Identification of genes involved in induction of plant hypersensitive cell death

The hypersensitive response (HR) is a form of programmed cell death commonly associated with immune response in plants. Incompatible N1141 strain of Acidovorax avenae elicits HR cell death in cultured rice cells, while flagellin-deficient N1141 mutant (Dfla-N1141) lost the ability to induce immune responses. We present evidence that initiation of HR cell death induced by the incompatible N1141 strain requires de novo protein synthesis. The protein kinase inhibitors, staurosporine and K252a, effectively suppressed HR cell death, while the protein phosphatase inhibitors, calyculin A and okadaic acid, did not affect the induction of HR cell death. To identify the key initiator of HR cell death, PCR subtraction analysis and microarray analysis were performed. PCR subtraction analysis identified 42 genes which are induced during HR cell death, and microarray analysis (22K) showed that 87 genes were induced during HR cell death. Among identified genes, OsNAC gene encoding plant specific transcription factor was identified in both analyses. Real-time reverse-transcription PCR analysis for several OsNAC family genes revealed that OsNAC4 gene was strongly and specifically induced during HR cell death in cultured rice cells. Results showed that OsNAC4 transcription factor is an influential candidate as a key initiator in plant HR cell death.