A systems approach of diatom responses to ocean acidification

Diatoms are unicellular photosynthetic eukaryotic algae that account for 40% of the marine primary production, they play a critical role in the marine carbon cycle, and over geological times have influenced the global climate. Our objective is to understand what the most important effects of climate change and ocean acidification will be on diatoms using a systems approach. The goal of a systems approach is to integrate all the measurements in order to formulate models that recapitulate all the observations and to predict new behavior in response to new environmental perturbations. We have conducted a genome-wide transcription profiling of the model diatom Thalassiosira pseudonana during growth at two CO2 levels: present day (400 ppm) and a doubling of the CO2 level (800 ppm), reflecting the projected scenario for the 21st century. In this presentation we will focus on replicate analyses of the physiological and molecular modes associated with the cells state (exponential and nutrient replete, stationary and nutrient depleted) under the two CO2 conditions. Our results show that most of the expressed genes associated with the difference in CO2 growth are unknown, not annotated or hypothetical genes (800 genes). These genes changed in expression mostly under stationary phase, when nutrients were depleted from the media and the cells were undergoing starvation