Abstract
In many plants, isoflavones are the main secondary metabolites that have various pharmacological activities, but the low water solubility of aglycones limits their usage. The O-glycosylation of (iso)flavones is a promising way to overcome this barrier. O-glycosyltransferases (UGTs) are key enzymes in the biosynthesis of (iso)flavonoid O-glycosides in plants. However, limited investigations on isoflavonoid O-UGTs have been reported, and they mainly focused on legumes. Iris domestica (L.) Goldblatt et Mabberley is a non-legume plant rich in various isoflavonoid glycosides. However, there are no reports regarding its glycosylation mechanism, despite the I. domestica transcriptome previously being annotated as having non-active isoflavone 7-O-UGTs. Our previous experiments indicated that isoflavonoid glycosides were induced by CuCl2 in I. domestica calli; therefore, we hypothesized that isoflavone O-UGTs may be induced by Cu2+. Thus, a comparative transcriptome analysis was performed using I. domestica seedlings treated with CuCl2, and eight new active BcUGTs were obtained. Biochemical analyses showed that most of the active BcUGTs had broad substrate spectra; however, substrates lacking 5-OH were rarely catalyzed. Real-time quantitative PCR results further indicated that the transcriptional levels of BcUGTs were remarkably induced by Cu2+. Our study increases the understanding of UGTs and isoflavone biosynthesis in non-legume plants.
Highlights
Secondary metabolites derived from plants play very important roles in organisms’ physiological activities, as well as human health
Our previous study showed that calli of I. domestica treated with copper chloride (CuCl2) accumulated 2.09 mg/g of tectoridin and iridin, while no isoflavonoid glycosides were detected in the control group
45-day-old I. domestica seedling roots treated with CuCl2 were used for Illumina sequencing after the RNA quality met specific criteria (Supplementary Figure 1)
Summary
Secondary metabolites derived from plants play very important roles in organisms’ physiological activities, as well as human health. Isoflavonoid glycosides are a class of significant secondary metabolites mainly found in legume plants, which are associated with the interactions between legumes and both symbiotic and pathogenic microorganisms (Krämer et al, 1984; Graham et al, 1990; Udomsuk et al, 2010; Li et al, 2014; Clúa et al, 2018; Karre et al, 2019). The low water solubility of isoflavonoid aglycones is a barrier to the clinical applications. Glycosylation is an effective way to increase water solubility and bioavailability. The apparent solubility of puerarin 7-O-glycoside is 18-fold that of puerarin (Jiang et al, 2008), and genistein 7-O-glycoside showed greater oral bioavailability than genistein (Kwon et al, 2007). O-glycosylation is the main glycosylation form, and O- UDP- sugar glycosyltransferases (O-UGTs) are responsible for the
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
