ABSTRACT
Western corn rootworm (Diabrotica virgifera virgifera) is a serious agricultural pest known for its high adaptability to various management strategies, giving rise to a continual need for new control options. Transgenic maize expressing insecticidal RNAs represents a novel mode of action for rootworm management that is dependent on the RNA interference (RNAi) pathways of the insect for efficacy. Preliminary evidence suggests that western corn rootworm could develop broad resistance to all insecticidal RNAs through changes in RNAi pathway genes; however, the likelihood of field-evolved resistance occurring through this mechanism remains unclear. In the current study, eight key genes involved in facilitating interference in the microRNA and small interfering RNA pathways were targeted for knockdown in order to evaluate impact on fitness of western corn rootworm. These genes include drosha, dicer-1, dicer-2, pasha, loquacious, r2d2, argonaute 1, and argonaute 2. Depletion of targeted transcripts in rootworm larvae led to changes in microRNA expression, decreased ability to pupate, reduced adult beetle emergence, and diminished reproductive capacity. The observed effects do not support evolution of resistance through changes in expression of these eight genes due to reduced insect fitness.
Subject(s)
RNA Interference , RNA, Double-Stranded/genetics , Zea mays/genetics , Animals , Coleoptera/growth & development , Coleoptera/physiology , Gene Expression Regulation , Insect Proteins/antagonists & inhibitors , Insect Proteins/genetics , Insect Proteins/metabolism , Larva/growth & development , Larva/metabolism , MicroRNAs/antagonists & inhibitors , MicroRNAs/genetics , MicroRNAs/metabolism , Plant Roots/genetics , Plant Roots/metabolism , Plant Roots/parasitology , Plants, Genetically Modified/genetics , Plants, Genetically Modified/metabolism , Plants, Genetically Modified/parasitology , RNA, Double-Stranded/metabolism , RNA, Small Interfering/antagonists & inhibitors , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , Ribonuclease III/antagonists & inhibitors , Ribonuclease III/genetics , Ribonuclease III/metabolism , Zea mays/metabolism , Zea mays/parasitologyABSTRACT
RNA interference (RNAi) in transgenic maize has recently emerged as an alternative mode of action for western corn rootworm (Diabrotica virgifera virgifera) control which can be combined with protein-based rootworm control options for improved root protection and resistance management. Currently, transgenic RNAi-based control has focused on suppression of genes that when silenced lead to larval mortality. We investigated control of western corn rootworm reproduction through RNAi by targeting two reproductive genes, dvvgr and dvbol, with the goal of reducing insect fecundity as a new tool for pest management. The results demonstrated that exposure of adult beetles, as well as larvae to dvvgr or dvbol dsRNA in artificial diet, caused reduction of fecundity. Furthermore, western corn rootworm beetles that emerged from larval feeding on transgenic maize roots expressing dvbol dsRNA also showed significant fecundity reduction. This is the first report of reduction of insect reproductive fitness through plant-mediated RNAi, demonstrating the feasibility of reproductive RNAi as a management tool for western corn rootworm.
