Genotype-dependent and temperature-induced modulation of secondary metabolites, antioxidative defense and gene expression profile in Solanum viraum Dunal

Abstract The medicinal plant, Solanum viarum Dunal includes a number of compounds with important pharmacological effects. The effect of temperature (heat and cold) stress on growth, secondary metabolite levels and defense mechanism in two genotypes (prickled and prickleless) of S. viarum was evaluated. The two thermal regimes (4°C for cold and 35°C for heat stress) were found to be the most optimum for the accumulation of metabolites (steroidal alkaloids and glycoalkaloids, phenolic acids as well as flavonoids). Prickleless genotype showed 4.08 and 1.51 fold higher total alkaloids/glycoalkaloid content at 35°C and 4°C temperatures respectively, in comparison with prickled plants. Prickleless plants also registered 2.03 and 2.28 higher fresh and dry biomass accumulation respectively, under cold stress over the control plants. The accretion of phenolic and flavonoid compounds under heat and cold stress is mainly contributed by gallic and ferulic acid in both the genotypes. The quantitative real-time PCR expression analysis showed the abundance of gene transcript involve in the biosynthesis of alkaloids/glycoalkaloid and phenolics/flavonoids that corroborates with the accumulation of their respective metabolites in prickleless plants under temperature stress. Results revealed that the prickleless plants inhibiting the reactive oxygen species (ROS) mediated oxidative damage by activating the enzymatic (superoxide dismutase, peroxidase, catalase and ascorbate peroxidase) and non-enzymatic (alkaloids, phenols, flavonoids, carotenoids and proline) antioxidants mechanism that confirms its efficiency to tolerate thermal stress under both the thermal regimes. The overall result showed that the prickleless genotype served as a better accumulator of biomass, secondary metabolites with an improved antioxidative mechanism in comparison to prickled genotype. Our findings suggest that thermal stress responses differ significantly between genotypes, emphasizing the necessity of maintaining genotypic diversity in adaptive evolution as in the context of global warming and climate change. The present study also opens the possibility of exploiting improved prickleless genotype of S. viarum as a potential system that can be cultivated under different temperature stress conditions to attain the phytopharmaceutical benefits.