The study reports cloning and characterization of complete biosynthetic gene cluster committed to glycyrrhizin biosynthesis along with their corresponding promoter regions from Glycyrrhiza glabra. The identified genes namely, β-amyrin synthase, β-amyrin-11-oxidase, 11-oxo-beta-amyrin 30-oxidase and UDP-dependent glucosyltransferase, were hetrologously expressed in Nicotiana benthamiana for functional validation. The phyto-hormone, naphthalene acetic acid was shown to prompt maximum up regulation (1.3-14.0 folds) of all the genes, followed by gibberellic acid (0.001-10.0 folds) and abscisic acid (0.2-7.7 folds) treatments. The promoter-GUS fusion constructs infiltrated leaves of the identified genes exhibited enhanced promoter activity of β-amyrin synthase (3.9 & 3.0 folds) and 11-oxo-beta-amyrin 30-oxidase (3.6 & 3.2 folds) under the GA3 and NAA treatments, respectively as compared to their respective untreated controls. The transcriptional control of the three phytohormones studied could be correlated to the cis-responsive elements present in the upstream regions of the individual genes. The study provided an insight into the intricate interaction between hormone-responsive motifs with the corresponding co-expression of the glycyrrhizin biosynthetic pathway genes. The study will help in understanding the phytohormones-mediated regulation of glycyrrhizin biosynthesis and its modulation in the plant.
Keywords: Glycyrrhiza glabra; Glycyrrhizin; Phytohormone; Promoter; Transcriptional regulation.
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