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-h ybrid system to identify its interacting proteins. One of the candidat e proteins, APX3, was identified as a putative peroxisomal membrane-bo und ascorbate peroxidase. Ascorbate peroxidases are important defense enzymes that protect plant cells from oxidative stress damage. DNA blo t analysis indicates that APX3 is encoded by a single-copy gene in the Arabidopsis genome. RNA blot analyses show that APX3 transcript level s increase slightly in response to cold, UV light, and treatments with hydrogen peroxide and paraquat. The activity of APX3 in Arabidopsis m ay be controlled in two ways: its enzymatic activity through protein-p rotein interactions and its transcription by transcriptional or posttr anscriptional regulation.