Abstract
Stress responsive NAC transcription factors including RD26 may function in crosstalk of ABA- and JA-related abiotic- and biotic-stress signal transduction. To analyze the role of RD26, the RD26 gene driven by the CaMV35S promoter was transformed into Arabidopsis. Although RD26 transcripts were highly accumulated in the RD26-OX plants, RD26 proteins were undetectable. The RD26 proteins were thought to be degraded by ubiquitin-proteasome system because a proteasome inhibitor MG132 treatment dramatically increased RD26 proteins in the RD26-OX protoplasts. To resolve the degradation process of RD26, we tried to identify RD26-specific ubiquitin ligase(s) necessary for the degradation. Five candidates of ubiquitin ligases were identified to interact with RD26. Over-expression of one of the candidates, RHG1a showed down-regulation of the RD26-regulated genes. These results indicate that the level of stress-responsive NAC transcription factors is regulated not only at transcriptional level but also at post-translational level.
