State Key Laboratory of Rice Biology, Ministry of Agriculture; and Institute of Insect Sciences, Zhejiang University, Hangzhou, People's Republic of China.
PLoS One. 2013;8(2):e56604. doi: 10.1371/journal.pone.0056604. Epub 2013 Feb 14.
Glutathione S-transferase (GST) genes control crucial traits for the metabolism of various toxins encountered by insects in host plants and the wider environment, including insecticides. The planthoppers Nilaparvata lugens and Sogatella furcifera are serious specialist pests of rice throughout eastern Asia. Their capacity to rapidly adapt to resistant rice varieties and to develop resistance to various insecticides has led to severe outbreaks over the last decade.
METHODOLOGY/PRINCIPAL FINDINGS: Using the genome sequence of N. lugens, we identified for the first time the complete GST gene family of a delphacid insect whilst nine GST gene orthologs were identified from the closely related species S. furcifera. Nilaparvata lugens has 11 GST genes belonging to six cytosolic subclasses and a microsomal class, many fewer than seen in other insects with known genomes. Sigma is the largest GST subclass, and the intron-exon pattern deviates significantly from that of other species. Higher GST gene expression in the N. lugens adult migratory form reflects the higher risk of this life stage in encountering the toxins of non-host plants. After exposure to a sub-lethal dose of four insecticides, chlorpyrifos, imidacloprid, buprofezin or beta-cypermethrin, more GST genes were upregulated in S. furcifera than in N. lugens. RNA interference targeting two N. lugens GST genes, NlGSTe1 and NlGSTm2, significantly increased the sensitivity of fourth instar nymphs to chlorpyrifos but not to beta-cypermethrin.
CONCLUSIONS/SIGNIFICANCE: This study provides the first elucidation of the nature of the GST gene family in a delphacid species, offering new insights into the evolution of metabolic enzyme genes in insects. Further, the use of RNA interference to identify the GST genes induced by insecticides illustrates likely mechanisms for the tolerance of these insects.
谷胱甘肽 S-转移酶 (GST) 基因控制着昆虫在宿主植物和更广泛的环境中遇到的各种毒素代谢的关键特征，包括杀虫剂。褐飞虱和白背飞虱是整个东亚水稻的严重专性害虫。它们迅速适应抗虫水稻品种和对各种杀虫剂产生抗性的能力，导致过去十年中严重爆发。
方法/主要发现：利用褐飞虱的基因组序列，我们首次鉴定了一种 delphacid 昆虫的完整 GST 基因家族，同时从亲缘关系密切的物种白背飞虱中鉴定了 9 个 GST 基因直系同源物。褐飞虱有 11 个 GST 基因属于六个细胞溶质亚类和一个微粒体类，比其他具有已知基因组的昆虫少得多。西格玛是最大的 GST 亚类，其内含子-外显子模式与其他物种明显不同。在 N. lugens 成虫迁徙形式中，GST 基因的高表达反映了这个生命阶段在遇到非宿主植物毒素时的更高风险。在接触亚致死剂量的四种杀虫剂（毒死蜱、吡虫啉、噻嗪酮或溴氰菊酯）后，S. furcifera 中上调的 GST 基因多于 N. lugens。针对两个 N. lugens GST 基因 NlGSTe1 和 NlGSTm2 的 RNA 干扰显著增加了第四龄若虫对毒死蜱的敏感性，但对溴氰菊酯没有影响。
结论/意义：本研究首次阐明了 delphacid 物种 GST 基因家族的性质，为昆虫代谢酶基因的进化提供了新的见解。此外，使用 RNA 干扰来鉴定杀虫剂诱导的 GST 基因，说明了这些昆虫对杀虫剂耐受的可能机制。
