Body Shape and Coloration of Silkworm Larvae Are Influenced by a Novel Cuticular Protein

• Published in: Genetics (Austin) 2017-11, Vol.207 (3), p.1053-1066
• Main Authors: Xiong, Gao, Tong, Xiaoling, Gai, Tingting, Li, Chunlin, Qiao, Liang, Monteiro, Antónia, Hu, Hai, Han, Minjin, Ding, Xin, Wu, Songyuan, Xiang, Zhonghuai, Lu, Cheng, Dai, Fangyin
• Format: Article
• Language: English
• Subjects: Amino acid sequence; Animals; Apoptosis; Bamboo; Biological evolution; Body Size; Bombyx - anatomy & histology; Bombyx - genetics; Bombyx - metabolism; Caterpillars; Cloning; Color; Coloration; CRISPR; Cuticles; Domestication; Epidermis; Gene expression; Gene mapping; Genetics; Genomics; Insect Proteins - genetics; Insect Proteins - metabolism; Insects; Investigations; Larva - anatomy & histology; Larva - metabolism; Larvae; Loss of Function Mutation; Mutation; Pigmentation; Proteins; RNA-mediated interference; Skin Pigmentation; Wnt1 Protein - genetics; Wnt1 Protein - metabolism
• ISSN: 1943-2631; 0016-6731; 1943-2631
• DOI: 10.1534/genetics.117.300300

The genetic basis of body shape and coloration patterns on caterpillars is often assumed to be regulated separately, but it is possible that common molecules affect both types of trait simultaneously. Here we examine the genetic basis of a spontaneous cuticle defect in silkworm, where larvae exhibit a bamboo-like body shape and decreased pigmentation. We performed linkage mapping and mutation screening to determine the gene product that affects body shape and coloration simultaneously. In these mutant larvae we identified a null mutation in , a gene encoding a cuticular protein with low complexity sequence. Spatiotemporal expression analyses showed that is expressed in the larval epidermis postecdysis. RNAi-mediated knockdown and CRISPR/Cas9-mediated knockout of produced the abnormal body shape and the inhibited pigment typical of the mutant phenotype. In addition, our results showed that may be involved in the synthesis of endocuticle and its disruption-induced apoptosis of epidermal cells that accompanied the reduced expression of R&R-type larval cuticle protein genes and pigmentation gene Strikingly, , a fast-evolving gene, has evolved a new function responsible for the assembly of silkworm larval cuticle and has evolved to be an indispensable factor maintaining the larval body shape and its coloration pattern. This is the first study to identify a molecule whose pleiotropic function affects the development of body shape and color patterns in insect larvae.