Pectin Under Stress: Pectin Methylesterases at the Core of Cell Wall Remodeling, Integrity, and Signaling in Plants

Plant cell walls are dynamic signaling platforms that integrate mechanical, biochemical, and immune cues during development and in response to environmental stress. Among wall polysaccharides, pectin has emerged as a central regulator of cell wall integrity and stress-responsive signaling. Here, we highlight pectin methylesterases and their regulators as a coordinated modulatory system controlling pectin remodeling in space and time during biotic and abiotic stresses. Recent discoveries on isoform-specific pectin methylesterase functions, proteolytic activation, and trafficking routes are discussed. During biotic interactions, pectin methylesterase activity promotes pectin remodeling for cell wall reinforcements. It also contributes to cell wall integrity sensing by supporting the generation of methanol and, indirectly, oligogalacturonides, and by enabling the formation of homogalacturonan structures that facilitate mechanosensor and receptor binding. Under abiotic stress, pectin methylesterase-driven de-methylesterification influences cell wall stiffness, mechanics, porosity, and ion homeostasis. This review highlights pectin methylesterases as central regulators of pectin dynamics that underlie cell wall remodeling, signaling, and stress responses, identifies key knowledge gaps and outlines future directions to enhance plant stress resilience.