title: Unconjugated Man5GlcNAc occurs in vegetative tissues of tomato.
abstract: Unconjugated Man alpha 1-->6(Man alpha 1-->3)Man alpha 1-->6(Man alpha 1-->3)Man beta 1-->4GlcNAc (Man5Glc NAc) delayed ripening when added exogenously at 10 ng g-1 fr. wt to both whole tomato fruit and excised pericarp tissue discs. In addition, Man5GlcNAc was one of 10 unconjugated N-glycans purified from tomato pericarp tissue. When applied exogenously at a concentration of 10 nM, Man5GlcNAc prevented the delay of ripening induced by tunicamycin, an inhibitor of its de novo synthesis. Since it was possible that this unconjugated N-glycan might be specifically related to ripening, we checked to see if it also occurred in fully expanded leaf and stem tissues using high-pH anion-exchange chromatography with pulsed amperometric detection. This method allowed us to detect 1 ng of oligosaccharide and to quantify accurately amounts in the range 60-600 ng per injection, significantly more sensitive than the amine-bonded HPLC method previously used to separate and quantify unconjugated N-glycans in tomato fruit pericarp tissue. Four high-mannosyl type unconjugated N-glycans were detected in tomato vegetative tissues, including Man5GlcNAc. These results support a potential role of Man5GlcNAc and/or other unconjugated N-glycans in plant developmental processes, in addition to its apparent role as a modulator of senescence of fruit. However, an initial experiment showed no effect of Man5GlcNAc on senescence of tomato leaf discs, as measured by chlorophyll loss.
authors.affiliation: USDA, Agricultural Research Service, Horticultural Crops Quality Laboratory, Beltsville, MD 20705-2350, USA.
authors.forename: H
authors.initials: H
authors.lastname: Yunovitz
authors.forename: J N
authors.initials: JN
authors.lastname: Livsey
authors.forename: K C
authors.initials: KC
authors.lastname: Gross
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D018551:Solanum lycopersicum / Q000737:chemistry*; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry* / Q000302:isolation & purification; D018515:Plant Leaves; D018547:Plant Stems; D011134:Polysaccharides / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D009844:Oligosaccharides; D011134:Polysaccharides