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

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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.

LanguageEnglish (US)
Pages208-220
Number of pages13
JournalPlant Journal
Volume82
Issue number2
DOIs
StatePublished - Apr 1 2015

Profile

Arabidopsis
pectins
Pectins
cotton
Arabidopsis thaliana
plant growth
Cell Wall
Growth
Methyltransferases
Proteins
Plant Development
cell walls
methyltransferases
Growth and Development
Polysaccharides
proteins
knockout mutants
pectin
Plant Proteins
plant development

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

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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.",
keywords = "Arabidopsis, cell wall, Golgi, methylesterification, methyltransferases, pectin",
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T1 - CGR2 and CGR3 have critical overlapping roles in pectin methylesterification and plant growth in Arabidopsis thaliana

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.

KW - Arabidopsis

KW - cell wall

KW - Golgi

KW - methylesterification

KW - methyltransferases

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