HudsonAlpha scientists among those examining tiny algae

HUNTSVILLE, Ala – When you think about walking through a tall meadow of grass, you likely envision peace and calm. But on a sunny day those grass blades are busy factories turning light into food energy through a complex mechanism of enzymes arranged in the photosynthetic pathway. Those grass cells can only act as factories because distant ancestors declared war on other cells and swallowed them whole, trapping and forcing them to work for the grass cell.
 


The history of this conflict can be seen in different stages through different forms of plants. Researchers at HudsonAlpha and 26 other institutions recently sequenced the nuclear genomes of two algae, or single-celled, plant-like organisms, which were frozen at different points in the process of trapping other cells. 
 


These algae actually have four genomes in their cells:  the original nuclear genome; the mitochondrial genome, reflecting a bacteria engulfed by ancestors a longer time ago; the chloroplast genome, reflecting a different bacterial engulfment; and a nucleomorph, or a remnant of the DNA of another algal cell from where these new algae declared war and swallowed part of them. 
 


To make matters more complicated, over time segments of DNA have been swapped between all four genomes. The genomic records indicate that this swapping went on for a period of time and then stopped. When genomicists examine the four genomes of these two algae today, they are looking at the equivalent of cave paintings or ancient tablets showing how different civilizations battled, merged and ultimately exchanged cultures and traditions. 
 


In the algae, important genes for photosynthesis and energy generation have transferred from the three engulfed genomes to the original nuclear genome, while other crucial genes have remained encoded in the three engulfed genomes. This means the four original organisms are now completely interdependent within one cell and every moment is a complex ballet between machinery originating from multiple places and evolutionary times. 
 


The work is published in the paper Cryptophyte and chlorarachniophyte nuclear genomes reveal evolutionary mosaicism and fate of nucleomorphs and appears in the journal Nature on 29 November 2012.