For establishing more efficient blue /pink heterozygous Tradescantia testers of mutagenicity, the young inflorescence-bearing nodal and/or axillary cuttings of clones BNL 02, KU 27, KU 7 and KU 20 were cultivated with nutrient solutions, and the flower production, stamen-hair growth, and spontaneous and induced somatic pink mutation frequencies in the stamen hairs observed in the cuttings of each clone were compared with those in the potted plants of the same clone. The cuttings tended to show poorer flower productions, smaller flower sizes and decreases in the number of hairs, as compared with potted plants, but the spontaneous and X-ray-induced somatic mutation frequencies were comparable to those in potted plants. Using the BNL 02 cuttings, however, the mutagenic effect of nitrofurazone was detected for the first time in higher plants. On the other hand, the shoots with roots of clone BNL 4430 divided from the potted plants and cultivated with a nutrient solution exhibited excellent results in all aspects; i.e., the flower production, flower size, stamen-hair growth, and X-ray-and MMS-induced mutation frequencies being almost identical with those in the potted plants, and the spontaneous (background) mutation frequency being lower than that in the potted plants. The shoots with roots of clone BNL 4430 were thus judged to be the best Tradescantia tester of mutagenicity, requiring much smaller space than using the potted plants and supplying much larger samples much more constantly than the cuttings of other clones.
Four kinds of circular plasmid-like DNA, designated Bl, B2, B3 and B4, have been found in the mitochondria of rice (Oryza sativa L.). We analyzed the distribution of families of plasmid-like DNAs homologous to those of O. sativa in 40 strains of the genus Oryza with AA, BB, BBCC, CC, CCDD and EE genomes. Plasmid-like DNAs were observed only strains having AA, CC and CCDD genomes. The distribution patterns of strains with AA genome were highly polymorphic. We amplified the plasmid-like DNAs from strains with the AA genome by PCR and examined restriction fragments length polymorphisms (RFLPs). RFLPs were detected among families of plasmid-like DNA amplified from different strains. This result indicated that some mutations, such as base substitutions and the insertion or deletion of a small fragment of DNA, had occurred and had accumulated during the differentiation of strains with an AA genome.
Phylogenetic relationships between four Phaseolus (P. angularis, P. calcaratus, P. coccineus and P. vulgaris (including six cultivars)) and two Vigna (V. sesquipedalis and V. sinensis) species were studied by restriction fragment length polymorphism (RFLP) analysis using 15 restriction enzymes and two ribosomal DNA fragments from rice and mung bean as probes. Based on the RFLP data, phylogenetic trees were constructed by the distance matrix and maximum parsimony methods. The two trees constructed by the distance matrix method and one tree constructed by the maximum parsimony method had congruent topology and recognized three clusters: one containing V. sesquipedalis and V. sinensis; a second containing P. angularis; and a third containing P. calcaratus, P. coccineus and six cultivars of P. vulgaris. Grouping of the six species based on the molecular taxonomic data obtained is compared with grouping based on previously reported cytological data.
The chromosomal locations of isozyme gene loci encoding isocitrate dehy-drogenase (IDE) and phosphoglucoisomerase (PGI) were investigated in shallot (Allium cepa L. Aggregatum group). The alien monosomic addition lines of A. fistulosum L. with the extra chromosomes (1A, 2A, 5A, 6A, 8A and other unidentified chromosomes) from A. cepa Aggregatum group were used as plant materials. Both gene loci, Idh-1 and Pgi-1, were located on the chromosome 5A. The present study established two new isozyme markers for the chromosome 5A in addition to the six previously reported isozyme markers for the chromosomes 1A, 2A, 6A and 8A.
To restore wild type phenotypes in mutants controlled by recessive genes, microinjection of whole genomic DNA into recipient macronucleus in Paramecium caudatum was performed. Donor DNA carrying three wild-type genetic markers (exocytosis, behavior and mating type) was introduced into a recipient cell which was a triple recessive homozygote for the corresponding genes. Of the three phenotypes, a trichocyst non-discharge mutant TND converted to wild type by microinjection of not only total genomic DNA but also fractionated restriction fragments, although the restored phenotype was not complete. This transformation was more efficient when injection was performed by using the recipient cells of S phase, compared with the cells of G1 phase. This successful restoration of wild type phenotype gives us hope for cloning mutated genes, especially when no information about gene products is available. We discuss the advantage of this total genomic DNA injection and the possibility of target gene cloning using this strategy.
RFLP analysis was carried out to clarify the nuclear genome differentiation in Asian rice varieties of Oryza sativa. Based on the restriction fragment patterns with two endonucleases, EcoRI and HindIII, using 12 single-copy rice DNA probes, 93 types of nuclear genome were found among 112 local varieties from 17 Asian countries. In a dendrogram showing genetic relationships among nuclear genome types, they were mainly divided into eight groups, A, B1, B2, C1, C2, D1, D2 and E. These results were compared with previous isozyme analysis and RFLP analysis on chloroplast genome using the same varieties. Classification on isozyme analysis matches well with that on nuclear genome, indicating synchronous differentiation of isozyme constitutions and nuclear genomes in Asian varieties. Considering the correspondence between them, nuclear genomes were grouped into Indica (A, B1 and B2), intermediate (C1, C2 and D1) and Japonica (D2 and E) types. From the comparison of chloroplast with nucleus for genome differentiation, two major chloroplast genomes (types 1 and 3) were found in the varieties with several nuclear genome types. However, Japonica group with D2 and E nuclear genomes has only type 1 chloroplast genome, whereas Indica and intermediate groups contain both two major chloroplast genomes. Especially, type 3 chloroplast genome which was not found in Japonica group is dominant type in Indica varieties. The results indicate the differentiation of nuclear genome has partially synchronized with that of chloroplast genome.