Gene amplification and microsatellite polymorphism underlie a recent insect host shift.
Host plant shifts of herbivorous insects may be a first step toward sympatric speciation and can create new pests of agriculturally important crops; however, the molecular mechanisms that mediate this process are poorly understood. Certain races of the polyphagous aphid Myzus persicae have recently adapted to feed on tobacco (Myzus persicae nicotianae) and show a reduced sensitivity to the plant alkaloid nicotine and cross-resistance to neonicotinoids a class of synthetic insecticides widely used for control. Here we show constitutive overexpression of a cytochrome P450 (CYP6CY3) allows tobacco-adapted races of M. persicae to efficiently detoxify nicotine and has preadapted them to resist neonicotinoid insecticides. CYP6CY3, is highly overexpressed in M. persicae nicotianae clones from three continents compared with M. persicae s.s. and expression level is significantly correlated with tolerance to nicotine. CYP6CY3 is highly efficient (compared with the primary human nicotine-metabolizing P450) at metabolizing nicotine and neonicotinoids to less toxic metabolites in vitro and generation of transgenic Drosophila expressing CYP6CY3 demonstrate that it confers resistance to both compounds in vivo. Overexpression of CYP6CY3 results from the expansion of a dinucleotide microsatellite in the promoter region and a recent gene amplification, with some aphid clones carrying up to 100 copies. We conclude that the mutations leading to overexpression of CYP6CY3 were a prerequisite for the host shift of M. persicae to tobacco and that gene amplification and microsatellite polymorphism are evolutionary drivers in insect host adaptation.
Department of Biological Chemistry and Crop Protection, Rothamsted Research, Harpenden AL5 2JQ, United Kingdom.
Chris
C
Bass
Christoph T
CT
Zimmer
Jacob M
JM
Riveron
Craig S
CS
Wilding
Charles S
CS
Wondji
Martin
M
Kaussmann
Linda M
LM
Field
Martin S
MS
Williamson
Ralf
R
Nauen
D000220:Adaptation, Biological / Q000235:genetics*; D000818:Animals; D001042:Aphids / Q000187:drug effects / Q000201:enzymology*; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D001483:Base Sequence; D002853:Chromatography, Liquid; D018900:Dinucleotide Repeats / Q000235:genetics*; D005784:Gene Amplification / Q000235:genetics*; D006790:Host-Parasite Interactions; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009538:Nicotine / Q000633:toxicity; D011110:Polymorphism, Genetic / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D053719:Tandem Mass Spectrometry; D014026:Nicotiana / Q000469:parasitology*
D009538:Nicotine; D001189:Aryl Hydrocarbon Hydroxylases