Senior Research Associate Complex Carbohydrate Research Ctr, Univ. of Georgia Athens, Georgia
Body of Abstract: Plant growth and development require plant cell wall extensibility to allow controlled cell expansion. Here we report that Arabidopsis galacturonosyltransferase 1 (GAUT1), a plant cell wall biosynthetic α-1,4-galacturonosyltransferase (GalAT) [1-3], synthesizes a pectic homogalacturonan (HG) that is indispensable for normal wall structural architecture and for plant cell expansion / extension. The gaut1-/- mutant was only recovered as tiny seedlings severely stunted in both shoot and root growth, while fertility and seed development were also negatively affected by the mutation. Detailed observations indicated significantly reduced cell expansion and/or elongation as the underlying defect of the mutant phenotype. Other aspects of growth, however, such as cell division and differentiation, were not directly affected.
A gaut1-/- suspension cell culture line was established as a source of cell walls for detailed biochemical analysis. Despite a modest reduction in microsomal HG:GalAT activity, total cell walls of gaut1-/- suspension cells showed surprisingly little or no altered GalA content compared to wild type (WT). However, analyses of wall fractions obtained via a six-step sequential extraction of cell walls with increasingly harsh chemicals revealed significantly reduced GalA in the first and final two extracts of gaut1-/- compared to WT walls. These and other data lead us to hypothesize that the specific HG synthesized by GAUT1 is tightly integrated into the walls, is critical for wall integrity, and is required for normal cell expansion/elongation.
Funding provided by The BioEnergy Science Center and The Center for Bioenergy Innovation, both a U.S. Department of Energy Research Center supported by the Office of Biological and Environmental Research in the DOE Office of Science.
1. Sterling, J.D. et al. (2006) PNAS103, 5236-41.
2. Atmodjo, M.A. et al. (2011) PNAS108, 20225-30.
3. Amos, R.A. et al. (2018) J. Biol. Chem.293,19047-63.