close correlation between the ct-DNA evolution and speciation in Nicotiana a high degree of cooperation and coordination betwen organellar and nuclear genomes is evident.
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    URL: http://dx.doi.org/10.1007/BF00261515
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    Origin and evolution of cultivated tetraploid potatoes via 2n gametes (1982)
    Springer
    Theoretical and applied genetics 61 (1982), S. 161-169 
    Details
    ISSN: 1432-2242
    Keywords: Cultivated potato ; Evolution ; Parallel spindles ; 2n gametes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A high gene frequency for ps (parallel spindles) is expected in cultivated tetraploid potatoes, S. tuberosum Group Tuberosum, if 2n pollen produced by ancestral diploid plants which were psps was involved in the origin and evolution of the potato. Fifty-six North American cultivars (varieties and advanced selections) were pollinated by diploid clones, either W 5295.7 or W 5337.3 which are homozygous recessive for ps. The segregation ratios in regard to 2n pollen production in derived tetraploid progenies, from 4x×2x crosses, reveal the genotype of ps in the cultivars. Microsporogenesis of 2n pollen producing 4x progeny was observed to avoid an overestimation of the frequency of 2n pollen producing plants due to mechanisms other than parallel spindles. More than 50% of the 56 cultivars are simplex (Pspspsps), since in each of these cultivars about 50% of their progeny produced 2n pollen. The ps gene frequency in the 56 cultivars was estimated as high as 0.69. The high frequency of ps in the tetraploid cultivars clearly supports the hypothesis that 2n pollen produced by plants homozygous recessive for ps have been involved in the origin of cultivated tetraploid potatoes, since a higher frequency of ps in the tetraploid than in the ancestral diploid population can be expected from sexual polyploidization but not from somatic doubling. The importance of meiotic mutants such as ps for the successful evolution of polysomic polyploids is emphasized.
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    URL: http://dx.doi.org/10.1007/BF00273885
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    Utilization of wild relatives in genetic improvement of Arachis hypogaea L. (1982)
    Springer
    Theoretical and applied genetics 61 (1982), S. 305-314 
    Details
    ISSN: 1432-2242
    Keywords: Arachis ; Karyomorphology ; D2 analysis and genetic distance ; Evolution ; Crop improvement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The chromosome complements of 12 taxa in section Arachis were karyotypically and meiotically analysed. In taxa with 2n=20 the arm ratio of the respective pair of chromosomes was taken as an independent quantitative character and statistically analysed by Mahalanobis D2. Two clusters were formed, one represented solely by A. batizocoi and the other consisting of the remaining 11 taxa. This grouping was confirmed by canonical analysis. In the larger group of species, A villosa and A. correntina were closely related karyotypically and on D2 distance, while A. cardenasii forms a distinct subgroup. A. cardenasii lacks the short “A” chromosome recorded in other species of this group, and A. batizocoi is no longer the only species to have a pair of chromosomes with a secondary constriction. The taxa with 2n=40, A. monticola and A. hypogaea, are karyotypically very similar, though there is a difference in the number of chromosome pairs with a secondary constriction. On the basis of karyomorphological affinity, especially in relation to marker chromosomes, A. cardenasii is probably one of the ancestors of the tetraploid species studied.
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    URL: http://dx.doi.org/10.1007/BF00272846
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    Endosperm Balance Number and the polar-nuclei activation hypotheses for endosperm development in interspecific crosses of Solanaceae and Gramineae, respectively (1995)
    Springer
    Theoretical and applied genetics 91 (1995), S. 848-855 
    Details
    ISSN: 1432-2242
    Keywords: Endosperm development ; Evolution ; Imprinting ; Incompatibility ; Reciprocal crosses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Endosperm Balance Number (EBN) and the polar-nuclei activation (PNA) hypotheses have been developed to interpret, explain and predict interspecific and interploidy crossabilities in the Solanums and the Gramineae, respectively. Although these two hypotheses evolved independently, they share a number of common features. Assignment of EBNs and ‘activation/response values’ (AVs/RVs) depend on plumpness, size, and germinability of hybrid seeds. Also, both hypotheses emphasize the importance of a balanced parental genic contribution for the normal development of endosperm. However, in the EBN hypothesis a 2 maternal∶1 paternal EBN ratio is a prerequisite for successful interspecific crossability, while the PNA hypothesis is based on the stimulative strength of the male nuclei to initiate mitotic divisions in the primary endosperm nucleus and is idependent on a 2∶1 ratio between the RV of the polar nuclei and the AV of the male gamete. Differences and similarities betweeen the EBN and PNA hypotheses are summarized and contrasted. It is proposed that EBN and PNA be considered as the same concept.
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    URL: http://dx.doi.org/10.1007/BF00223891
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    Identification of genetic factors controlling domestication-related traits of rice using an F2 population of a cross between Oryza sativa and O. rufipogon (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 243-251 
    Details
    ISSN: 1432-2242
    Keywords: Key words Common wild rice ; Cultivated rice ; Evolution ; Genetic analysis ; Molecular marker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Domesticated rice differs from the wild progenitor in large arrays of morphological and physiological traits. The present study was conducted to identify the genetic factors controlling the differences between cultivated rice and its wild progenitor, with the intention to assess the genetic basis of the changes associated with the processes of rice domestication. A total of 19 traits, including seven qualitative and 12 quantitative traits, that are related to domestication were scored in an F2 population from a cross between a variety of the Asian cultivated rice (Oryza sativa) and an accession of the common wild rice (O. rufipogon). Loci controlling the inheritance of these traits were determined by making use of a molecular linkage map consisting of 348 molecular-marker loci (313 RFLPs, 12 SSRs and 23 AFLPs) based on this F2 population. All seven qualitative traits were each controlled by a single Mendelian locus. Analysis of the 12 quantitative traits resolved a total of 44 putative QTLs with an average of 3.7 QTLs per trait. The amount of variation explained by individual QTLs ranged from a low of 6.9% to a high of 59.8%, and many of the QTLs accounted for more than 20% of the variation. Thus, genes of both major and minor effect were involved in the differences between wild and cultivated rice. The results also showed that most of the genetic factors (qualitative or QTLs) controlling the domestication-related traits were concentrated in a few chromosomal blocks. Such a clustered distribution of the genes may provide explanations for the genetic basis of the “domestication syndrome” observed in evolutionary studies and also for the “linkage drag” that occurs in many breeding programs. The information on the genetic basis of some desirable traits possessed by the wild parent may also be useful for facilitating the utilization of these traits in rice-breeding programs.
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    URL: http://dx.doi.org/10.1007/s001220051064
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    Structural chromosome differentiation between Triticum timopheevii and T. turgidum and T. aestivum (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 744-750 
    Details
    ISSN: 1432-2242
    Keywords: Key words Chromosome pairing ; Translocations ; T. timopheevii ; T. turgidum ; T. aestivum ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract.  Chromosome pairing at metaphase-I was analyzed in F1 hybrids among T. turgidum (AABB), T. aestivum (AABBDD), and T. timopheevii (AtAtGG) to study the chromosome structure of T. timopheevii relative to durum (T. turgidum) and bread (T. aestivum) wheats. Individual chromosomes and their arms were identified by means of C-banding. Homologous pairing between the A-genome chromosomes was similar in the three hybrid types AAtBG, AAtBGD, and AABBD. However, associations of B-G were less frequent than B-B. Homoeologous associations were also observed, especially in the AAtBGD hybrids. T. timopheevii chromosomes 1At, 2At, 5At, 7At, 2G, 3G, 5G, and 6G do not differ structurally from their counterpart in the A and B genomes. Thus, these three polyploid species inherited translocation 5AL/4AL from the diploid A-genome donor. Chromosome rearrangements that occurred at the tetraploid level were different in T. turgidum and T. timopheevii. Translocation 4AL/7BS and a pericentric inversion of chromosome 4A originated only in the T. turgidum lineage. The two lines of T. timophevii studied carry four different translocations, 6AtS/1GS, 1GS/4GS, 4GS/4AtL, and 4AtL/3AtL, which most likely arose in that sequence. These structural differences support a diphyletic origin of polyploid wheats.
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    URL: http://dx.doi.org/10.1007/s001220051130
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    p-SINE1-like intron of the CatA catalase homologs and phylogenetic relationships among AA-genome Oryza and related species (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 853-861 
    Details
    ISSN: 1432-2242
    Keywords: Key words Catalase ; Oryza ; Rice ; Evolution ; p-SINE1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Intron-2 of the Oryza sativa CatA catalase gene is similar in nucleotide sequence to p-SINE1, a retroposon, and seems to have been added to the ancestral genome of rice. To examine when the p-SINE1-like intron was inserted into CatA during the evolutionary divergence of Oryza species, and to elucidate the evolutionary relationships among Oryza species using the sequence of the intron as a marker, we performed polymerase chain reaction (PCR) analyses of 32 accessions of 17 Oryza species with various genome types. Agarose-gel electrophoresis of the PCR products revealed that all the Oryza species with an AA genome have the CatA homolog with the intron, whereas other Oryza species have the CatA homolog without the intron. These results indicate that intron-2 of CatA is a good marker for distinguishing species with an AA genome among Oryza species. Sequencing of the PCR products showed that all the introns are similar to p-SINE1, though with slight variations in length. We also performed PCR analyses using four accessions of three species in genera related to Oryza, and found that there is an intron in the CatA homolog of Leersia perrieri. On the other hand, the CatA homolog of Porteresia coarctata has no intron. Sequence data showed that the L. perrieri homolog has a p-SINE1-like intron similar to that in Oryza species with an AA genome. These results suggest that the p-SINE1-like intron was already present in the common ancestor of Oryza and L. perrieri and was then lost in the ancestors of P. coarctata and of the Oryza species other than those with an AA genome. The phylogenetic tree of Oryza species with an AA genome based on the nucleotide sequences of the introns leads us to propose that Oryza species with an AA genome evolved from an ancestor of Oryza longistaminata.
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    URL: http://dx.doi.org/10.1007/s001220051144
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    Evolutionary relationship of plant catalase genes inferred from exon-intron structures: isozyme divergence after the separation of monocots and dicots (1998)
    Springer
    Theoretical and applied genetics 97 (1998), S. 9-19 
    Details
    ISSN: 1432-2242
    Keywords: Key words Catalase ; Rice ; Gene structure ; Evolution ; Transposon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to understand the molecular evolution of catalase genes in higher plants, we compared the exon-intron structures of 12 genomic sequences from six plant species. It was assumed that the putative single primordial catalase gene had seven introns, because only those catalase genes having this structure are found in the monocotyledonae and dicotyledonae classes. After the evolutionary divergence of monocots from dicots, consecutive duplication of the primordial gene followed by the differential loss of introns occurred in each class to form three (or possibly four in dicots) diverse isozyme genes. In monocots, three ancestral isozyme genes were formed before the divergence of ancestral rice and maize. One of the rice genes, CatA, has an entirely new short intron which was not found in any other plant catalase gene examined. We have investigated the existence of the intron in the CatA homolog in other rice species by polymerase chain reaction (PCR) analysis. One major PCR product was found with the genomic DNAs from O. sativa (indica and japonica types), O. rufipogon and O. glaberrima. DNAs from several accessions of O. longistaminata showed variation in both the number and size of the DNA fragments amplified. PCR analyses and sequencing of the PCR products revealed that there are several CatA homologs having different sequences in some accessions of O. longistaminata. We have extended our study to other species in the Poaceae. The results suggest that the gain of the intron, most likely by insertion of a retroposon, took place in the ancestral genome of rice after its evolutionary divergence from other ancestral cereals such as barley, wheat and oat.
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    URL: http://dx.doi.org/10.1007/s001220050861
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    The occurrence and frequency of 2n pollen in three diploid solanums from Northwest Argentina (1980)
    Springer
    Theoretical and applied genetics 56 (1980), S. 11-15 
    Details
    ISSN: 1432-2242
    Keywords: Diploid pollen ; Evolution ; Sexual polyploidization ; Solanum ; Tuberosa ; Diplandroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A group of wild, tuber-bearing species from Northwest Argentina, belonging to the series Tuberosa, Solarium spegazzini Bitt. (spg, 2n=2x=24), S. gourlayi Hawkes (grl, 2n=2x=24 and 2n=4x=48) and S. oplocense Hawkes (opl, 2n=6x=72), and Cuneolata, S. infundibuliforme Phil (ifd, 2n=2x=24), is being used to investigate the mode of origin of polyploids in the genus Solanum. 2n gametes have been detected in the diploid species ifd and spg and in a diploid race of grl, using cytological and breeding approaches. Twenty-two introductions of spg, 8 of grl and 26 of ifd have been tested for 2n pollen; 59%, 63% and 54% of them, respectively, had at least one 2n pollen producing plant. These introductions comprised 238, 76 and 235 plant respectively, of which 20, 16, and 32 plant produced 5% or more 2n pollen. The mechanism of 2n pollen formation was determined in several plant of 2x spg, 2x grl and 2x ifd. All of them were found to form diplandroids via parallel spindles. This mechanism, which gives meiotic products genetically equivalent to first division restitution gametes, is under control of the Mendelian recessive ps. The results suggest that the allele ps is widely distributed in natural populations of the three diploids, and that its frequency is very high. These species are seen as valuable material for population genetic studies, and for the eventual incorporation into a breeding scheme involving sexual polyploidization via 2n gametes.
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    URL: http://dx.doi.org/10.1007/BF00264421
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    The significance of genic balance to endosperm development in interspecific crosses (1980)
    Springer
    Theoretical and applied genetics 57 (1980), S. 5-9 
    Details
    ISSN: 1432-2242
    Keywords: Endosperm ; Evolution ; Interspecific crosses ; Solanums ; 2n gametes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The endosperm has played a significant role in the evolution of angiosperms because of its physiological and genetic relationships to the embryo. One manifestation of this evolutionary role is its abnormal development in interploidy crosses. It is now established that the endosperm develops abnormally in interploidy-intraspecific crosses when the maternal: paternal genome ratio deviates from 2∶1 in the endosperm itself. We propose an Endosperm Balance Number (EBN) hypothesis to explain endosperm development in both interploidy-intraspecific and interspecific crosses. Each species is assigned an EBN on the basis of its crossing behavior to a standard species. It is the EBN which determines the effective ploidy in the endosperm of each species, and it is the EBNs which must be in a 2∶1, maternal:paternal ratio. The EBN of a species may be determined by a few genes rather than the whole genome. This hypothesis brings most intraspecific-interploidy and interspecific crossing data under a single concept with respect to endosperm function. The implications of this hypothesis to isolating mechanisms, 2n gametes, the evolution of disomic polyploids, and reciprocal differences in seed development are discussed.
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    URL: http://dx.doi.org/10.1007/BF00276002
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    Cytophotometrical measurement of nuclear DNA content in some coniferous and deciduous trees (1980)
    Springer
    Theoretical and applied genetics 58 (1980), S. 187-191 
    Details
    ISSN: 1432-2242
    Keywords: Conifers ; Deciduous tree ; Polyploidy ; Endoploidy ; Evolution ; Cytophotometry ; DNA content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The DNA content of nuclei from meristematic root tip cells of five coniferous and one deciduous tree species and, for comparison, ofVicia faba was cytophotometrically determined. The DNA values of diploid nuclei fromGinkgo biloba are approximately a quarter lower than those fromVicia faba. The nuclear DNA values of the other tree species are merely a third to a ninth part of those ofVicia faba. In three tree species, as well as diploid, we have found nuclei of different polyploid level. The reliability of different cytochemical methods, which are used for determination of the nuclear DNA content, is critically analyzed. The DNA values of the investigated tree species are discussed in connection with the evolution of the DNA content in higher plants.
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    URL: http://dx.doi.org/10.1007/BF00279713
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    “Complement fractionation” in natural diploid orchid species (1982)
    Springer
    Theoretical and applied genetics 61 (1982), S. 91-95 
    Details
    ISSN: 1432-2242
    Keywords: Complement fractionation ; Excess sporads ; Diploid orchid species ; Phaius tribe ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Four out of 10 diploid orchid species showed “complement fractionation” a complex cytological phenomenon, hitherto reported only in polyploid plants. The manifestation of this phenomenon during meiosis is the formation of chromosome subgroups resulting eventually in cells with more than the usual four sporads; five or six being the optimum number in the investigated orchid species. No implications whatsoever can be deduced as to the genetic or genomic constitution of the end products. The presence of the phenomenon in these orchid species could perhaps indicate a polyploid ancestry or concealed hybridity. The operation of “complement fractionation”, however, could be interpreted as an alternative evolutionary pathway opposed to polyploidy.
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    URL: http://dx.doi.org/10.1007/BF00261517
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    Chromosome and nucleotide sequence differentiation in genomes of polyploid Triticum species (1982)
    Springer
    Theoretical and applied genetics 63 (1982), S. 349-360 
    Details
    ISSN: 1432-2242
    Keywords: Chromosomes ; Nucleotides ; Evolution ; Polyploids ; Triticum ; Heterochromatin ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nature of genome change during polyploid evolution was studied by analysing selected species within the tribe Triticeae. The levels of genome changes examined included structural alterations (translocations, inversions), heterochromatinization, and nucleotide sequence change in the rDNA regions. These analyses provided data for evaluating models of genome evolution in polyploids in the genus Triticum, postulated on the basis of chromosome pairing at metaphase I in interspecies hybrids. The significance of structural chromosome alterations with respect to reduced MI chromosome pairing in interspecific hybrids was assayed by determining the incidence of heterozygosity for translocations and paracentric inversions in the A and B genomes of T. timopheevii ssp. araraticum (referred to as T. araraticum) represented by two lines, 1760 and 2541, and T. aestivum cv. Chinese Spring. Line 1760 differed from Chinese Spring by translocations in chromosomes 1A, 3A, 4A, 6A, 7A, 3B, 4B, 7B and possibly 2B. Line 2541 differed from Chinese Spring by translocations in chromosomes 3A, 6A, 6B and possibly 2B. Line 1760 also differed from Chinese Spring by paracentric inversions in arms 1AL and 4AL whereas line 2541 differed by inversions in 1BL and 4AL (not all chromosomes arms were assayed). The incidence of structural changes in the A and B genomes did not coincide with the more extensive differentiation of the B genomes relative to the A genomes as reflected by chromosome pairing studies. To assay changing degrees of heterochromatinization among species of the genus Triticum, all the diploid and polyploid species were C-banded. No general agreement was observed between the amount of heterochromatin and the ability of the respective chromosomes to pair with chromosomes of the ancestral species. Marked changes in the amount of heterochromatin were found to have occurred during the evolution of some of the polyploids. The analysis of the rDNA region provided evidence for rapid “fixation” of new repeated sequences at two levels, namely, among the 130 bp repeated sequences of the spacer and at the level of the repeated arrays of the 9 kb rDNA units. These occurred both within a given rDNA region and between rDNA regions on nonhomologous chromosomes. The levels of change in the rDNA regions provided good precedent for expecting extensive nucleotide sequence changes associated with differentiation of Triticum genomes and these processes are argued to be the principal cause of genome differentiation as revealed by chromosome pairing studies.
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    Successive domestication and evolution of the Andean potatoes as revealed by chloroplast DNA restriction endonuclease analysis (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 356-363 
    Details
    ISSN: 1432-2242
    Keywords: Domestication ; Potato ; Chloroplast DNA ; Solanum stenotomum ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Five chloroplast DNA (ctDNA) types (W, T, C, S, and A) have previously been identified in the Andean tetraploid cultivated potatoes (Solanum tuberosum ssp. andigena) and three types (C, S, and A) in diploid cultivated potatoes (S. stenotomum). In this study, ctDNA types were determined for an additional 35 accessions of S. stenotomum and 97 accessions of putative ancestral wild species (15 of S. brevicaule, 26 of S. bukasovii, 4 of S. candolleanum, 25 of S. canasense, 17 of S. leptophyes, and 10 of S. multidissectum). The first five ctDNA types were also identified in S. stenotomum. The wild species were also polymorphic for ctDNA types except for S. brevicaule, which had only W-type ctDNA. T-type ctDNA was not found in any of the wild species and could have originated from W-type ctDNA after S. stenotomum arose. The other types of ctDNA evolved in wild species. The geographical distribution of each ctDNA type indicated that A-type ctDNA arose in central Peru and T-type ctDNA in the Bolivia-Argentine boundary. It is implied that potatoes were successively domesticated and that, in parallel, several wild species were differentiated from time to time and place to place from the ‘ancestral species’ complex. Subsequent sexual polyploidization formed a wide ctDNA diversity among the Andean tetraploid potatoes, and selection from them formed the limited ctDNA diversity found in Chilean tetraploid potatoes (ssp. tuberosum).
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    Contrasting patterns of genetic diversity in two tropical pines: Pinus kesiya (Royle ex Gordon) and P. merkusii (Jungh et De Vriese) (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 436-441 
    Details
    ISSN: 1432-2242
    Keywords: Key words  Pinus ; Allozymes ; Chloroplast DNA ; Genetic variation ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   We studied allozyme and chloroplast (cp) DNA variation in natural populations of Pinus kesiya and P. merkusii from Thailand and Vietnam. The results showed striking differences between the two species in the amount and distribution of allozyme variation. P. kesiya harboured considerable allozyme variation and showed weak interpopulational differentiation. In contrast, P. merkusii had very low intrapopulational variability but a high level of interpopulational differentiation. The average Nei's genetic distance separating the two species was exceptionally high (0.701) taking into account their close taxonomic placement in the same subsection Sylvestres. The constructed phylogenetic trees revealed very early divergence of P. kesiya and P. merkusii. The present analysis of cpDNA variation also confirmed the dissimilar character of these two species and was compatible with other evidence indicating the outstanding position of P. merkusii as compared to other Asian members of the subsection Sylvestres. Analysis of cpDNA variation in sympatric populations of P. kesiya and P. merkusii revealed that they are pure representatives of the species in question. This result indicates that despite an overlapping distribution P. kesiya and P. merkusii do not hybridise in nature. We suggest that the distinctive character of P. merkusii is a result of an early separation from other Eurasian pines. Despite spatial proximity, P. kesiya and P. merkusii are kept apart by strong reproductive barriers. The low genetic variability of P. merkusii may be explained by previous bottlenecks, reduced gene flow among populations, and an inbreeding due to small population size and asynchronous flowering.
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    Cloning and analysis of a 6.8-kb rDNA intergenic spacer region of the European ash (Fraxinus excelsior L.) (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 1003-1008 
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    ISSN: 1432-2242
    Keywords: Fraxinus ; Evolution ; rDNA ; IGS structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 6.8-kb rDNA intergenic spacer region of F. excelsior was isolated from a CsCl/actinomycin-D gradient and cloned into pUC18 for further characterization. We observed the presence of subrepeats delimited by HaeIII enzyme sites. These subrepeats were sub-cloned and 11 clones were sequenced. These corresponded to subrepeated elements of either 32 bp or 41 bp that shared a 23-bp common sequence in the 5′ end. Within each family of subrepeats, the percentage of common nucleotides was 84.4% for the 5 32-bp subrepeats and 67.4% for the 640-bp subrepeats. Non-repeated HaeIII fragments of 450 bp and 650 bp were also sub-cloned. To compare homology at the IGS region between the rDNA spacers of F. excelsior and the three related species (F. oxyphylla, F. americana, F. ornus), we conducted Southern hybridization analyses using each member of the 32-bp and 40-bp subrepeat families and the unique 450-bp and 650-bp fragments as probes. These analyses indicated that (1) the American ash is more genetically distant from the other three species that the latter are from each other and (2) F. oxyphylla and F. excelsior are more closely related to each other than to F. ornus.
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    Cloning and analysis of a 6.8-kb rDNA intergenic spacer region of the European ash (Fraxinus excelsior L.) (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 1003-1008 
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    ISSN: 1432-2242
    Keywords: Key words Fraxinus ; Evolution ; rDNA ; IGS structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The 6.8-kb rDNA intergenic spacer region of F. excelsior was isolated from a CsCl/actinomycin-D gradient and cloned into pUC18 for further characterization. We observed the presence of subrepeats delimited by HaeIII enzyme sites. These subrepeats were sub-cloned and 11 clones were sequenced. These corresponded to subrepeated elements of either 32 bp or 41 bp that shared a 23-bp common sequence in the 5′ end. Within each family of subrepeats, the percentage of common nucleotides was 84.4% for the 5 32-bp subrepeats and 67.4% for the 6 40-bp subrepeats. Non-repeated HaeIII fragments of 450 bp and 650 bp were also sub-cloned. To compare homology at the IGS region between the rDNA spacers of F. excelsior and the three related species (F. oxyphylla, F. americana, F. ornus), we conducted Southern hybridization analyses using each member of the 32-bp and 40-bp subrepeat families and the unique 450-bp and 650-bp fragments as probes. These analyses indicated that (1) the American ash is more genetically distant from the other three species that the latter are from each other and (2) F. oxyphylla and F. excelsior are more closely related to each other than to F. ornus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050222
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    Uses and usefulness of endosperm balance number (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 478-484 
    Details
    ISSN: 1432-2242
    Keywords: Key words Endosperm development ; Evolution ; 2n gametes ; Breeding ; Potato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The Endosperm Balance Number (EBN) hypothesis was developed in the early ’80s to explain the basis for normal seed development after intra- and inter-specific crosses, first in the potato and then in several other crop species. According to this hypothesis, each species has a genome-specific effective ploidy, the EBN, which must be in a 2 : 1 maternal to paternal ratio in the hybrid endosperm for normal development of the endosperm itself. This paper reviews how the EBN may act as a powerful isolating mechanism in sexual reproduction, maintaining the genome integrity of the species and playing an important role in the speciation of polyploids from diploids. We also provide further evidence that EBN is more important than chromosome ploidy in determining the success or failure of interspecific crosses. In fact, results from inter-ploidy and inter-EBN crosses to infuse 1EBN Solanum commersonii into 4EBN S. tuberosum demonstrated that the knowledge and manipulation of EBN is a useful tool in designing breeding schemes and in predicting the offspring ploidy and EBN. In this paper we also discuss the exceptions to the 2 : 1 EBN ratio, and report the evidence for endomitosis in the polar nuclei to explain exceptions to the EBN model in the potato.
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    URL: http://dx.doi.org/10.1007/s001220051095
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    Chloroplast DNA variation and evolution in the genus Lens Mill (1997)
    Springer
    Theoretical and applied genetics 94 (1997), S. 452-457 
    Details
    ISSN: 1432-2242
    Keywords: Key words Lentil ; Evolution ; Domestication ; cpDNA ; Plastid inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Chloroplast DNA (cpDNA) restriction site diversity was assessed by 21 enzyme/probe combinations in 30 accessions of six Lens species, including the recently recognized L. lamottei and L. tomentosus. A total of 118 fragments were scored and 26 restriction site mutations were identified. The cpDNA restriction pattern supports circumscribing L. lamottei and L. tomentosus as independent species. The value of the data for reconstructing phylogeny in the genus is discussed. The cpDNA of all 13 accessions of the lentil’s wild progenitor, L. culinaris subsp. orientalis, differed from that of the single lentil cultivars used in this study. This diversity indicates that other populations of this subspecies from Turkey and Syria examined by Mayer and Soltis (1994) are potentially the founder members of lentil. Examination of L. lamottei×L. nigricans hybrids between accessions having different restriction patterns showed paternal plastid inheritance in L. nigricans.
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    URL: http://dx.doi.org/10.1007/s001220050436
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    Phylogenetic analysis in the Festuca-Lolium complex using molecular markers and ITS rDNA (1997)
    Springer
    Theoretical and applied genetics 94 (1997), S. 1038-1046 
    Details
    ISSN: 1432-2242
    Keywords: Key words Lolium ; Festuca ; Phylogeny ; Chloroplast DNA ; ITS sequence ; Genetic distance ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Molecular markers were used to investigate phylogenetic relationships among the eight species of ryegrass (Lolium) and 11 species of fescue (Festuca). RAPD and RFLP analyses were carried out on total bulked DNA from each population. Factorial analysis of a phenetic distance matrix yielded three major groups: (1) fine-leaved fescues, (2) broad-leaved fescues and (3) ryegrasses. Six non-coding regions of chloroplastic DNA were PCR-amplified, then digested by 20 restriction enzymes. Nuclear rDNA sequences, including internal transcribed spacers (ITSs) were used to estimate the average proportion of nucleotide substitutions. The correlation between substitution rate estimated from ITS sequences and that estimated from organelle DNA restriction sites was very high (0.94), and the corresponding UPGMA trees were very similar, with a slightly better resolution of the ITS tree in the Lolium genus. The time-scale inferred from substitution rates indicated that the period since divergence of the broad-leaved fescues from the fine-leaved fescues was four times as long as that since divergence of the genus Lolium from the former. Among the broad-leaved fescues, meadow fescue was closer to the Lolium group, while F. glaucescens and tall fescue were very closely related. North-African fescues were clustered together and giant fescue was the most differentiated species in this group. Our dataset was merged with ITS sequences recovered from the EMBL database, and the neighbor-joining method was used to draw a phylogenetic tree. In this tree, the tribe Poeae was clearly monophyletic, and more closely related to the Aveneae than to the Triticeae or Bromoideae. The genus Festuca appeared somewhat artificial, since Vulpia myuros and Dactylis glomerata were placed between fine-leaved and broad-leaved fescues.
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    URL: http://dx.doi.org/10.1007/s001220050512
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    Variation in the psbC gene region of gymnosperms and angiosperms as detected by a single restriction site polymorphism (1997)
    Springer
    Theoretical and applied genetics 94 (1997), S. 1065-1071 
    Details
    ISSN: 1432-2242
    Keywords: Key words Trees ; Chloroplast DNA ; PCR-RFLP ; Genetic variation ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  This paper reports on a PCR-RFLP analysis in a chloroplast DNA region consisting of coding and intergenic spacer sequences of trnS and the adjacent psbC gene. This region was PCR-amplified in 62 woody plant species, predominantly tree species, that represent a broad systematic range in both gymnosperms and dicotyledonous angiosperms. The amplification products were digested by the restriction endonuclease HaeIII (GG↓CC). Fourteen different restriction patterns occurred, 5 of which characterised representatives of the gymnosperms, and 9 angiosperm representatives. A single restriction site polymorphism revealed most of the species to share restriction patterns. Groups formed which showed relationships to plant systematic units. This phenomenon is discussed with regard to the psbC gene and the GGCC motif for tracing species’ relationships on a high taxonomic level of gymnosperms and angiosperms.
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    URL: http://dx.doi.org/10.1007/s001220050516
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    The structure of the Aegilops tauschii genepool and the evolution of hexaploid wheat (1998)
    Springer
    Theoretical and applied genetics 97 (1998), S. 657-670 
    Details
    ISSN: 1432-2242
    Keywords: Key words Triticum aestivum ; Phylogeny ; Genetic distance ; Genome ; Introgression ; Allopolyploidy ; RFLP ; Glutenin ; rRNA ; Non-transcribed spacers ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Polymorphism in the lengths of restriction fragments at 53 single-copy loci, the rRNA locus Nor3, and the high-molecular-weight glutenin locus Glu1 was investigated in the D genome of hexaploid Triticum aestivum and that of Aegilops tauschii, the source of the T. aestivum D genome. The distribution of genetic variation in Ae. tauschii suggests gene flow between Ae. tauschii ssp. strangulata and ssp. tauschii in Iran but less in Transcaucasia. The “strangulata” genepool is wider than it appears on the basis of morphology and includes ssp. strangulata in Transcaucasia and southeastern (SE) Caspian Iran and ssp. tauschii in north-central Iran and southwestern (SW) Caspian Iran. In the latter region, Ae. tauschii morphological varieties ‘meyeri’ and ‘typica’ are equidistant to ssp. strangulata in Transcaucasia, and both belong to the “strangulata” genepool. A model of the evolution of Ae. tauschii is presented. On the geographic region basis, the D genomes of all investigated forms of T. aestivum are most closely related to the “strangulata” genepool in Transcaucasia, Armenia in particular, and SW Caspian Iran. It is suggested that the principal area of the origin of T. aestivum is Armenia, but the SW coastal area of the Caspian Sea and a corridor between the two areas may have played a role as well. Little genetic differentiation was found among the D genomes of all investigated free-threshing and hulled forms of T. aestivum, and all appear to share a single D-genome genepool, in spite of the fact that several Ae. tauschii parents were involved in the evolution of T. aestivum.
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    URL: http://dx.doi.org/10.1007/s001220050942
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    Biased primary sex ratio in the bushcricket Poecilimon veluchianus, an insect with sex chromosomes (1996)
    Springer
    Behavioral ecology and sociobiology 39 (1996), S. 189-194 
    Details
    ISSN: 1432-0762
    Keywords: Key words Sex ratio ; Evolution ; Heterogeneity ; Orthoptera ; Motility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Offspring sex ratio at hatching was examined in the bushcricket Poecilimon veluchianus. Offspring sex ratios varied significantly between females (Fig. 1). Low mortality prior to sex determination established that this heterogeneity was already present in the primary offspring sex ratio. Sperm age and female age had no influence on offspring sex ratio (Fig. 2). Male age at copulation, however, correlated significantly with offspring sex ratio (Fig. 3). There were two types of males: one type produced predominantly daughters when young and an increasing proportion of sons with age. The other type produced, independent of age, 1:1 offspring sex ratios (Fig. 4). The two types of males seem to occur in approximately equal numbers. Sex ratio variation (1) may adaptively compensate for local sex ratio biases caused by sex-specific motility, or (2) it may be adaptive if there is a sex-differential effect of laying date on offspring fitness.
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    URL: http://dx.doi.org/10.1007/s002650050280
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    Echolocation and foraging behavior of the lesser bulldog bat, Noctilio albiventris : preadaptations for piscivory? (1998)
    Springer
    Behavioral ecology and sociobiology 42 (1998), S. 305-319 
    Details
    ISSN: 1432-0762
    Keywords: Key words Bats ; Echolocation ; Foraging ; Evolution ; Piscivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied variability in foraging behavior of Noctilio albiventris (Chiroptera: Noctilionidae) in Costa Rica and Panamá and related it to properties of its echolocation behavior. N. albiventris searches for prey in high (〉20 cm) or low (〈20 cm) search flight, mostly over water. It captures insects in mid-air (aerial captures) and from the water surface (pointed dip). We once observed an individual dragging its feet through the water (directed random rake). In search flight, N. albiventris emits groups of echolocation signals (duration 10–11 ms) containing mixed signals with constant-frequency (CF) and frequency-modulated (FM) components, or pure CF signals. Sometimes, mostly over land, it produces long FM signals (duration 15–21 ms). When N. albiventris approaches prey in a pointed dip or in aerial captures, pulse duration and pulse interval are reduced, the CF component is eliminated, and a terminal phase with short FM signals (duration 2 ms) at high repetition rates (150–170 Hz) is emitted. Except for the last pulses in the terminal phase N. albiventris avoids overlap between emitted signals and echoes returning from prey. During rakes, echolocation behavior is similar to that in high search flight. We compare N. albiventris with its larger congener, N. leporinus, and discuss behavioral and morphological specializations that can be interpreted as preadaptations favoring the evolution of piscivory as seen in N. leporinus. Prominent among these specializations are the CF components of the echolocation signals which allow detection and evaluation of fluttering prey amidst clutter-echoes, high variability in foraging strategy and the associated echolocation behavior, as well as morphological specializations such as enlarged feet for capturing prey from the water surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002650050443
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