Abstract
The hypersensitive response (HR) is a common feature of plant immune responses and a type of programmed cell death. We recently reported that plant-specific transcription factor OsNAC4 is a positive regulator of HR-cell death in rice. To clarify the induction mechanism of HR cell death mediated by OsNAC4, we first examined the subcellular localization of OsNAC4 during HR cell death. OsNAC4 was translocated into the nucleus during HR cell death in a phosphorylation-dependent manner. N-terminal and C-terminal region of NAC domain was important for the regulation of OsNAC4 translocation. Gene expression profiling comparing rice cells and OsNAC4 knock-down transformants using a rice cDNA microarray showed that OsNAC4 controls the transcription of at least 139 genes. To clarify the transcriptional regulatory mechanism, yeast two-hybrid analysis using OsNAC4 as bait was performed. OsNAC3, a member of the same subfamily with OsNAC4, was specifically interacted with OsNAC4. When OsNAC4 was overexpressed in rice, clear HR cell death induced. These data suggest the possibility that dimerization between OsNAC3 and OsNAC4 is necessary to the transcriptional regulation of HR-related genes.
