Genetic and molecular investigations were carried out with 10 Japanese Drosophila melanogaster strains on P-M system of hybrid dysgenesis. The strains used here were collected in the years from 1952 to 1984 from various natural populations, and have been maintained in our laboratory. The whole genomic Southern hybridization was performed by using the 2.9-kb P element and the internal fragments as probes. Five strains possessed no P element copy and the other 5 strains possessed mainly incomplete P elements which had internal deletions. The former 5 strains were M, 2 of the latter were Q, and the remaing 3 were M' strains. Hikone-R, collected in 1952, had no P element copy, while Hikone-H, collected in 1957, was the earliest observed to possess multicopies of an incomplete P element. This revealed that P elements in Drosophila melanogaster were present more than 30 years ago in Japan, as already shown to have been the case on the American continent.
The t complex in the mouse is essential to embryonic development. The semidominant mutation, T, is embryonic lethal in homozygotes. In T/T embryos, proper morphogenetic movement is hindered, causing the number of mesodermal cells to be reduced. The other effect of T mutation is shortening of the tail in heterozygotes, T/+ and T/t. t is a series of recessive mutations in the t complex. A detailed examination of tail shortening indicated the T and t mutations to exert various effects, such as the derangement of the pattern of necrosis, fusion or duplication of the neural tube and gut. The most severly affected structure is the notochord. The t mutation augments the effect of T mutation in the formation of normal notochord. A gradient of phenotypic severity along anteroposterior axis of an embryo appeared to exist correlative to the dosage of the T gene. Should the products of the T gene be responsible for inducing mesoderm and the establishment of the anteroposterior axis of an embryo, diverse effects of the T mutation on embryogenesis can be explained collectively.
Genetic study on emigration behavior of Drosophila melanogaster in the Ishinomaki population was conducted with 140 2nd chromosome lines. Fourteen sets of 5 × 5 partial diallel cross experiments were made to examine the emigration activity of F1 progeny. Emigration activity was scored using the method of Sakai et al. (1958). Additive genetic variance was 0.0377 ± 0.0069 and dominance variance 0.0076 ± 0.0032. The average degree of dominance of mildly deleterious genes for emigration activity in an equilibrium population was 0.069 ± 0.042. The estimated degree of dominance at a gene locus affecting emigration activity was 0.067, which revealed nearly complete dominance for the tendency of heterozygote flies to move from their original place to another. Average degree of dominance of lethal gene for emigration activity was 0.012.
Young inflorescences of Tradescantia BNL 02 clone heterozygous for flower color (blue/pink; the blue color being deminant) were treated with 0.1 to 0.5% aqueous solutions of ethyl methanesulfonate (EMS) for 2 to 16 hr, or with 0.005 and 0.01% aqueous solutions of methyl methanesulfonate (MMS) for 16 hr. Somatic pink mutations induced in the stamen hairs were scored, and the mutation frequencies expressed as the number of pink mutant events per 103 hairs and per 104 hair-cell divisions were calculated. The mutation frequencies increased with increasing EMS or MMS dose in %·hr, and the slopes of the dose-response curves on log-log graphs were about 1.2 when the mutation frequencies (minus controls) pooled for 7-day peak periods (post-treatment days 8-14 to 10-16) were plotted agaist EMS dose. It was also found that MMS was about ten times more effective than EMS in inducing pink mutations. The mutation frequencies observed were roughly comparable to those induced by 4 to 300 mGy (0.4 to 30 rad) of acute X rays.
In order to establish a gene transfer system for yeast by promiscuous conjugation, we constructed plasmid pAY101 which contained an oriT sequence derived from RK2 (IncP) and the yeast TRP1 and ARS1 genes. A conjugation mixture consisted of yeast Saccharomyces cerevisiae, E. coli harboring pAY101, and E. coli carrying a helper plasmid with mob and tra. In the conjugation mixture a tryptophan-requiring yeast mutant (trp1) was converted to be prototrophic for tryptophan at a frequency of about 10-5 to 10-3 per recipient cell. This E. coli-yeast conjugation system required the mob, tra, oriT, TRP1 and ARS1 genes. The mob and tra genes were trans-acting elements as in an E. coli conjugation system. The mobilization was inhibited by nalidixic acid as in a typical bacterial conjugation. DNA analysis indicated that the plasmid pAY101 was transferred from E. coli to S. cerevisiae, and retained its original structure and function in yeast host cells.
Two experiments were performed with the aim of clarifying the genetic basis of variation in the number of primary spermatocytes per cyst in the B12 strain of Drosophila virilis and identifying the chromosome responsible for the variation. First, crosses between B12, showing a mean cell numbr of 11.81, and strain TK with a mean of 7.91, were performed. From the results obtained, it was considered that there were two factors, i.e., a recessive gene and certain modifiers, which shifted the cell number toward a higher value in B12. Second, chromosomal analysis with a marker strain and the B12 strain revealed that the third chromosome of B12 was responsible for the major effect of changing the primary spermatocyte number, although this chromosome did not exert a sufficient effect alone, and furthermore that at least one of the modifiers located on the second chromosome.
Using Imperial rye chromosome addition lines of wheat, we identified the rye chromosome that carries the gene for mugineic acid (MA) synthetase catalyzing synthesis of MA from 2'-deoxymugineic acid (DMA) and the gene for 3-hydroxymugineic acid (HMA) synthetase catalyzing synthesis of HMA from MA. Plants of seven addition lines, Chinese Spring wheat and Imperial rye were water-cultured, and chlorosis was induced by depletion of Fe from the culture medium. The root-washing from each plant was analyzed with HPLC to detect mugineic acid-family phytosiderophores (MAs). Chinese Spring wheat secreted only DMA, while Imperial rye secreted DMA, MA and HMA. In the case of addition lines, a 5R addition line secreted DMA, MA and HMA, but the others secreted only DMA. Therefore, 5R of Imperial rye was concluded as a carrier of the two genes which encode enzymes that catalyze MA-synthesis from DMA and HMA-synthesis from MA.
A semi-wild wheat, Triticum aestivum ssp. tibetanum, collected in Tibet and taxonomically classified by Shao et al. (1980), was investigated for its phylogenetic relationship to common wheat. Ssp. tibetanum is a hexaploid spelt wheat showing wedge-type disarticulation of the ear, and it is assumed to be somewhat unstable genetically. F1 hybrids between ssp. tibetanum and other common wheats are fully fertile in both sexes, although three interchanges exist between them. The haploid genotype for hybrid necrosis and hybrid chlorosis is ne1ne2ch1ch2; the Ch2 allele, common in both Aegilopssquarrosa and common wheat, including Chinese cultivars, is missing. The chloroplast genome is similar, and the mitochondrial genome is only slightly different from their counterparts in common wheats. Its cytoplasm does not induce male sterility in the all common wheat genotypes studied. These facts suggest that it is an offtype of Tibetan common wheat.
To develop detailed linkage maps of restriction fragment length polymorphism (RFLP) sites in wheat chromosomes, it was necessary to construct a genomic DNA library and to characterize the clones obtained. Forty-nine per cent of the clones were of single or low copy number per genome. With 91 clones of this class, as probes, and with two to four restriction endonucleases, for DNA digestion, RFLPs were examined among eight common wheats and a single emmer wheat. About 20% of the probes, and 13% of the probe-enzyme combinations revealed genetic polymorphism among the common wheats. DNA deletions account for most of the genetic differences among these wheat genomes. Based on the RFLP data, phylogenetic distances among the nine polyploid wheats were estimated, and a dendrogram showing the genetic relationships among them was constructed.
It has been discovered that expression of promoter activity can be inhibited by visible light when specific fragments of E. coli DNA are inserted in a vector system designed to assay for promoter activity. These fragments have been located on regions of the E. coli chromosome to which no gene has been assigned to date. The effective wavelength of light that produces this phenomenon has been determined.