RNA interference of genes inhibits chitin biosynthesis and affects larval performance in (Say).

Dietary introduction of bacterially expressed double-stranded RNA (dsRNA) has great potential for management of . Identification of the most attractive candidate genes for RNA interference (RNAi) is the first step. In the present paper, three complete chitin synthase cDNA sequences (, and ) were cloned. and , two splicing variants of gene, were highly expressed in ectodermally-derived epidermal cells forming epidermis, trachea, foregut and hindgut, whereas was mainly transcribed in midgut cells. Feeding bacterially expressed ds (derived from a common fragment of and ), ds, ds and ds in the second- and fourth-instar larvae specifically knocked down their target mRNAs. RNAi of + and lowered chitin contents in whole body and integument samples, and thinned tracheal taenidia. The resulting larvae failed to ecdyse, pupate, or emerge as adults. Comparably, knockdown of mainly affected pupal-adult molting. The RNAi pupae did not completely shed the old larval exuviae, which caused failure of adult emergence. In contrast, silencing of significantly reduced foliage consumption, decreased chitin content in midgut sample, damaged midgut peritrophic matrix, and retarded larval growth. As a result, the development of the RNAi hypomorphs was arrested. Our data reveal that these s are among the effective candidate genes for an RNAi-based control strategy against .