CGR3： A Golgi-Localized Protein Influencing Homogalacturonan Methylesterification  

作　　者：Michael A. Held Evan Be Starla Zemelis Saunia Withers Curtis Wilkerson Federica Brandizzi 

机构地区：[1]Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI 48824, USA [2]MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI 48824, USA [3]Present address： Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701, USA [4]Department of Biochemistry and Molecuiar Biology, Michigan State University, East Lansing, MI 48824, USA

出　　处：《Molecular Plant》2011年第5期832-844,共13页分子植物（英文版）

摘　　要：Plant cell walls are complex structures that offer structural and mechanical support to plant cells and are ultimately responsible for plant architecture and form. Pectins are a large group of complex polysaccharides of the plant cell wall that are made in the Golgi and secreted to the wall. The methylesterification of pectins is believed to be an important factor for the dynamic properties of the cell wall. Here, we report on a protein of unknown function discovered using an extensive proteomics analysis of cotton Golgi. Through bioinformatic analyses, we identified the ortholog of such protein, here named cotton Golgi-related 3 （CGR3） in Arabidopsis and found that it shares conserved residues with S- adenosylmethionine methyltransferases. We established that CGR3 is localized at the Golgi apparatus and that the expression of the CGR3 gene is correlated with that of several cell wall biosynthetic genes, suggesting a possible role of the protein in pectin modifications. Consistent with this hypothesis, immunofluorescence microscopy with antibodies for homogalacturonan pectins （HG） indicated that the celt wails of cgr3 knockout mutants and plants overexpressing CGR3 are decreased and increased in HG methylesterification, respectively. Our results suggest that CGR3 plays a role in the methylesterification of homogalacturonan in Arabidopsis.Plant cell walls are complex structures that offer structural and mechanical support to plant cells and are ultimately responsible for plant architecture and form. Pectins are a large group of complex polysaccharides of the plant cell wall that are made in the Golgi and secreted to the wall. The methylesterification of pectins is believed to be an important factor for the dynamic properties of the cell wall. Here, we report on a protein of unknown function discovered using an extensive proteomics analysis of cotton Golgi. Through bioinformatic analyses, we identified the ortholog of such protein, here named cotton Golgi-related 3 （CGR3） in Arabidopsis and found that it shares conserved residues with S- adenosylmethionine methyltransferases. We established that CGR3 is localized at the Golgi apparatus and that the expression of the CGR3 gene is correlated with that of several cell wall biosynthetic genes, suggesting a possible role of the protein in pectin modifications. Consistent with this hypothesis, immunofluorescence microscopy with antibodies for homogalacturonan pectins （HG） indicated that the celt wails of cgr3 knockout mutants and plants overexpressing CGR3 are decreased and increased in HG methylesterification, respectively. Our results suggest that CGR3 plays a role in the methylesterification of homogalacturonan in Arabidopsis.

关 键 词：GOLGI METHYLTRANSFERASE HOMOGALACTURONAN pectin. 

分 类 号：Q51[生物学—生物化学] Q244