Characteristic expression of three heat shock-responsive genes during larval diapause in the bamboo borer Omphisa fuscidentalis.

Three heat shock-responsive genes, Ofhsp70, Ofhsc70, and Ofhsp90, were identified in Omphisa fuscidentalis. These genes encode proteins with molecular weights of 70, 72, and 82 kDa, respectively, and were upregulated during heat shock. Ofhsp70 was expressed actively in the pre-diapause period, but its expression was low during diapause. While Ofhsc70 expression was low during pre-diapause and the first half of diapause, its expression increased greatly in the second half before diapause termination. In contrast, Ofhsp90 expression decreased by half during the transition to diapause and conspicuously decreased during late diapause. The results suggest that Ofhsp90 is associated with the maintenance of diapause and Ofhsc70 with the termination of diapause, whereas the expression of Ofhsp70 is unrelated to diapause. The insect molting hormone 20-hydroxyecdysone (20E) and juvenile hormone analog (JHA) caused increases in the mRNA expression of Ofhsc70, but not Ofhsp70 or Ofhsp90, in diapausing larvae. These transcriptional responses to 20E are consistent with the changes in ecdysteroid titer in the hemolymph relative to gene expression during diapause.