Citrus Research and Education Center, Department of Entomology and Nematology, University of Florida, IFAS, 700 Experiment Station Road, Lake Alfred, FL 33850, USA. Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720, USA.
Environ Microbiol Rep. 2011 Dec;3(6):791-7. doi: 10.1111/j.1758-2229.2011.00288.x. Epub 2011 Sep 23.
Many bacterial plant pathogens have a gene-for-gene relationship that determines host specificity. However, there are pathogens such as the xylem-limited bacterium Xylella fastidiosa that do not carry genes considered essential for the gene-for-gene model, such as those coding for a type III secretion system and effector molecules. Nevertheless, X. fastidiosa subspecies are host specific. A comparison of symptom development and host colonization after infection of plants with several mutant strains in two hosts, grapevines and almonds, indicated that X. fastidiosa virulence mechanisms are similar in those plants. Thus, we tested if modification of gene regulation patterns, by affecting the production of a cell-cell signalling molecule (DSF), impacted host specificity in X. fastidiosa. Results show that disruption of the rpfF locus, required for DSF synthesis, in a strain incapable of causing disease in grapevines, leads to symptom development in that host. These data are indicative that the core machinery required for the colonization of grapevines is present in that strain, and that changes in gene regulation alone can lead X. fastidiosa to exploit a novel host. The study of the evolution and mechanisms of host specificity mediated by gene regulation at the genome level could lead to important insights on the emergence of new diseases.
许多植物病原菌都存在基因对基因关系，决定了宿主的特异性。然而，有些病原菌，如木质部限性细菌 Xylella fastidiosa，并不携带被认为是基因对基因模型所必需的基因，如编码 III 型分泌系统和效应分子的基因。尽管如此，X. fastidiosa 亚种仍具有宿主特异性。对两种宿主（葡萄和杏仁）中几种突变株感染植物后的症状发展和宿主定殖的比较表明，X. fastidiosa 的毒力机制在这些植物中是相似的。因此，我们测试了通过影响细胞间信号分子（DSF）的产生来改变基因调控模式是否会影响 X. fastidiosa 的宿主特异性。结果表明，破坏不能引起葡萄藤疾病的菌株中合成 DSF 所需的 rpfF 基因座，会导致该宿主出现症状。这些数据表明，该菌株中存在定植葡萄藤所需的核心机制，而且仅改变基因调控就可以使 X. fastidiosa 利用新的宿主。从基因组水平上研究基因调控介导的宿主特异性的进化和机制，可以深入了解新疾病的出现。
