Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Straße 10, D-35043 Marburg, Germany.
Nature. 2011 Oct 5;478(7369):395-8. doi: 10.1038/nature10454.
Maize smut caused by the fungus Ustilago maydis is a widespread disease characterized by the development of large plant tumours. U. maydis is a biotrophic pathogen that requires living plant tissue for its development and establishes an intimate interaction zone between fungal hyphae and the plant plasma membrane. U. maydis actively suppresses plant defence responses by secreted protein effectors. Its effector repertoire comprises at least 386 genes mostly encoding proteins of unknown function and expressed exclusively during the biotrophic stage. The U. maydis secretome also contains about 150 proteins with probable roles in fungal nutrition, fungal cell wall modification and host penetration as well as proteins unlikely to act in the fungal-host interface like a chorismate mutase. Chorismate mutases are key enzymes of the shikimate pathway and catalyse the conversion of chorismate to prephenate, the precursor for tyrosine and phenylalanine synthesis. Root-knot nematodes inject a secreted chorismate mutase into plant cells likely to affect development. Here we show that the chorismate mutase Cmu1 secreted by U. maydis is a virulence factor. The enzyme is taken up by plant cells, can spread to neighbouring cells and changes the metabolic status of these cells through metabolic priming. Secreted chorismate mutases are found in many plant-associated microbes and might serve as general tools for host manipulation.
玉米黑粉病由真菌玉蜀黍黑粉菌引起，其特征是植物形成大型肿瘤。玉蜀黍黑粉菌是一种活体营养型病原体，其生长发育需要活的植物组织，并在真菌菌丝和植物质膜之间建立密切的相互作用区。玉蜀黍黑粉菌通过分泌蛋白效应子主动抑制植物防御反应。其效应子组至少包含 386 个基因，这些基因主要编码未知功能的蛋白，并且仅在活体营养阶段表达。玉蜀黍黑粉菌的分泌组还包含大约 150 种可能在真菌营养、真菌细胞壁修饰和宿主穿透中起作用的蛋白，以及不太可能在真菌-宿主界面起作用的蛋白，如分支酸变位酶。分支酸变位酶是莽草酸途径的关键酶，催化分支酸转化为预苯酸，这是酪氨酸和苯丙氨酸合成的前体。根结线虫将分泌的分支酸变位酶注入植物细胞，可能会影响其发育。在这里，我们表明，玉蜀黍黑粉菌分泌的分支酸变位酶 Cmu1 是一种毒力因子。该酶被植物细胞摄取，并能在细胞间扩散，通过代谢引发改变这些细胞的代谢状态。分泌的分支酸变位酶存在于许多与植物相关的微生物中，可能作为宿主操纵的通用工具。
