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Fujii T, Kakino K, Fukumori H, Hino M, Lee JM, Kusakabe T, Banno Y. Non-molting dwarf (nm-d) as a mutant of Bombyx mori with a defect in purine synthesis. Insect Biochem Mol Biol 2021; 138:103636. [PMID: 34478812 DOI: 10.1016/j.ibmb.2021.103636] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 07/21/2021] [Accepted: 08/10/2021] [Indexed: 06/13/2023]
Abstract
There are several known non-molting mutations of the silkworm, Bombyx mori, including non-molting dwarf (nm-d). Larvae with this mutation hatch normally and start eating leaves, but die before the completion of the first ecdysis. Genetic analysis of the nm-d mutation would contribute to the isolation of essential genes for the larval development of lepidopteran insects. To identify the causative gene of the nm-d locus, we conducted RNA-seq based rough mapping. Using two sets of RNA-seq data, one from a pooled sample of normal larvae, and one from a pooled sample of nm-d larvae, the nm-d locus was narrowed to a 500 kb region. Among the genes located in this region, a nm-d-specific exon loss was identified in the Bombyx homolog of the ATIC (5-aminoimidazole-4-carboxamide ribonucleotide transformylase/Inosine 5'-monophosphate cyclohydrolase) (BmATIC) gene, which catalyzes the final two steps of the de novo purine biosynthetic pathway in mammals. PCR and subsequent sequencing analysis revealed that a region containing exon 9 of the BmATIC gene is deleted in the nm-d larvae. A knockout allele of the BmATIC gene (BmATICKO), that was generated using the CRISPR/Cas9 system, revealed that first instar knockout larvae died while exhibiting the dark brown larval body that is a typical feature of mutants that lack uric acid in the integument. Lethal larvae resulted from crosses between +/BmATICKO moths. The uric acid content in the whole-body of the first instar was drastically reduced in the nm-d larvae compared to normal larvae. These results indicated that the BmATIC gene is responsible for the nm-d phenotype, and that nm-d larvae have a defect in purine biosynthesis, including uric acid. We also discuss the possibility that the BmATIC mRNA is maternally transmitted to eggs. Our results indicated that RNA-seq based mapping using pooled samples is a practical method for the identification of the causative genes of lethal mutations.
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Affiliation(s)
- Tsuguru Fujii
- Laboratory of Creative Science for Insect Industries, Kyushu University Graduate School of Bioresource and Bioenvironmental Sciences, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan.
| | - Kohei Kakino
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Sciences, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Hisayoshi Fukumori
- Laboratory of Silkworm Genetic Resources, Institute of Genetic Resources, Kyushu University Graduate School of BioResources and Bioenvironmental Science, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Masato Hino
- Laboratory of Sanitary Entomology, Faculty of Agriculture, Kyushu University, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Jae Man Lee
- Laboratory of Creative Science for Insect Industries, Kyushu University Graduate School of Bioresource and Bioenvironmental Sciences, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Takahiro Kusakabe
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Sciences, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Yutaka Banno
- Laboratory of Silkworm Genetic Resources, Institute of Genetic Resources, Kyushu University Graduate School of BioResources and Bioenvironmental Science, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan
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