RRM Transcription Factors Interact with NLRs and Regulate Broad-Spectrum Blast Resistance in Rice. RRM Transcription Factors Interact with NLRs and Regulate Broad-Spectrum Blast Resistance in Rice

Nucleotide-binding site leucine-rich repeat (NLR) receptors perceive pathogen effectors and trigger plant immunity. However, the mechanisms underlying NLR-triggered defense responses remain obscure. The recently discovered Pigm locus in rice encodes a cluster of NLRs, including PigmR, which confers broad-spectrum resistance to blast fungus. Here, we identify PIBP1 (PigmR-INTERACTING and BLAST RESISTANCE PROTEIN 1), an RRM (RNA-recognition motif) protein that specifically interacts with PigmR and other similar NLRs to trigger blast resistance. PigmR-promoted nuclear accumulation of PIBP1 ensures full blast resistance. We find that PIBP1 and a homolog, Os06 g02240, bind DNA and function as unconventional transcription factors at the promoters of the defense genes OsWAK14 and OsPAL1, activating their expression. Knockout of PIBP1 and Os06g02240 greatly attenuated blast resistance. Collectively, our study discovers previously unappreciated RRM transcription factors that directly interact with NLRs to activate plant defense, establishing a direct link between transcriptional activation of immune responses with NLR-mediated pathogen perception Overall design: Genome-wide analysis of the transcriptome of PIBP1 RNAi and corresponding wild type NIL-Pigm treatment with blast isolate TH12.

核苷酸结合富亮氨酸重复序列（Nucleotide-binding site leucine-rich repeat, NLR）受体可识别病原菌效应蛋白并触发植物免疫。然而，NLR介导的防御反应的分子机制仍未阐明。近期在水稻中鉴定的Pigm基因座编码一组NLR受体，其中包含PigmR蛋白，该蛋白可赋予水稻对稻瘟病菌的广谱抗性。本研究鉴定得到PIBP1（PigmR互作与稻瘟病抗性蛋白1，PigmR-INTERACTING and BLAST RESISTANCE PROTEIN 1），这是一类携带RNA识别基序（RNA-recognition motif, RRM）的蛋白，可特异性结合PigmR及其他同类NLR受体，从而介导稻瘟病抗性。PigmR介导的PIBP1核积累是水稻获得完全稻瘟病抗性的关键保障。研究发现，PIBP1及其同源蛋白Os06g02240可结合DNA，并作为非典型转录因子靶向防御基因OsWAK14与OsPAL1的启动子区域，激活二者的转录表达。敲除PIBP1与Os06g02240会显著削弱水稻的稻瘟病抗性。综上，本研究发现了一类此前未被认知的RRM类转录因子，它们可直接结合NLR受体以激活植物防御反应，从而在免疫反应的转录激活与NLR介导的病原菌识别之间建立了直接关联。实验设计：对经稻瘟病菌菌株TH12接种处理的PIBP1 RNA干扰（RNAi）植株及其对应的野生型NIL-Pigm材料开展全基因组转录组分析。