Abstract
Rice α-amylases were known to be encoded by multigene, and 20 isoforms were identified and characterized in the germinating seeds and tissue culture. α-Amylase I-1 (RAmy1A) was a glycoprotein bearing N-linked carbohydrate chain, that was actively synthesized and secreted from the secretory tissues. However, immunocytochemical analyses with specific anti-α-amylase I-1 antibodies revealed that α-amylase I-1 locates in the amyloplasts or chloroplasts of living cells of rice. To determine the intracellular localization of different α-amylase isoforms, we investigate the expression and targeting of enzyme/GFP fused protein in onion epidermal cells. The fluorescence-labeled α-amylase I-1 was found to be co-localized with the plastid, whereas the targeting ratios of the other isoforms into plastid were different from that of α-amylase I-1. We will discuss a possible mechanism for plastid targeting of α-amylase I-1 and difference of physiological function of each α-amylase isoform.
