Biotic and abiotic stress induces the expression of Hsp70/90 organizing protein gene in silkworm, Bombyx mori.

The heat shock 70/90 organizing protein is one of the stress-induced proteins and has extensively been studied in mammals. It mediates the interaction of Hsp70 and Hsp 90 as cochaperone and also implicated in infection-related processes. However, the biological role of heat shock 70/90 organizing protein in silkworm remains to elucidate. Herein, we identified and molecularly characterized a heat shock 70/90 organizing protein homolog gene from the silkworm, Bombyx mori (Hereafter BmHop). The identified BmHop fragment contained a 1626 base pair (bp) open reading frame (ORF), encoding a polypeptide of 541 amino acid residues. The deduced amino acid sequence had a molecular weight of 16.13 kDa and comprised of three tetratricopeptides repeated motif domains (TPR1, TPR2A, and TPR2B) as described in other Hops. Quantitative RT-PCR analysis revealed that BmHop ubiquitously transcribed in various tissues and developmental stages. Thermal stress strongly influenced the transcription levels of BmHop in both the fat body and hemocyte. Additionally, we analyzed the expression patterns of this gene after bacterial treatment, which strongly induced the gene's expression in the immune tissues. Overall, our data suggest that BmHop expression is influenced by both thermal stress and microbial challenge, and possibly in other insects.