A water-saving drought survival strategy in a wheat TILLING mutant involves metabolic and phosphorylation reprogramming

Drought tolerance in crops often involves trade-offs between water conservation, growth and reproduction. Understanding how water-saving strategies are implemented at physiological and metabolic levels remains critical for improving crop performance under water-limited conditions. Here, we characterize a wheat TILLING mutant, WS1, which exhibits enhanced survival under drought stress. WS1 showed reduced stomatal conductance and transpiration rates, accompanied by increased carbon isotope discrimination, indicating improved water-use efficiency. Despite these traits, WS1 displayed weak stomatal responses to exogenous abscisic acid, suggesting that its water-saving behaviour is not primarily driven by canonical ABA signalling. Metabolomic analyses revealed substantial accumulation of proline and alterations in nitrogen and carbon metabolism, consistent with a survival-oriented metabolic state under water limitation. Phosphoproteomic profiling further identified distinct phosphorylation patterns associated with energy-related signalling components, including proteins linked to SnRK1-mediated pathways. These molecular features were not interpreted as causal drivers but rather as indicators of an altered energy-sensing and metabolic state supporting drought survival. Notably, WS1 exhibited reduced fertility, highlighting an intrinsic trade-off between survival and reproductive investment. Together, our results demonstrate that WS1 adopts a water-saving drought survival strategy characterized by coordinated physiological and metabolic reprogramming. This study provides an integrated framework for understanding survival-oriented drought responses in wheat and offers a basis for future genetic dissection of water-use strategies in crops.