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.
Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology, The University of Georgia, 315 Riverbend Road, GA 30602-4712, Athens, USA.
Bradley L
BL
Reuhs
Joshua
J
Glenn
Samuel B
SB
Stephens
John S
JS
Kim
D Benjamin
DB
Christie
John G
JG
Glushka
Earl
E
Zablackis
Peter
P
Albersheim
Alan G
AG
Darvill
Malcolm A
MA
O'Neill
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