Ahmed Moustafa’s Science Paper Online
As mentioned previously, Ahmed Moustafa had his manuscript accepted by Science and it has recently been posted online. This work provides insight into the evolution of diatoms (pics here and here) and provides unexpected analytical data from their genome, shedding light into a convoluted evolution. A perspective was also published in the same issue of Science providing some background and commentary on Ahmed’s paper. Huge congrats to you Ahmed, nice job!
From Ahmed: Although the world’s oceans are currently dominated by phytoplankton such as diatoms and dinoflagellates that contain photosynthetic organelles (plastids) stolen from red algae, it was not always this way. Before the great end Permian extinction about 250 million years ago, the ocean was green, dominated by prasinophyte and other green algae. A clue to this major shift in the algal flora was provided by the recent comparative genome analysis by Moustafa et al. of two diatom species, Thalassiosira and Phaeodactylum. Using a phylogenomic pipeline designed and built in the Bhattacharya lab at the University of Iowa, the authors determined the origin of all 11,000 genes in each of these taxa. This work shows surprisingly that about 1,800 genes in each taxon are of green algal origin. This result provides strong evidence that diatoms and other marine phytoplankton that currently harbor a red algal derived plastid once contained a green algal endosymbiont that provided these “hidden” genes to their genome. This ancient cryptic endosymbiosis, rather than being an oddity, appears to have outfitted chromalveolates with genes from two taxonomically distantly related groups (green, followed by red algae), allowing them to complement their genetic potential. Many of the retained green genes provide key functions to chromalveolates such as enhanced photoprotection and a host of metabolite transporters to more effectively use dissolved nutrients in the environment, whereas many others likely have equally important but currently unknown functions. These data may therefore help to explain the rise to dominance of chromalveolates in the oceans. The work also reveals the genomic gymnastics that have occurred over millions of years in the marine environment resulting in highly chimeric nuclear genomes shaped by serial endosymbiosis.