Abstract
Cation/H+ exchanger (CAX) is an active transporter, which transports divalent cation using a H+ gradient. There are five CAX in rice; OsCAX1a, OsCAX1b, OsCAX1c, OsCAX2, and OsCAX3. OsCAX3 belongs to the Type IB, which might transport heavy metals, such as Mn2+ and Cd2+. However, the physiological function of OsCAX3 has not been revealed. OsCAX3 was expressed in the whole plant and conferred the Ca2+ and Mn2+ tolerance to the yeast. The present study aims to elucidate the physiological function of OsCAX3. First, we determined the tissue specificity using promoter-GUS transgenic rice. OsCAX3 was expressed in embryo, aleurone layer, root steles, root tip, shoot apical, vascular bundle and trichome. Second, the subcellular localization was determined using GFP fusion protein (GFP-OsCAX3). When the protein was expressed in protoplast prepared from rice callus, the green fluorescence was observed in dotted organelles moving in the cytosol. Now, we are trying to identify the organelles.
