title: Overexpression of a cytosol-localized rhamnose biosynthesis protein encoded by Arabidopsis RHM1 gene increases rhamnose content in cell wall.
abstract: l-Rhamnose (Rha) is an important constituent of pectic polysaccharides, a major component of the cell walls of Arabidopsis, which is synthesized by three enzymes encoded by AtRHM1, AtRHM2/AtMUM4, and AtRHM3. Despite the finding that RHM1 is involved in root hair formation in Arabidopsis, experimental evidence is still lacking for the in vivo enzymatic activity and subcellular compartmentation of AtRHM1 protein. AtRHM1 displays high similarity to the other members of RHM family in Arabidopsis and in other plant species such as rice and grape. Expression studies with AtRHM1 promoter-GUS fusion gene showed that AtRHM1 was expressed almost ubiquitously, with stronger expression in roots and cotyledons of young seedlings and inflorescences. GFP::AtRHM1 fusion protein was found to be localized in the cytosol of cotyledon cells and of petiole cells of cotyledon, indicating that AtRHM1 is a cytosol-localized protein. The overexpression of AtRHM1 gene in Arabidopsis resulted in an increase of rhamnose content as much as 40% in the leaf cell wall compared to the wild type as well as an alteration in the contents of galactose and glucose. Fourier-transform infrared analyses revealed that surplus rhamnose upon AtRHM1 overexpression contributes to the construction of rhamnogalacturonan.
authors.affiliation: Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Wang
authors.forename: Qinmei
authors.initials: Q
authors.lastname: Ji
authors.forename: Ling
authors.initials: L
authors.lastname: Jiang
authors.forename: Songdong
authors.initials: S
authors.lastname: Shen
authors.forename: Yunliu
authors.initials: Y
authors.lastname: Fan
authors.forename: Chunyi
authors.initials: C
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000096:biosynthesis* / Q000235:genetics*; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism*; D018548:Cotyledon; D003600:Cytosol; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005964:Glucosyltransferases / Q000096:biosynthesis* / Q000235:genetics*; D008969:Molecular Sequence Data; D010368:Pectins / Q000096:biosynthesis / Q000235:genetics; D018517:Plant Roots; D030821:Plants, Genetically Modified; D012210:Rhamnose / Q000096:biosynthesis* / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D029681:Arabidopsis Proteins; C042491:rhamnogalacturonan I; D010368:Pectins; D005964:Glucosyltransferases; C519657:RHM1 protein, Arabidopsis; D012210:Rhamnose