The exogenous application of AtPGLR, an endo‐polygalacturonase, triggers pollen tube burst and repair. (28th April 2020)

• Record Type: Journal Article
• Authors: Hocq, Ludivine; Guinand, Sophie; Habrylo, Olivier; Voxeur, Aline; Tabi, Wafae; Safran, Josip; Fournet, Françoise; Domon, Jean‐Marc; Mollet, Jean‐Claude; Pilard, Serge; Pau‐Roblot, Corinne; Lehner, Arnaud; Pelloux, Jérôme; Lefebvre, Valérie
• Is Part Of: Plant journal. Volume 103:Number 2(2020)
• Page Start: 617
• Page End: 633
• Publication Date: 2020-04-28
• Subjects: Arabidopsis thaliana -- Amaryllis belladonna -- polygalacturonase -- pectins -- oligogalacturonides -- elongation -- pollen tube; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.14753
• Languages: English
• ISSNs: 0960-7412

Abstract

SUMMARY: Plant cell wall remodeling plays a key role in the control of cell elongation and differentiation. In particular, fine‐tuning of the degree of methylesterification of pectins was previously reported to control developmental processes as diverse as pollen germination, pollen tube elongation, emergence of primordia or elongation of dark‐grown hypocotyls. However, how pectin degradation can modulate plant development has remained elusive. Here we report the characterization of a polygalacturonase (PG), AtPGLR, the gene for which is highly expressed at the onset of lateral root emergence in Arabidopsis. Due to gene compensation mechanisms, mutant approaches failed to determine the involvement of AtPGLR in plant growth. To overcome this issue, AtPGLR has been expressed heterologously in the yeast Pichia pastoris and biochemically characterized. We showed that AtPGLR is an endo ‐PG that preferentially releases non‐methylesterified oligogalacturonides with a short degree of polymerization (< 8) at acidic pH. The application of the purified recombinant protein on Amaryllis pollen tubes, an excellent model for studying cell wall remodeling at acidic pH, induced abnormal pollen tubes or cytoplasmic leakage in the subapical dome of the pollen tube tip, where non‐methylesterified pectin epitopes are detected. Those leaks could either be repaired by new β‐glucan deposits (mostly callose) in the cell wall or promoted dramatic burst of the pollen tube. Our work presents the full biochemical characterization of an Arabidopsis PG and highlights the importance of pectin integrity in pollen tube elongation. Significance Statement: Polygalacturonases (PGs) control cell wall chemistry and mechanics through degradation of pectins, which play a key role in the regulation of developmental processes in plants. Here, we report the full biochemical characterization of an Arabidopsis PG, AtPGLR, unraveling its mode of action as well as its effects on pollen tube elongation.