Laboratory of Creative Science for Insect Industries, Kyushu University Graduate School of Bioresource and Bioenvironmental Sciences, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan.
Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Sciences, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan.
Insect Biochem Mol Biol. 2020 Nov;126:103458. doi: 10.1016/j.ibmb.2020.103458. Epub 2020 Aug 27.
p-oily (op) is a novel mutant of Bombyx mori exhibiting translucent larval integument and male infertility. Elucidation of the causative gene of the op mutant will help understand the genetic mechanism underlying larval integument coloration and male fertility. Using polymorphisms between B. mori and B. mandarina, the op locus was narrowed down to a 375-kb region. Using RNA-seq analysis, we found that op mutants have a frameshift mutation in the KWMTBOMO13770 gene located in the 375-kb region. A database search indicated that this gene is the human cytosolic 5'-nucleotidase II gene (cN-II) homolog in Bombyx, which mediates the conversion of inosine monophosphate (IMP) to inosine, a precursor of uric acid. CRISPR/Cas9-mediated knockout mutants of the Bm-cN-II gene showed translucent integuments, and there appeared translucent larvae in the crosses between knockout moths and +/op moths. Moreover, the translucent phenotype of, and decreased uric acid content in the larval integument caused by the mutations in the Bm-cN-II gene were rescued by oral administration of inosine. These results indicated that the Bm-cN-II gene is responsible for the op phenotype and that the molecular function of the Bm-cN-II gene is the conversion of IMP to inosine. We also discuss the genetic relationship between the Bm-cN-II gene and male fertility.
p-油性(op)是一种新型的家蚕突变体，表现为半透明的幼虫表皮和雄性不育。阐明 op 突变体的致病基因将有助于理解幼虫表皮颜色和雄性生育力的遗传机制。利用家蚕和中华蜜蜂之间的多态性，将 op 基因座缩小到 375kb 区域。通过 RNA-seq 分析，我们发现 op 突变体在位于 375kb 区域的 KWMTBOMO13770 基因中存在移码突变。数据库搜索表明，该基因是家蚕中人类胞质 5'-核苷酸酶 II 基因(cN-II)的同源物，介导肌苷单磷酸(IMP)转化为尿酸的前体肌苷。CRISPR/Cas9 介导的 Bm-cN-II 基因敲除突变体表现出半透明的表皮，并且在敲除蛾和+/op 蛾之间的杂交中出现半透明的幼虫。此外，Bm-cN-II 基因突变导致的幼虫表皮中尿酸含量降低和半透明表型可通过肌苷口服给药得到挽救。这些结果表明，Bm-cN-II 基因负责 op 表型，Bm-cN-II 基因的分子功能是将 IMP 转化为肌苷。我们还讨论了 Bm-cN-II 基因与雄性生育力之间的遗传关系。
