Transcriptional signatures of salinity tolerance in Egyptian wheat: unveiling WRKY-mediated defense mechanisms

Abstract

Abstract Background Salinity stress severely constrains wheat productivity by impairing growth, photosynthetic efficiency, and cellular redox homeostasis. Understanding the physiological and transcriptional mechanisms underlying salinity tolerance is essential for developing resilient wheat cultivars. Results In this study, four Egyptian wheat (Triticum aestivum L.) genotypes (Giza 171; Sakha 95; Gemmiza 11, and Misr 3) were evaluated under 0 (control), 6.25, and 12.5 dS m⁻¹ NaCl to elucidate genotype-specific physiological, biochemical, and molecular responses to salinity stress. Increasing salinity significantly reduced germination percentage, biomass accumulation, and leaf chlorophyll content, with more pronounced inhibition at 12.5 dS m⁻¹, particularly in salt-sensitive genotypes. Salinity stress markedly increased oxidative damage, as indicated by elevated hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) levels, and increased electrolyte leakage. In contrast, salt-tolerant genotypes (Sakha 95 and Giza 171) exhibited enhanced antioxidative capacity, characterized by increased activities of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and polyphenol oxidase, as well as higher accumulation of phenolic and flavonoid compounds. Transcriptional analysis revealed significant salinity-induced upregulation of WRKY transcription factors (WRKY1, WRKY20, WRKY33, and WRKY53), as well as TaSOS1 and LEA-1, with stronger induction in tolerant genotypes, indicating coordinated regulation of ion homeostasis, oxidative stress defense, and cellular protection mechanisms. Conclusions Our findings demonstrate that salinity tolerance in wheat is governed by an integrated network linking physiological performance, antioxidant defense, and transcriptional reprogramming of key stress-responsive genes. Sakha 95 and Giza 171 emerge as promising genetic resources for breeding programs to enhance salinity tolerance in wheat.