Evolution of phototrophy in eukaryotes

The conventional view that the biological utilization of solar energy in eukaryotes is solely through photosynthesis was challenged by the recent discoveries of proton-pumping rhodopsins (PRs) in microbial eukaryotes. These eukaryotic plankton groups most probably acquired rhodopsins through lateral gene transfer (LGT) events from bacteria. I will study microbial eukaryotes communities in various aquatic environments to further elucidate origin, diversity, and abundance of PRs The eukaryotic-targeted metagenomic studies will allow to (1) identify the diversity of eukaryotic PRs, (2) establish phylogeny of eukaryotic PRs and detect LGT events. Metatranscriptomic analyses will enable elucidating the abundance of eukaryotic PRs and the extent to which rhodopsin-based phototrophy is used relative to O2- evolving photosynthesis.

Photosynthesis in eukaryotes evolved thanks to the endosymbiotic event with a cyanobacterium and establishment of plastids. I am studying two aspects of plastid evolution: (1) the initial steps of the enslavement of endosymbiont and order of events in this phase of transition from prey to endosymbiont and (2) the loss of photosynthetic function and indispensable functions of the vestigial plastids. To address those questions, I am planning to study algae models and their genomes and transcriptomes. To understand the order of events accompanying plastid enslavement, I have chosen to study kleptoplasty, which resembles the early stages of endosymbiosis. Kleptoplasty is a photosynthetic association, resulting from the maintenance of functional chloroplasts—the ‘kleptoplasts’—in the non-photosynthetic host. To understand functions of the vestigial plastids, I will study colourless algae and their photosynthetic counterparts from the several lineages of primary and secondary endosymbionts and reconstruct in silico the minimal plastid proteome of remnant plastids.