Reframing Pathogenesis-Related proteins: from plant immune drivers to stress resilience integration nodes

Abstract

Plants are constantly exposed to biotic and abiotic stresses, but the molecular mechanisms integrating these signals remain underexplored. Traditionally viewed as defense proteins against pathogen infection, pathogenesis-related (PR) proteins comprise 19 diverse families encompassing defense-related enzymes (glucanases, chitinases, nucleases, proteases), antimicrobial peptides, enzyme inhibitors and reactive oxygen species (ROS)-generating proteins. While their significance during biotic stresses is well-documented, research has started to emerge on their dynamic regulation and functional roles in abiotic stresses, e.g. salinity, drought, heavy metal exposure, temperature and flooding. By synthesizing recent insights and critical knowledge gaps, we propose that PR proteins are global plant stress integration nodes, linking responses to abiotic and biotic stresses. We distill the core molecular principles and regulatory mechanisms underpinning the abiotic regulation of PR genes and proteins, implicating the central importance of plant hormone and ROS signaling pathways. We also critically examine the functional diversity and versatility of PR proteins, as they orchestrate cell wall remodeling, membrane stabilization, ion homeostasis, proteolytic balance and ROS metabolism in stress resilience pathways. Overall, a detailed understanding of the abiotic regulation and function of PR proteins offers rich insights into how plants coordinate survival under environmental challenge and has significant implications for developing stress-resilient crops.