Over-expression of PaSOD in transgenic potato enhances photosynthetic performance under drought

Drought stress enhances the production of superoxide radical (O2 ._) and superoxide dismutase catalyses dismutation of it to H2O2 and O2, and hence provides a first line of defense against oxidative stress. Over-expression of a cytosolic copper-zinc superoxide dismutase, cloned from Potentilla atrosanguinea (PaSOD), in potato (Solanum tuberosum ssp. tuberosum L. cv. Kufri Sutlej) resulted in enhanced net photosynthetic rates (PN) and stomatal conductance (gs) compared to that in the wild type (WT) plants under control (irrigated) as well as drought stress conditions. Drought stress declined leaf water potential, PN, gs, photosystem II activity, and chlorophyll content, but increased proline and O2 ._ content more in WT than transgenic potato plants (SS5). The significantly higher SOD activity in SS5 coincided well with lower O2 ._ content suggesting its role in maintaining higher gs and PN in transgenic potato plants.