Transgenic Potato Plants Overexpressing SOD and APX Exhibit Enhanced Lignification and Starch Biosynthesis with Improved Salt Stress Tolerance

Potato (Solanum tuberosum L.) is a major crop worldwide and its productivity is severely reduced by high soil salinity. The aim of the current study was to gain insights into the response and regulation of the antioxidant system in the transgenic potato, overexpressing two genes viz. thermostable CuZn-superoxide dismutase (PaSOD) gene from polyextremophile high-altitude plant Potentilla atrosanguinea and ascorbate peroxide (RaAPX) gene from Rheum australe under salinity stress. Transgenic lines and wild type (WT) were assessed under 50, 100, and 150 mM concentrations of NaCl treatment at the anatomical, transcriptional and metabolic levels. Although superoxide dismutase (SOD) and ascorbate peroxide (APX) activities in transgenic lines were significantly higher than WT under salt stress, the secondary cell wall lignification was profoundly affected by the modulated antioxidant enzymes activities and the corresponding H2O2 levels in transgenic. Expression profiles showed that the several genes and transcription factors directly involved in lignin biosynthesis were profoundly induced in transgenic lines as compared to WT. In addition, transgenic plants harbored increased starch accumulation, improved growth attributes, and reduced accumulation of reactive oxygen species than WT plants. Together, these results indicated that the expression of SOD and APX genes in transgenic potato may function as a positive set of physiological, anatomical, and molecular adjustments in the H2O2 regulated lignin biosynthesis signaling pathway, enabling the plants to withstand severe saline conditions.