De novo biosynthesis of C-arabinosylated flavones by utilization of indica rice C-glycosyltransferases

Zhuo Chen,Qian Zhang,Yulian Zhang,Guangyi Wang,Yuwei Sun,Ying Zhang,Jianhua Li,Yong Wang

doi:10.1186/s40643-021-00404-3

Abstract

Flavone C-arabinosides/xylosides are plant-originated glycoconjugates with various bioactivities. However, the potential utility of these molecules is hindered by their low abundance in nature. Engineering biosynthesis pathway in heterologous bacterial chassis provides a sustainable source of these C-glycosides. We previously reported bifunctional C-glucosyl/C-arabinosyltransferases in Oryza sativa japonica and O. sativa indica, which influence the C-glycoside spectrum in different rice varieties. In this study, we proved the C-arabinosyl-transferring activity of rice C-glycosyltransferases (CGTs) on the mono-C-glucoside substrate nothofagin, followed by taking advantage of specific CGTs and introducing heterologous UDP-pentose supply, to realize the production of eight different C-arabinosides/xylosides in recombinant E. coli. Fed-batch fermentation and precursor supplement maximized the titer of rice-originated C-arabinosides to 20–110 mg/L in an E. coli chassis. The optimized final titer of schaftoside and apigenin di-C-arabinoside reached 19.87 and 113.16 mg/L, respectively. We demonstrate here the success of de novo bio-production of C-arabinosylated and C-xylosylated flavones by heterologous pathway reconstitution. These results lay a foundation for further optimal manufacture of complex flavonoid compounds in microbial cell factories.

Highlights

Flavone C-arabinosides are one of the less common classes of flavonoid glycosides occurring in nature
Rice CGTs responsible for varietal di‐C‐glycosides In our ongoing investigation of Gramineae CGTs, we first compared the differences of C-glycoside spectrum between two rice subspecies in detail (Fig. 1a)
Because most of the flavone C-glycosides in rice share the common aglycone apigenin (Api) or luteolin (Lut) (Besson et al 1985), we determined to focus on five representative groups of Api/Lut-C-glycosides, corresponding to monopentosides, monohexosides, dipentosides, pentosylhexosides and dihexosides

Summary

Introduction

Flavone C-arabinosides are one of the less common classes of flavonoid glycosides occurring in nature. The chemical diversity of flavone C-glycosides in Gramineae family does reflect the promiscuity of their CGTs, as both C-glucosyl and C-arabinosyl-carrying metabolites were frequently found in these grasses represented by rice (Besson et al 1985; Melo et al 2005; Talhi and Silva 2012). Japonica accumulate a high proportion of flavone C-pentosylhexosides mainly represented by (iso)schaftoside and (iso)carlinoside (Sun et al 2020). Such metabolite profiles indicate that CGTs from the rice may be excellent candidates for the production of flavone C-glycosides, especially flavone di-C-glycosides carrying hexosyl (i.e., glucosyl) and pentosyl (i.e., arabinosyl). A similar productivity of Sch/Isosch and no significant difference of accumulation pattern of intermediates between SmUxs and SmUxs (Fig. 3a), we used SmUxs for further experiments

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Results

Conclusion