Gene-specific primer pairs designed from cDNA conserved motifs of BE, SSS, GBSS and SP, a group of enzymes involved in starch biosynthesis, were used in RT-PCR cloning on the polyA mRNA of premature mung bean (Vigna radiata L. cv Tainan no. 5). Only SBE F1 and SBE R1 pairs were successfully amplify a partial-length of cDNA (794 bp) encoding starch branching enzyme (SBEI; 2.4.1.18). The internal sequence of the amplicon was searched in the GCG database and found to have 97% similarity with Phaseolus vulgaris BE I (kbe1; accession no. AB029548; 3,360 bp) and 84% similarity with Ipomoea batatas (sweet potato) SBE II (AB071286; 3,123 bp) within the overlapped regions and thus designated VrbeIp. Besides, it was also shown to be located in the central region of the postulated full-length cDNA by PileUp alignment and was then cloned into pGEM T-Eazy vector, designated pVrbeIp for further use. In order to pursue a full-length clone, internal primers were designed from VrbeIp sequence to conduct RACE on the first strand cDNA library. 3'-RACE was performed more smoothly than 5'-RACE and a 1,200 bp fragment were generated and currently subjected to sequencing.
