我科学家发现白叶枯病菌侵害水稻机理

华中农业大学作物遗传改良国家重点实验室王石平教授课题组的研究表明，白叶枯病菌会利用水稻生长繁殖必不可少的显性Xa13基因，减少铜在水稻导管中的分布而侵害水稻。该研究不仅揭示了病原细菌利用宿主基因征服宿主的一种新机理，同时也揭示了可能涉及水稻与病原共进化一个典型例子。相关研究论文日前在国际植物生物学研究领域的顶级杂志《植物细胞》上以重点推荐形式在线发表，同时配发了介绍文章。 研究发现，有的白叶枯病菌对铜非常敏感，提高培养基中铜的含量可抑制这类白叶枯病菌的生长繁殖。水稻从根部吸收铜，通过导管将铜运输到植株的各个部位，而白叶枯病菌正是通过导管在水稻体内蔓延引起病害。增加导管内铜的含量，会抑制白叶枯病菌的生长繁殖。进一步研究表明，“狡猾”的白叶枯病菌会利用激活水稻自身不可或缺的Xa13基因——该基因对水稻花粉发育必不可少，来消除导管中铜的抑制影响。白叶枯病菌通过激活Xa13基因的表达，调控铜在水稻体内的重新分布侵害水稻。Xa13蛋白和另外两个蛋白质COPT1和COPT5在细胞膜上共同作用，将细胞外的铜运输进细胞内，从而减少导管中的铜，使白叶枯病菌能够在导管中繁殖并蔓延，造成水稻病害。 了解病原菌如何侵害植物的机理，将有助于有效控制农作物病害。据王石平介绍，由白叶枯病菌引起的白叶枯病是水稻的重要病害之一，曾令全球水稻减产70%。了解白叶枯病菌侵害水稻的这一机制，将有助于设计有效途径培育抗病水稻品种。来源：科技日报（记者刘志伟 通讯员范敬群）论文摘要：Pathogen effectors are virulence factors causing plant diseases. How the host targets of these effectors facilitate pathogen infection is largely unknown. An effector of Xanthomonas oryzae pv oryzae (Xoo) transcriptionally activates rice (Oryza sativa) susceptibility gene Xa13 to cause bacterial blight disease. Xa13 encodes an indispensable plasma membrane protein of the MtN3/saliva family, which is prevalent in eukaryotes with unknown biochemical function. We show that the XA13 protein cooperates with two other proteins, COPT1 and COPT5, to promote removal of copper from xylem vessels, where Xoo multiplies and spreads to cause disease. Copper, an essential micronutrient of plants and an important element for a number of pesticides in agriculture, suppresses Xoo growth. Xoo strain PXO99 is more sensitive to copper than other strains; its infection of rice is associated with activation of XA13, COPT1, and COPT5, which modulate copper redistribution in rice. The involvement of XA13 in copper redistribution has led us to propose a mechanism of bacterial virulence.