Exploring the evolution of the Contractile Vacuole.

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Movement of material within the cell, as well as import, export, and cell surface presentation is mediated by the membrane trafficking system (MTS). Its appropriate and successful operation underpins effective cellular function, whether in plants of agricultural importance, parasites of economic impact or algae and protists key to ecosystem balance. Evolving an MTS was key to establishing the eukaryotic cellular configuration and giving rise to nearly all of the biological diversity that we see today. My research program examines the patterns and processes driving the evolution of the MTS. This work provides insights into the fundamental forces that shaped our cellular history and yields important information about modern cell biology. Intriguingly, we have uncovered protein machinery widely present outside of animals and fungi: the cell biology of membrane-trafficking in diverse eukaryotes may differ from well-characterized model systems in ways that are only beginning to be understood. Similarly, while some membrane-trafficking organelles are conserved across eukaryotes, poorly understood organelles are present outside the well-known model systems that are ripe for exploration. The Contractile Vacuole (CV) is an osmoregulatory organelle found in ecologically important freshwater and soil-dwelling organisms. However, it is often not reported as present in parasites or marine organisms, raising questions of whether organelles identified as contractile vacuoles are truly orthologous between diverse eukaryotes. We will use molecular evolutionary and transcriptomic analysis to examine the evolution and function of the CV by two short-term goals, each with sub-projects defined within them. 1: In order to test the simplest null hypothesis that the CV derived from a single homologous ancestor, a sampling of eukaryotes with CVs from across the eukaryotic tree will be investigated. Transcriptomics will be used to determine genes that are differentially expressed upon induction of CV function by osmotic stress. The identity and evolution of these genes will be assessed with the explicit prediction that a common core gene set associated with CV function would imply homology. 2: To complement this taxonomically broad approach, analysis will be focused on a single lineage possessing well-characterized CVs, the ciliates. Molecular evolutionary and transcriptomics across the full taxonomic range of ciliates will assess the machinery that is conserved in CV function, again predicting the presence of a conserved core set. By identifying the genes of importance in CV function and their distribution in eukaryotes, we gain information about the workings of an organelle present in ecologically crucial lineages of eukaryotes. By understanding the evolution of the CV, we will be able to integrate an important organelle into the larger framework of membrane-trafficking evolution and gain a better understanding into the rise of eukaryotic life on Earth.