Suppression of Calcineurin Enhances the Toxicity of Cry1Ac to Helicoverpa armigera.

Jizhen Wei,Shuo Yang,Qingbo Tang,Shiheng An,Xiaoguang Liu,Mengfang Du,Shaokai Liu,Xue Yao,Junjuan Cen,Shuai Zhou

doi:10.3389/fmicb.2021.634619

Abstract

Insect resistance to Bacillus thuringiensis (Bt) insecticidal proteins has rapidly evolved with the expansion of the planting area of transgenic Bt crops. Pyramiding RNA interference (RNAi) and Bt in crops is urgently needed to counter the rapid increase in pest resistance. The ideal “pyramid” strategy simultaneously targets different action pathways that exert synergetic effects on each other. Here, we identified a dephosphatase, namely, Helicoverpa armigera calcineurin (HaCAN), which might enhance the insecticidal activity of Cry1Ac against Helicoverpa armigera by regulating immune gene expression via dephosphatase activity, but not by acting as a receptor. Notably, blocking enzyme activity or knocking down endogenous HaCAN significantly promoted the enhancement in Cry1Ac toxicity to insect larvae and cells. Correspondingly, the increase in HaCAN activity reduced the cytotoxicity of Cry1Ac as shown by the heterologous expression of HaCAN. Our results provide a probable that HaCAN is an important candidate gene for pyramiding RNAi and Cry1Ac crops to control cotton bollworm.

Highlights

Transgenic Bacillus thuringiensis (Bt) Cry1Ac crops have provided significantly economic and environmental benefits since they were first introduced in 1996 for the control of major Lepidopteran pests (Mendelsohn et al, 2003; Hutchison et al, 2010; Tabashnik et al, 2010; Naranjo, 2011; Lu et al, 2012; Downes et al, 2017)
The results demonstrated that the cells transfected with Helicoverpa armigera calcineurin (HaCAN) double-stranded RNA (dsRNA) showed significantly higher mortality than those transfected with enhanced green fluorescent protein (EGFP) dsRNA (P = 0.0349) (Figure 6C)
Four main types of receptors, including cadherin, aminopeptidase, alkaline phosphatase, and ATP-binding cassette (ABC) transporters, have been identified (Wei et al, 2019c) on the basis of their capabilities to bind with Bt proteins and their involvement in Bt resistance

Summary

INTRODUCTION

Transgenic Bacillus thuringiensis (Bt) Cry1Ac crops have provided significantly economic and environmental benefits since they were first introduced in 1996 for the control of major Lepidopteran pests (Mendelsohn et al, 2003; Hutchison et al, 2010; Tabashnik et al, 2010; Naranjo, 2011; Lu et al, 2012; Downes et al, 2017). The simultaneous expression of multiple Bt toxins in crops has been considered as a principal strategy for insecticide resistance management to delay pest adaptation (Brévault et al, 2013). Immune genes have attracted the attention of researchers, and are considered as candidate genes for the RNAi + Bt for insect control strategy Some immune genes, such as p38, jnk, C-type lectins, and HSP70 that participate in insect defense and immune responses, are reportedly involved in Bt toxicity (Huffman et al, 2004; Chai et al, 2008; Cancino-Rodezno et al, 2010; Oppert et al, 2012; Xia et al, 2016; Portugal et al, 2017). Our results provided a probable that HaCAN is an important candidate gene for pyramiding RNAi and Cry1Ac in crops to control cotton bollworm

MATERIALS AND METHODS

DISCUSSION

Findings

DATA AVAILABILITY STATEMENT