Function and Interaction of the Coupled Genes Responsible for <i>Pik-h</i> Encoded Rice Blast Resistance

Pik-h, an allele of Pik, confers resistance against the rice blast pathogen Magnaporthe oryzae. Its positional cloning has shown that it comprises a pair of NBS-LRR genes, Pikh-1 and Pikh-2. While Pikh-1 appears to be constitutively transcribed, the transcript abundance of Pikh-2 responds to pathogen challenge. The Pikh-1 CC (coiled coil) domain interacts directly with both AvrPik-h and Pikh-2. Transient expression assays demonstrated that Pikh-2 mediates the initiation of the host defence response. Nucleocytoplasmic partitioning of both Pikh-1 and Pikh-2 is required for their functionalities. In a proposed mechanistic model of Pik-h resistance, it is suggested that Pikh-1 acts as an adaptor between AvrPik-h and Pikh-2, while Pikh-2 transduces the signal to trigger Pik-h-specific resistance.Pik-h作为Pik的等位基因，可赋予水稻对稻瘟病菌（Magnaporthe oryzae）的抗性。对其进行的图位克隆（positional cloning）研究显示，该基因由一对核苷酸结合位点-亮氨酸重复序列（NBS-LRR）基因Pikh-1与Pikh-2组成。其中Pikh-1呈现组成型转录特征，而Pikh-2的转录本丰度会响应病原菌侵染而发生变化。Pikh-1的卷曲螺旋（coiled coil, CC）结构域可直接与AvrPik-h及Pikh-2相互作用。瞬时表达实验结果表明，Pikh-2可介导宿主防御反应的启动。Pikh-1与Pikh-2的核质分配均是其发挥功能所必需的。在已提出的Pik-h抗性作用机制模型中，Pikh-1充当AvrPik-h与Pikh-2之间的接头蛋白，而Pikh-2则负责转导信号以触发Pik-h特异性抗性。