A spatially resolved subcellular proteome map provides insight into protein function and trace metal distribution in Thalassiosira pseudonana

Thousands of chemical reactions take place simultaneously within each phytoplankton cell. These reactions—collectively, metabolism—depend on specific molecular machinery (proteins) and specific subcellular conditions to occur. Eukaryotic phytoplankton compartmentalize these reactions within organelles, where the necessary conditions and proteins are maintained. Understanding the subcellular locations of proteins and their proximity to other proteins and cofactors (such as metals) is therefore essential for understanding phytoplankton metabolism. We developed a "spatial omics" method that uses precise cell lysis followed by ultracentrifugation to separate intact and viable organelles into several distinct fractions. We then applied a combination of untargeted mass spectrometry-based proteomics, metalloproteomics, and enzyme rate measurements to study these organellar fractions in detail. With this approach, we constructed a spatially resolved subcellular proteome map of the diatom Thalassiosira pseudonana, which we used to probe the subcellular locations of thousands of proteins in a single experiment. This enabled us to gain deeper insight into protein function and protein resource allocation in phytoplankton. Further, by integrating trace metal and metabolic rate measurements into these subcellular proteome maps, we can examine the elemental distribution within phytoplankton cells, the roles of metals in metabolism, and the potential impact of shifts in chemical gradients on ocean metabolism and ultimately biogeochemistry. 

Presentation Preference: Oral

Primary Presenter: Loay Jabre, Woods Hole Oceanographic Institution (loay.jabre@whoi.edu)

Authors:

Loay Jabre, Woods Hole Oceanographic Institution  (loay.jabre@whoi.edu)

Matthew Mcilvin, Woods Hole Oceanographic Institution  (mmcilvin@whoi.edu)

Mak Saito, Woods Hole Oceanographic Institution  (msaito@whoi.edu)