Silencing Chitinase Genes Increases Susceptibility ofTetranychus cinnabarinus(Boisduval) to Scopoletin

Abstract

The carmine spider miteTetranychus cinnabarinusis a major pest of crop and vegetable plants worldwide. Previous studies have shown that scopoletin is a promising acaricidal compound againstTetranychus cinnabarinus.However, the acaricidal mechanism of scopoletin remains unclear. In the present study, 12 full-length cDNAs of chitinase (CHIT) genes fromTetranychus cinnabarinus(designatedTcCHITs) were cloned and characterized. AlthoughTcCHITswere expressed throughout all life stages, their expression levels were significantly upregulated during the larval and nymphal stages.TcCHITswere downregulated 24 h after treatment with scopoletin and upregulated 24 h after treatment with diflubenzuron (DFB, a chitin synthesis inhibitor). Feeding double-stranded RNA effectively silencedTcCHITtranscription inTetranychus cinnabarinus, thus increasing its susceptibility to scopoletin but reducing that to DFB. Meanwhile,TcCHITsilencing in larvae and adult resulted in an extremely low molting rate (7.3%) and high mortality rate (53.3%), respectively, compared with those in the control group. CHIT genes are closely related to arthropod survival, molting, and development inTetranychus cinnabarinus, suggesting that acaricidal mechanisms of scopoletin and DFB may occur by inhibition and activation of CHIT gene expression, respectively.TcCHITconstitutes a possible target of scopoletin and DFB inTetranychus cinnabarinus.