Soil salinization, an overwhelming problem exacerbated by climate change and anthropogenic activities, poses a significant threat to global food security by impairing plant growth, development, and crop productivity. Salinity stress induces osmotic, ionic, and oxidative stresses, disrupting physiological and biochemical processes in plants. Anthocyanins, a class of flavonoids, have emerged as key players in mitigating salt stress through their antioxidant properties, ROS scavenging, and regulation of stress-responsive pathways. During salt stress, ROS act as damaging agents and signaling molecules, upregulating anthocyanin-related genes to mitigate oxidative stress and maintain cellular homeostasis. Anthocyanins mitigate salt stress by regulating osmotic balance, ion homeostasis, and antioxidant defenses. Their biosynthesis is regulated by a network of structural and regulatory genes, including MYB, bHLH, and WD40 transcription factors, influenced by epigenetic modifications and hormonal signaling pathways such as ABA, JA, and SA. Advances in genetic engineering, including CRISPR/Cas9-mediated gene editing, have enabled the development of anthocyanin-rich transgenic plants with enhanced salt tolerance. For instance, transgenic plants overexpressing anthocyanin biosynthesis genes like DFR and ANS have demonstrated enhanced salt tolerance in crops such as tomatoes and rice. However, challenges such as variability in anthocyanin accumulation and stability under environmental stressors remain. This review highlights the translational potential of anthocyanins in crop improvement, emphasizing the need for integrated multi-omics approaches and field trials to validate their efficacy. By elucidating the molecular mechanisms of salt stress and anthocyanin-mediated stress alleviation, this work provides a foundation for developing resilient crops to address the growing challenges of soil salinization.

Among various abiotic stresses, secondary soil salinization poses a significant threat to plant productivity and survival. Cultivated chrysanthemums (Chrysanthemum morifolium), widely grown as ornamental crops, are highly susceptible to salt stress, and their complex polyploid genome complicates the identification of stress resistance genes. In contrast, C. indicum, a native diploid species with robust stress tolerance, serves as a valuable genetic resource for uncovering stress-responsive genes and improving the resilience of ornamental chrysanthemum cultivars. In this study, we cloned, overexpressed (OE-CiHY5), and silenced (RNAi-CiHY5) the CiHY5 gene in C. indicum. OE-CiHY5 plants exhibited larger leaves, sturdier stalks, and higher chlorophyll content compared to wild-type plants, while RNAi-CiHY5 plants displayed weaker growth. Under salt stress, OE-CiHY5 plants demonstrated significantly improved growth, enhanced osmotic adjustment, and effective ROS scavenging. In contrast, RNAi-CiHY5 plants were more sensitive to salinity, showing higher electrolyte leakage and impaired osmotic regulation. Transcriptomic analyses revealed that CiHY5 regulates key hormonal pathways such as zeatin (one of cytokinins), abscisic acid and jasmonic acid, as well as metabolic pathways, including photosynthesis, carbohydrate metabolism, which collectively contribute to the enhanced stress resilience of OE-CiHY5 plants. Promoter-binding assays further confirmed that CiHY5 directly interacts with the CiABF3 promoter, highlighting its critical role in ABA signaling. Evolutionary analyses showed that HY5 is conserved across plant lineages, from early algae to advanced angiosperms, with consistent responsiveness to salt and other abiotic stresses in multiple Chrysanthemum species. These findings establish CiHY5 as a key regulator of salt tolerance in C. indicum, orchestrating a complex network of hormonal and metabolic pathways to mitigate salinity-induced damage. Given the conserved nature of HY5 and its responsiveness to various stresses, HY5 gene provides valuable insights into the molecular mechanisms underlying stress adaptation and represents a promising genetic target for enhancing salt stress resilience in chrysanthemums.