Downregulation of chitin synthase A gene by diallyl trisulfide, an active substance from garlic essential oil, inhibits oviposition and alters the morphology of adult Sitotroga cerealella

Abstract

The Angoumois grain moth, Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae), is the most serious and destructive pest of stored commodities around the globe, particularly on wheat, rice and maize. Previously, we confirmed that diallyl trisulfide (DAT), an active substance from garlic essential oil, reduced oviposition of females after a fumigation at the sublethal concentration (LC20 = 0.015 µL/L); meanwhile, through transcriptome sequencing, we found that DAT significantly downregulates the expression of chitin synthase A (CHSA) gene. To gain a broader insight, we assessed effects of DAT and dsRNA of CHSA gene of S. cerealella (dsScerCHSA) on the morphology, physiology and oviposition of adult S. cerealella, and we found that ScerCHSA was expressed in the adult stage and observed higher in the cuticle. Furthermore, results indicated that DAT fumigation significantly downregulated the mRNA expression of ScerCHSA and inhibited moth oviposition at the sublethal concentration. Downregulation of ScerCHSA resulted in chitin reduction, epidermal disruption, morphological and physiological alterations. Meanwhile, silencing of ScerCHSA resulted in the oviposition reduction of the moth; moreover, the morphological and physiological alterations were similar to the group treated with DAT. Therefore, we conclude that DAT could regulate the expression of ScerCHSA at the transcriptional level, cause histological and morphological alteration and finally inhibit the moth oviposition, which proves DAT possesses the great potential for being used in pest control as a friendly biopesticide.