Cellular and metabolic integration of symbiotic organelles in the ciliate Mesodinium rubrum

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

Photosynthetic life (plants and algae) has a complex evolutionary history due to symbiotic interactions that have resulted in the transfer of chloroplasts (the photosynthetic organelle) among unrelated groups of organisms. While there is abundant evidence for the role of symbiosis in these evolutionary events, little is known regarding how organisms adapt to become "green". This project will investigate early events in the acquisition of a chloroplast and how an organism has restructured its entire metabolism in order to use photosynthesis, despite lacking the genes necessary to run it. The investigators will focus on a common marine ciliate that is known to feed on one particular group of algae, and steal its cellular machinery (i.e. the organelles: chloroplasts, mitochondria, and nucleus). The ciliate is able to incorporate these organelles into its own cell, and even replicate them as the cell divides, by utilizing genes expressed from the temporary stolen nucleus. The investigators will use next generation (transcriptomics, proteomics, metabolomics) and traditional (microscopy, cell physiology) techniques to discover how organisms can adapt to a photosynthetic metabolism and incorporate foreign organelles into their own cell. The investigators will focus on how the ciliate is able to steal a nucleus and facilitate its gene expression, and the subsequent targeting of proteins back to the stolen organelles that are reorganized within its cell. This foreign nucleus cannot divide in the ciliate, and therefore must be routinely replaced by feeding after the cell divides. These results will have broad applications to studies of symbiosis (including parasitism), and will reshape how we think about the role of symbiosis in eukaryotic evolution. The investigators will work with students (grades 8-12) in collaboration with the Zephyr Education Foundation, to expand marine science literacy and to teach about symbiosis. They will also train under-represented undergraduates through laboratory research projects.