Expression analysis of several antiviral related genes to BmNPV in different resistant strains of silkworm, Bombyx mori

Abstract

Bombyx mori L. (Lepidoptera: Bombycidae) nucleopolyhedrovirus (BmNPV) is a highly pathogenic virus in the sericultural industry, often causing severe damage leading to large economic losses. The immune mechanisms of B. mori against this virus remain obscure. Previous studies had demonstrated Bmlipase-1, BmNox and Bmserine protease-2 showing antiviral activity in vitro, but data on the transcription levels of these proteins in different resistant strains were not reported. In order to determine the resistance level of the four different strains (P50, A35, A40, A53) and gain a better understanding of the mechanism of resistance to BmNPV in B. mori, the relative expression level of the genes coding the three antiviral proteins in larval haemolymph and midgut of different B. mori strains resistant to BmNPV was determined. The results showed that these genes expressed significantly higher in the resistant strains compared to the susceptible strain, and the differential expression levels were consistent with the LC50 values in different strains. The transcription level of the target genes almost all up-regulated in the larvae midgut and down-regulated in the haemolymph. The results indicate the correlation of these genes to BmNPV resistance in B. mori.

Keywords: BmNox; Bmlipase-1; Bmserine protease-2; Bombyx mori nucleopolyhedrovirus; expression analysis.

Figure 1.

Relative expression level of antiviral genes in Bombyx mori hemolymph and midgut of different strains. A, B, and C refer to relative expression levels of Bmlipase-1 , BmNox and Bmserine protease-2 in hemolymph, respectively. D, E, and F refer to the same, but in the midgut. The bars from left to right indicate P50, A40, A53, and A35 respectively. *, P < 0.05; **, P < 0.01 (ANOVA and LSD aposteriori test). Error bars ± SEM. High quality figures are available online.