RNA-Seq analysis of Polyrhachis vicina Roger and insights into the heat shock protein 90 and 70 families.

The heat shock protein 90 (Hsp90) and heat shock cognate proteins (Hsc70) have been identified as chaperones of the ecdysone receptor (EcR)/ultraspiracle protein (USP) heterocomplex. However, little is known about the status of Hsp90 and Hsc70 in Polyrhachis vicina Roger. Here, we sequenced the transcriptomes of adult ants in P. vicina for the first time. Clean reads in female, male, and worker ants were annotated into 40,147 transcripts, and 37,488, 28,300, and 33,638 unigenes were assembled in female, male, and worker ants, respectively. According to RPKM, the numbers of differentially expressed genes between female and male ants, between female and worker ants, and between male and worker ants and the common differentially expressed genes were 12,657, 21,630, 15,112 and 3704, respectively. These results reveal that caste differentiation, caste specificity formation, and social divisions of P. vicina ants may be due to gene expression differences. Moreover, PvEcR and PvUSP were also detected as differentially expressed genes in the ants; specifically, PvUSP expression was higher than PvEcR expression in all castes. We speculate that PvUSP may have a role similar to that of juvenile hormone receptor. Four identified PvHsp90 family members and 23 identified PvHsp70 family members were found in the ants, and 2 PvHsp90 genes and 8 PvHsp70 genes were analyzed by qRT-PCR. Among those genes, the expression of 2 PvHsp90 genes and 5 PvHsp70 genes coincided with the expression profiles of PvEcR and PvUSP, which suggest that the characterization of PvHsp90 and PvHsc70 may be as EcR/USP molecular chaperones in P. vicina.