Environmentally-informed functional characterisation of the secondary red chloroplast proteome

"Photosynthesis in the ocean is as significant as that of land plants, and is performed by a wide range of cyanobacteria and eukaryotic algae, the most abundant of which have originated through the secondary endosymbioses of red algae. Previously, I have shown that these ""secondary red chloroplasts"" are evolutionary mosaics, supported by nucleus-encoded proteins of symbiont, host and horizontally acquired origin; and that the most successful of these groups (diatoms, haptophytes and dinoflagellates) are connected to one another via chloroplast endosymbioses.

My research programme will answer a question of fundamental importance to the evolutionary history, and future ecology of the planet: why is the secondary red chloroplast so successful in the modern ocean? I will perform next-generation proteomic (LOPIT) characterisation of the dinoflagellate chloroplast, whose composition remains unknown; phylogenomic and spatial reconstruction of the pan-secondary red chloroplast proteome, using environmental sequence data from the Tara Oceans expedition; and phenotyping of proteins via CRISPR/Cas9 mutagenesis in the model diatom Phaeodactylum. I will focus on defining the proteins that underpin the dominant contributions of secondary red chloroplasts to marine primary production; and their unique success in high oceanic latitudes.

Thus far, I have characterised a mitochondria-associated transporter that facilitates photo-acclimation in secondary red chloroplasts under Fe limitation; and a complete glycolytic pathway that regulates diatom chloroplast metabolism in polar oceans. The phylogenetically-grounded insights from this project will connect a defining event in eukaryotic evolution, the endosymbiotic evolution of chloroplasts, to the functional biology of marine ecosystems; identify new proteins for optimising photosynthetic production in cultivable species; and define new biomarkers for the resilience of algal communities to anthropogenic climate change.

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