Nitrogen status defines grapevine (Vitis vinifera L.) metabolic response to sulfur deficiency

Sulfur is an essential macronutrient, yet its role in grapevine (Vitis vinifera L.) physiology is poorly understood. Following reduced atmospheric sulfur deposition, sulfur fertilisation is increasingly required to prevent deficiencies, which are difficult to diagnose before they impair grapevine and subsequent wine quality. Therefore, the metabolic responses of grapevines to isolated and combined sulfur and nitrogen deficiencies were investigated. Using a non-targeted metabolomics and ionomics approach under controlled sulfur and nitrogen supplies, it was shown that isolated sulfur deficiency led to a massive accumulation of nitrogen rich amino acids and activation of the GABA shunt. This metabolic imbalance, and its disruptive effect on the concentration of other plant nutrients, was significantly alleviated under combined sulfur deficiency and low nitrogen, while additive effects also occurred. Sulfur deficiency uniquely induced a drastic increase in transpiration, significantly reducing intrinsic water use efficiency. We identified specific metabolic markers for each nutrient status and evaluated diagnostic indicators. The interaction between sulfur and nitrogen is important and demonstrates that adequate sulfate nutrition is essential for optimising water use efficiency and metabolic balance, suggesting nitrogen management strategies should consider sulfur availability to ensure crop resilience in a changing climate.