Pectin under stress: Pectin methylesterases at the core of cell wall remodeling, integrity sensing, and signaling in plants.

Plant cell walls are dynamic signaling platforms that integrate mechanical, biochemical, and immune cues during development and environmental stress responses. Among wall polysaccharides, pectin has emerged as a central regulator of cell wall integrity (CWI) and stress-responsive signaling. Here, we highlight pectin methylesterases (PMEs) and their regulators as a coordinated modulatory system that enables spatiotemporal control of pectin remodeling during biotic and abiotic stress responses. We discuss recent discoveries regarding isoform-specific PME functions, proteolytic activation, and trafficking routes. During biotic interactions, PME activity promotes pectin remodeling for cell wall reinforcement. It also contributes to CWI sensing by supporting the generation of methanol and, indirectly, oligogalacturonides (OGs), and by enabling the formation of homogalacturonan (HG) structures that facilitate mechanosensor and receptor binding. Under abiotic stress, PME-driven de-methylesterification modulates cell wall stiffness, mechanics, porosity, and ion homeostasis. This review highlights PMEs as central regulators of pectin dynamics that underlie cell wall remodeling, signaling, and stress responses, identifies key knowledge gaps, and outlines future directions for enhancing plant stress resilience.