Data from: The transcriptome of Nacobbus aberrans reveals insights into the evolution of sedentary endoparasitism in plant-parasitic nematodes

Within the phylum Nematoda, plant-parasitism is hypothesized to have arisen independently on at least four occasions. The most economically damaging plant-parasitic nematode species, and consequently the most widely studied, are those that feed as they migrate destructively through host roots causing necrotic lesions (migratory endoparasites) and those that modify host root tissue to create a nutrient sink from which they feed (sedentary endoparasites). The false root-knot nematode Nacobbus aberrans is the only known species to have both migratory endoparasitic and sedentary endoparasitic stages within its life cycle. Moreover, its sedentary stage appears to have characteristics of both the root-knot and the cyst nematodes. We present the first large-scale genetic resource of any false-root knot nematode species. We use RNAseq to describe relative abundance changes in all expressed genes across the life cycle to provide interesting insights into the biology of this nematode as it transitions between modes of parasitism. A multigene phylogenetic analysis of N. aberrans with respect to plant-parasitic nematodes of all groups confirms its proximity to both cyst and root-knot nematodes. We present a transcriptome-wide analysis of both lateral gene transfer events and the effector complement. Comparing parasitism genes of typical root-knot and cyst nematodes to those of N. aberrans has revealed interesting similarities. Importantly, genes that were believed to be either cyst nematode, or root-knot nematode, “specific” have both been identified in N. aberrans. Our results provide insights into the characteristics of a common ancestor and the evolution of sedentary endoparasitism of plants by nematodes.

在线虫动物门（Nematoda）中，植物寄生习性被推测至少独立起源了四次。造成经济损失最严重的植物寄生线虫类群，亦是研究最为广泛的类群，可分为两类：一类是在宿主根内破坏性迁移取食并引发坏死病斑的移动型内寄生线虫（migratory endoparasites），另一类是通过改造宿主根组织形成营养库以完成取食的固着型内寄生线虫（sedentary endoparasites）。伪根结线虫（false root-knot nematode）Nacobbus aberrans是目前已知唯一在生命周期中兼具移动型内寄生和固着型内寄生阶段的线虫物种。此外，该物种的固着寄生阶段同时兼具根结线虫与胞囊线虫的特征。本研究报道了首个伪根结线虫物种的大规模遗传资源。本研究通过RNA测序（RNAseq）分析该线虫生命周期内所有表达基因的相对丰度变化，以揭示其在两种寄生模式转换过程中的生物学特性，获得了极具价值的研究见解。针对所有植物寄生线虫类群开展的N. aberrans多基因系统发育分析证实，其与胞囊线虫及根结线虫的亲缘关系均较为接近。本研究还开展了全转录组水平的水平基因转移（lateral gene transfer）事件与效应因子组分析。通过对比典型根结线虫、胞囊线虫与N. aberrans的寄生基因，本研究发现了二者间存在诸多有趣的相似性。尤为重要的是，此前被认为仅存在于胞囊线虫或根结线虫中的"特异性"基因，均在N. aberrans中被检测到。本研究结果为解析植物寄生线虫的共同祖先特征，以及线虫固着型植物寄生习性的演化历程提供了重要见解。