Transcriptional Profiling Shows that BHR4 and E74A Are the Regulators of CPH33 and CPH34 Gene Expression
Authors: Md. Saheb Ali, Md. Tarek Hossain, Birendra Mishra
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Our endeavor is to identify with the basic system that regulates sequentially expressed cuticular protein genes around pupation. The present study was conducted to clarify the regulatory mechanism of a cuticular protein gene of Bombyx mori, BmorCPH33, whose expression in wing discs was atypical from others and peaked at wandering stage day 3 (W3) early to W3 late stage when ecdysteroid began to decrease before pupation. We compared the expression profiles of BmorCPH33 and BmorCPH34 to clarify their regulatory mechanism. Developmental profile of BmorCPH33 resembled BHR4, therefore we compared the expression profile of this transcription factor with that of BmorCPH33. BHR4 transcripts increased by the addition of 20E. BmorCPH33 expression was also induced by the addition of 20E, which was inhibited by cycloheximide. Both BHR4 and BmorCPH33 transcripts were induced after 6h 20E removal after exposure to 20E, but they were inhibited by the addition of cycloheximide. Thus, the results showed relatedness of BmorCPH33 and BHR4. Through this culture system it is suggested that BHR4 is a regulator of insect metamorphosis. The expression profiles of BmorCPH34 resembled those of E74A, therefore we compared the expression profiles of this transcription factor with BmorCPH34. BmorCPH34, E74A transcripts were up-regulated by the 20E pulse treatment. The results showed the relatedness of BmorCPH34 and E74A. The present findings showed different regulation of cuticular protein genes by ecdysone-responsive transcription factors at the pre-pupal stage of wing discs of B. mori.