Award: EF-1316206

Intellectual Merit: Diatoms are unicellular photosynthetic eukaryotic algae that account for about 40% of total marine primary production. They form the base of many food webs in coastal and upwelling areas, that support important fisheries and livelihoods. Diatoms are central to the biogeochemical cycling of important nutrients such as carbon, nitrogen and silicon and have influenced the world?s climate by changing the flux of carbon into the oceans. Using the model species Thalassiosira pseudonana, we demonstrated in a detailed physiological and gene survey that approximately 40 percent of the transcriptome varied significantly and recurrently, reflecting large, reproducible cell-states and cell- transitions between four principal states: I) light, II) dark, III) exponential growth and nutrient replete, IV) stationary phase and nutrient depleted. Repeated shifts in the gene expresision levels of hundreds of genes encoding sensory, signaling, and regulatory functions accompanied the four cell-state transitions, provided a map of the highly coordinated regulatory program under varying conditions. These results explain, in detail, how the diatom operates under varying environmental conditions. Furthermore, we have shown that T. pseudonana rapidly responds to increasing CO2 by a shift in regulation and metabolism re-arrangement. Additionally, we also recently demonstrated that diatoms are more sensitive to collapse when at low carbon and facing multiple perturbations and suggest that ocean acidification will stabilize diatom populations with a potential to see an increase in their distribution. In addition, we have integrated all existing publicly available data for the diatom models T. pseudonana and Phaeodactylum tricornutum online, and is explorable through the Diatom Portal. This detailed knowledge of the dynamic molecular process is invaluable for new hypothesis generation and the interpretation of genetic, and environmental data. The diatom portal is popular with the research community, and actively visited from more than 80 countries. Broader Impacts: We successfully integrated interdisciplinary research and education efforts. We developed an inquiry-based high school education module to teach the process of systems biology in the context of climate change, carbon cycling and ocean acidification using T. pseudonana as a model system. We have improved science education and making STEM more accessible to all students and teachers. Through our program, the students develop their own hypotheses and experiments related to the overall topic, perform experiments, and analyze data. Students are exposed to the idea that large, systems-level problems need to be studied from several angles, and groups of students focus on different approaches. At the end, the students synthesize results from all approaches. Our website is widely accessed (https://see.systemsbiology.net/ocean-acidification-module/overview/) and an average of 25,000 students complete these lessons each month. In addition, this curriculum has been incorporated into the California State High School Three-course model framework. This framework and the curriculum within are used by approximately 1.8 million public high school students each year. Last Modified: 11/16/2018 Submitted by: Monica Orellana