Alteration in anti-oxidant defense system and protein expression in response to varied concentrations of EMS in Psoralea corylifolia

Abstract

Germplasm of Psoralea corylifolia L., one of the most important endangered medicinal plants of Chinese and Indian Pharmacopeia were treated with ethyl methane sulphonate (0, 0.1, 0.25, 0.50, 0.75 and 1 %) and sampled for observations in the form of growth, non enzymatic systems and stress proteins at pre-and post-flowering stages of development. Higher concentrations of EMS showed significant (P < 0.001) inhibition in the germination percentage from 3.88 to 35.46 % at pre-flowering stage and from 4.90 to 35.97 % at post-flowering stage when compared to control. Other growth related parameters viz shoot growth and root growth also declined within increase in the dose as compared to control plants. Root growth was severely affected as compared to shoot growth. Roots showed a significant correlation with tolerance index as increasing concentration of EMS progressively inhibited the root growth. Plants developed from treated germplasm at higher doses exhibit higher activity of ascorbate peroxidase (APX), up to flowering and after that declined. Contrast to that, total soluble protein (TSP) content decreased in age and dose wise manner. The EMS dose applied and oxidative stress was correlated and derived from the increased antioxidant activities and decrease in total glutathione content from 122.75 % (GSH) and 103.29 % (GSSG) in plants raised from treated germplasm towards the post-flowering stage. Pronounced accumulation of psoralen from 10.74 to 93.24 % was observed following higher doses of EMS at post-flowering stage, where EMS induced oxidative stress-enhanced proline accumulation and lipid peroxidation. In addition, the prevalence of maximum antioxidant activity, psoralen accumulation was an efficient process in acclimatizing P. corylifolia to stress. 2-Dimensional gel electrophoresis (2D-GE) of the protein expression profile and MALDI TOF–MS revealed an expression of 20 different proteins which are associated with such functions as cellular detoxification, stress defense, psoralen production, photosynthesis, signal transduction, and cell cycle. The increase in the psoralen pool after EMS treatment proved to be a best protective antioxidant to counterbalance EMS-induced ROS detoxification and can be used as a biomarker and a scavenger in stress physiology.