Wybouw N, Van Leeuwen T, Dermauw W
Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, the Netherlands.
Laboratory of Agrozoology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
Insect Mol Biol. 2018 Jun;27(3):333-351. doi: 10.1111/imb.12374. Epub 2018 Jan 29.
A number of horizontal gene transfers (HGTs) have been identified in the spider mite Tetranychus urticae, a chelicerate herbivore. However, the genome of this mite species has at present not been thoroughly mined for the presence of HGT genes. Here, we performed a systematic screen for HGT genes in the T. urticae genome using the h-index metric. Our results not only validated previously identified HGT genes but also uncovered 25 novel HGT genes. In addition to HGT genes with a predicted biochemical function in carbohydrate, lipid and folate metabolism, we also identified the horizontal transfer of a ketopantoate hydroxymethyltransferase and a pantoate β-alanine ligase gene. In plants and bacteria, both genes are essential for vitamin B5 biosynthesis and their presence in the mite genome strongly suggests that spider mites, similar to Bemisia tabaci and nematodes, can synthesize their own vitamin B5. We further show that HGT genes were physically embedded within the mite genome and were expressed in different life stages. By screening chelicerate genomes and transcriptomes, we were able to estimate the evolutionary histories of these HGTs during chelicerate evolution. Our study suggests that HGT has made a significant and underestimated impact on the metabolic repertoire of plant-feeding spider mites.
在叶螨科植食性螨虫二斑叶螨（Tetranychus urticae）中，已经鉴定出了一些水平基因转移（HGT）事件。然而，目前尚未对该螨类物种的基因组进行全面挖掘以寻找HGT基因。在此，我们使用h指数度量法对二斑叶螨基因组中的HGT基因进行了系统筛选。我们的结果不仅验证了先前鉴定出的HGT基因，还发现了25个新的HGT基因。除了在碳水化合物、脂质和叶酸代谢中具有预测生化功能的HGT基因外，我们还鉴定出了酮泛解酸羟甲基转移酶和泛解酸β-丙氨酸连接酶基因的水平转移。在植物和细菌中，这两个基因对于维生素B5的生物合成至关重要，它们在螨类基因组中的存在强烈表明，与烟粉虱和线虫类似，二斑叶螨能够合成自身的维生素B5。我们进一步表明，HGT基因在物理上嵌入在螨类基因组中，并在不同的生命阶段表达。通过筛选螯肢动物的基因组和转录组，我们能够估计这些HGT在螯肢动物进化过程中的进化历史。我们的研究表明，HGT对以植物为食的叶螨的代谢库产生了重大且被低估的影响。
