Positional cloning of a gene responsible for the cts mutation of the silkworm, Bombyx mori

• Published in: Genome Vol. 55; no. 7; pp. 493 - 504
• Main Authors: Ito, Katsuhiko, Kidokoro, Kurako, Katsuma, Susumu, Shimada, Toru, Yamamoto, Kimiko, Mita, Kazuei, Kadono-Okuda, Keiko
• Format: Journal Article
• Language: English
• Published: Canada NRC Research Press 01.07.2012; Canadian Science Publishing NRC Research Press
• Subjects: Amino Acid Sequence; Amino acids; Animals; Base Sequence; Bombyx - genetics; Bombyx - metabolism; Bombyx mori; Butterflies & moths; chromosome 16; Chromosomes; clonage positionnel; Cloning; Cloning, Organism; cts mutant; Cuticles; DNA testing; Evolutionary genetics; Gene expression; Gene mutations; Genes, Insect; Genetic aspects; Genotype & phenotype; Identification and classification; Insect Proteins - genetics; Insect Proteins - metabolism; Integument; major facilitator superfamily (MFS); Melanin; Membrane proteins; Membrane structure; MFS protein; Molecular Sequence Data; Molting; mRNA; mutant cts; Mutation; mélanine; Phenotype; Polymerase chain reaction; positional cloning; Protein structure; RNA, Messenger - metabolism; Sequence Alignment; Sequence Analysis, DNA; Silkworms; superfamille MFS; Transmembrane domains; Japan
• ISSN: 1480-3321; 0831-2796; 1480-3321
• DOI: 10.1139/g2012-033

The larval head cuticle and anal plates of the silkworm mutant cheek and tail spot (cts) have chocolate-colored spots, unlike the entirely white appearance of the wild-type (WT) strain. We report the identification and characterization of the gene responsible for the cts mutation. Positional cloning revealed a cts candidate on chromosome 16, designated BmMFS, based on the high similarity of the deduced amino acid sequence between the candidate gene from the WT strain and the major facilitator superfamily (MFS) protein. BmMFS likely encodes a membrane protein with 11 putative transmembrane domains, while the putative structure deduced from the cts-type allele possesses only 10-pass transmembrane domains owing to a deletion in its coding region. Quantitative RT–PCR analysis showed that BmMFS mRNA was strongly expressed in the integument of the head and tail, where the cts phenotype is observed; expression markedly increased at the molting and newly ecdysed stages. These results indicate that the novel BmMFS gene is cts and the membrane structure of its protein accounts for the cts phenotype. These expression profiles and the cts phenotype are quite similar to those of melanin-related genes, such as Bmyellow-e and Bm-iAANAT, suggesting that BmMFS is involved in the melanin synthesis pathway.