Molecular characterization and expression patterns of Spodoptera litura heat shock protein 70/90, and their response to zinc stress

Heat shock proteins (hsps) are highly evolutionarily conserved, whose expressions are altered with varying degrees in response to stress factors. Here, hsp70 and hsp90 cDNA were cloned from Spodoptera litura, and two hsps comprised corresponding family protein sequences, signature sequences and EEVD motif. They showed high homology to their counterparts in other species, and the phylogenetic analysis of hsp90 was consistent with the known insect classification. The hsp70/90 transcripts were present in S. litura midgut, cuticle and fat body, of which the highest levels of both were detected in fat body. The expression levels of both were different during four life stages, and the lowest and highest levels were detected in fifth instar larvae and adults, respectively. The hsp70 expression was induced significantly after the insects were exposed to 150 mg Zn/kg, but the down-regulation in other treatments showed significantly negative correlation with Zn accumulations in the body. The hsp90 expression was induced in all treated pupae and 150–450 mg Zn/kg treated larvae, while inhibited effects were observed in larvae exposed to 600–750 mg Zn/kg. Our results showed the induced response of S. litura hsp90 to Zn was more sensitive than hsp70, whereas inhibited response of hsp70 was much stronger than hsp90.