Identification of Epidermal Chitin Synthaes BmCHSA-2a in Bombyx mori and Its Response to Hormones

In this study, exon 1 (141 bp) and exon 2a (106 bp) of BmCHSA-2a were cloned by using 5'Race, and the mRNA levels of BmCHSA-2a in response to hormones were analyzed by using the primers based on the sequence of exon 2a, which is conservative in insects. The results showed that the expression of BmCHSA-2a was inhibited by ecdysone (20E), but was indirectly induced by juvenile hormone (JH). Promoter activity determination confirmed that the transcription of BmCHSA-2a was inhibited. Further analysis revealed that a lot of BmFTZ-F1 cis-regulation elements existed in the promoter sequence of BmCHSA-2a, and the expression of transcription factor BmFTZ-F1, which belongs to 20E pathway and binds to CRE of BmFTZ-F1 , was inhibited by 20E. The results in this study demonstrate the relationship between hormones and BmCHSA-2a and provide the foundation for further study of possible target gene used for pest control.