Plant cells lack antioxidative enzyme-mediated reactions for quenching singlet oxygen (1O2) making it the major cause of damage to plants during daytime. A chlorophyll biosynthesis intermediate protochlorophyllide is a photosensitizer that absorbs light and transfers the energy to O2to generate 1O2.Higher the 1O2 production, greater is the oxidative damage to the plants. Protochlorophyllide oxidoreductase (POR) is a light-dependent enzyme that phototransforms protochlorophyllide to chlorophyllide using light energy as the substrate. Waterstress severely down regulates the gene and protein expression of POR leading to reduced synthesis of POR enzyme. Therefore, the oil seed crop Brassica juncea over expressing the C isoform of POR i.e., PORC along with wildtype (WT) plants were exposed to water stress to ascertain the role of PORC in the protection of plants from drought. The stress treatment was applied to mustard WT and PORC over-expressers (PORCx) plants by withholding water supply up to 8 days. Recovery from stress was monitored up to 48 h after re-watering the drought-treated plants. WT plants wilted after 8th day of drought stress and had lower PSII-dependent electron transport rate (ETR) and initial chlorophyll a fluorescence (Fo)during stress and recovery phase than the PORC over-expressers. Reduced 1O2 produced in BjPORCx plants minimized damage to the photosynthetic machinery allowing for a faster recovery from water stress than the WT plants. Therefore, PORC could be genetically modulated in crop plants to protect them from water-stress.
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