Pectin is synthesized in a highly methylesterified form in the Golgi cisternae and partially de‐methylesterified in muro by pectin methylesterases (PMEs). Arabidopsis thaliana produces a local and strong induction of PME activity during the infection of the necrotrophic fungus Botrytis cinerea. AtPME17 is a putative A. thaliana PME highly induced in response to B. cinerea. Here, a fine tuning of AtPME17 expression by different defence hormones was identified. Our genetic evidence demonstrates that AtPME17 strongly contributes to the pathogen‐induced PME activity and resistance against B. cinerea by triggering jasmonic acid–ethylene‐dependent PDF1.2 expression. AtPME17 belongs to group 2 isoforms of PMEs characterized by a PME domain preceded by an N‐terminal PRO region. However, the biochemical evidence for AtPME17 as a functional PME is still lacking and the role played by its PRO region is not known. Using the Pichia pastoris expression system, we demonstrate that AtPME17 is a functional PME with activity favoured by an increase in pH. AtPME17 performs a blockwise pattern of pectin de‐methylesterification that favours the formation of egg‐box structures between homogalacturonans. Recombinant AtPME17 expression in Escherichia coli reveals that the PRO region acts as an intramolecular inhibitor of AtPME17 activity.

中文翻译：

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AtPME17是一种功能性拟南芥果胶甲基酯酶，受其PRO区域调控，在对灰葡萄孢的抗性中触发PME活性

果胶在高尔基池中以高度甲基酯化的形式合成，在果胶中被果胶甲基酯酶（PME）部分脱甲基化。拟南芥在坏死性灰霉病葡萄灰霉病感染期间会产生局部强烈的PME活性诱导。AtPME17是一种假定的拟南芥PME，对灰葡萄球菌高度应答。在这里，通过不同的防御激素对AtPME17表达进行了微调。我们的遗传证据表明，AtPME17通过触发茉莉酸-乙烯依赖性PDF1.2，极大地促进了病原体诱导的PME活性和对灰葡萄孢的抵抗。表达。AtPME17属于PME的第2组同工型，其特征是在PME域之前带有N端PRO区。然而，仍缺乏AtPME17作为功能性PME的生化证据，其PRO区域所起的作用尚不清楚。使用巴斯德毕赤酵母表达系统，我们证明AtPME17是功能性PME，其活性受pH值增加的影响。AtPME17执行果胶脱甲基酯化的逐段模式，有利于在同型半乳糖醛酸之间形成卵盒结构。大肠杆菌中AtPME17的重组表达表明PRO区充当AtPME17活性的分子内抑制剂。