Analysis of physiological and proteomic changes in marigold (Calendula officinalis) in response to short term cold stress

Abstract

C. officinalis, pot marigold, is an important plant growing in China, Europe and USA which can withstand harsh winters in Kashmir Himalayan region in India. We investigated the cold stress tolerance mechanism in Calendula officinalis by assessing various physiological dimensions and two dimensional (2D) proteomic analysis on exposure to 4 °C at different time intervals. Seeds of C. officinalis were grown at 25 °C for two weeks, transferred to growth chamber set at 4 °C and tissues were analyzed every after 24 h for one week for physiological and proteomic alterations. Differentially expressed proteins were subjected to MALDI-TOF-MS analysis. The plant shows an increased dry weight with an increased relative water content maintaining the cell turgidity and photosynthetic activity during cold stress. The enhancement of ascorbate-glutathione pathway and accumulation of various non-enzymatic antioxidants (AsA, GSH and GSSG) protects the plant against the oxidative damage during cold stress. Total of 24 proteins spots exhibit significant changes at least after 24 h cold stress. The up-regulated proteins in response to cold stress belonged to photosynthesis, respiration, stress resistance, fatty acid metabolism, antioxidant defense, plant development and signal transduction. Three proteins corresponding to spot 90, 136 and 356 were found to be unique which may play a crucial role in cold tolerance mechanism in C. officinalis. Besides, some cold responsive proteins identified in C. officinalis are also involved in salt, heavy metal and abiotic stress response, which strongly suggest their cross-tolerance to biotic and abiotic stress. The transcript expression of some selected cold responsive proteins demonstrates a correlation with the proteomic data, which suggests that the proteomic data is reliable and can be used for further studies. Furthermore, this is the first report of proteomic study on C. officinalis in response to cold stress that opens novel insights in understanding the mechanism of cold tolerance in ornamental plants, which are important source of gene pool for plant breeding initiatives leading to the development of cold resilient commercial crops.