Role of Pectin Methylesterases in cell growth


Principal investigator: Alain Mareck/Arnaud Lehner

Participants: Jean Claude Mollet, Marie-Christine Kiefer-Meyer, Gaƫlle Durambur, Patrice Lerouge, Azeddine Driouich.


Homogalacturonan (HG) is the simplest pectic polymer of primary cell walls. It is composed of a linear chain of a(1,4)-GalA residues synthesised in the Golgi apparatus in a fully methylated form. HG is then demethylated in the cell wall by Pectin Methyl Esterases (PMEs). It is well established that demethylation affects cell wall plasticity, pectin remodelling by pectin-modifying enzymes and plant growth (Pelloux et al., 2007). In addition to PMEs, plants express PME inhibitors (PMEI) capable of maintaining the PME in an inactive state during the secretion and/or in the cell wall. We propose to investigate the function of PME-PMEI interaction in pectin methylesterification, cell elongation and growth. Studies will be carried out on two models: Arabidopsis dark-grown hypocotyls which exhibit cell elongation without any cell division and pollen tubes which exhibit rapid cell growth and distinct HG pattern with high level of methylesterified HG at the tube tip and low methylesterified HG back from the tip (Dardelle et al., 2010). Among the 66 predicted PMEs and the 69 predicted PMEIs, a limited number of PME (5) and PMEI (3) are expressed in hypocotyls whereas 14 putative PME and 12 putative PMEI transcripts are pollen specific. In this program, we will mainly investigate whether PME-PMEI pairs exist and how they control pectin demethylation, hypocotyl elongation rate and in vivo and in vitro pollen tube growth dynamic. This project will be carried out through the analysis of PME and PMEI mutants, the biochemical characterisation of PME specificities, the study of specific PME-PMEI interaction and the monitoring of pectin methylation patterns in wild-type and mutants.

Guenin et al., 2011