著者

Matsuo Yoshinori

出版者

The Genetics Society of Japan

雑誌

Genes & genetic systems (ISSN:13417568)

巻号頁・発行日

vol.78, no.4, pp.309-318, 2003-08-25

被引用文献数

7

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The molecular evolution of the histone multigene family was studied by cloning and determining the nucleotide sequences of the histone 3 genes in seven <i>Drosophila</i> species, <i>D. takahashii, D. lutescens, D. ficusphila, D. persimilis, D.pseudoobscura, D. americana</i> and <i>D. immigrans</i>. CT repeats, a TATA box and an AGTG motif in the 5' region, and a hairpin loop and purine-rich motifs (CAA(T/G)GAGA) in the 3' region were conserved even in distantly related species. In <i>D. hydei</i> and <i>D.americana,</i> the GC content at the third codon position in the protein coding region was relatively low (49% and 45%), while in <i>D. takahashii</i> and <i>D. lutescens</i> it was relatively high (64% and 65%). The non- significant correlation between the GC contents in the 3' region and at the third codon position as well as the evidence of less constraint in the 3' region suggested that mutational bias may not be the major mechanism responsible for the biased nucleotide change at the third codon position or for codon usage bias.<br>

著者

Sachihiro Matsunaga

出版者

The Genetics Society of Japan

雑誌

Genes & Genetic Systems (ISSN:13417568)

巻号頁・発行日

vol.81, no.4, pp.219-226, 2006 (Released:2006-10-11)

参考文献数

78

被引用文献数

16 22

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Recent studies of plant sex chromosome-linked genes have revealed many interesting characteristics, although there are limited reports about heteromorphic sex chromosomes in flowering plants. Sex chromosome-linked genes in angiosperms have been characterized mainly in the dioecious plant Silene latifolia. Although all such genes were isolated from transcripts of male flower buds of S. latifolia, most seem to be housekeeping genes except for the petal- and stamen-specific MADS box gene on the Y chromosome (SlAP3Y) and the male reproductive organ-specific gene on the X chromosome (MROS3X). Recent evolutionary studies have revealed at least three evolutionary strata on the X chromosome that are related to stepwise loss of recombination between the sex chromosomes. Moreover, genetic maps showed conservation of gene organization on the X chromosome in the genus Silene and substantial pericentric inversion between the X and Y chromosomes of S. latifolia during evolution. A comparison between paralogs on the sex chromosomes revealed that introns of the Y-linked genes are longer than those of X-linked paralogs. Although analyses of sex chromosome-linked genes suggest that degeneration of the Y chromosome has occurred, the Y chromosome in flowering plants remains the largest in the male genome, unlike that of mammals. Accumulation of repetitive sequences and the entire chloroplast genome on the Y chromosome appear to have contributed to this large size. However, more detailed studies will be required to help explain the basis for the fact that heteromorphic sex chromosomes in angiosperms are large.

著者

Chikashi Shimoda Akiko Itadani Akio Sugino Mitsuru Furusawa

出版者

The Genetics Society of Japan

雑誌

Genes & Genetic Systems (ISSN:13417568)

巻号頁・発行日

vol.81, no.6, pp.391-397, 2006 (Released:2007-02-03)

参考文献数

16

被引用文献数

24 32

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Eukaryotic DNA polymerases δ and ε, both of which are required for chromosomal DNA replication, contain proofreading 3’→5’exonuclease activity. DNA polymerases lacking proofreading activity act as strong mutators. Here we report isolation of thermotolerant mutants by using a proofreading-deficient DNA polymerase δ variant encoded by pol3-01 in the yeast Saccharomyces cerevisiae. The parental pol3-01 strain grew only poorly at temperatures higher than 38°C. By stepwise elevation of the incubation temperature, thermotolerant mutants that could proliferate at 40°C were successfully obtained; however, no such mutants were isolated with the isogenic POL3 strain. The recessive hot1-1 mutation was defined by genetic analysis of a weak thermotolerant mutant. Strong thermotolerance to 40°C was attained by multiple mutations, at least one of which was recessive. These results indicate that a proofreading-deficient DNA δ polymerase variant is an effective mutator for obtaining yeast mutants that have gained useful characteristics, such as the ability to proliferate in harsh environments.