Successively expressed cuticular protein genes at the prepupal stage in wing discs of Bombyx mori

Abstract

BackgroundWe classified cuticular protein genes expressed at prepupal stage in wing discs of Bombyx mori into six groups according to their developmental expression and ecdysone responsiveness. Their expression pattern is suggested to be regulated by ecdysone-responsive transcription factors, whose transcripts showed resemblance with those of cuticular protein gene expression.ResultGroup1 and Group2 CP genes showed peak expression at stage W2. Group3 CP genes showed high expression at stage W3E and W3L and were upregulated by 20E addition, showing a peak 12 h after 20E pulse treatment. Group4 CP gene transcripts started expression from stage V5 and peaked at stage W3L. Some genes showed significant increase 4 or 6 h after 20E addition and were induced 6 h and showed a peak 18 h after the 20E pulse treatment. Group5 CP gene transcripts peaked at the same stage W3L. Some Group5 genes showed significant increase 6 h after the 20E addition, while others were not induced by the 20E addition. These different sub-groups showed different expression profiles in the feeding stage. Transcripts of this group genes were induced 12 h and showed a peak 18 h after the 20E pulse treatment. Group6 CP genes peaked at the stage P0, were not induced by the 20E addition, and showed a peak 24 h after the 20E pulse treatment. Group3, 4, 5, and 6 CP genes are suggested to be regulated by BHR4, BR-C, E74A, and βFTZ-F1, respectively. ERTFs showed different responsiveness to 20E concentration. BR-C was most and E74A was least insensitive. The addition of cycloheximide inhibited BR-C, E74A, and βFTZ-F1 expression depending on the length of treatment after ecdysone pulse treatment, which suggests that BHR4 induced BR-C, E74A, and βFTZ-F1.ConclusionExpression patterns of CPs were determined by the ecdysone-responsiveness and the related ERTFs expressed in the prepupal stage in B. mori wing discs.