title: Rhamnogalacturonan I in Solanum tuberosum tubers contains complex arabinogalactan structures.
abstract: A rhamnogalacturonan I polysaccharide was isolated from potato (Solanum tuberosum cv. Posmo) tuber cell walls and characterised by enzymatic digestion with an endo-beta-1 --> 4-galactanase and an endo-alpha-1 --> 5-arabinanase, individually or in combination. The reaction products were separated using size-exclusion chromatography and further analysed for monosaccharide composition and presence of epitopes using the LM5 anti-beta-1 --> 4-galactan and LM6 anti-alpha-1 --> 5-arabinan monoclonal antibodies. The analyses point to distinct structural features of potato tuber rhamnogalacturonan I, such as the abundance of beta-1 --> 4-galactan side chains that are poorly substituted with short arabinose-containing side chains, the presence of alpha-1 --> 5-arabinan side chains substituted with beta-1 --> 4-galactan oligomers (degree of polymerisation > 4), and the presence of alpha-1 --> 5-arabinans that resist enzymatic degradation. A synergy between the enzymes was observed towards the degradation of arabinans but not towards the degradation of galactans. The effect of the enzymes on isolated RG I is discussed in relation to documented effects of enzymes heterologously expressed in potato tubers. In addition, a novel and rapid method for the determination of the monosaccharide and uronic acid composition of cell wall polysaccharides using high-performance anion exchange chromatography with pulsed amperometric detection is described.
authors.affiliation: Biotechnology Group, Danish Institute of Agricultural Sciences, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: ØBro
authors.forename: Jesper
authors.initials: J
authors.lastname: Harholt
authors.forename: Henrik Vibe
authors.initials: HV
authors.lastname: Scheller
authors.forename: Caroline
authors.initials: C
authors.lastname: Orfila
mesh_terms: D002473:Cell Wall / Q000737:chemistry*; D005685:Galactans / Q000032:analysis*; D010368:Pectins / Q000737:chemistry* / Q000302:isolation & purification; D018517:Plant Roots / Q000737:chemistry*; D011198:Solanum tuberosum / Q000737:chemistry*
chemical_list: D005685:Galactans; C042491:rhamnogalacturonan I; D010368:Pectins; C005653:arabinogalactan