Root architecture in rice (Oryza sativa) is critically shaped by ethylene–auxin crosstalk, enabling adaptation to contrasting environments like flooded paddies and drought-prone uplands. In paddy systems, hypoxia triggers ethylene accumulation, which stabilizes OsEIL1 to upregulate auxin biosynthesis (YUC8), inhibiting primary root elongation but promoting aerenchyma formation and adventitious root growth for oxygen diffusion. Auxin transport and signaling are essential for these ethylene-mediated responses, as evidenced by mutants like iaa13, which fail to form aerenchyma. Conversely, upland rice prioritizes deep rooting (via DRO1) and lateral root proliferation under drought, where ethylene–auxin interactions shift to restrict elongation while enhancing radial expansion and root hair development. Mechanical stress in compacted soils further modulates this crosstalk, with ABA-induced OsYUCCA8 driving auxin-mediated root hair elongation. Molecular breeding targets like OsEIN2, OsWOX11, and DRO1 leverage these pathways to improve stress resilience, though tissue-specific manipulation is crucial to avoid yield trade-offs. Systems biology approaches, integrating spatiotemporal hormone dynamics and mechanosensing, offer promising strategies to optimize root traits for diverse agroecologies. This review synthesizes mechanistic insights and agronomic applications of ethylene–auxin interactions, highlighting their pivotal role in rice root plasticity and climate adaptation.
C. M. Naik (Wed,) studied this question.