Biomedical subjects

K Yukuhiro

Publications and source records attributed to K Yukuhiro.

4 recordsLinked to original sources

PubMed1999

Structure and expression of tandemly duplicated xanthine dehydrogenase genes of the silkworm (Bombyx mori).

Xanthine dehydrogenase (XDH) is a molybdoenzyme which catalyses oxidation of xanthine and hypoxanthine to uric acid. We isolated genomic clones of silkworm (Bombyx mori) XDH genes (BmXDH1 and BmXDH2). The BmXDH2 gene is located upstream from the BmXDH1 gene and they show a tandemly duplicated structure. Both BmXDH genes were expressed in the fat body and Malpighian tubules, whereas only the BmXDH1 gene was expressed in the midgut. Phylogenetic analysis indicates that BmXDH gene duplication occurred after the divergence of the silkworm and dipteran species. Intron insertion site comparison shows that some introns were lost during insect XDH gene evolution.

Amino Acid Sequence↗

PubMed1997

Preferential codon usage and two types of repetitive motifs in the fibroin gene of the Chinese oak silkworm, Antheraea pernyi.

In this paper we describe the peculiar structures and preferential codon usage found in wild silkworm fibroin genes. We determined a 1350 bp nucleotide sequence from the Chinese oak silkworm, Antheraea pernyi. The deduced amino acid sequence was partitioned into thirteen polyalanine-containing repetitive motifs, which was one of the characteristics of Antheraea fibroins. Eleven of these arrays can be classified into two types of motifs depending on difference in amino acid sequences following polyalanine. Repetitive motifs structurally similar to those of A. pernyi were detected in a homologue of the Japanese oak silkworm, Antheraea yamamai. The most remarkable feature of this study was preferential codon usage, especially seen in alanine synonymous codons within both homologues of Antheraea: isocodon GCA most frequently occurred in alanine isocodons. In contrast, GCU isocodon was the most abundant in Bombyx mori fibroin heavy chain that lacks polyalanine arrays. This result strongly suggests different modes of selective constraint between the two types of fibroin gene. The similar finding that GCA isocodon was most frequent in two dragline silk sequences of the spider, Nephila clavipes, is consistent with our results because of the repetitive polyalanine-containing arrays seen in spider dragline silk.

Amino Acid Sequence↗

PubMed1993

A type of incompatibility between genes and their genetic background inducing decrease in heterozygote viability approximately equal to that of homozygotes, found in a natural population of Drosophila.

In the Osaka population of Drosophila melanogaster, we found an incompatibility between second chromosomes and their genetic backgrounds, where a decrease in the average viability of heterozygotes in the foreign genetic background relative to that of the native one (A'/A = 0.889) was about equal to that in non-lethal homozygotes (C'/C = 0.874). This feature is different from that of the incompatibility found in the Ishigakijima population, where little difference in average viabilities of heterozygotes between the native and foreign backgrounds was found, whereas in mean non-lethal homozygotes viabilities a large decrease was seen. This feature is supposed to be induced by the P-M hybrid dysgenesis, as strong P-transposase activity was shown in this population with the GD sterility test. Although a property similar to that of the Osaka population had been detected in the Katsunuma population, an increased frequency of the lethal-carrying chromosomes had been found in the foreign genetic background relative to the native one, and was not seen in the Osaka population.

Animals↗

PubMed1990

Transposition rates of movable genetic elements in Drosophila melanogaster.

A considerable proportion of visible mutations is reported to be caused by the insertion of mobile genetic elements in Drosophila and other organisms. We estimated transposition rates of some Drosophila mobile elements by using the lines AW and JH in which spontaneous mutations have been accumulated independently for about 400 generations. Occupied sites of the mobile elements were detected by in situ hybridization on the salivary gland chromosomes sampled from 40 AW and 30 JH lines. The rates of insertion and excision of the copia and two copia-like elements, 412 and 17.6, are very low: Insertions occurred at up to 10(-3) per second chromosome per generation (17.6) and excision occurred at about 10(-5) per site per generation (copia and 412). Insertions of the I and hobo elements occurred much more frequently. These estimates are not only important for assessing the actual rate of various types of mutations but also for developing an evolutionary theory of mobile elements themselves.

Animals↗