Journal
PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY
Volume 188, Issue -, Pages -Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.pestbp.2022.105269
Keywords
Cry1Ac resistance; Serpin; Midgut protease; Protease activity; Helicoverpa armigera
Categories
Funding
- Agriculture Research System of China
- [CARS -15-20]
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Up-regulation of serpin gene inhibits trypsin and chymotrypsin activities, leading to reduced activation of protoxins and insect resistance to Bt. The LF30 resistant strain exhibits higher relative expression of serpin-e gene compared to the susceptible strain.
Insect resistance to Bacillus thuringiensis (Bt) is a critical limiting factor for applying the Bt crops. Some studies indicated that decreased protoxin activation because of lower enzymatic activities of trypsin and chymotrypsin and increased expression of serpin might involve in Bt resistance. Our previous study identified an endogenous serpin could inhibit the midgut proteases to activate Cry1Ac and reduce the insecticide activity to Helicoverpa armigera. We hypothesis that up-regulated serpin involve in resistance via inhibiting enzymatic activities of trypsin and chymotrypsin to decrease protoxin activation. Herein, we found the serpin-e gene relative expression in midgut was significantly higher in the LF30 resistant strain than that in the susceptible strain during all developmental stages. Importantly, RNAi-mediated silencing of serpin-e gene expression caused 4.46-fold mortality changes in LF30 strain, but the trypsin and chymotrypsin proteases activities were only changed 0.79-fold and 2.22-fold. In addition, although proteases activities were significantly lower in LF30 strain than that in the susceptible strain, the resistance ratios of LF30 to Cry1Ac protoxin and to activated Cry1Ac toxin were no difference. The results indicated serpins caused insect resistance to Cry1Ac protoxins partly through inhibiting the trypsin and chymotrypsin proteases activities, but it also existed other mechanisms in LF30.
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