Characterization of five CYP4 genes from Asian citrus psyllid and their expression levels in Candidatus Liberibacter asiaticus infected and uninfected psyllids

In the current study, we investigated the expression level of family 4 cytochrome P450 (CYP4) genes in Las (Candidatus Liberibacter asiaticus)-infected and uninfected Diphorina citri adults to better understand the possible mechanisms associated with reduced levels of cytochrome P450 monooxygenases previously documented in Las-infected adults. Five novel CYP4 genes (CYP4C67, CYP4DA1, CYP4C68, CYP4DB1 and CYP4G70) were identified from Las-infected and uninfected D. citri adults. Four of the five CYP4 genes were expressed at significantly higher levels in uninfected than Las-infected males, whereas only one CYP4 gene was expressed at significantly higher levels in uninfected than Las-infected females. These results suggest that levels of cytochrome P450 monooxygenase proteins in D. citri may be linked to the expression levels of these CYP4 genes. In addition, expression of some of these CYP4 genes appears sex-specific. Expression of all five CYP4 genes was induced by exposure of D. citri to imidacloprid suggesting their involvement in metabolism of this toxin. These five CYP4 genes are promising candidates for RNA-interference to silence overexpression of genes associated with insecticide resistance in D. citri. These newly identified genes may also serve as a DNA-based biomarkers for screening of cytochrome P450-mediated insecticide resistance in field populations of D. citri.