Karrikinolide alleviates salt stress in wheat by regulating the redox and K+/Na+ homeostasis

Abstract

Karrikinolide (KAR₁), identified in biochars, has gained research attention because of its significant role in seed germination, seedling development, root development, and abiotic stresses. However, KAR₁ regulation of salt stress in wheat is elusive. This study investigated the physiological mechanism involved in KAR₁ alleviation of salt stress in wheat. The results showed KAR₁ boosted seed germination percentage under salinity stress via stimulating the relative expression of genes regulating gibberellins biosynthesis and decreasing the expression levels of abscisic acid biosynthesis and signaling genes. As seen in seed germination, exogenous supplementation of KAR₁ dramatically mitigated the salt stress also in wheat seedling, resulting in increased root and shoot growth as measured in biomass as compared to salt stress alone. Salt stress significantly induced the endogenous hydrogen peroxide and malondialdehyde levels, whereas KAR₁ strictly counterbalanced them. Under salt stress, KAR₁ supplementation showed significant induction in reduced glutathione (GSH) and reduction in oxidized glutathione (GSSG) content, which improved GSH/GSSG ratio in wheat seedlings. Exogenous supplementation of KAR₁ significantly promoted the activities of enzymatic antioxidants in wheat seedlings exposed to salt stress. KAR₁ induced the relative expression of genes regulating the biosynthesis of antioxidants in wheat seedlings under salinity. Moreover, KAR₁ induced the expression level of K⁺/Na⁺ homeostasis genes, reduced Na⁺ concentration, and induced K⁺ concentration in wheat seedling under salt stress. The results suggest that KAR₁ supplementation maintained the redox and K⁺/Na⁺ homeostasis in wheat seedling under salinity, which might be a crucial part of physiological mechanisms in KAR₁ induced tolerance to salt stress. In conclusion, we exposed the protective role of KAR₁ against salt stress in wheat.

Keywords: K(+)/Na(+) homeostasis; Karrikinolide; Redox homeostasis; Salt stress tolerance; Wheat.