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.

由稻瘟病菌引起的稻瘟病是最具破坏性的水稻病害之一。 Pi-ta或Pi-ta2等抗病基因对于保护水稻生产免受稻瘟病的侵害至关重要。已发表的工作报告称， Pi-ta编码一种核苷酸结合且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，这一模型受到了最近发现的挑战，即 Pi-ta2 耐药性（也依赖于 AVR-Pita 检测）是由非常规耐药基因Ptr赋予的，该基因编码具有细胞质犰狳重复结构域的膜蛋白。在这里，利用NLR Pi-ta和Ptr RNAi 敲低以及 CRISPR/Cas9 敲除突变水稻品系，我们发现 AVR-Pita 识别仅依赖于Ptr ，而NLR Pi-ta对此没有任何作用，这表明它不是Pita抗性基因。 Ptr的不同等位基因赋予不同的识别特异性。 Ptr ( PtrA ) 的 A 等位基因检测效应子的所有自然序列变异并赋予 Pi-ta2 抗性，而Ptr ( PtrB ) 的 B 等位基因识别一组有限的AVR-Pita等位基因，从而赋予 Pi-ta 抗性。对AVR-Pita以及突变体和转基因菌株的天然多样性的分析鉴定了控制逃避PtrB介导的抗性的效应子序列中的一种特定多态性。总而言之，我们的工作表明M. 水稻效应子AVR-Pita通过非常规水稻抗性蛋白Ptr以等位基因特异性方式检测，并且NLR Pi-ta在Pi-ta抗性和AVR-Pita识别中没有功能。