Abstract
RNA interference (RNAi) is a promising new technology for corn rootworm control. This paper presents the discovery of new gene targets - dvssj1 and dvssj2, in western corn rootworm (WCR). Dvssj1 and dvssj2 are orthologs of the Drosophila genes snakeskin (ssk) and mesh, respectively. These genes encode membrane proteins associated with smooth septate junctions (SSJ) which are required for intestinal barrier function. Based on bioinformatics analysis, dvssj1 appears to be an arthropod-specific gene. Diet based insect feeding assays using double-stranded RNA (dsRNA) targeting dvssj1 and dvssj2 demonstrate targeted mRNA suppression, larval growth inhibition, and mortality. In RNAi treated WCR, injury to the midgut was manifested by “blebbing” of the midgut epithelium into the gut lumen. Ultrastructural examination of midgut epithelial cells revealed apoptosis and regenerative activities. Transgenic plants expressing dsRNA targeting dvssj1 show insecticidal activity and significant plant protection from WCR damage. The data indicate that dvssj1 and dvssj2 are effective gene targets for the control of WCR using RNAi technology, by apparent suppression of production of their respective smooth septate junction membrane proteins located within the intestinal lining, leading to growth inhibition and mortality.
Highlights
The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is one of the most devastating pests in maize that can cause economic losses exceeding $1 billion annually in the U.S.A.1
septate junctions (SJ) are subdivided into several morphological types that vary among different animal phyla and different types of SJ have been described in different epithelia within an individual in several phyla[25]
In ssk-and mesh-deficient midguts, Lethal (2) giant larvae (Lgl), Cora and Fasciclin III (FasIII) are mislocalized but Discs large (Dlg) is not[31]. The functions of these pleated SJ (PSJ) proteins in smooth SJ (SSJ) remain uncertain since Dlg, Lgl, Cora and FasIII are not required for the SSJ localization of MESH and SSK, and are dispensable for SSJ formation[28]
Summary
The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is one of the most devastating pests in maize that can cause economic losses exceeding $1 billion annually in the U.S.A.1. Many genes have been reported to be potential targets in WCR following the provision of dsRNA in diet bioassay[13,15,16] and demonstrate that WCR is sensitive to orally delivered dsRNA, providing a new management approach for this important pest[17,18]. In ssk-and mesh-deficient midguts, Lgl, Cora and FasIII are mislocalized but Dlg is not[31] The functions of these PSJ proteins in SSJs remain uncertain since Dlg, Lgl, Cora and FasIII are not required for the SSJ localization of MESH and SSK, and are dispensable for SSJ formation[28]. Ssk and mesh are required for Drosophila development, SSJ formation and midgut paracellular barrier function[30,31]
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