Grant: Discovery Grants Program - Individual

Cellular and molecular evolution is generally considered to proceed by many slow, gradual changes, but certain kinds of events can also lead to rapid, drastic changes. Although rare, such events can have a substantial impacts on the cell and genome where they take place, so their overall importance rivals that of the more gradual processes. We are studying the effects of two such events in complex microbial cells. (A) Lateral gene transfer is the non-sexual movement of genes between different organisms, and we have shown that collectively such transfers have played an important role in shaping the content of genomes in protozoa and algae. One gene we discovered is EFL, a member of the translation factor family thought to play a key role in cellular information flow. We showed EFL has the highest known frequency of transfer between eukaryotes, and is now scattered among distantly related lineages. We will use environmental methods to determine the abundance and distribution of EFL in nature, and will also carry out the first direct tests of its function, revealing the impact of its frequent transfers between cells. (B) Endosymbiosis is the fusion and genetic integration of two cells, which drives the generation and spread of new functional organelles. The exchange of information is key to this process, and will examine how proteins from one compartment are specifically targeted to another in a complex cell where one eukaryote lives within another, and four genome-containing compartments have been retained. Because of this genetic integration, organelles are difficult to lose entirely. We will characterise plastid relicts in non-photosynthetic lineages believed to have once contained plastids, and determining how biochemical functions were redistributed in the cell during organelle degeneration. Lastly, cellular mergers create redundancy in structures and metabolic activities. Redundancy is normally eliminated in one of the partner cells, but we have identified a cell where many redundant features f two eukaryotes are retained, uniquely including both mitochondria. Using genomic sequencing we will compare the functions of co-habiting organelles. Altogether this work will represent major advances in several directions for our understanding of rare but transformative events that shape cells and genomes.