Nitric Oxide Enhances Salt Tolerance in Ginger Seedlings Through Phytohormone Homeostasis and Starch and Sugar Metabolism

Background: Nitric oxide (NO) is a key signaling molecule regulating plant physiological and biochemical processes as well as stress responses. In our study, the NO donor sodium nitroprusside (SNP) significantly promoted ginger seedling growth under salt stress, while treatment with the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) reversed these effects, confirming the critical role of NO in enhancing salt tolerance. Meanwhile, NO enhanced antioxidant enzyme activities and reduced ROS accumulation to alleviate oxidative damage. To further investigate the molecular mechanisms by which NO alleviates salt stress in ginger seedlings, transcriptomic analysis was performed on ginger leaves. Results: This analysis identified 2,252 DEGs under salt stress, which were enriched in 55 KEGG pathways, primarily including plant hormone signal transduction and starch and sucrose metabolism pathways. Specifically, further analysis showed that 19 DEGs were enriched in plant hormone signal transduction, while 16 DEGs were enriched in starch and sugar metabolism. NO treatment increased the levels of indole-3-acetic acid (IAA), gibberellin 3 (GA3) and trans-zeatin (ZR), while reducing the levels of abscisic acid (ABA), methyl jasmonate (MeJA) and brassinosteroids (BR). Moreover, NO promoted the accumulation of soluble sugars and sucrose and enhanced the activities of key enzymes involved in starch and sucrose metabolism, thereby effectively improving osmotic adjustment. All of these SNP-induced effects were reversed by cPTIO. Conclusions: Taken together, our results demonstrate that NO improves antioxidant capacity, maintains endogenous phytohormone balance and enhances osmotic adjustment, ultimately alleviating salt stress damage in ginger seedlings.