Two closely related cDNAs encoding starch branching enzyme from Arabidopsis thaliana.

Two starch branching enzyme (SBE) cDNAs were identified in an Arabidopsis seedling hypocotyl library using maize Sbe1 and Sbe2 cDNAs as probes. The two cDNAs have diverged 5' and 3' ends, but encode proteins which share 90% identity over an extensive region with 70% identity to maize SBE IIb [12]. Genomic Southern blots suggest that the two cDNAs are the products of single, independent genes, and that additional, more distantly related SBE genes may exist in the Arabidopsis genome. The two cDNAs hybridize to transcripts which show similar expression patterns in Arabidopsis vegetative and reproductive tissues, including seedlings, inflorescence rachis, mature leaves, and flowers. This is the first report of the identification of cDNAs encoding two closely related starch branching enzymes from the same species.