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Courtship behavior and reproductive isolation between nine strains of Drosophila lini and its siblings from Taiwan (TWN), Dinghushan (DHS) and Nankunshan (NKS) in China, and Pyinoolwin (MMY) and Yangon (RGN) in Myanmar were investigated. No premating and postmating isolation between the Taiwan and mainland China strains were found. Crosses between mainland China (DHS and NKS) or the TWN strain and the MMY or RGN strain produced fertile F1 hybrid females and sterile F1 hybrid males. Crosses between MMY strains and RGN strains which showed strong premating isolation produced either no F1 hybrids, or fertile F1 hybrid females and sterile males in some cases. These results suggest the existence of at least three genetically distinct sibling species of D. lini.

Using DNA sequence data of 18 genes from 14 mammals, we analyzed how the average molecular evolution rate per year per site (Vy) depends on the generation time (g). (I) Assuming the relation Vy varies; is directly proportional to g(-alpha), the index of generation time effect, (alpha) was estimated to be about 0.14 for amino acid replacement substitutions (A), and about 0.32 for synonymous substitutions (S). (II) Assuming the relation Vy = V(m)g g-1 + V(e)y, where V(m)g and V(e)y are constant independent of g, the fraction, r(e) = V(e)y/Vy, of the mutation rate independent part (V(e)y) in the total evolution rate (Vy) was estimated under the assumptions of the star phylogeny and the constancy of the mutation rate per generation. r(e) was smallest for mouse with the shortest generation time among our analyzed species, and it was estimated to be about 0.57 for A and 0.31 for S. Both results do not support the view that Vy is equal to the neutral mutation rate per site both for A and for S. They are in line with the thesis that, at least for A and probably even for S, the molecular evolution rate is influenced by some causes other than the mutation rate, such as changing environment.

cDNA corresponding to two hsp70-related genes (OLHSC70 and CEHSC70) were isolated from two lines of cultured fish cells derived from the genus Oryzias. OLHSC70 was 2,261 bp in length and encoded a protein of 686 amino acids with a predicted molecular mass of 76,120 daltons. CEHSC70 was 2,114 bp in length and it lacked the 5' region found in OLHSC70. Two-dimensional electrophoresis revealed that Oryzias latipes has at least three heat-inducible proteins with molecular masses of about 70,000 daltons. One of these proteins (Hsp70.1) was barely expressed under normal conditions but its high-level expression was induced by hyperthermia. The other two proteins (Hsc70.1, and Hsc70.2) were constitutively expressed under normal conditions and only slightly enhanced levels were induced by hyperthermia. Transfection with the cloned sequence, RNA dot-blot analysis and the two-dimensional electrophoresis of proteins showed that OLHSC70 encoded Hsc70.1.

The S2 line of Drosophila simulans, an isofemale line from a natural population at Mishima, Japan, was found to have high crossability with D. melanogaster. Over 80% of the S2 females mated with D. melanogaster males, while only 2.4- 14.2% of control females from other D. simulans lines mated. The reciprocal mating (D. melanogaster female x S2 males) was in normal range (35-50%). The crossability of the F1 females between the S2 and other normal simulans lines was slightly higher than the control females. The high crossability is caused by at least two genes, one on the second and the other on the third chromosome which act additively.

The enzyme activity for cytosine deaminase, which converts cytosine to uracil in bacterial, is usually undetected in higher plants and animals. The enzyme also catalyzes conversion of non-toxic 5-fluorocytosine (5-FC) to 5- fluorouracil (5-FU), a toxic compound for plant growth. The gene encoding cytosine deaminase (codA) from Escherichia coli was fused to cauliflower mosaic virus (CaMV) 35S promoter (P35S), and cloned into a binary vector pLABR101. The resulting plasmid pLABR102 contained two marker genes for plants: a positive marker gene, bialaphos resistance (bar) gene driven by the promoter from nopaline synthase gene (Pnos) and a negative one, P35S-codA. The binary vector pLABR102 was transformed into Arabidopsis thaliana via Agrobacterium-mediated transformation. In transgenic progenies (T3) of the second (T2) generation heterozygous for a single T-DNA insertion, a 3:1 segregation ratio was observed on both bialaphos (resistance to sensitive) and 5-FC (sensitive to unaffected). From T2 plants homozygous for the T-DNA insert, on the other hand, no segregation was detected: all the T3 seedlings were resistant to bialaphos and sensitive to 5-FC. PCR and Northern analyses showed that the 5-FC sensitivity in transgenic descendants was caused by the integration and expression of the chimeric codA gene in the Arabidopsis genome. The results indicated that cytosine deaminase from E. coli is functional and useful for negative selection in Arabidopsis, and that sensitivity to 5-FC as well as the positive bialaphos resistance are dominant traits in Arabidopsis.

A family of repetitive DNA sequences in the genome of the sawfly, Strongylogaster osmundae (Hymenoptera: Tenthredinidae) was characterized. The family consists of a tandemly arranged array whose basic repeat unit is 1.0 kb. According to the compositions and arrangements of bases, the basic repeat unit can be divided into three distinct domains. Three domains share nucleotide sequence homology of 88, 74 and 89%, respectively, between members in this family. Second domain which had lower homology with the other two domains was found characteristically rich with polypurine/polypyrimidine sequences.

Homozygous stocks for the second or the third chromosome of Drosophila melanogaster with a single insertional plwB element were screened for high crossability with D. simulans. Reciprocal crosses between each of these stocks and D. simulans were made, and the insemination rate at two or three days was examined. From two cycles of screening of the original 575 stocks, one stock (# 687) which showed high insemination rate was selected and was backcrossed to a w strain to substitute the background. We obtained a stock which showed 10% insemination rate with D. simulans males (control was 0%). No stocks exhibiting a high crossability with D. simulans females were acquired. Revertant strains, from which the P element had been lost, were obtained from the backcrossed # 687 stock. The insemination rates of 13 revertants to D. simulans males ranged from 1% to 33%. Seven of these 13 were not significantly different from the control line but were significantly different from the backcrossed # 687 stock. It was concluded that the mutation showing high crossability with D. simulans males was caused by the P element transposition.

The tef-1 gene encoding translation elongation factor 1 alpha was cloned from the ascomycete fungus Neurospora crassa. The sequences of genomic DNA and cDNA clones showed that the tef-1 gene contained one ORF of 1380 bp length that is interrupted by three short introns. The deduced polypeptide contained 460 amino acid residues, and the sequence had a high similarity with those of EF-1 alpha polypeptides from other species. The level of tef-1 mRNA was low in conidia but high in growing cells. When mycelia were transferred to poor nutrient media, the level of tef-1 gene mRNA decreased remarkably. The pattern of tef-1 expression was similar to the expression of genes for ribosomal proteins. The tef-1 gene was mapped between arg-3 and leu-4 loci on linkage group I by restriction fragment length polymorphism mapping. Southern blot analysis showed that Neurospora genomic DNA contained only one copy of the tef-1 gene in a genome.

Five Drosophila melanogaster strains showing high interspecific crossability with D. simulans males, derived from the previous screening of a set of autosomal plwB transposants, were selected and the effect of the plwB insertion under the same genetic background (white strain) on the interspecific crossability was examined. This phenotype was recessive in the two strains but semidominant in the other three strains. Trans-heterozygotes, however, showed high interspecific crossability compared with the parental homozygotes, suggesting some epistatic interactions between them. In three strains, the effect of the plwB insertion region in different backgrounds (w1118 strain) on the crossability was also tested. Homozygotes of a strain (#687) showed high interspecific crossability comparable to the w background, while homozygotes of both #68 and #783 strains showed lower crossability than w1118. Although #783 heterozygotes showed intermediate values between #783 homozygotes and w1118, #68 heterozygotes showed a significantly higher insemination rate than w1118 and the #68 homozygotes. These results suggest that the region around the plwB insertion sites of #68 and #783 affects the interspecific crossability either positively or negatively depending on the genetic background. In all the stocks, positive correlation between interspecific crossability and the intraspecific mating speed was detected.

Hybrids from the cross between males of Drosophila melanogaster and females of its sibling species (D. simulans, D. mauritiana, or D. sechellia) are embryonic lethal when they carry the wild type allele of zygotic hybrid rescue (zhr) from D. melanogaster. The zhr gene has been mapped in the proximal region of the X heterochromatin slightly distal to the proximal breakpoint of In(1)sc8, the region rich in 1.688 g/cm3 satellite DNA. Since this satellite DNA does not exist in the sibling species, the satellite DNA was considered to be involved in the hybrid lethality. We examined the hypothesis molecular cytogenetically. The results are (1) three Df(1)zhr chromosomes carried this satellite DNA, and (2) hybrids were viable even if the amount of the satellite DNA in hybrids was increased by adding minichromosomes Dp(1;f)1205 and Dp(1;f)1187 into the genome. These results do not support the above hypothesis.