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Pectin Methylesterase Is Induced in Arabidopsis upon Infection and Is Necessary for a Successful Colonization by Necrotrophic Pathogens

¹Department of Land, Environment, Agriculture and Forestry, University of Padua, Legnaro (PD) Italy; ²Istituto Pasteur Cenci Bolognetti, Department of Biology and Biotechnologies “C. Darwin”, Sapienza University of Rome, Rome; ³Swedish University of Agricultural Sciences, Department of Forest Genetics and Plant Physiology, Umeå, Sweden

The ability of bacterial or fungal necrotrophs to produce enzymes capable of degrading pectin is often related to a successful initiation of the infective process. Pectin is synthesized in a highly methylesterified form and is subsequently de-esterified in muro by pectin methylesterase. De-esterification makes pectin more susceptible to the degradation by pectic enzymes such as endopolygalacturonases (endoPG) and pectate lyases secreted by necrotrophic pathogens during the first stages of infection. We show that, upon infection, Pectobacterium carotovorum and Botrytis cinerea induce in Arabidopsis a rapid expression of AtPME3 that acts as a susceptibility factor and is required for the initial colonization of the host tissue.