Environmentally-informed functional characterisation of the secondary red chloroplast proteome

Introduction

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. The most successful of these groups (diatoms, haptophytes, and dinoflagellates) are connected to one another via chloroplast endosymbioses.

Research Question

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?

Methodology

I will perform the following:

1. Next-generation proteomic (LOPIT) characterization of the dinoflagellate chloroplast, whose composition remains unknown.
2. Phylogenomic and spatial reconstruction of the pan-secondary red chloroplast proteome, using environmental sequence data from the Tara Oceans expedition.
3. 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.

Previous Findings

Thus far, I have characterized:

• A mitochondria-associated transporter that facilitates photo-acclimation in secondary red chloroplasts under Fe limitation.
• A complete glycolytic pathway that regulates diatom chloroplast metabolism in polar oceans.

Expected Outcomes

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 optimizing photosynthetic production in cultivable species.
• Define new biomarkers for the resilience of algal communities to anthropogenic climate change.