Identification and Expression Profiling of a New β-amyrin Synthase Gene (GmBAS3) from Soybean

Abstract—Cyclization of 2,3-oxidosqualene by different oxidosqualene cyclase (OSC) genes is responsible for sapogenin heterogeneity. The very first phase is the conversion of 2,3-oxidosqualene into β-amyrin by β‑amyrin synthase (BAS) gene, a member of OSC family, in soy saponin biosynthesis pathway. This paper reports the identification of a new BAS gene (GmBAS3) and its expression pattern in soybean (Glycine max (L.) Merr.). GmBAS3 gene was identified by PCR/RACE method with an open reading frame of 2286 bp nucleotides encoding a 762 amino acid long protein devouring a characteristic QW motif repeated five times and DCTAE motif. GmBAS3 shared 96 and 92% homology with Glycyrrhiza uralensis BAS and Lotus japonicus putative BAS respectively. Expression of the gene was detected by RT-PCR in regard to seedlings age and tissue type. A spatio-temporal expression of GmBAS3 was found in 21-day-old seedlings in the hypocotyls, young leaves and mature leaves but not observed in stem and root tissues. No expression was perceived in 10‑day-old seedling. This study also support the premise that β-amyrin synthesis hang on more than one type of BAS genes with there expression in different plant parts at different times.