Molecular and Functional Characterization of a Rice Thioredoxin m Isoform and Its Interaction Proteins

Although subcellular localization and substrate specificity of thioredoxin isoforms have been characterized, there is little information on the specific functions of mtype plant thioredoxins or their interaction targets. Here, we describe the functional characterization of an Oryza sativa thioredoxin m (OsTrxm). We undertook yeast twohybrid screening using OsTrxm as a bait and found three interaction proteins, Pex14 and two Pex5 variants. Furthermore, two cysteines of OsTrxm were sufficient for the interaction between OsTrxm and these peroxisome proteins. To verify whether OsTrxm and the target proteins can be co-localized in vivo, we examined subcellular localization of OsTrxm-GFP and a peroxisomal marker RFP-SKL in Arabidopsis protoplast cells. Surprisingly, we detected OsTrxm localization in the cytosol and chloroplast. We confirmed these results by 2-D PAGE and Western blot analysis. Our results indicate that OsTrxm may play important roles in the cytoplasm for peroxisome biogenesis as well as in redox regulation of chloroplast proteins.