Multi-scale analysis reveals beneficial effect of calcium silicate supply in alleviating salinity stress in Brassica napus L. seedlings

• Salinity increases Na + /K + ratio and oxidative stress, while reducing chlorophyll content. • Si improves osmoregulation and antioxidant defenses and reduces Na⁺/K⁺ imbalance under salinity. • Proteomics revealed 1059 Si-responsive proteins linked to photosynthesis and cell homeostasis. Silicon (Si) is known to improve plant tolerance to abiotic stresses. However, its action at the molecular levels in Brassica napus L., during seed germination and seedling growth, has yet to be fully elucidated. Therefore, this study aimed at investigating the effect of exogenous calcium silicate (Si) on seed germination and seedlings growth of B. napus under salinity and to explore the tolerance mechanisms using physio-biochemical and proteomic approaches. Results showed that salinity increased Na + /K + ratio and induced an oxidative stress in B. napus seedlings. However, the Si supply increased the ability of B. napus seedlings to withstand salinity through increased Si content, osmoregulation process and antioxidant system, while decreased Na + /K + and oxidative stress markers. Moreover, the proteome analysis identified a total of 1059 differentially accumulated proteins (DAPs) in response to Si, of which 864 under salinity. These DAPs are associated with varied biological processes, including protein targeting and import in chloroplast and endoplasmic reticulum, photosynthesis and light-harvesting complexes, translation and protein biosynthesis and transport and homeostasis, contributing as a result to the resilience of B. napus seedlings to salinity. Together, these results show that Si confers multifactorial tolerance to salinity in B. napus , acting simultaneously on physiological parameters, biochemical protection and proteomic regulation. The beneficial effects of Si on B. napus seedlings subjected to salt stress suggest that calcium silicate could be alternative way to promote the establishment of this crop under salt stress conditions.