Global mean temperatures are expected to rise by 2-4.5 degrees C by 2100, accompanied by an increase in frequency and amplitude of extreme temperature events. Greater climatic extremes and an expanded range of cultivation will expose rice to increasing stress in the future. Understanding gene expression in disparate thermal regimes is important for the engineering of cultivars with tolerance to nonoptimal temperatures. Our study investigated the proteomic responses of rice cell suspension cultures to sudden temperature changes. Cell cultures grown at 28 degrees C were subjected to 3-day exposure to 12 or 20 degrees C for low-temperature stress, and 36 or 44 degrees C for high-temperature stress. Quantitative label-free shotgun proteomic analysis was performed on biological triplicates of each treatment. Over 1900 proteins were expressed in one or more temperature treatments, and, of these, more than 850 were found to be responsive to either of the temperature extremes. These temperature-responsive proteins included more than 300 proteins which were uniquely expressed at either 12 or 44 degrees C. Our study also identified 40 novel stress-response proteins and observed that switching between the classical and the alternative pathways of sucrose metabolism occurs in response to extremes of temperature.