Structure of ten free N-glycans in ripening tomato fruit. Arabinose is a constituent of a plant N-glycan.
The concentration-dependent stimulatory and inhibitory effect of N-glycans on tomato (Lycopersicon esculentum Mill.) fruit ripening was recently reported (B. Priem and K.C. Gross [1992] Plant Physiol 98: 399-401). We report here the structure of 10 free N-glycans in mature green tomatoes. N-Glycans were purified from fruit pericarp by ethanolic extraction, desalting, concanavalin A-Sepharose chromatography, and amine-bonded silica high performance liquid chromatography. N-Glycan structures were determined using 500 MHz 1H-nuclear magnetic resonance spectroscopy, fast atom bombardment mass spectrometry, and glycosyl linkage methylation analysis by gas chromatography-mass spectrometry. A novel arabinosyl-containing N-glycan, Man alpha 1-->6(Ara alpha 1-->2)Man beta 1-->4GlcNAc beta 1-->4(Fuc alpha 1-->3)GlcNAc, was purified from a retarded concanavalin A fraction. The location of the arabinosyl residue was the same as the xylosyl residue in complex N-glycans. GlcNAc[5']Man3(Xyl)GlcNAc(Fuc)GlcNAc and GlcNAc[5']Man2GlcNAc(Fuc)GlcNAc were also purified from the weakly retained fraction. The oligomannosyl N-glycans Man5GlcNAc, Man6GlcNAc, Man7GlcNAc, and Man8GlcNAc were purified from a strongly retained concanavalin A fraction. The finding of free Man5GlcNAc in situ was important physiologically because previously we had described it as a promoter of tomato ripening when added exogenously. Mature green pericarp tissue contained more than 1 microgram of total free N-glycan/g fresh weight. Changes in N-glycan composition were determined during ripening by comparing glycosyl and glycosyl-linkage composition of oligosaccharidic extracts from fruit at different developmental stages. N-Glycans were present in pericarp tissue at all stages of development. However, the amount increased during ripening, as did the relative amount of xylosyl-containing N-glycans.
Priem
B
B
Horticultural Crops Quality Laboratory, Beltsville Agricultural Research Center, Maryland 20705.
Gitti
R
R
Bush
C A
CA
Gross
K C
KC
D002240:Carbohydrate Sequence; D002241:Carbohydrates / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009844:Oligosaccharides / Q000737:chemistry; D063245:Plant Development; D010944:Plants / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry*; D012995:Solubility; D014675:Vegetables / Q000737:chemistry / Q000235:genetics
D002241:Carbohydrates; D009844:Oligosaccharides; D011134:Polysaccharides