Download Résumé_ Pelloux

Defect in the expression of a pectin methylesterase triggers compensation
mechanisms with consequent effects on cell wall mechanics
Fabien Sénéchala, Olivier Habryloa, Ludivine Hocqa, François Joberta,b, Sophie Boutona, Alexis Peaucellec, Yves Assoumou
Ndonga, Françoise Fourneta, Hervé Demaillyb, Paulo Marcelod, Alain Marecke, Patrice Lerougee, Brett Savaryf, Herman
Höftec, Grégory Mouillec, Laurent Gutierrezb, Valérie Lefebvrea, Jérôme Pellouxa
1
: EA3900-BIOPI Biologie des Plantes et Innovation, Amiens, France. 2 : Centre de Ressources Régionales en Biologie
Moléculaire Amiens, France. 3 : INRA, Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, Versailles, France. 4 :
Plateforme d’Ingénierie Cellulaire & Analyses des Protéines ICAP, Amiens, France.
5
: Normandie Univ, Laboratoire
Glycobiologie et Matrice Extracellulaire Végétale, EA 4358, Mont-Saint-Aignan, France. 6: Arkansas State University,
Jonesboro, USA.
Changes in plant cell wall structure are key elements that control plant growth. However, the way it is
spatially and temporally achieved remains poorly documented. Here we report biochemical and functional
characterization of PME32, a pectin methylesterase strongly expressed in Arabidopsis dark-grown hypocotyl. We
showed that PME32 encodes an enzyme that has an acidic pH optimum. Mutants impaired in the expression of
PME32 displayed an increase in hypocotyl length that was related to a decrease in cell wall stiffness. In these
mutants, an unexpected increase in total PME activity lead to increased demethylesterification of the cell wall
pectins, which could induce changes in stiffness. This suggests that putative compensation mechanisms among the
large PME and PMEI multigenic families can be triggered in the context of a pme mutant. We identified two
PMEIs, PMEI4 and PMEI7, whose decrease in gene expression in the context of pme32 mutant could play a key
role in the observed increased PME activity. We further showed that the decrease in stiffness is unlikely to be
related to the increased expression of pectin degrading enzymes polygalacturonases and pectin/pectate lyases.
Other wall components might therefore play a role in the phenotype of the pme32 mutants. This work highlights
the complexity of the regulation of pectin structure affecting growth. Our model proposes the
identification/existence of possible compensating isoforms in PME-mutant backgrounds as well as the probable
interplay between cell wall components.