In mitochondrial DNA (mtDNA) heteroplasmy in Drosophila, we previously reported that mtDNA was selectively transmitted depending on temperature (Matsuura et al., 1991). To investigate the effects of nuclear genome on the temperature-dependent transmission, two sets of heteroplasmy were constructed by germ-plasm transplantation, and changes in the relative proportion of two types of mtDNA were examined at 19°C and 25°C. In heteroplasmy possessing D. melanogaster and D. mauritiana mtDNA, two different nuclear genomes of D. melanogaster were examined after reciprocally substituting the nuclear genomes. In heteroplasmy possessing D. simulans and D. mauritiana mtDNA, nuclear genomes of D. melanogaster, D. simulans and D. mauritiana were used. For each set of mtDNA combination, the modes of temperature-dependent transmission of mtDNA differed according to the nuclear genome used. From these and our previous results (Matsuura et al., 1991; Tsujimoto et al., 1991), it is clear that the temperature-dependent transmission of mtDNA is affected by nuclear genome. This suggests that the nuclear genome is involved in determining the temperature-dependency of mtDNA transmission.
Replicating DNA regions on barley chromosomes were investigated by a replication banding technique. Of all chromosomal regions, the late replicating regions, in which DNA replicated in the last third of S phase, were detected as exceptionally distinct bands. Each late replicating region had its own timing and duration to replicate, which were not influenced by any translocations. This suggested that the late replication was highly associated with the structure of its related chromosomal region. By using the series of translocated chromosome lines, the late replication banding patterns of seven barley chromosomes were identified. The late replication banding pattern was similar to the C-banding pattern. The relationships of the late replicating regions with heterochromatin and C-banding regions are also discussed.
RIRE1 is a retrotransposon present in wild rice Oryza australiensis in an extraordinary number of copies, and only a portion of the LTR sequence has been determined previously. Here, we isolated and sequenced DNA segments of various portions of RIRE1, revealing that the sequences of LTR and the internal region were 1523 and 5277 bp in length, respectively. The internal region shows homology with the pol region in copia, a Drosophila retrotransposon, indicating that RIRE1 is a copia-like retrotransposon. The internal region of RIRE1 contained an open reading frame coding for genes, gag, pro, int, rt and rh, like copia and retroelements related to it. A clone screened from a library of the O. australiensis genomic DNA contained solo LTR, which was flanked by direct repeats of a 5-bp sequence. This suggests that RIRE1 generates a duplication of the target sequence of 5 bp upon retroposition. We observed that many RIRE1 members were nested by another RIRE1 member. This indicates that these RIRE1 members have received another RIRE1 to make an extraordinary number of copies in the O. australiensis genome without giving a deleterious effect on the growth of rice cells.
A new stable mutant of Arabidopsis thaliana with a spotted pigment in the seed coat, named anthocyanin spotted testa (ast), was induced by carbon ion irradiation. The spotted pigmentation of ast mutant was observed in immature seeds from 1-2 days after flowering (DAF), at the integument of the ovule, and spread as the seed coat formed. Anthocyanin accumulation was about 6 times higher in ast mutant than in the wild-type at 6 DAF of the immature seeds, but was almost the same in mature dry seeds. A higher anthocyanin accumulation was not observed in the seedlings, leaves or floral buds of ast mutant compared with the wild-type, which suggests that a high accumulation of anthocyanins is specific to the seed coat of the immature ast seeds. Reciprocal crosses between ast mutant and the wild-type indicated that ast is a single recessive gene mutation and segregates as a delayed inher-itance. The results of crossing with tt7 and ttg mutants also confirmed that the AST gene is probably a regulatory locus that controls flavonoid biosynthesis. A mapping analysis revealed that the gene is located on chromosome I and is closely linked to the SSLP DNA marker nga280 with a distance of 3.2 cM. AST has been registered as a new mutant of Arabidopsis.
High-performance liquid chromatography (HPLC) analyses using a series of alien monosomic addition lines (AMALs) of Japanese bunching onion (Allium fistulosum L.) having extra chromosomes from shallot (A. cepa L. Aggregatum group) were performed to determine the chromosomal locations of the genes for flavonoid and anthocyanin production in leaf sheaths of A. cepa Aggregatum group. In HPLC profiles both at 360 and 520 nm, several peaks were observed in A. cepa Aggregatum group and AMAL with chromosome 5A from A. cepa Aggregatum group but no peak was observed in A. fistulosum and other AMALs. Four of the compounds observed at 360 nm were identified as known flavonoids, i.e., apigenin, kaempferol, quercetin, and rutin. Five out of the total 18 compounds at 520 nm were identified as known anthocyanins, i.e., cyanidin-3-glucoside, cyanidin-3-laminariobioside, peonidin-3-glucoside, cyanidin-3-malonylglucoside, and cyanidin-3-malonyllaminariobioside. These results reveal that a group of the genes related to the flavonoid and anthocyanin production in the leaf sheath of A. cepa Aggregatum group are located on the chromosome 5A.
To study the phylogeny and domestication of tetraploid wheat species, variations in nuclear DNA of the cultivated and wild species were investigated by RFLP analy-sis. Twenty-two accessions representing 11 species of cultivated tetraploid wheat (Emmer wheat and Timopheevi wheat), 16 accessions of wild Emmer wheat (Triticum dicoccoides Körn.), 14 accessions of wild Timopheevi wheat (T. araraticum Jakubz.), and an accession of common wheat (T. aestivum) were analyzed, using 29 combinations of two restriction enzymes and 20 probes. Based on this result, the genetic distances (d) between all pairs of accessions were estimated. An average d was 0.0189 in the Emmer group and 0.0024 in the Timopheevi group, while that between the groups was 0.0698. Cluster analysis using UPGMA, NJ (neighbor joining) and maximum parsimony method showed clear differentiation of Emmer wheat and Timopheevi wheat. Among the cultivated Emmer wheat T. dicoccum Schübl. showed the largest nucleotide diversity (π=0.0180) which was close to that (0.0186) in the wild ancestral species, T. dicoccoides. All the cultivated species, except for T. dicoccum and T. paleocolchicum Men., were grouped into a distinct cluster in the phylogenetic trees. All but one accessions of T. dicoccoides were grouped in another. The large genetic diversity in T. dicoccum, the non-free threshing species, supports the archeological evidence that T. dicoccum was the earliest domesticated tetraploid wheat.
Two Japanese sugar beet line with incomplete monogermity, TK-80-2BR2mm-CMS and its maintainer TK-80-2BR 2mm-O, were analyzed with a probe linked with a major gene of monogermity, M-m, for restriction fragment length polymorphism (RFLP). The relationship between monogermity and the RFLP pattern was suggested, although the ambiguous phenotypes were sometimes observed.
A gene (designated ldcC) mapped at 4.6 min on the Escherichia coli chromosome codes for a protein of 713 amino acids (aa) that shows strong similarities in both size and amino-acid sequence (69% identical residues and 85% conserved residues) to lysine decarboxylase (LDC) from E. coli (CadA, acid-inducible LDC, 715 aa) or from Hafnia alvei (739 aa). A pUC18 derivative carrying the ldcC gene conferred high LDC activities on an E. coli strain devoid of the functional cadA gene, even when the bacteria were grown under non-inducing conditions at physiological pH. Thus, the gene encodes another lysine decarboxylase, probably a constitutively expressed enzyme, the presence of which was suggested from the previous observations that low LDC activities were detectable in cadA- mutant and non-induced wild-type cells.