Transcriptome profiling and functional analysis suggest that the constitutive overexpression of four cytochrome P450s confers resistance to abamectin in Tetranychus urticae from China

BACKGROUND The two-spotted spider mite Tetranychus urticae is a polyphagous and cosmopolitan pest that has developed high resistance to abamectin, making it difficult to control. Although 'target resistance' related to glutamate-gated chloride channel mutations was found in T. urticae field populations in China, other resistance mechanisms appear to be involved. Here, we conducted genome-wide transcriptome profiling using RNA-sequencing of two abamectin-resistant populations (NB-ZJ and SY-BJ) and one susceptible strain (Lab-SS) to identify differentially expressed genes that might contribute to the resistance of T. urticae to abamectin in China. RESULTS Our experiments showed that abamectin resistance was synergized by piperonyl butoxide (PBO) and triphenyl phosphate (TPP), with synergistic ratios (SR) of 2.95-fold and 2.21-fold for PBO and 3.55-fold and 2.84-fold for TPP in NB-ZJ and SY-BJ populations, respectively. Transcriptome data and quantitative real-time PCR (qRT-PCR) revealed that seven detoxification enzyme genes were overexpressed in the two resistant populations. Furthermore, functional analysis by RNA interference (RNAi) indicated that the mortality caused by abamectin was significantly increased by the separate silencing of the P450 genes CYP389C10, CYP392D8, CYP392A11, and CYP392A12. CONCLUSION qRT-PCR expression and RNAi data suggest that the overexpression of P450 genes CYP389C10, CYP392D8, CYP392A11, and CYP392A12 may be involved in the abamectin-resistance of field populations of T. urticae in China. This knowledge could facilitate the elucidation of resistance mechanisms and the development of resistance management of T. urticae field populations.

Automated summary

The two field populations of T. urticae in China, NB-ZJ and SY-BJ, exhibited high resistance to abamectin, potentially due to the overexpression of P450 genes.