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Sibo Wang:
Algae Genome Studies Reveal the Evolutionary History of Green Plants

Date: 10-05-2021    Supervisor: Morten Petersen




The origin of the photosynthetic eukaryotes changed the evolutionary trajectory of earth life. In the common ancestor of the supergroup Archaeplastida, a single cyanobacterial primary endosymbiosis is thought to have occurred., resulting in the evolutionary origin of Viridiplantae, Rhodophyta and Glaucoplantae algae. The Viridiplantae is one of the largest oxygen photosynthetic eukaryotes groups, and current theories reflect the early discrepancy of two ancient Viridiplantae classes.

Chlorophyte contains the early divergent prasinophytes that have given rise to the core chlorophytes. Another clade, the Streptophyta, contains the green algae and land-dwelling plants. Due to scarce molecular data from Chlorophyta and Streptophyta algae data, there are several concerns about phylogenetic studies in the complex relationships of green algae, especially for the orders of early branching Prasinophyte lineages and the phylogeny between the Streptophyta algae. With the decreased sequencing cost, we entered the genome era. Large scale nuclear genome sequencing projects allow researchers to perform more accurate phylogeny analysis by phylogenomics. Besides, genome data is also a valuable source for comparative genomics, which is now the main method to mining genome evolutionary innovation, decode species evolutionary history and secret.

During my Ph.D. study, two early-diverging streptophyte algae (Mesostigma viride and Chlorokybus atmophyticus) and one early-diverging Chlorophyta algae (Prasinoderma coloniale) were selected and sequenced. By combining phylogenetic analysis and broad-scale comparative genomics, we discovered a novel 3 rd phylum of the green lineage, called the Prasinodermophyta, and established genome evolutionary innovation as the first step on the long path to plant terrestrialization. Overall, these genome studies of green algae provide insights into the evolutionary history of green plant.