XVI International Botanical Congess

Multiple forms of starch branching enzyme, RBE1, RBE3, and RBE4, were purified from developing rice seeds. The amino-terminal sequence of RBE4, AGAPGKVLVPGGGSDDLL, was highly divergent to those of RBE1 and RBE3. To identify the cDNA clones encoding for RBE4, we screened a developing rice seed cDNA library by a synthesized oligonucleotide corresponding to the amino-terminal sequence of RBE4, and 6 positive clones were obtained. Northern blot analysis demonstrates that the gene encoding RBE4 is expressed in earlier stages of seed development, in comparison with RBE1 and RBE3. Expression systems for the cDNA fragments encoding RBE1, RBE3, and RBE4 were established in E. coli. The branched a-glucans which were produced by recombinant RBEs from potato amylose as a substrate had different chain distributions.