Comparative genomic analysis of P450 genes reveals CYP6CX4 is associated with differential clothianidin resistance between Bemisia tabaci B/MEAM1 and Q/MED.

BACKGROUND

Bemisia tabaci is a globally invasive agricultural pest. The B. tabaci Q/MED has rapidly replaced B/MEAM1, largely due to Q/MED's high resistance to neonicotinoid insecticides. Although cytochrome P450s (P450s) are major detoxification enzymes involved in insecticide resistance, the genome-wide identification and functional contributions to differential clothianidin resistance between B/MEAM1 and Q/MED remain poorly understood.

RESULTS

A total of 129 P450 genes were identified in both B/MEAM1 and Q/MED genomes, with marked expansions observed in clan 3 and clan 4. Comparative chromosomal mapping of P450 genes revealed a largely conserved genomic organization between B/MEAM1 and Q/MED, together with lineage-specific rearrangements. Transcriptional profiling across developmental stages identified a distinct stage-specific high expression cluster in post-embryonic stages, especially in Q/MED. Among the high expression genes, CYP6DV4 was up-regulated in clothianidin-resistant populations of both B/MEAM1 and Q/MED B. tabaci and CYP6CX4 was consistently overexpressed specifically in two Q/MED clothianidin-resistant populations. Crucially, functional characterisation revealed that CYP6CX4 confers resistance in vivo by RNA interference and can metabolise clothianidin into clothianidin-guanidine in vitro via Ultra-Performance Liquid Chromatography-Mass Spectrometry (UPLC/MS) analysis.

CONCLUSION

This study provides a comprehensive overview of the P450 gene family, facilitating a better understanding of its evolution and potential functions in B. tabaci B/MEAM1 and Q/MED. More importantly, our results suggest that CYP6CX4 may contribute to clothianidin resistance in Q/MED but not in B/MEAM1. These findings improve our understanding of P450-mediated resistance and provide useful targets for resistance monitoring and management in B. tabaci. © 2026 Society of Chemical Industry.