Arabinogalactan-proteins from non-coniferous gymnosperms have unusual structural features. (1st June 2021) - Baumann, Alexander
Highlights: AGPs from gymnosperms Ginkgo, Cycas, Ephedra and Encephalartos were characterized. The unusual monosaccharide acofriose was found in AGPs from Ginkgo, Ephedra and Encephalartos. A unique attribute of Ginkgo AGP is a glycan part mixed of type I and II AGs. Bioinformatic investigations on glycosyltransferases complete analytical results. The study contributes to understanding of evolution of AGPs during life on land. Abstract: Arabinogalactan-proteins (AGPs), important signalling molecules of the plant cell wall, are structurally extensively investigated in angiosperms, but information on AGPs in gymnosperms is still limited. We characterized AGPs from the gymnosperms Ginkgo biloba, Ephedra distachya, Encephalartos longifolius and Cycas revoluta . The protein contents are comparable to that of angiosperm AGPs. Hydroxyproline is the site of linking the carbohydrate part and was detected in all AGPs with highest concentration in Cycas AGP (1.1 % of the AGP). Interestingly, with the exception of Cycas, all AGPs contained the monosaccharide 3- O -methylrhamnose not present in angiosperm polysaccharides. The carbohydrate moieties of Cycas and Ephredra showed the main components 1, 3, 6-linked galactose and terminal arabinose typical of angiosperm AGPs, whereas that of Ginkgo AGP was unique with 1, 4-linked galactose as dominant structural element. Bioinformatic search for glycosyltransferases in Ginkgo genome also revealed a lower number of galactosyltransferases responsible for biosynthesis of the 1, 3-Gal/1, 6-Gal AGP backbone.