Abstract：
Blast disease caused by the fungus Magnaporthe oryzae is one of the most devastating rice diseases. Disease resistance genes such as Pi-ta or Pi-ta2 are critical in protecting rice production from blast. Published work reports that Pi-ta codes for a nucleotide-binding and leucine-rich repeat domain protein (NLR) that recognizes the fungal protease-like effector AVR-Pita by direct binding. However, this model was challenged by the recent discovery that Pi-ta2 resistance, which also relies on AVR-Pita detection, is conferred by the unconventional resistance gene Ptr, which codes for a membrane protein with a cytoplasmic armadillo repeat domain. Here, using NLR Pi-ta and Ptr RNAi knockdown and CRISPR/Cas9 knockout mutant rice lines, we found that AVR-Pita recognition relies solely on Ptr and that the NLR Pi-ta has no role in it, indicating that it is not the Pi-ta resistance gene. Different alleles of Ptr confer different recognition specificities. The A allele of Ptr (PtrA) detects all natural sequence variants of the effector and confers Pi-ta2 resistance, while the B allele of Ptr (PtrB) recognizes a restricted set of AVR-Pita alleles and, thereby, confers Pi-ta resistance. Analysis of the natural diversity in AVR-Pita and of mutant and transgenic strains identified one specific polymorphism in the effector sequence that controls escape from PtrB-mediated resistance. Taken together, our work establishes that the M. oryzae effector AVR-Pita is detected in an allele-specific manner by the unconventional rice resistance protein Ptr and that the NLR Pi-ta has no function in Pi-ta resistance and the recognition of AVR-Pita.
摘要：
由真菌稻瘟病引起的稻瘟病是最具破坏性的水稻疾病之一。诸如Pi-ta或Pi-ta2的抗病基因在保护水稻生产免受稻瘟病中是关键的。已发表的工作报道Pi-ta编码核苷酸结合和富含亮氨酸的重复结构域蛋白（NLR），该蛋白通过直接结合识别真菌蛋白酶样效应子AVR-Pita。然而,这个模型受到了最近发现Pi-ta2抗性的挑战，这也依赖于AVR-Pita检测，由非常规抗性基因Ptr赋予，它编码具有细胞质Armadillo重复结构域的膜蛋白。这里,使用NLRPi-ta和PtrRNAi敲低和CRISPR/Cas9敲除突变水稻品系，我们发现AVR-Pita识别仅依赖于Ptr，而NLRPi-ta在其中没有作用，表明它不是Pi-ta抗性基因。Ptr的不同等位基因赋予不同的识别特异性。Ptr的A等位基因（PtrA）检测效应子的所有天然序列变体并赋予Pi-ta2抗性，而Ptr(PtrB)的B等位基因识别一组受限的AVR-Pita等位基因,因此，赋予Pi-ta抵抗。对AVR-Pita以及突变体和转基因菌株的天然多样性的分析确定了效应子序列中的一个特定多态性，该多态性控制了PtrB介导的抗性。一起来看,我们的工作确定，非常规水稻抗性蛋白Ptr以等位基因特异性方式检测到米曲霉效应子AVR-Pita，并且NLRPi-ta在Pi-ta抗性和AVR-Pita识别中没有功能。
