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Abstract:
Many phloem-feeding insects are considered severe pests of agriculture and are controlled mainly by chemical
insecticides. Continued extensive use of these inputs is environmentally undesirable, and also leads to the development
of insecticide resistance. Here, we used a plant-mediated RNA interference (RNAi) approach, to
develop a new control strategy for phloem-feeding insects. The approach aims to silence “key” detoxification
genes, involved in the insect's ability to neutralize defensive and toxic plant chemistry. We targeted a glutathione
S-transferase (GST) gene, BtGSTs5, in the phloem-feeding whitefly Bemisia tabaci, a devastating global agricultural
pest. We report three major findings. First, significant down regulation of the BtGSTs5 gene was obtained
in the gut of B. tabaci when the insects were fed on Arabidopsis thaliana transgenic plants expressing
dsRNA against BtGSTs5 under a phloem-specific promoter. This brings evidence that phloem-feeding insects can
be efficiently targeted by plant-mediated RNAi. Second, in-silico and in-vitro analyses indicated that the BtGSTs5
enzyme can accept as substrates, hydrolyzed aliphatic- and indolic-glucosinolates, and produce their corresponding
detoxified conjugates. Third, performance assays suggested that the BtGSTs5 gene silencing prolongs
the developmental period of B. tabaci nymphs. Taken together, these findings suggest that BtGSTs5 is likely to
play an important role in enabling B. tabaci to successfully feed on glucosinolate-producing plants. Targeting the
gene by RNAi in Brassicaceae cropping systems, will likely not eliminate the pest populations from the fields but
will significantly reduce their success over the growing season, support prominent activity of natural enemies,
eventually allowing the establishment of stable and sustainable agroecosystem.