title: Overexpression of pectin methylesterase inhibitors in Arabidopsis restricts fungal infection by Botrytis cinerea.
abstract: Pectin, one of the main components of plant cell wall, is secreted in a highly methylesterified form and is demethylesterified in muro by pectin methylesterase (PME). The action of PME is important in plant development and defense and makes pectin susceptible to hydrolysis by enzymes such as endopolygalacturonases. Regulation of PME activity by specific protein inhibitors (PMEIs) can, therefore, play a role in plant development as well as in defense by influencing the susceptibility of the wall to microbial endopolygalacturonases. To test this hypothesis, we have constitutively expressed the genes AtPMEI-1 and AtPMEI-2 in Arabidopsis (Arabidopsis thaliana) and targeted the proteins into the apoplast. The overexpression of the inhibitors resulted in a decrease of PME activity in transgenic plants, and two PME isoforms were identified that interacted with both inhibitors. While the content of uronic acids in transformed plants was not significantly different from that of wild type, the degree of pectin methylesterification was increased by about 16%. Moreover, differences in the fine structure of pectins of transformed plants were observed by enzymatic fingerprinting. Transformed plants showed a slight but significant increase in root length and were more resistant to the necrotrophic fungus Botrytis cinerea. The reduced symptoms caused by the fungus on transgenic plants were related to its impaired ability to grow on methylesterified pectins.
authors.affiliation: Dipartimento di Biologia Vegetale, Università di Roma La Sapienza, 00185 Rome, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Lionetti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Raiola
authors.forename: Laura
authors.initials: L
authors.lastname: Camardella
authors.forename: Alfonso
authors.initials: A
authors.lastname: Giovane
authors.forename: Nicolai
authors.initials: N
authors.lastname: Obel
authors.forename: Markus
authors.initials: M
authors.lastname: Pauly
authors.forename: Francesco
authors.initials: F
authors.lastname: Favaron
authors.forename: Felice
authors.initials: F
authors.lastname: Cervone
authors.forename: Daniela
authors.initials: D
authors.lastname: Bellincampi
mesh_terms: D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism* / Q000382:microbiology; D001483:Base Sequence; D020171:Botrytis / Q000472:pathogenicity*; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors*; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000378:metabolism / Q000382:microbiology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D017931:DNA Primers; D004791:Enzyme Inhibitors; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase