The elicitor-responsive gene for a GRAS family protein, <i>CIGR2</i>, suppresses cell death in rice inoculated with rice blast fungus via activation of a heat shock transcription factor, <i>OsHsf23</i>

We show that a rice GRAS family protein, CIGR2, is a <i>bonafide</i> transcriptional activator, and through this function, targets the B-type heat shock protein-encoding gene <i>OsHsf23</i> (Os09g0456800). <i>CIGR2</i> (Os07g0583600) is an <i>N</i>-acetylchitooligosaccharide elicitor-responsive gene whose activity, through the direct transcriptional control of <i>OsHsf23</i>, is required for mediating hypersensitive cell death activation during pathogen infection. RNAi lines of <i>CIGR2</i> and <i>OsHsf23</i> similarly exhibited the higher level of granulation in the epidermal cells of leaf sheath inoculated with an avirulent isolate of rice blast fungus. Interestingly, we did not observe altered levels of resistance, suggesting that CIGR2 suppresses excessive cell death in the incompatible interaction with blast fungus via activation of <i>OsHsf23</i>.