RNAi Targeting Chitin synthase Genes Specifically Affects Larval Performance in Tuta absoluta

ABSTRACT An RNA interference (RNAi)‐based management strategy has a great potential for control of the tomato leafminer Tuta absoluta , a microlepidoptera pest damaging a broad range of Solanaceae hosts. Nevertheless, whether RNAi efficiency of the target genes is affected by dsRNA reachability and mRNA levels remains to be established in T. absoluta . Two chitin synthase genes, TaChSA and TaChSB , were highly expressed in ectodermally‐derived cells and midgut respectively, facilitating to test dsRNA reachability using oral delivery. According to the 2 − ΔCT value, TaChSA average level was much higher than that of TaChSB , allowing us to compare the mRNA levels on RNAi effectiveness. We found that ingestion of bacterially‐expressed ds ChSA or ds ChSB for 24 h identically decreased the target mRNA levels in whole body, and in the head, epidermis, foregut and hindgut. Feeding ds ChSA affected larval growth and leaf mining, caused 19.7% larval lethality and 31.6% non‐emerged adults. Moreover, RNAi against TaChSA damaged rectum integrity, decreased cuticle thickness, and thinned tracheae. By contrast, ingesting ds ChSB decreased larval weight, led to 3.8% larval lethality and 43.2% of resulting pupae failing to emerge. Taken together, ds ChSA and ds ChSB might be systemically transported, and exerted a strong RNAi efficiency irrespective of target mRNA levels. Our results indicate a possible application of bacterially‐expressed ds ChSA and ds ChSB in the field to protect growing crops against T. absoluta .