Organelle genetic systems in green algae

Over the past several decades my laboratory has studied the evolution of genomes in green algae, the group from which land plants arose. The main focus of our work is on organelle genomes, i.e., those in mitochondria and chloroplasts, the sites of respiration and photosynthesis, respectively; the presence of genomes in mitochondria and chloroplasts is normally essential to the functioning of these organelles. The overriding theme of our efforts has been to document and explain the diversity of organelle genome features, like intact vs. fragmented; circular vs. linear, GC-rich vs. AT-rich, and compact vs. bloated (i.e., high vs. low fraction of the genome has a coding function). The proposed work for the next grant period focuses on three main activities: (1) testing the mutational-burden hypothesis as an explanation for the compactness variation in mitochondrial, chloroplast and nuclear genomes in selected unicellular green algal species; (2) confirming and explaining the origin of mitochondrial genetic disease in the Oogamochlamys-clade of green algae; and (3) testing the hypothesis that the degenerate chloroplast in the green alga Polytomella parva, which contains no chlorophyll and no longer performs photosynthesis, has lost its genome and gene expression system. In recent years there has been an increased interest in green algae as a possible source of renewable energy, so basic knowledge about these organisms, especially when it concerns their mitochondrial and chloroplast genomes, could be valuable in unexpected ways. Finally, the association of deleterious changes in mitochondrial DNA with aging and certain genetic diseases in humans is now well established but the cause or causes for these mutations is less clear. Studying genetic dysfunction in green algal mitochondria is technically much easier than in humans and other mammals and may yield knowledge of value to the animal studies.