Osmotic stress relieving action of silicon by fatty acid accumulation in Finger millet (Eleusine coracana (L.) Gaertn)

Finger millet is a vital cereal crop for food security due to its nutritional quality and main source of food for resource poor population. It is considered as a drought tolerant crop, however, contradictory literature exists on tolerance to abiotic stresses. It is well documented that silicon (Si) has a beneficial effect on osmotic stress tolerance but underlying molecular mechanisms were elusive. To understand the Si triggered molecular change conferring osmotic stress tolerance we analyzed transcriptome and metabolome of finger millet seedlings treated with DW (control), Si (10 ppm), PEG (15%) and PEG (15%) + Si (10 ppm). PEG-induced osmotic stress affected the seedling growth which was significantly relieved by Si supplementation. Silicon amendment under stress leads to up-regulation of glycolysis elevating the breakdown of glucose to acetyl CoA via pyruvate. The fate of acetyl CoA towards TCA cycle diverted to lipid biosynthesis. Moreover, degradation of fatty acid by beta oxidation was also down-regulated. However, the catabolism of amino acids leading to biosynthesis of acetyl CoA was up-regulated. The concentration of linolenic acid has decreased and jasmonic acid increases significantly in PEG+Si. Evident expression of transcripts to metabolites in different treatments was confirmed using metabolite analysis based on LC-QTOF-MS. This study shows the significant role of Si in osmotic stress tolerance by regulation of fatty acids in finger millet.