Analysis of Salt Stress Mitigation by Selenium Application in Proso Millet

In order to withstand abiotic stress conditions, plants accumulate a wide range of metabolic products such as proline. There exists a co-relation between proline accumulation and salt stress alleviation in plants, suggesting its role in stress mitigation and osmotic adjustments. In this study, we assessed the effect of selenium (Se) under salt (NaCl) stress on pyrroline-5-carboxylate synthase (P5CS), proline dehydrogenase (ProDH), and ornithine aminotransferase (OAT) proteins using in silico and in vitro studies. Based on in silico analysis, it was found that these enzymes demonstrated a better interaction with Se in comparison to NaCl. The analysis of P5CS, OAT, and ProDH showed the number of amino acid (716, 474, and 484), helices percentage (81%, 71.9%, and 75.4%), residue percentage in Ramachandran favored region (93.82%, 95.15%, and 89.49%), and docking affinities with Se (− 3.2, − 3.5, and − 3.4). This implied the merit of using Se as a NaCl stress mitigant. The morphological results revealed a decline in the growth parameters of plants under NaCl stress in a dose-dependent manner. However, the application of Se relieved the NaCl-induced symptoms. Succeeding NaCl stress (150 mM and 200 mM) with Se 1 µM resulted in increased leaf width (35.29% and 43.75%), total chlorophyll (8.41% and 35.6%), anthocyanin (186.8% and 12.5%), caroteniods (42% and 58.9%), flavonoids (28.37% and 77.98%), MSI (29% and 151.6%), and proline (6.46% and 97%), respectively. Evidently, there was a decrease in H2O2 (17.66% and 9.01%), LP (11.76% and 14.43%), and EL (48.56% and 65.6%) under these treatments and thus revealing the effective mitigation of NaCl stress by Se. The transcriptomic studies also showed that Se up-regulated the expression of P5CS and OAT whereas ProDH was down-regulated. The idea that a mitigant (Se) would outcompete the stressor (NaCl) by strong intermolecular interactions was validated by various in silico parameters. Se showed high binding affinities with proline biosynthesis enzymes (P5CS, OAT, and ProDH) and thus stabilizes them in comparison to stressor (NaCl) resulting in accumulation of proline leading to better performance of plants. This approach could be a step in the direction of smart and sustainable agriculture for our future, and proso millet is the suitable candidate with credentials for growing on marginal lands.