Specific loops D, E and F of nicotinic acetylcholine receptor o1 subunit may confer imidacloprid selectivity between Myzus persicae and its predatory enemy Pardosa pseudoannulata

摘要

One nicotinic acetylcholine receptor non-l subunit was cloned from the pond wolf spider, Pardosa pseudoannulata, an important predatory enemy of some insect pests with agricultural importance, such as the green peach aphid Myzus persicae. The subunit shows high amino acid identities to insect o1 subunits (7478%), and was denoted as Ppo1. Although high identities are found between Ppo1 and insect o1 subunits, amino acid differences are found within loops D, E and F, important segments contributing to ligand binding. The effects of amino acid differences within these loops were evaluated by introducing loops of insect or spider o1 subunits into rat o2 subunit and co-expressing with insect l subunit. The corresponding regions of rat o2 chimera o2Mpo1 (o2 with loops D, E and F from M. persicae o1 subunit Mpo1) were replaced by loops D, E and F of Ppo1 singly or together to construct different chimeras. When these chimeras were co-expressed with insect Nll1, it was found that the replacement of loops D, E and F of o2Mpo1 by that of Ppo1 resulted in a right-ward shift of the imidacloprid doseresponse curves, reflecting increases in EC50, compared to Nll1/o2Mpo1. By contrast, the influences on ACh potency were minimal. The further study showed that R81Q, N137G and F190W differences, within loops D, E and F respectively, contributed mainly to these sensitivity changes. This study contributes to our understanding of the molecular mechanism underlying selectivity of neonicotinoids against insects over spiders.