A Water-Saving Drought Survival Phenotype in a Wheat TILLING Mutant Involves Survival-Biased Metabolic and...

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 characterise a wheat TILLING mutant, WS1, that exhibits enhanced survival under drought stress. WS1 showed reduced stomatal conductance and transpiration, together with increased carbon isotope discrimination, consistent with reduced water loss. Despite these traits, WS1 displayed weak stomatal responses to exogenous abscisic acid (ABA), indicating that its water-saving behaviour is not primarily explained by canonical ABA signalling. Metabolomic analyses revealed substantial accumulation of proline and changes in nitrogen and carbon metabolism, suggesting a shift toward a survival-oriented metabolic state. Phosphoproteomic profiling further identified distinct phosphorylation patterns associated with energy-related signalling components, including proteins linked to SnRK1 pathways. These molecular features likely reflect an altered energy-sensing and regulatory state rather than direct causal drivers of the phenotype. Notably, WS1 exhibited reduced fertility, indicating a trade-off between survival and reproductive investment. Together, our results suggest that WS1 adopts a water-saving drought survival phenotype characterised by coordinated physiological and metabolic reprogramming, providing a framework for understanding survival-oriented drought responses and resource allocation strategies in wheat.