PGPR-Mediated Plant Immunity: From Microbial Recognition to Epigenetic Priming

The increasing demand for sustainable agriculture has intensified interest in beneficial microbes as eco-friendly alternatives to chemical pesticides for plant disease control. Among these, plant growth-promoting rhizobacteria (PGPR) have attracted great interest because they can suppress plant pathogens and strengthen plant health through molecular mechanisms. Recent studies suggest that PGPR protect plants from disease not only by directly attacking pathogens but also by changing how plant immune genes are expressed through epigenetic processes. This review brings together current knowledge on epigenetic regulation in plant–PGPR interactions, focusing on DNA methylation, histone modifications, and non-coding RNA pathways. PGPR colonization activates plant immune signaling through pattern recognition receptors, MAPK cascades, reactive oxygen species, and plant hormones. The review also covers the range of bacterial signals—including lipopolysaccharides, flagellin, cyclic lipopeptides, and volatile organic compounds—that prepare plant defenses, and explains how the recognition of these signals reshapes chromatin structure at defense genes. In addition, the review discusses how these changes may influence induced systemic resistance and examines emerging, though still limited, evidence on whether they could potentially be transmitted to subsequent generations. A better understanding of how microbial signals regulate host epigenetics may reveal new ways to improve plant immunity and balance growth with defense. Overall, available evidence indicates that PGPR-induced epigenetic changes represent a promising and environmentally friendly approach to crop protection; however, field-level validation and mechanistic confirmation in non-model crop species remain necessary before this strategy can be considered practically applicable.