Auxin–rhizomicrobiome interactions as a driver of climate-resilient root architecture: a conceptual framework for sustainable agriculture

Abiotic stresses such as drought and salinity represent major constraints to global crop productivity, necessitating innovative strategies for enhancing plant resilience. As a critical regulator of root system architecture, auxin (specifically indole-3-acetic acid (IAA)) functions as a vital cross-kingdom signaling molecule that mediates dynamic interactions between plants and auxin-synthesizing rhizosphere microorganisms. This review explores the role of auxin as a cross-kingdom signaling molecule mediating interactions between plants and the rhizosphere microbiome. Auxin-producing plant growth-promoting rhizobacteria (PGPR) such as Pseudomonas , Bacillus , and Azospirillum can modify root system architecture by stimulating lateral root formation, root hair development, and root elongation. These structural changes enhance soil exploration, improving water and nutrient acquisition under stress conditions. In addition, root exudates released by plants recruit beneficial microbial communities, establishing a feedback loop that stabilizes plant–microbe interactions in the rhizosphere. While previous studies have largely treated plant hormonal signaling and rhizosphere ecology as separate domains, this review bridges these silos by proposing the Auxin–Rhizomicrobiome–Root Architecture (ARRA) model; an integrative framework demonstrating how microbial hormone production and plant signaling networks jointly program adaptive root traits under climate stress. Ultimately, the ARRA framework provides a conceptual and practical blueprint for deploying auxin-producing bioinoculants and engineered rhizomicrobiome consortia, offering a scalable strategy to enhance crop resilience and sustainable food security under accelerating climate scenarios.