Abstract: 【Aim】 This study aims to investigate the effect of short-time heat shock on the resistance of the silkworm, Bombyx mori to nucleopolyhedrovirus, so as to provide references for further study on the antiviral immune mechanism of the silkworm in response to heat shock. 【Methods】 The 5th instar larvae of B. mori were exposed to 42℃ for 15 min, and then fed with B. mori nucleopolyhedrovirus (BmNPV) (5.4×10⁶ PIBs/individual). All the tested larvae were reared as usual. The transcription levels of seven major antimicrobial genes (BmcecD, Bmmor, Bmglve2, BmdefeB, Bmatta1, Bmenbo2 and Bmlebo3) and six heat shock protein genes (Bmhsp90, Bmhsp70, Bmhsp40, Bmhsp19.9, Bmhsp21.4 and Bmhsp25.4) in the midgut of the 5th instar larvae after heat-shock treatment were analyzed by quantitative real-time PCR. The amino acid sequences of all BmHSPs were also phylogenetically analyzed using MEGA 5.0. 【Results】 Short-time heat shock significantly increased the survival rate of the BmNPV-infected 5th instar larvae of B. mori, as compared with the nonheat shock group. Quantitative real-time PCR results showed that the expression levels of Bmglve2 and Bmhsp25.4 were significantly up-regulated in the midgut of the BmNPV-infected 5th instar larvae of B. mori exposed to heat shock in comparison with the non-heat shock groups. The phylogenetic analysis showed that BmHSP25.4 was special in evolution, and individually classified into the same cluster with large HSPs (BmHSP90, BmHSP70 and BmHSP40). 【Conclusion】 Short-time heat shock before BmNPV feeding can enhance the resistance of B. mori to BmNPV. Bmhsp25.4 and Bmglve2 may relatively function in the immunity induction of B. mori against BmNPV through heat shock response.

Key words:  Bombyx mori, heat shock, BmNPV, antimicrobial peptide, heat shock protein, mRNA expression level