Hydrogen sulfide priming enhanced salinity tolerance in sunflower by modulating ion hemostasis, cellular redox balance, and gene expression

BACKGROUND: The salinity threat represents an environmental challenge that drastically affects plant growth and yield. Besides salinity stress, the escalating world population will greatly influence the world’s food security in the future. Therefore, searching for effective strategies to improve crop salinity resilience and sustain agricultural productivity under high salinity is a must. Seed priming is a reliable, simple, low-risk, and low-cost technique. Therefore, this work aimed to evaluate the impact of seed priming with 0.5 mM NaHS, as a donor of H(2)S, in mitigating salinity effects on sunflower seedlings. Primed and nonprime seeds were established in nonsaline soil irrigated with tape water for 14 d, and then exposed to 150 mM NaCl for 7 d. RESULTS: Salinity stress significantly reduced the seedling growth, biomass accumulation, K(+), Ca(2+), and salinity tolerance index while elevating Na(+) uptake and translocation. Salinity-induced adverse effects were significantly alleviated by H(2)S priming. Upregulation in gene expression (HaSOS2, HaGST) under NaCl stress was further enhanced by H(2)S priming. Also, H(2)S reduced lipid peroxidation, electrolyte leakage, and H(2)O(2) content, but elevated the antioxidant defense system. NaCl-induced levels of ascorbate, glutathione, and α tocopherol, as well as the activities of AsA-GSH cycle enzymes: ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, and glutathione S-transferase, were further enhanced by H(2)S priming. Increased level of H(2)S and total thiol by NaCl was also further stimulated by H(2)S priming. CONCLUSION: H(2)S priming has proved to be an efficient strategy to improve sunflower seedlings’ salinity tolerance by retaining ion homeostasis, detoxifying oxidative damage, modulating gene expression involved in ion homeostasis and ROS scavenging, and boosting endogenous H(2)S. These findings suggested that H(2)S acts as a regulatory molecule activating the functional processes responsible for sunflower adaptive mechanisms and could be adopted as a crucial crop management strategy to combat saline conditions. However, it would be of great interest to conduct further studies in the natural saline field to broaden our understanding of crop adaptive mechanisms and to support our claims.