Abstract
RNA interference (RNAi) based methods are being developed for pest management. A few products for control of coleopteran pests are expected to be commercialized soon. However, variability in RNAi efficiency among insects is preventing the widespread use of this technology. In this study, we conducted research to identify reasons for variability in RNAi efficiency among thirty-seven (37) insects belonging to five orders. Studies on double-stranded RNA (dsRNA) degradation by dsRNases and processing of labeled dsRNA to siRNA showed that both dsRNA degradation and processing are variable among insects belonging to different orders as well as among different insect species within the same order. We identified homologs of key RNAi genes in the genomes of some of these insects and studied their domain architecture. These data suggest that dsRNA digestion by dsRNases and its processing to siRNAs in the cells are among the major factors contributing to differential RNAi efficiency reported among insects.
Highlights
There is a constant competition between insects and plants for their co-existence in nature
DsRNA molecules are cleaved by an endonuclease, Dicer, into 21–23 bp short interfering RNAs, which are recruited to a multi-protein RNA-induced silencing complex (RISC) and guided to the complementary mRNA for degradation[8,9]
Epilachna varivestis, Coccinella septempunctata, Disonycha glabrata, Leptinotarsa decemlineata, Acalymna vittatum, Epitrix fuscula, Diabrotica undecimpunctata, Chauliognathus pensylvanicus, Tribolium castaneum and Agrilus planipennis from order Coleoptera were included in the study
Summary
There is a constant competition between insects and plants for their co-existence in nature. Modified crops, expressing insecticidal proteins derived from the bacterium, Bacillus thuringiensis (Bt)[2] provide a good method to control many economically important insect pests. This is not a foolproof strategy as all the insect species are not sensitive to Bt toxins and insects have started developing resistance against these toxins[3]. RNA interference (RNAi) could be one of the promising tools for developing target specific insect pest management methods[4,5]. Schistocerca gregaria, an orthopteran insect, significant knockdown of target genes was observed after dsRNA injection, but the RNAi response was much less after dsRNA feeding[25]. We studied dsRNA degradation and processing using naked and labeled dsRNA, respectively
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