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

ABSTRACT

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.