Membrane Proteins Associated with Heat-Induced Leaf Senescence in a Cool-Season Grass Species

Heat-induced leaf senescence is a major symptom of heat stress in cool-season plant species. The objective of this study was to identify membrane proteins associated with leaf senescence for a cool-season grass species subjected to heat stress. Two lines (ColxCB169 and COLXCB190) of creeping bentgrass (Agrostis stolonifera L.) x colonial bentgrass (A. capilaris L.) hybrids were exposed to heat stress (38 and 35 degrees C day and night) for 28 d in growth chambers. Leaf senescence was evaluated by turf quality rating, leaf chlorophyll content, and leaf electrolyte leakage, and the data demonstrated that COLXCB169 exhibited a significantly lesser degree of leaf senescence than COLXCB190 under prolonged heat stress. Membrane proteins analyzed using two-dimensional gel electrophoresis showed significant differences in abundance between lines, which were mainly classified into three functional categories: energy production, metabolism, and stress defense. The majority of membrane proteins in leaves were downregulated due to heat stress but the abundance of proteins involved in energy metabolism including ATP-synthase, Cytochrome b6f, chloroplast oxygen-evolving enhancer protein, and pyruvate dehydrogenase kinase, as well as antioxidant proteins such as catalase and peroxidase, decreased later and to a lesser extent in leaves of ColxCB169. Transcript levels of ATP-synthase, Cytochrome b6f, and peroxidase were downregulated to a greater degree in ColxCB190 than in COLXCB169. The results suggested that membrane proteins involved in ATP metabolism, light harvesting, and photosynthetic photochemical reactions as well as proteins for efficient processing of photorespiratory products and reactive oxygen species may serve important roles in regulating leaf senescence in bentgrass (Agrostis spp.) under heat stress.