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 Os06 g02240 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. [Display omitted] •PIBP1 interacts with the NLR PigmR and functions in NLR-mediated blast resistance•PigmR promotes nuclear accumulation of PIBP1 to activate immunity•PIBP1 directly binds the OsWAK14 and OsPAL1 promoters and activates their expression•PIBP1 and its homolog are transcription factors functioning in plant immunity How nucleotide-binding site leucine-rich repeat (NLR) receptors trigger immune transcriptional activation remains obscure. Zhai et al. discover an RRM class of transcription factors, PIBP1s, that directly interacts with the rice broad-spectrum blast resistance NLRs, resulting in their nuclear accumulation and direct activation of defense genes, including OsWAK14 and OsPAL1.