Diatoms are an abundant and widespread functional group of phytoplankton, responsible for significant amounts of primary production in the ocean. As such, they exert a profound influence on the global cycling of carbon. In recognition of this significance, the diatom Thalassiosira pseudonana was the first eukaryotic marine phytoplankton model selected for whole genome sequencing. The genome of this model diatom highlighted unexpected aspects of T. pseudonana metabolism (e.g. a mosaic of pathways derived from plant and animal ancestors), and emphasized that despite their importance, there are fundamental gaps in our understanding of diatom physiology and how these organisms function in the sea. The supply of micronutrients (e.g. iron) and macronutrients (e.g. phosphorus) are considered to be primary drivers of diatom biomass in many marine systems. In fact, models predict there are large regions of both the Atlantic and the Pacific where diatoms are limited by these nutrients. This research project will use transcriptional and proteomic profiling to examine the underlying molecular mechanisms involved in the response of marine diatoms to iron and phosphorus limitation. Since multiple factors can be limiting for growth in the environment, we are also proposing experiments to dissect the impact of nutrient co-limitation on marine diatoms with a molecular test of Liebig's Law. This genome-enabled work will first be pursued with T. pseudonana using transcriptome profiling and advanced mass spectrometry for the proteome profiling, with the T. pseudonana genome as a frame-work for gene discovery and annotation. These investigators will then apply these methods to understand how nutrient limitation impacts other ecologically important, unsequenced diatom species. This project will address key gaps in our understanding of diatom physiological ecology, and bring together four early-career investigators and their combined expertise in marine functional genomics towards this important yet understudied oceanographic concept of co-limitation. The investigators will also provide a public database with access to the gene expression and protein expression data for others interested in phytoplankton genomics and the biology of diatoms, and promote science learning in children (ages 8-14) using an interactive educational website (www.whyville.net) that has 25,000 users daily. Through this effort the investigators will have the opportunity to teach key concepts in phytoplankton biology and oceanography, and the process of scientific inquiry, to millions of children. This project will also promote graduate education and mentoring by NSF ADVANCE funded investigators that serves to broaden participation of women in science and provides mentoring support for graduate students.
