l-Galactose replaces l-fucose in the pectic polysaccharide rhamnogalacturonan II synthesized by the l-fucose-deficient mur1 Arabidopsis mutant.
Arabidopsis thaliana mur1 is a dwarf mutant with altered cell-wall properties, in which l-fucose is partially replaced by l-galactose in the xyloglucan and glycoproteins. We found that the mur1 mutation also affects the primary structure of the pectic polysaccharide rhamnogalacturonan II (RG-II). In mur1 RG-II a non-reducing terminal 2- O-methyl l-galactosyl residue and a 3,4-linked l-galactosyl residue replace the non-reducing terminal 2- O-methyl l-fucosyl residue and the 3,4-linked l-fucosyl residue, respectively, that are present in wild-type RG-II. Furthermore, we found that a terminal non-reducing l-galactosyl residue, rather than the previously reported d-galactosyl residue, is present on the 2- O-methyl xylose-containing side chain of RG-II in both wild type and mur1 plants. Approximately 95% of the RG-II from wild type and mur1 plants is solubilized as a high-molecular-weight (>100 kDa) complex, by treating walls with aqueous potassium phosphate. The molecular mass of RG-II in this complex was reduced to 5-10 kDa by treatment with endopolygalacturonase, providing additional evidence that RG-II is covalently linked to homogalacturonan. The results of this study provide additional information on the structure of RG-II and the role of this pectic polysaccharide in the plant cell wall.
Reuhs
Bradley L
BL
Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology, The University of Georgia, 315 Riverbend Road, GA 30602-4712, Athens, USA.
Glenn
Joshua
J
Stephens
Samuel B
SB
Kim
John S
JS
Christie
D Benjamin
DB
Glushka
John G
JG
Zablackis
Earl
E
Albersheim
Peter
P
Darvill
Alan G
AG
O'Neill
Malcolm A
MA
D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002473:Cell Wall / Q000737:chemistry; D002478:Cells, Cultured; D005643:Fucose / Q000031:analogs & derivatives / Q000032:analysis*; D005690:Galactose / Q000031:analogs & derivatives / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D009154:Mutation; D010368:Pectins / Q000737:chemistry* / Q000378:metabolism; D018515:Plant Leaves / Q000737:chemistry / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization
D029681:Arabidopsis Proteins; C476110:mur1 protein, Arabidopsis; C042492:rhamnogalacturonan II; D005643:Fucose; D010368:Pectins; D005690:Galactose