Specific Expression of Maize SBEIIb Promoter Mediated by Different Promoter Region in Transgenic Tobacco Plants

Starch branching enzyme (SBE) catalyzes the biosynthesis of amylopectin. We described the isolation and characterization of SBEIIb promoter and their expression patterns in transgenic tobacco. Using the genomic DNA of maize cultivar Lunuo 1 as template, the SBEIIb promoter was isolated by PCR and was cloned into pMD18-T vector. To study SEBIIb gene regulation at the cellular level, SBEIIb promoter was fused to the β-glucuronidase (GUS) report gene. The results of the fluorometric GUS assays indicate that the sbeIIb-GUS fusion directed a seed-specific expression. Four series of constructs were made with the promoter and the GUS reporter gene to investigate the cis-acting analysis, showing that the four different constructs all can drive expression of the GUS gene in seed plumule and cotyledon and the GUS activity was apparently decreased with the progressive loss of promoter 5′ end.