[Fine mapping of the mutant gene varnished eye in the silkworm]

The varnished eye (ve) mutant is one of the rare natural recessive mutants related to the abnormal phenotypes in the compound eye of silkworm (Bombyx mori). The compound eyes of the ve adults are smaller and glossier than those of the wild-type Dazao (Dz) and many tumor-like bumps are present on their surface; their small eyes are irregularly arranged and are smaller and fewer than those of the wild-type. The mutant gene ve has been located at the 32.2 locus of chromosome 6 in the classic genetic linkage map. However, it still remains unknown about the mechanism responsible for the mutant. In this study, we got a BC1 generation using male F1 (ve×Dz) with female ve for fine mapping of this mutant gene. The results showed that ve was located in a region between SNP3 and SNP6. The physical distance is approximately 1.2 Mb in the low density linkage map. By constructing a high-density map using 1563 BC1 individuals, the ve mutant gene was further mapped into a region between the SNP5 and SNP61. The physical region is about 221.8 kb and contains six potential genes but no specific mutations were found in the CDSs of these candidate genes. RT-PCR showed that the expression of BGIBMGA013642 was decreased obviously compared with that in wild type, suggesting it might be a key candidate gene for further studying the ve mutant.