The Three Members of the Arabidopsis thaliana Glycosyltransferase Family 92 are Functional β-1,4-Galactan Synthases

Berit Ebert, Devon Birdseye, April J. M. Liwanag, Tomas Laursen, Emilie A. Rennie, Xiaoyuan Guo, Michela Catena, Carsten Rautengarten, Solomon H. Stonebloom, Pawel Gluza, Venkataramana Pidatala, Mathias Christian Franch Andersen, Roshan Cheetamun, Jenny C. Mortimer, Joshua L Heazlewood, Antony Bacic, Mads H. Clausen, William G T Willats, Henrik V. Scheller*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Pectin is a major component of primary cell walls and performs a plethora of functions crucial for plant growth, development and plant-defense responses. Despite the importance of pectic polysaccharides their biosynthesis is poorly understood. Several genes have been implicated in pectin biosynthesis by mutant analysis, but biochemical activity has been shown for very few.We used reverse genetics and biochemical analysis to study members of Glycosyltransferase Family 92 (GT92) in Arabidopsis thaliana. Biochemical analysis gave detailed insight into the properties of GALS1 (Galactan synthase 1) and showed galactan synthase activity of GALS2 and GALS3. All proteins are responsible for adding galactose onto existing galactose residues attached to the rhamnogalacturonan-I (RG-I) backbone. Significant GALS activity was observed with galactopentaose as acceptor but longer acceptors are favored. Overexpression of the GALS proteins in Arabidopsis resulted in accumulation of unbranched β-1,4-galactan. Plants in which all three genes were inactivated had no detectable β-1,4-galactan, and surprisingly these plants exhibited no obvious developmental phenotypes under standard growth conditions. RG-I in the triple mutants retained branching indicating that the initial Gal substitutions on the RG-I backbone are added by enzymes different from GALS.
Original languageEnglish
JournalPlant and Cell Physiology
Volume59
Issue number12
Pages (from-to)2624-2636
Number of pages13
ISSN0032-0781
DOIs
Publication statusPublished - 2018

Keywords

  • Arabidopsis
  • Cell wall
  • Galactan
  • Glycosyltransferases
  • Galactosyltransferases
  • Pectin
  • Rhamnogalacturonan-I

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