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Crop Biotech Update

Knockdown of Northern Armyworm Chitinase Genes thru Oral Delivery of RNAi Effectors

March 8, 2017

RNA interference is a technology for silencing of target genes via sequence-specific manner, and has been used for developing anti-pathogenic crops. The Northern armyworm (Mythimna separata) belongs to the Noctuidae family of lepidopterans and is posing threat to crops of economic importance. Inner Mongolia University researchers aim to develop a new control for these insects.

The team targeted chitinase genes as they are expressed predominantly in the gut tissue and are ideal silencing targets in several insect species. Interfering sequences against the target genes were cloned into the L4440 vector to produce sequence-specific dsRNAs (double-stranded RNAs). Recombinant L4440 vectors were then transformed into Escherichia coli strain HT115 (DE3) with defective dsRNA degradation activity, to preserve the dsRNA from degradation. The bacteria were then mixed with artificial diet and were fed to M. separata.

Oral delivery of bacterially-expressed dsRNA led to RNAi effects in the recipient insect. PCR results showed that expression levels of targets MseChi1 and MseChi2 in the gut tissue of M. separata were downregulated after oral delivery of engineered bacteria expressing the corresponding dsRNA. Knockdown of MseChi1 and MseChi2 resulted in increased mortality and reduced body weight of the feeding larvae.

This research provides an experimental foundation for using RNAi technology as a tool for loss-of-function study of important developmental and regulatory genes in Northern armyworm.

For more on this study, read the article in BMC Biotechnology.