Grant: Discovery Grants Program - Individual

If I asked a random research biologist to name a green alga, they would likely say Chlamydomonas reinhardtii or Volvox carteri. Indeed, these two closely related species are among the best-studied photosynthetic microbes on Earth. However, the phylogenetic order to which this duo belongs (the Chlamydomonadales) harbours many other fascinating species, some of which have proven to be reservoirs of unconventional genomes. For instance, the Chlamydomonadales captures the entire known size range of chloroplast genomes across all eukaryotes and includes the first example of genome loss within an organelle. My proposed research program employs chlamydomonadalean algae to explore how major transitions in evolution, "extreme" lifestyles, and underlying DNA maintenance machineries impact (and are impacted by) genomic architecture. My trainees and I will investigate species spanning a range of environments (e.g., high vs. low light), lifestyles (e.g., photo- vs. heterotrophic), and cellular organizations (e.g., uni- vs. multicellular). A key focus of the program will be algae that have independently lost photosynthetic capabilities as well as those that have transitioned to an obligate cold-temperature existence. We will also target taxa known to have especially unusual genomes, such as those with linear mitochondrial chromosomes. Using next-generation sequencing, bioinformatics, and classic molecular biology techniques, we will generate draft mitochondrial, chloroplast, and nuclear genome/transcriptome sequences (and in some cases proteomes and metabolomes) for our algae of interest. These data will serve as the foundation for downstream comparative multi-omics and population-genetic analyses. My objectives are to 1) expand our knowledge of the diversity and limits of genomic complexity; 2) test and develop contemporary hypotheses on genome evolution; 3) examine the link between distinct life history, physiological, and/or environmental traits with specific genomic features (e.g., gene duplications); and 4) untangle the varying roles that adaptive and non-adaptive forces have in shaping genomes. For example, why have some non-photosynthetic chlamydomonadaleans lost their chloroplast genomes while others have undergone severe chloroplast genome expansion? What role does the underlying chloroplast DNA maintenance machinery (which is nuclear encoded) play in this process? And are these different outcomes primarily the consequence of natural selection or genetic drift? The impact of this research could be far-reaching. Remember, among the deadliest parasites on Earth is a non-photosynthetic alga (Plasmodium). Although the non-photosynthetic species we aim to study are free living, they are an excellent comparison point for better understanding parasitic algae. Similarly, many of the cold-adapted algae in this proposal are threatened by a warming planet, meaning they have their fingers-or, rather, their flagella-on the pulse of climate change.