Cloning and expression of an Arabidopsis gene encoding a putative peroxisomal ascorbate peroxidase

An Arabidopsis 14-3-3 protein, AFT1, was used as a 'bait' in the two-hybrid system to identify its interacting proteins. One of the candidate proteins, APX3, was identified as a putative peroxisomal membrane-bound ascorbate peroxidase. Ascorbate peroxidases are important defense enzymes that protect plant cells from oxidative stress damage. DNA blot analysis indicates that APX3 is encoded by a single-copy gene in the Arabidopsis genome. RNA blot analyses show that APX3 transcript levels increase slightly in response to cold, UV light, and treatments with hydrogen peroxide and paraquat. The activity of APX3 in Arabidopsis may be controlled in two ways: its enzymatic activity through protein-protein interactions and its transcription by transcriptional or posttranscriptional regulation.