Differential physiological and proteomic responses of barley genotypes to sulfur availability

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Sulfur (S) is essential for plant growth, influencing protein synthesis and metabolic processes. However, S deficiency in agricultural soils is becoming more prevalent, negatively affecting crop yields and quality. In barley, where grain protein composition is crucial for malting and brewing, understanding the impact of S on nutrient balance and protein profiles is imperative. This study investigated the effects of S deficiency and supplementation on growth, mineral nutrition, amino acids, proteomics, and yield in two barley cultivars, ZheDa-9 (ZD-9) and Gairdner. Results show that S deprivation significantly reduced plant height, biomass, chlorophyll content, and grain yield, with Gairdner experiencing a 25.7% greater yield loss than ZD-9, indicating its higher sensitivity to S deficiency. Ionomic profiling revealed tissue-specific nutrient depletion, with Gairdner grains showing more pronounced reductions in S (–33.2%), N (–17.1%), Ca (–42.9%), Zn (–16.8%), and Cu (–33.0%). S-deficient grains exhibited altered amino acid profiles, characterized by N-rich amino acid accumulation and S-amino acid depletion. Genotype-specific patterns were observed: ZD-9 showed a 21.4% greater reduction in cysteine, while Gairdner exhibited a 25.4% decline in methionine, exacerbating N: S imbalance. Proteomic analysis revealed genotype-specific responses to S deficiency, with ZD-9 upregulating beta-amylase precursor and alpha-amylase inhibitor CMb, while gamma 3 hordein was downregulated compared to Gairdner. These findings highlight the importance of cultivar-specific sulfur management strategies, offering insights for optimizing S fertilization and selecting S-efficient barley genotypes to improve nutrient homeostasis, yield stability, and malting quality, particularly in low-S soils.