Free N-glycans already occur at an early stage of seed development.
As a part of our studies to elucidate the physiological significance of free N-glycans in differentiating or growing plant cells, we first demonstrate that two kinds of free N-glycans already occur at an early stage of seed development. In this report, we used the developing Ginkgo biloba seeds as a model plant, since we have already revealed a functional feature of the Ginkgo endo-beta-N-acetylglucosaminidase and structural features of N-glycans linked to storage glycoproteins in the developing seeds [Kimura, Y. et al. (1998) Biosci. Biotechnol. Biochem. 62, 253-261; Kimura, Y. and Matsuo, S. (2000) Biosci. Biotechnol. Biochem. 64, 562-568]. The structures of free N-glycans, which were determined by a combination of ESI-MS, sequential a-mannosidase digestions, partial acetolysis, and two dimensional sugar chain map, fell into two categories. One dominant species is a high-mannose type structure having one GlcNAc residue at the reducing end (Man(9-5)GlcNAc(1)). The concentration of this type of free glycan (as the pyridylaminated derivatives) is about 2.2 nmol in 1 g fresh weight. The detailed structural analysis revealed that the high-mannose type structures have a common core unit; Manalpha1-6(Man1-3)Manalpha1-6(Manalpha1-3)Ma nbeta1-4GlcNAc. The other minor species of free N-glycans is the plant complex type structure having an N-acetylchitobiose unit at the reducing end (Man(3)Xyl(1)Fuc(1)GlcNAc(2)). The concentration of this type of free glycan (as the pyridylaminated derivative) was about 75 pmol in 1 g fresh weight.
Kimura
Y
Y
Department of Bioresources Chemistry, Faculty of Agriculture, Okayama University, Okayama 700-8530, Japan. yosh8mar@cc.okayama-u.ac.jp
Matsuo
S
S
D000117:Acetylglucosamine / Q000032:analysis; D000631:Aminopyridines / Q000737:chemistry; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D020441:Ginkgo biloba; D008358:Mannose / Q000032:analysis; D008361:Mannosidases / Q000737:chemistry; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000032:analysis / Q000302:isolation & purification; D010946:Plants, Medicinal; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification*; D012639:Seeds / Q000737:chemistry* / Q000254:growth & development*; D012685:Sepharose / Q000031:analogs & derivatives*; D014994:Xylose / Q000032:analysis
D000631:Aminopyridines; D009844:Oligosaccharides; D011134:Polysaccharides; C028326:concanavalin A-sepharose; D012685:Sepharose; D014994:Xylose; D008361:Mannosidases; D008358:Mannose; D000117:Acetylglucosamine; C032439:alpha-aminopyridine