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  • 1
    Electronic Resource
    Electronic Resource
    Chromosome endoreduplication in endosperm cells of two maize genotypes and their progenies (1995)
    Springer
    Protoplasma 189 (1995), S. 156-162 
    Details
    ISSN: 1615-6102
    Keywords: Chromosome endoreduplication ; Endosperm ; Protein accumulation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chromosome endoreduplication is a very common process in higher plants but its function and genetic control are still to be clarified. In our experiments we analyzed, by Feulgen cytophotometry, chromosome endoreduplication in endosperm cells of two maize genotypes, IHP and ILP, having high and low protein content in their seed, respectively. Chromosome endoreduplication occurs in both lines within 24 days after pollination, attaining a maximum ploidy level of 384C (7 DNA replication rounds) in IHP and of 192C (6 replication rounds) in ILP. In the mature seed, endosperms of the two lines show different mean ploidy level. In reciprocal crosses between IHP and ILP the f1 endosperms have mean ploidy levels analogous to that of the maternal parent, showing that the difference in ploidy level between the two genotypes is maintained. After selfing of the f1 plants, the difference in ploidy level between the two F2 populations is reduced. In F2 the mean ploidy level is as variable as in f1, indicating the absence of genetic segregation. From our data, it is apparent that both the genetic constitution (cytoplasmic and nuclear) of the maternal parent and the genotype of the individual endosperms influence the ploidy level. An analysis of the protein content in endosperms carried out on the same seed sample as analyzed cytophotometrically showed that the protein content increases, during seed development, parallel to chromosome endoreduplication and varies, in the two lines, in reciprocal crosses and their progeny, according to the same trend as mean ploidy level, suggesting a correlation between the two parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280169
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  • 2
    Electronic Resource
    Electronic Resource
    Diploidy and chromosome endoreduplication in the development of epidermal cell lines in the first foliage leaf of durum wheat (Triticum durum Desf.) (1983)
    Springer
    Protoplasma 118 (1983), S. 36-43 
    Details
    ISSN: 1615-6102
    Keywords: Chromosome endoreduplication ; Diploidy ; Durum wheat ; Leaf epidermis ; Triticum durum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of epidermal cell lines in the first foliage leaf ofTriticum durum was studied with a combined cytological and DNA cytophotometric analysis. It was shown that: (1) At emergence, the distal portion of the leaf is made of the cells pre-existing in the embryonic leaf and the mitotic activity is localized at the base of the leaf lamina (basal meristem). (2) The proliferating protoderm (outermost cell layer of the basal meristem) contains a meristematic cell population and a differentiating cell population. The cells produced by the protoderm differentiate with 2C, 4C, 8C, and 16 C nuclear DNA contents. (3) The endoreduplicated cells (EC) together with 4C cells form prominent cell rows in the leaf epidermis. The interstomatal cells (ISC) are all 2 C and the inter-hairs cells (IHC) are mostly 2 C (rare 4 C cells lie adjacent to the EC). (4) In the fully developed leaf, the frequency distribution of EC (8 C and 16 C) and 4C cells in a given epidermal segment (Fig. 1) corresponds to the frequency established in the epidermis differentiation zone (zone b, segment 1) at the time of development of that segment:e.g., segment 6 developed at 1–2 days after seed germination, segment 5 at 3 days after germination and so on. (5) Epidermal cell elongation starts in segment 1 and reachs its maximum in the older leaf segments, 5 and 6. The rate of cell elongation is independent of nuclear DNA content; chromosome endoreduplication precedes elongation. (6) The possibility of using epidermal cell parameters in studies on first leaf growth inT. durum is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01284744
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear DNA content in differentiated tissues of sunflower (Helianthus annuus L.) (1986)
    Springer
    Protoplasma 130 (1986), S. 91-97 
    Details
    ISSN: 1615-6102
    Keywords: Helianthus annuus ; Tissue differentiation ; Nuclear DNA content ; Chromosome endoreduplication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Scanning cytophotometry following Feulgen-staining was used to determine nuclear DNA content in many differentiated tissues of nine cultivars, hybrids or selfed lines ofHelianthus annuus. Apart from such ephemeral tissues as endosperm and anther tapetum, it was found that tissue differentiation in sunflower occurs in the diploid condition, cells being arrested in the DNA presynthetic phase (G1). In certain cases, however, the nuclear DNA content of differentiated G1 cells does not exactly match the 2C DNA content found in meristematic cells, but may be either higher or lower. In endosperm and anther tapetum cells, nuclear DNA content may be as high as 24 C and 32 C, respectively. Cytological and autoradiographic analyses after3H-thymidine incorporation reveal that polyploidy in the tapetal cells is due to chromosome endoreduplication. No detectable difference between male-fertile and male-sterile plants exists as far as occurrence and level of cell polyploidy are concerned. The results are discussed in the context of previous investigations on the nuclear condition of differentiatedHelianthus annuus tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276590
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of chromatin and DNA during chromosome endoreduplication in the endosperm ofTriticum durum Desf. (1998)
    Springer
    Protoplasma 203 (1998), S. 175-185 
    Details
    ISSN: 1615-6102
    Keywords: Chromatin ; Chromosome endoreduplication ; DNA methylation ; Durum wheat ; Endosperm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chromatin structure was studied in nuclei of the endosperm of durum wheat (Triticum durum Desf., cv. Creso), where a large number of cells undergo chromosome endoreduplication during caryopsis development. Optical density profiles of interphase nuclei at different ploidy levels after Feulgen staining were determined cytophotometrically. It was observed that, within each development stage, polyploid nuclei (6–12C and 12–24C) show more condensed chromatin than euploid nuclei (3–6C): this should indicate that endoreduplication is accompanied by some reduction of nuclear activity. Within the same ploidy level, 3–6C and 6–12C nuclei become increasingly condensed with development (except for the last stage), while 12-24C nuclei are identical at all stages. DNA methylation at different stages of caryopsis development was then analyzed in genomic DNA, highly repeated sequences and ribosomal DNA, by digestion with cytosine-methylation-sensitive restriction enzymes. We observed that (i), depending on the enzyme, DNA from caryopses may show higher mean length than DNA from shoot apices and variations occur during endosperm development; (ii) highly repeated DNA sequences also show some variation in base methylation between apices and endosperms and among endosperm development stages, even though to a lesser extent than genomic DNA; (iii) rDNA shows variations only between endosperm and apices while no variation was observed among endosperm development stages in relation to chromosome endoreduplication. Our data may be explained by assuming the occurrence, during endosperm development, of processes of chromatin condensation possibly involved in silencing the activity of extra copies of DNA resulting from chromosome endoreduplication. At least in part, DNA methylation is involved in the process of chromatin condensation. rDNA shows no variation during endosperm development: this suggests that rDNA copies are actively transcribed in both triploid and endoreduplicated nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279474
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