CGR2 and CGR3 have critical overlapping roles in pectin methylesterification and plant growth in Arabidopsis thaliana

Sang Jin Kim, Michael A. Held, Starla Zemelis, Curtis Wilkerson, Federica Brandizzi

    Research output: Contribution to journalArticle

    • 13 Citations

    Abstract

    Summary Pectins are critical polysaccharides of the cell wall that are involved in key aspects of a plant's life, including cell-wall stiffness, cell-to-cell adhesion, and mechanical strength. Pectins undergo methylesterification, which affects their cellular roles. Pectin methyltransferases are believed to methylesterify pectins in the Golgi, but little is known about their identity. To date, there is only circumstantial evidence to support a role for QUASIMODO2 (QUA2)-like proteins and an unrelated plant-specific protein, cotton Golgi-related 3 (CGR3), in pectin methylesterification. To add to the knowledge of pectin biosynthesis, here we characterized a close homolog of CGR3, named CGR2, and evaluated the effect of loss-of-function mutants and over-expression lines of CGR2 and CGR3 in planta. Our results show that, similar to CGR3, CGR2 is a Golgi protein whose enzyme active site is located in the Golgi lumen where pectin methylesterification occurs. Through phenotypical analyses, we also established that simultaneous loss of CGR2 and CGR3 causes severe defects in plant growth and development, supporting critical but overlapping functional roles of these proteins. Qualitative and quantitative cell-wall analytical assays of the double knockout mutant demonstrated reduced levels of pectin methylesterification, coupled with decreased microsomal pectin methyltransferase activity. Conversely, CGR2 and CGR3 over-expression lines have markedly opposite phenotypes to the double knockout mutant, with increased cell-wall methylesterification levels and microsomal pectin methyltransferase activity. Based on these findings, we propose that CGR2 and CGR3 are critical proteins in plant growth and development that act redundantly in pectin methylesterification in the Golgi apparatus. Significance Statement Pectins are essential polysaccharides of the cell wall but only a handful of proteins involved in their biosynthesis have been identified to date. Pectins are secreted as highly methylesterified polymers but the enzymes involved in methylesterification processes are largely unknown. In this work we report on the characterization of two proteins for which we show largely overlapping roles in pectin methylesterification in the model plant species Arabidopsis thaliana.

    Original languageEnglish (US)
    Pages (from-to)208-220
    Number of pages13
    JournalPlant Journal
    Volume82
    Issue number2
    DOIs
    StatePublished - Apr 1 2015

    Profile

    Arabidopsis
    Proteins
    pectins
    Pectins
    Cell Wall
    cotton
    Methyltransferases
    proteins
    Plant Development
    Polysaccharides
    Enzymes
    cell walls
    methyltransferases
    plant growth
    Plant Proteins
    Golgi Apparatus
    Cell Adhesion
    Catalytic Domain
    Polymers
    Phenotype

    Keywords

    • Arabidopsis
    • cell wall
    • Golgi
    • methylesterification
    • methyltransferases
    • pectin

    ASJC Scopus subject areas

    • Plant Science
    • Cell Biology
    • Genetics

    Cite this

    CGR2 and CGR3 have critical overlapping roles in pectin methylesterification and plant growth in Arabidopsis thaliana. / Kim, Sang Jin; Held, Michael A.; Zemelis, Starla; Wilkerson, Curtis; Brandizzi, Federica.

    In: Plant Journal, Vol. 82, No. 2, 01.04.2015, p. 208-220.

    Research output: Contribution to journalArticle

    Kim, Sang Jin; Held, Michael A.; Zemelis, Starla; Wilkerson, Curtis; Brandizzi, Federica / CGR2 and CGR3 have critical overlapping roles in pectin methylesterification and plant growth in Arabidopsis thaliana.

    In: Plant Journal, Vol. 82, No. 2, 01.04.2015, p. 208-220.

    Research output: Contribution to journalArticle

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    abstract = "Summary Pectins are critical polysaccharides of the cell wall that are involved in key aspects of a plant's life, including cell-wall stiffness, cell-to-cell adhesion, and mechanical strength. Pectins undergo methylesterification, which affects their cellular roles. Pectin methyltransferases are believed to methylesterify pectins in the Golgi, but little is known about their identity. To date, there is only circumstantial evidence to support a role for QUASIMODO2 (QUA2)-like proteins and an unrelated plant-specific protein, cotton Golgi-related 3 (CGR3), in pectin methylesterification. To add to the knowledge of pectin biosynthesis, here we characterized a close homolog of CGR3, named CGR2, and evaluated the effect of loss-of-function mutants and over-expression lines of CGR2 and CGR3 in planta. Our results show that, similar to CGR3, CGR2 is a Golgi protein whose enzyme active site is located in the Golgi lumen where pectin methylesterification occurs. Through phenotypical analyses, we also established that simultaneous loss of CGR2 and CGR3 causes severe defects in plant growth and development, supporting critical but overlapping functional roles of these proteins. Qualitative and quantitative cell-wall analytical assays of the double knockout mutant demonstrated reduced levels of pectin methylesterification, coupled with decreased microsomal pectin methyltransferase activity. Conversely, CGR2 and CGR3 over-expression lines have markedly opposite phenotypes to the double knockout mutant, with increased cell-wall methylesterification levels and microsomal pectin methyltransferase activity. Based on these findings, we propose that CGR2 and CGR3 are critical proteins in plant growth and development that act redundantly in pectin methylesterification in the Golgi apparatus. Significance Statement Pectins are essential polysaccharides of the cell wall but only a handful of proteins involved in their biosynthesis have been identified to date. Pectins are secreted as highly methylesterified polymers but the enzymes involved in methylesterification processes are largely unknown. In this work we report on the characterization of two proteins for which we show largely overlapping roles in pectin methylesterification in the model plant species Arabidopsis thaliana.",
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    AU - Kim,Sang Jin

    AU - Held,Michael A.

    AU - Zemelis,Starla

    AU - Wilkerson,Curtis

    AU - Brandizzi,Federica

    PY - 2015/4/1

    Y1 - 2015/4/1

    N2 - Summary Pectins are critical polysaccharides of the cell wall that are involved in key aspects of a plant's life, including cell-wall stiffness, cell-to-cell adhesion, and mechanical strength. Pectins undergo methylesterification, which affects their cellular roles. Pectin methyltransferases are believed to methylesterify pectins in the Golgi, but little is known about their identity. To date, there is only circumstantial evidence to support a role for QUASIMODO2 (QUA2)-like proteins and an unrelated plant-specific protein, cotton Golgi-related 3 (CGR3), in pectin methylesterification. To add to the knowledge of pectin biosynthesis, here we characterized a close homolog of CGR3, named CGR2, and evaluated the effect of loss-of-function mutants and over-expression lines of CGR2 and CGR3 in planta. Our results show that, similar to CGR3, CGR2 is a Golgi protein whose enzyme active site is located in the Golgi lumen where pectin methylesterification occurs. Through phenotypical analyses, we also established that simultaneous loss of CGR2 and CGR3 causes severe defects in plant growth and development, supporting critical but overlapping functional roles of these proteins. Qualitative and quantitative cell-wall analytical assays of the double knockout mutant demonstrated reduced levels of pectin methylesterification, coupled with decreased microsomal pectin methyltransferase activity. Conversely, CGR2 and CGR3 over-expression lines have markedly opposite phenotypes to the double knockout mutant, with increased cell-wall methylesterification levels and microsomal pectin methyltransferase activity. Based on these findings, we propose that CGR2 and CGR3 are critical proteins in plant growth and development that act redundantly in pectin methylesterification in the Golgi apparatus. Significance Statement Pectins are essential polysaccharides of the cell wall but only a handful of proteins involved in their biosynthesis have been identified to date. Pectins are secreted as highly methylesterified polymers but the enzymes involved in methylesterification processes are largely unknown. In this work we report on the characterization of two proteins for which we show largely overlapping roles in pectin methylesterification in the model plant species Arabidopsis thaliana.

    AB - Summary Pectins are critical polysaccharides of the cell wall that are involved in key aspects of a plant's life, including cell-wall stiffness, cell-to-cell adhesion, and mechanical strength. Pectins undergo methylesterification, which affects their cellular roles. Pectin methyltransferases are believed to methylesterify pectins in the Golgi, but little is known about their identity. To date, there is only circumstantial evidence to support a role for QUASIMODO2 (QUA2)-like proteins and an unrelated plant-specific protein, cotton Golgi-related 3 (CGR3), in pectin methylesterification. To add to the knowledge of pectin biosynthesis, here we characterized a close homolog of CGR3, named CGR2, and evaluated the effect of loss-of-function mutants and over-expression lines of CGR2 and CGR3 in planta. Our results show that, similar to CGR3, CGR2 is a Golgi protein whose enzyme active site is located in the Golgi lumen where pectin methylesterification occurs. Through phenotypical analyses, we also established that simultaneous loss of CGR2 and CGR3 causes severe defects in plant growth and development, supporting critical but overlapping functional roles of these proteins. Qualitative and quantitative cell-wall analytical assays of the double knockout mutant demonstrated reduced levels of pectin methylesterification, coupled with decreased microsomal pectin methyltransferase activity. Conversely, CGR2 and CGR3 over-expression lines have markedly opposite phenotypes to the double knockout mutant, with increased cell-wall methylesterification levels and microsomal pectin methyltransferase activity. Based on these findings, we propose that CGR2 and CGR3 are critical proteins in plant growth and development that act redundantly in pectin methylesterification in the Golgi apparatus. Significance Statement Pectins are essential polysaccharides of the cell wall but only a handful of proteins involved in their biosynthesis have been identified to date. Pectins are secreted as highly methylesterified polymers but the enzymes involved in methylesterification processes are largely unknown. In this work we report on the characterization of two proteins for which we show largely overlapping roles in pectin methylesterification in the model plant species Arabidopsis thaliana.

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