Physiological and Molecular Mechanisms of Ethylene in Sculpting Rice Root System Architecture

The root system of rice (Oryza sativa L.) is a central determinant of stress resilience and yield, functioning in resource acquisition, anchorage, and environmental sensing. This review synthesizes recent advances in understanding how the gaseous hormone ethylene acts as a master regulator to sculpt root system architecture by spatiotemporally integrating developmental cues and stress signals. We detail the core molecular machinery of ethylene in rice, encompassing its biosynthesis, perception, and signal transduction pathways. Ethylene modulates root development through intricate crosstalk with auxin, abscisic acid, and jasmonic acid, inhibiting primary root elongation while promoting lateral root initiation, adventitious rooting, root hair development, and aerenchyma formation. The review further dissects the context-dependent role of ethylene signaling in mediating adaptive responses to key abiotic stresses, including drought, hypoxia, salinity, and heavy metal stress. It also examines how ethylene influences root-microbe interactions, shaping the rhizosphere microbiome. Finally, we discuss root trait optimization strategies that leverage the ethylene signaling network, providing a mechanistic foundation for breeding next-generation rice varieties with enhanced stress tolerance and resource-use efficiency.