Identification and functional characterization of a flax UDP-glycosyltransferase glucosylating secoisolariciresinol (SECO) into secoisolariciresinol monoglucoside (SMG) and diglucoside (SDG)

Abstract

BackgroundLignans are a class of diphenolic nonsteroidal phytoestrogens often found glycosylated in planta. Flax seeds are a rich source of secoisolariciresinol diglucoside (SDG) lignans. Glycosylation is a process by which a glycosyl group is covalently attached to an aglycone substrate and is catalyzed by uridine diphosphate glycosyltransferases (UGTs). Until now, very little information was available on UGT genes that may play a role in flax SDG biosynthesis. Here we report on the identification, structural and functional characterization of 5 putative UGTs potentially involved in secoisolariciresinol (SECO) glucosylation in flax.ResultsFive UGT genes belonging to the glycosyltransferases’ family 1 (EC 2.4.x.y) were cloned and characterized. They fall under four UGT families corresponding to five sub-families referred to as UGT74S1, UGT74T1, UGT89B3, UGT94H1, UGT712B1 that all display the characteristic plant secondary product glycosyltransferase (PSPG) conserved motif. However, diversity was observed within this 44 amino acid sequence, especially in the two peptide sequences WAPQV and HCGWNS known to play a key role in the recognition and binding of diverse aglycone substrates and in the sugar donor specificity. In developing flax seeds, UGT74S1 and UGT94H1 showed a coordinated gene expression with that of pinoresinol-lariciresinol reductase (PLR) and their gene expression patterns correlated with SDG biosynthesis. Enzyme assays of the five heterologously expressed UGTs identified UGT74S1 as the only one using SECO as substrate, forming SECO monoglucoside (SMG) and then SDG in a sequential manner.ConclusionWe have cloned and characterized five flax UGTs and provided evidence that UGT74S1 uses SECO as substrate to form SDG in vitro. This study allowed us to propose a model for the missing step in SDG lignan biosynthesis.

Therapeutic effect of Linum usitatissimum L. in STZ-nicotinamide induced diabetic nephropathy via inhibition of AGE’s and oxidative stress

“…The hydroalcoholicic extract was subjected to column chromatography and its 20% (chloroform: methanol; 20: 80) fraction showed single spot on TLC and also have positive tests for phenolics. The UV k max (265 & 358) and IR peaks (cm 1346,1279,1240,1208,1130,1067,1052,991,941,921,867,849,682,584,472] Secoisolariciresinol;325, 319, 281, 273, 247, 199, 183, 133, 73;Ricci and Piccolella 2012;Ghose et al 2014] provides the confirmation of Secoisolariciresinol diglycoside (Fig. 1).…”

Suppressing ABA uridine diphosphate glucosyltransferase (SlUGT75C1) alters fruit ripening and the stress response in tomato

“…The glycosylation of low‐molecular‐weight compounds typically alters acceptors by increasing their solubility and accumulation and regulating their bioactivity, such as antioxidant and disease‐resistant activities (Yonekura‐Sakakibara and Hanada, ; Ghose et al . ; Dong et al ., ). ABA conjugates are inactive forms that are stored in the vacuole and transported through the xylem (Jiang and Hartung, ).…”

Glutathione S-transferases and UDP-glycosyltransferases Are Involved in Response to Aluminum Stress in Flax

“…The alterations in the expression of UGTs under Al exposure were observed in rice (Huang et al, 2009), buckwheat (Yokosho et al, 2014), and maize (Mattiello et al, 2014). In flax, UGTs attract special attention because of their participation in the biosynthesis of lignans—phytoestrogens with antimicrobial, antifungal, antiviral, and antioxidant activity—which have therapeutic effects against human diseases (Dixon, 2004; Pan et al, 2009; Barvkar et al, 2012; Ghose et al, 2014; Imran et al, 2015). UGTs catalyze the glucose conjugation of monolignols that is essential for normal cell wall lignification (Lin et al, 2016).…”