Bird David McK, Opperman Charles H, Davies Keith G
Center for the Biology of Nematode Parasitism, Box 7253, North Carolina State University, Raleigh, NC 27695, USA.
Int J Parasitol. 2003 Sep 30;33(11):1269-76. doi: 10.1016/s0020-7519(03)00160-7.
Based on genome-to-genome analyses of gene sequences obtained from plant-parasitic, root-knot nematodes (Meloidogyne spp.), it seems likely that certain genes have been derived from bacteria by horizontal gene transfer. Strikingly, a common theme underpinning the function of these genes is their apparent direct relationship to the nematodes' parasitic lifestyle. Phylogenetic analyses implicate rhizobacteria as the predominant group of 'gene donor' bacteria. Root-knot nematodes and rhizobia occupy similar niches in the soil and in roots, and thus the opportunity for genetic exchange may be omnipresent. Further, both organisms establish intimate developmental interactions with host plants, and mounting evidence suggests that the mechanisms for these interactions are shared too. We propose that the origin of parasitism in Meloidogyne may have been facilitated by acquisition of genetic material from soil bacteria through horizontal transfer, and that such events represented key steps in speciation of plant-parasitic nematodes. To further understand the mechanisms of horizontal gene transfer, and also to provide experimental tools to manipulate this promising bio-control agent, we have initiated a genomic sequence of the bacterial hyper-parasite of plant parasitic nematodes, Pasteuria penetrans. Initial data have established that P. penetrans is closely related to Bacillus spp., to the extent that considerable genome synteny is apparent. Hence, Bacillus serves as a model for Pasteuria, and vice versa.
基于对从植物寄生根结线虫（根结线虫属）获得的基因序列进行的全基因组分析，某些基因似乎可能是通过水平基因转移从细菌中获得的。引人注目的是，这些基因功能的一个共同主题是它们与线虫寄生生活方式的明显直接关系。系统发育分析表明，根际细菌是“基因供体”细菌的主要群体。根结线虫和根瘤菌在土壤和根中占据相似的生态位，因此基因交换的机会可能无处不在。此外，这两种生物都与宿主植物建立了密切的发育相互作用，越来越多的证据表明这些相互作用的机制也是共享的。我们提出，根结线虫寄生现象的起源可能是通过水平转移从土壤细菌中获取遗传物质而得以促进的，而且此类事件代表了植物寄生线虫物种形成的关键步骤。为了进一步了解水平基因转移的机制，并提供实验工具来操控这种有前景的生物防治剂，我们已启动了植物寄生线虫的细菌超级寄生菌——穿透巴氏杆菌的基因组测序。初步数据表明，穿透巴氏杆菌与芽孢杆菌属密切相关，以至于明显存在相当程度的基因组共线性。因此，芽孢杆菌可作为巴氏杆菌的模型，反之亦然。
