Characterization of genes encoding Starch Branching Enzyme I from Triticum monococcum and its diploid wheat relatives

The Starch Branching Enzyme I (SBEI) gene plays an important role in amylopectin synthesis. Here, we isolated and characterized the full-length cDNA and DNA sequences of SBEI gene from diploid Triticeae species, Triticum monococcum, T. urartu, Aegilopsspeltoides, and Ae. tauschii. Then we predicted its protein structure, analyzed its evolutionary relationship with other species, and explored its expression patterns using real-time quantitative PCR. The SBEI cDNA includes a 2,490-bp open reading frame (ORF) encoding 829 amino acids. The genomic DNA of SBEI is 5,526-bp in length, containes fourteen exons and thirteen introns, and shares a similar structure with its homologous genes from other cereal plants. Sequence similarity ranging from 70.50% to 98.02% in exons and from 15.50% to 83.63% in introns was detected. Results of phylogenetic tree based on the deduced amino acid sequences from T. monococcum and other plants indicated that T. monococcum SBEI is more closely related to T. boeoticum and T. urartu. Expression analysis revealed that T. monococcum SBEI and AGPase genes were highly expressed in the seeds at middle developmental stage. This is the first report on characterization of the SBEI gene in T. monococcum. These results could be used to explore the roles of this enzyme in amylopectin synthesis.