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The Unique Genome of Coral Symbionts

The genome of dinoflagellates, a type of eukaryotic coral symbiont, has been found to have a particularly unique genome. New research reveals that its genome has been organized in a new and unusual way. Scientists call this new discovery groundwork for future genomic discoveries to come. 

This research comes from KAUST, which is the King Abdullah University of Science & Technology, with a team of U.S. and German researchers. They examined the genomic organization of the coral symbiont dinoflagellate Symbiodinium microadriaticum. They found that its genome had been sequenced into segments called scaffolds, but lacked a chromosome level assembly. 

“The team used a technique known as Hi-C to detect interactions in the dinoflagellate’s chromatin, the combination of DNA and protein that makes up a chromosome. By analyzing these interactions, they could figure out how the scaffolds were connected together into chromosomes, giving them a view into the spatial and structural organization of the genome,” says an article written by KAUST.

The main finding was the the genome organized itself in alternating unidirectional blocks. “That’s really, really different to what you see in other organisms,” says Octavio Salazar, a Ph.D. student in Manuel Aranda’s group at KAUST and one of the lead authors of the study. While the orientation of genes on a typical chromosome is typically random, the dinoflagellate were consistently oriented in one way or the other.

The article goes on to explain the detailed findings and methods. “This organization is also reflected in the three-dimensional structure of the genome, which the team inferred comprises rod-shaped chromosomes that fold into structural domains at the boundaries where gene blocks converge. Even more intriguingly, this structure appears to be dependent on transcriptional activity. When the researchers treated cells with a chemical that blocks gene transcription, the structural domains disappeared.”

This unique structure of the dinoflagellates genome paves the way for so many new discoveries to come. The dinoflagellate genome defies the expectation and dogmas built from studying other eukaryotes. “It shows that nature can work in a completely different way than we thought,” says Salazar. “There are so many possibilities for what could have happened as life evolved.” The genomes of different animals provide new discoveries every day.

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