Journal of Insect Biotechnology and Sericology
Online ISSN : 1884-7978
Print ISSN : 1346-8073
ISSN-L : 1346-8073
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  • Akihiro Wada, Hiroki Sakaguchi, Masanobu Itoh, Kenji Yukuhiro, Yasuko ...
    2019 Volume 88 Issue 3 Pages 3_049-3_054
    Published: 2019
    Released: December 16, 2019

     Current populations of the wild mulberry silkworm, Bombyx mandarina Moore (Lepidoptera: Bombycidae), inhabiting Japan were previously shown to be divided in four groups by a genetic variation in the mitochondrial cytochrome c oxidase subunit I (COI) gene. According to the geographic divisions, their phylogeographic natures were suggested to be involved in those of the mulberry trees. This hypothesis was based on a data set of many samples collected from 2008 to 2016, although it is not obvious whether such a compilation is appropriate to depict a snapshot of genetic variation of B. mandarina populations in a wide range. For understanding spatial and temporal stability of the mitochondrial DNA (mtDNA) haplotypes in those populations, we examined the frequencies of COI haplotypes in current populations. The geographic boundary between the genetic groups 1 and 2 was similarly detected in Kansai as previously found. In addition, the frequency of COI haplotypes were shown to be inherited stably for at least seven generations in a population, despite of neighbor populations carrying quite different haplotypes. These results support the previous picture of the geographic distribution pattern of COI haplotypes in B. mandarina in Japan.

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  • Sumiharu Nagaoka, Nao Tani, Miki Sakakura, Chikayo Kimura
    2019 Volume 88 Issue 3 Pages 3_055-3_064
    Published: 2019
    Released: December 16, 2019

     Fructose 1, 6-bisphosphate aldolase (EC 4.1. 2.13.; ALD) is a key enzyme in cellular carbon–carbon bond formation or breakage, and plays roles in both glycolysis and gluconeogenesis in the cytoplasm of higher organisms. Here we report the identification, expression analysis and functional characterization of ALD genes from the silkworm, Bombyx mori. In contrast to the single gene in Drosophila melanogaster, the lepidopteran silkworm genome was found to possess two ALD genes, BmALD1 and BmALD2. The phylogenetic tree of the arthropod ALD clearly showed that insect ALDs can be classified into two classes, the typical ALDs present in various insect species (group I; including BmALD1) and the lepidopteran-specific ALDs (group II; including BmALD2). Among the eight larval organs examined, BmALD1 mRNA showed the highest expression in muscle, followed by the head, and BmALD2 was widely expressed except in the head and mid-gut; the highest expression was observed in muscle. The homo-tetramer enzymes of BmALD1 and BmALD2 were expressed as recombinant proteins in Escherichia coli (rBmALD1 and rBmALD2, respectively), from which they were purified to homogeneity. Two types of ALD could be distinguished by the activity ratio towards the two substrates fructose 1, 6-bisphosphate (FBP)/fructose 1-phosphate (F1P) and the effect of pH on the activities, and these properties of rBmALD1 resembled those of Drosophila ALD. The results of this study show the indispensable role of B. mori ALDs in the control of tissue-specific sugar-phosphate metabolisms, and will provide a basis for studying the evolution of insect ALD genes.

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  • Hiroki Yamada, Nao Niimi, Masanobu Itoh, Yutaka Inoue, Yasuko Kato
    2019 Volume 88 Issue 3 Pages 3_065-3_073
    Published: 2019
    Released: December 16, 2019

     Pax genes are crucial for eye development in various organisms including Drosophila melanogaster. Eye gone (eyg) is one of the Pax genes and is involved in head and eye development in Drosophila. Eye missing (eym) is known as a recessive mutation that shows an eye-loss phenotype. Although the responsible gene was mapped as 3-67.9 on the recombination map, the gene and the molecular mechanism inducing its phenotype have not been clarified. Here we show that eym1 has a nucleotide replacement in the eyg intron and that much of the CD enhancer required for the eyg expression in the second instar larvae is deleted. The eyg mRNA expression is drastically reduced in the second instar eym1 mutants and eyg overexpression compensates for the eym eye-loss phenotype. In eym eye discs, cell proliferation and neural cell differentiation is inhibited. The wg protein is misexpressed in the dorsoventral compartment boundary in eym1 eye discs. Taking these data together, we demonstrate that eym is a new allele of eyg, thus eygeym, and the reduction of eyg transcription in the second instar larvae causes an eye-loss phenotype via the deletion of its enhancer.

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