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The expression of histone genes during Drosophila melanogaster oogenesis (1998)

Walker, Janis ; Bownes, M.

Springer

Development genes and evolution 207 (1998), S. 535-541

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ISSN: 1432-041X

Keywords: Key words Histones ; Oogenesis ; Drosophila

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract A genomic fragment was cloned from a DNA library constructed from a Drosophila enhancer trap line in which reporter gene expression was observed at the anterior-most tip of the ovaries and testes. This genomic clone was identified as the L-repeat of the Drosophila melanogaster histone gene cluster. Northern blotting and in situ hybridisation to RNA in tissues with individual cDNAs and PCR-generated probes for each histone confirmed that gene expression was greatest at the anterior portion of each ovariole, in the germarium, and was also elevated in a few individual nurse cells and somatic follicle cells within the egg chamber during early developmental stages. Histone H1 and each of the core histones had a similar expression pattern which was correlated to cell division. Maternal stores of histone transcripts were also transported to the mature oocyte from the nurse cells at a later stage of oogenesis (stage 10), when virtually all the nurse cells contained high levels of histone transcripts. The results are consistent with expression of the somatic histone gene cluster during oogenesis as a co-ordinate unit. There does not seem to be a reduced level of somatic type H1 in the germ-line, as is observed in some other species. The relationship between the P[lacZ] expression pattern in the germarium and the overall expression of the histone cluster suggests there are specific regulatory elements for germ-line expression.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004270050144

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A human metallothionein pseudogene containing AG/CT repetitive elements (1990)

Walker, Janis M. ; Gedamu, Lashitew

Springer

Journal of molecular evolution 31 (1990), S. 211-220

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ISSN: 1432-1432

Keywords: Metallothionein ; Repetitive elements ; Pseudogene ; Genomic DNA ; Hybridization

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary A lambda phage recombinant clone, 25 S, which contains a 15.5-kb EcoRI human genomic DNA fragment, has been characterized. Restriction mapping and Southern blot hybridization indicated a 3.0-kb HindIII fragment containing metallothionein (MT)-like sequences. Several interesting features were found upon comparison of this nucleotide sequence with that of other human MT genes: (1) sequences representing the 5′ regulatory region, the 5′ untranslated region, and the first exon are not contained in the 3.0-kb HindIII fragment; (2) the coding sequence of the second exon (amino acids 10–31 encoding a portion of the β-domain of the MT protein) has 11 amino acid changes out of a total of 21, whereas, the third exon (amino acids 32–61, representing the complete α-domain of the MT protein) has only 4 amino acid substitutions; however, all cysteine residues are conserved; (3) this MT-like gene retains intron sequences and processing signals; (4) Southern blot analysis of human genomic DNA indicated this MT-like gene is located on a 10.5-kb EcoRI genomic DNA fragment; and (5) unusual AG/CT-rich repetitive elements are located within the second intron and upstream of the second exon of this MT-like gene. This gene is not expressed in response to metal induction in two human cell lines, as shown by northern blot analyses. Based on these observations, this MT-like gene represents a unique nonprocessed pseudogene of the human MT multigene family.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02109498

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High efficiency transformation ofBrassica napus usingAgrobacterium vectors (1989)

Moloney, Maurice M. ; Walker, Janis M. ; Sharma, Kiran K.

Springer

Plant cell reports 8 (1989), S. 238-242

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ISSN: 1432-203X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract An efficient procedure for obtaining transgenicBrassica napus plants usingAgrobacterium binary vectors is described. The target tissue for the transformation is the cut end of cotyledonary petioles. These tissues, when cultured with their lamina intact, show a regeneration frequency of more than 80%. The cells of this cut surface, which undergo organogenesis, are very susceptible to topical infection byAgrobacterium. The cocultivation method used does not require feeder layers or use of exogenously applied promoters of virulence. After 72h of infection withAgrobacterium the explants were transferred to selective regeneration medium. Using kanamycin (15μg cm−3) for selection, transgenic plantlets emerged within 3 weeks. These plantlets which appeared on over half the explants were excised and rooted for a further 7–10 days. When the plants were large enough, leaves were taken for assay of NPT II activity using dot blots. Most of the plants surviving the selection showed substantial NPT II activity. The frequency of transformation and yield of transgenic plants was higher than in previously reported methods with this species. Southern blotting revealed that integration of the T-DNA frequently occurred in multiple copies and at multiple loci in the genome. The transgenicB. napus plants all grew normally and developed fertile flowers. The transgenic plants were self-pollinated and their progeny studied by two methods. The first was a single-embryo NPT II assay performed on developing seeds of these selfed-plants. The second was a leaf bleaching assay performed by selection of germinating seedlings of the selfed progeny. Both assays yielded segregation ratios consistent with the number of integration events indicated by Southern blots. The method should have broad application in studies of gene expression in theBrassicaceae and will be a cost-effective alternative to those seeking to improveBrassica crops by introduction of foreign genes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00778542

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