An ankyrin repeat-containing protein plays a role in both disease resistance and antioxidation metabolism

The Arabidopsis ankyrin repeat-containing protein AKR2 was identified as a GF14lambda-interacting protein in a yeast two-hybrid screening (GF14lambda is a 14-3-3 protein). Reduced expression of AKR2 by using the antisense technique results in small necrotic areas in leaves accompanied by higher production of H2O2, similar to the hypersensitive response to pathogen infection in plant disease resistance. Transcripts of genes encoding pathogen-induced protein PR-1 (pathogen-related protein 1) and stress-responsive protein GST6 (glutathione S-transferase 6) are increased in antisense plants. The resistance to a bacterial pathogen infection was also increased by at least 10-fold in antisense plants. AKR2 also interacts with another GF14lambda-interacting protein, the ascorbate peroxidase 3 that scavenges H2O2 in plant cells. These data suggest that AKR2 may be a negative regulator of PR-1 expression, and is probably involved in the regulation of antioxidation metabolism that is shared by both disease resistance and stress responses.