Mechanistic insights and biotechnological applications of Streptomyces secondary metabolites in plant abiotic stress mitigation.

Abiotic stresses such as salinity, drought, heat, and ultraviolet radiation are among the most serious constraints on global crop productivity. These stresses disrupt photosynthesis, nutrient uptake, and cellular redox balance, leading to major agricultural losses under changing climatic conditions. Members of the genus Streptomyces, long recognized for their exceptional capacity to produce secondary metabolites, have recently emerged as promising bioresources for enhancing plant tolerance to such stresses. Their metabolites include polyketides, phenazines, melanin-like pigments, siderophores, volatile organic compounds, and phytohormone analogs. Collectively, these compounds can improve plant performance by scavenging reactive oxygen species, supporting osmotic adjustment and ion regulation, and modulating hormonal signaling and root architecture. This review summarizes recent progress in understanding how Streptomyces-derived metabolites contribute to abiotic stress alleviation in plants, with emphasis on molecular mechanisms and rhizosphere ecology. Genomics and metabolomics studies further reveal extensive biosynthetic gene clusters with untapped potential for novel bioactive compounds. Evidence from major crops shows improved growth, antioxidant activity, and stress recovery following Streptomyces inoculation or metabolite application. However, key challenges remain, including linking specific metabolites to defined plant responses, standardizing assays, ensuring safety, and scaling production for field use. Integrating multi-omics, co-culture strategies, and formulation technologies will be essential to translate experimental findings into sustainable agricultural practice. Overall, Streptomyces secondary metabolites represent a promising frontier for environmentally sound solutions to abiotic stress in crops.