Neofunctionalization of Duplicated P450 Genes Drives the Evolution of Insecticide Resistance in the Brown Planthopper

Christoph T Zimmer,William T Garrood,Kumar Saurabh Singh,Emma Randall,Bettina Lueke,Oliver Gutbrod,Svend Matthiesen,Maxie Kohler,Ralf Nauen,T.G Emyr Davies,Chris Bass

doi:10.1016/j.cub.2017.11.060

Christoph T Zimmer, William T Garrood + Show 9 more

Open Access

https://doi.org/10.1016/j.cub.2017.11.060

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Abstract

SummaryGene duplication is a major source of genetic variation that has been shown to underpin the evolution of a wide range of adaptive traits [1, 2]. For example, duplication or amplification of genes encoding detoxification enzymes has been shown to play an important role in the evolution of insecticide resistance [3, 4, 5]. In this context, gene duplication performs an adaptive function as a result of its effects on gene dosage and not as a source of functional novelty [3, 6, 7, 8]. Here, we show that duplication and neofunctionalization of a cytochrome P450, CYP6ER1, led to the evolution of insecticide resistance in the brown planthopper. Considerable genetic variation was observed in the coding sequence of CYP6ER1 in populations of brown planthopper collected from across Asia, but just two sequence variants are highly overexpressed in resistant strains and metabolize imidacloprid. Both variants are characterized by profound amino-acid alterations in substrate recognition sites, and the introduction of these mutations into a susceptible P450 sequence is sufficient to confer resistance. CYP6ER1 is duplicated in resistant strains with individuals carrying paralogs with and without the gain-of-function mutations. Despite numerical parity in the genome, the susceptible and mutant copies exhibit marked asymmetry in their expression with the resistant paralogs overexpressed. In the primary resistance-conferring CYP6ER1 variant, this results from an extended region of novel sequence upstream of the gene that provides enhanced expression. Our findings illustrate the versatility of gene duplication in providing opportunities for functional and regulatory innovation during the evolution of an adaptive trait.

Highlights

To test this, we expressed CYP6ER1vA, CYP6ER1vB, the lab susceptible variant CYP6ER1vL, and its closest relatives observed in the field, CYP6ER1vF and CYP6ER1vC, in vitro and examined their capacity to metabolize imidacloprid
We previously demonstrated that resistance to the insecticide imidacloprid in the brown planthopper (BPH), Nilaparvata lugens, is associated with the overexpression of the cytochrome P450, CYP6ER1 [9]
We demonstrate that CYP6ER1 is duplicated in resistant strains and show that resistant individuals carry one copy with the gain-of-function mutations and one without

Summary

Introduction

We expressed CYP6ER1vA, CYP6ER1vB, the lab susceptible variant CYP6ER1vL, and its closest relatives observed in the field, CYP6ER1vF and CYP6ER1vC, in vitro and examined their capacity to metabolize imidacloprid. Liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis demonstrated that CYP6ER1vA and, to a lesser extent, CYP6ER1vB are effective metabolizers of imidacloprid, converting it to 4/5-hydroxy imidacloprid and 6-chloronicotinic acid (6-CNA) (Figure 1D). No significant metabolism of imidacloprid was observed in the case of CYP6ER1vC, CYP6ER1vL, or CYP6ER1vF (Figure 1D)

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Discussion

Conclusion