title: Functional Characterization of UDP-apiose Synthases from Bryophytes and Green Algae Provides Insight into the Appearance of Apiose-containing Glycans during Plant Evolution.
abstract: Apiose is a branched monosaccharide that is present in the cell wall pectic polysaccharides rhamnogalacturonan II and apiogalacturonan and in numerous plant secondary metabolites. These apiose-containing glycans are synthesized using UDP-apiose as the donor. UDP-apiose (UDP-Api) together with UDP-xylose is formed from UDP-glucuronic acid (UDP-GlcA) by UDP-Api synthase (UAS). It was hypothesized that the ability to form Api distinguishes vascular plants from the avascular plants and green algae. UAS from several dicotyledonous plants has been characterized; however, it is not known if avascular plants or green algae produce this enzyme. Here we report the identification and functional characterization of UAS homologs from avascular plants (mosses, liverwort, and hornwort), from streptophyte green algae, and from a monocot (duckweed). The recombinant UAS homologs all form UDP-Api from UDP-glucuronic acid albeit in different amounts. Apiose was detected in aqueous methanolic extracts of these plants. Apiose was detected in duckweed cell walls but not in the walls of the avascular plants and algae. Overexpressing duckweed UAS in the moss Physcomitrella patens led to an increase in the amounts of aqueous methanol-acetonitrile-soluble apiose but did not result in discernible amounts of cell wall-associated apiose. Thus, bryophytes and algae likely lack the glycosyltransferase machinery required to synthesize apiose-containing cell wall glycans. Nevertheless, these plants may have the ability to form apiosylated secondary metabolites. Our data are the first to provide evidence that the ability to form apiose existed prior to the appearance of rhamnogalacturonan II and apiogalacturonan and provide new insights into the evolution of apiose-containing glycans.
authors.affiliation: From the Complex Carbohydrate Research Center and.|Departments of Biochemistry and Molecular Biology and.
authors.forename: James
authors.initials: J
authors.lastname: Smith
authors.affiliation: Plant Biology, University of Georgia, Athens, Georgia 30602.
authors.forename: Yiwen
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Departments of Biochemistry and Molecular Biology and.
authors.forename: Shahar
authors.initials: S
authors.lastname: Levy
authors.affiliation: Departments of Biochemistry and Molecular Biology and.
authors.forename: Oluwatoyin Oluwayemi
authors.initials: OO
authors.lastname: Adelusi
authors.affiliation: From the Complex Carbohydrate Research Center and.|Plant Biology, University of Georgia, Athens, Georgia 30602.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hahn
authors.affiliation: From the Complex Carbohydrate Research Center and.
authors.forename: Malcolm A
authors.initials: MA
authors.lastname: O'Neill
authors.affiliation: From the Complex Carbohydrate Research Center and peled@ccrc.uga.edu.|Plant Biology, University of Georgia, Athens, Georgia 30602.
authors.forename: Maor
authors.initials: M
authors.lastname: Bar-Peled
mesh_terms: D019068:Bryopsida / Q000235:genetics / Q000378:metabolism*; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D000460:Chlorophyta / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011134:Polysaccharides / Q000096:biosynthesis / Q000235:genetics; D014539:Uridine Diphosphate Sugars / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D010940:Plant Proteins; D011134:Polysaccharides; C511616:UDP-apiose; D014539:Uridine Diphosphate Sugars; D002262:Carboxy-Lyases
keywords: algae; decarboxylase; glycosyltransferase; plant cell wall; vascular