Typical features of genomes in the mamiellophyceae

Abstract

In surveys of marine phytoplankton diversity, prasinophyte algae are commonly found and are often a major component, especially in coastal areas. They form a paraphyletic assemblage of at least nine clades, with the Mamiellophyceae (prasinophyte clade II) being a major group. In the order Mamiellales, the three genera Bathycoccus , Micromonas and Ostreococcus are the dominant picoeukaryotic organisms in many different oceanic areas, as witnessed by their abundance in analyses of environmental DNA samples. Each of the six complete genomes analyzed from cultured representatives of this group has revealed densely packed coding sequences, with strong evolutionary divergence from its nearest phylogenetically defined neighbors. These species lie at the base of the green lineage, but various metabolic processes reflect their marine lifestyles and distinguish them from land plants, including a high proportion of selenoprotein enzymes and C4 photosynthesis. They all possess two unusual chromosomes with lower GC content and atypical gene content, whose function so far remains enigmatic.