Signal transduction and regulatory networks of the rice root system under soil water deficit

Soil water deficit is a major abiotic stress limiting rice productivity and stability, posing serious threats to food security under changing climatic conditions. As the primary organ responsible for sensing and responding to drought signals, the rice root system plays a pivotal role in orchestrating adaptive responses to water scarcity. However, our current understanding of the integrative signaling networks coordinating root morphological and physiological responses remains fragmented. This review systematically explores the signal perception, transduction pathways, and regulatory networks activated in rice roots under drought stress. It highlights recent progress in identifying key signaling molecules, such as phytohormones, calcium ions and reactive oxygen species. It also focuses on their crosstalk during the regulation of root architecture, osmotic adjustment, antioxidant defense and gene expression. Particular emphasis is placed on the interplay between abscisic acid, auxin and jasmonic acid pathways, as well as the integration of ion signaling and redox dynamics. This paper further discusses existing research gaps, such as the lack of spatiotemporal signal frameworks, underestimation of rhizosphere heterogeneity, and disconnection between root traits and yield formation. Finally, future research directions are proposed, including multi-omics integration, field-oriented signal modeling, and CRISPR-based gene editing to enhance drought resilience. By advancing a systems-level understanding of rice root responses to soil water deficit, this review aims to inform both fundamental research and the development of drought-adaptive rice varieties for sustainable water management.