Abstract
Tiny marine green algae issued from two deep branches of the Chlorophyta, the Mamiellophyceae and Chloropicophyceae, dominate different regions of the oceans and play key roles in planktonic communities. Considering that the Mamiellophyceae is the sole lineage of prasinophyte algae that has been intensively investigated, the extent to which these two algal groups differ in their metabolic capacities and cellular processes is currently unknown. To address this gap of knowledge, we investigate here the nuclear genome sequence of a member of the Chloropicophyceae, Chloropicon primus. Among the main biological insights that emerge from this 17.4 Mb genome, we find an unexpected diploid structure for most chromosomes and a propionate detoxification pathway in green algae. Our results support the notion that separate events of genome minimization, which entailed differential losses of genes/pathways, have occurred in the Chloropicophyceae and Mamiellophyceae, suggesting different strategies of adaptation to oceanic environments.
Highlights
Tiny marine green algae issued from two deep branches of the Chlorophyta, the Mamiellophyceae and Chloropicophyceae, dominate different regions of the oceans and play key roles in planktonic communities
The genomes of a number of photosynthetic green algae, mainly from the Chlorophyta, have been sequenced to unravel the evolutionary trajectories followed by ancestral green algae[4,5,6,7], decipher cellular mechanisms such as the basis of multicellularity[8,9,10,11], pinpoint genes linked to adaptations to ecological niches[12,13,14,15], and investigate metabolic networks, including routes for the biosynthesis of highly valuable compounds for the industry[16,17,18,19]
We report the nuclear genome sequence of Chloropicon primus, a member of the Chloropicophyceae
Summary
Tiny marine green algae issued from two deep branches of the Chlorophyta, the Mamiellophyceae and Chloropicophyceae, dominate different regions of the oceans and play key roles in planktonic communities. The genomes of a number of photosynthetic green algae, mainly from the Chlorophyta, have been sequenced to unravel the evolutionary trajectories followed by ancestral green algae[4,5,6,7], decipher cellular mechanisms such as the basis of multicellularity[8,9,10,11], pinpoint genes linked to adaptations to ecological niches[12,13,14,15], and investigate metabolic networks, including routes for the biosynthesis of highly valuable compounds for the industry[16,17,18,19] Known for their important role in the global carbon cycle, the green algae traditionally considered as prasinophytes constitute a paraphyletic assemblage of unicellular, predominantly marine organisms at the base of the Chlorophyta[2,20,21] (Fig. 1a). The tiny algae belonging to the three genera from the order Mamiellales—Ostreococcus, Micromonas (no scales and one flagellum), and Bathycoccus
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