Proteomics Study of Switchgrass for Drought Stress

Abstract: Drought tolerance of Switchgrass (Panicum virgatum) is among the highly demanded trait to reduce the potential competition for irrigation water resources of this candidate bioenergy plant with food crop production. The depth of roots reaching underground during a gradual water deficit process could play a key role to determine if the plants can survive the spells of drought stress, especially during seedling stages when plants are establishing in the field. In this study, a “sandwich” system simulating a gradual water deletion process was developed to apply drought treatments of switchgrass seedlings. Comparative quantitative proteomics analysis, using iTRAQ and TMT followed by nano-scale liquid chromatography mass spectrometry (nano-LC-MS/MS) analysis, were conducted to identify drought-induced proteins in leaf and root-tip tissues. Results show that the significantly changed leaf proteins are involved in transcription and translation, cell division, cell wall modification, phyto-hormone metabolism and signaling transduction pathways, and metabolic pathways of carbohydrates, amino acids and fatty acids. A scheme of abscisic acid (ABA)-biosynthesis and ABA responsive signal transduction pathway was reconstructed using these drought-induced significant proteins, showing systemic regulation at protein level to deploy the respective mechanism. Also removal of highly abundant proteins in leaf protein sample enhanced the capacity in the quantification of low-abundance proteins. The drought-induced root proteins appear to be related to cellular functions in root tips and the regions behind. Proteins affecting cell division and elongation in root tips were identified. Information provided in this study will have an immediate as well as long term impacts on developing new lines (transgenic lines) and management of switchgrass in water saving production. The project is supported by NIFA-CBG- Award 2012-02466