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Tube anemone has the largest animal mitochondrial genome


Tube anemone has the largest animal mitochondrial genome

Pachycerianthus magnus. Regards: Sergio Stampar

Anemone of the tube Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of each animal that has been sequenced so far with 80,923 base pairs. The human mitochondrial genome (mitogen), for example, contains 16,569 base pairs.

Tube Anemones (Ceriantharia) are the focus of an article recently published Scientific reports describing the results of a study led by Sergio Nassimento Stampar, a professor at the Sao Paulo State University School of Science and Letters (FCL-UNESP) in Assisi, Brazil.

The study is supported by FAPESP through a regular Grant for the Cariantharia (Cnidaria) Evolution and Diversity Project and through its Sao Paulo Researchers Program in International Cooperation (SPRINT) under a Cooperation Agreement with the University of North Carolina (UNC) in Charlotte, USA .

Mitogenoma is simpler than the nuclear genome, which in the case of I. nocturnus is not yet sequenced, Stampar explained. The human nuclear genome includes about 3 billion base pairs, for example. Another finding reported in the article is that I. nocturnus and Pachycerianthus magnus (another species studied by the Stampar group, 77,828 base pairs) have linear genomes such as medusae (Medusozoa), while other species in their class (Anthozoa) and in fact most animals have circular genomes.

I. nocturnus is located in the Atlantic Ocean off the coast of Patagonia in Argentina, north, on the east coast of the United States. P. magnus lives in the marine environment around the island of Taiwan in Asia. Both inhabit the waters at a maximum of 15 m depth.

"Mitogen of I. nocturnus is almost five times larger than the human mitogen," says Stampar. "We tend to think we are more molecularly complex, but in fact our genome has been more filtered during our evolution." Maintaining this giant genome is probably more expensive in terms of energy costs. "

The form of the mitogenes in these two types of tubular anemones and the gene sequences they contain are more surprising than their size.

Since they are closely related species, their gene sequences must be similar, but I. nocturnus has five chromosomes, whereas P. magnus has eight and each has a different gene composition. This type of variation has been found only in jellyfish, mushrooms and some crustaceans.

"People and bone fish are more similar than these two anemones to the structure of their mitochondrial DNA," Stampar said.

The coast of Sao Paulo and the South China Sea

To reach these results, researchers have captured specimens in Sao Sebastião, which is located on the coast of Sao Paulo state in Brazil and outside Taiwan in the South China Sea. Small pieces of animal tentacles were used to arrange their mitogenes.

The genomes of the two types so far accessible from the databases were incomplete due to the difficulty of stacking. Upon completion of the study, researchers publish the genomes by donating them to GenBan, a database maintained in the United States by the National Biotechnology Information Center (NCBI) at the National Institute of Health (NIH).

Another obstacle to consistency is the difficulty in collecting these animals because of their elusive behavior. In response to any potential threat, tubular anemone lies in the long leather tube, which distinguishes it from true marine anemones, making capture impossible.

"You have to dig a hole around it, sometimes as deep as a meter, and stop the part of the tube buried in the sand, all of which must be done underwater while wearing diving equipment, otherwise it is hidden in the buried part of the pipe and you just can not keep it, "Stampar said.

Thanks to the support of the FAPESP SPRINT program, Stampar and Marymegan Daly, a colleague from Ohio University in the United States, established a partnership with Adam Reitzel and Jason Macrander at UNC Charlotte. Macrander, then a post-graduate student at Reichel, is a professor at Florida South College.

Reitzel and Macrander specialize in the use of bioinformatics to filter genomic data and collect millions of small pieces of mitochondrial DNA in one sequence. They used this technique to reach full mitochondrial genomes for both species.

"With this technique you arrange the genome of the genome and connect it to a circle, the problem is that it only works with circular genomes." Since we could not find a piece to close the circle, we realized the genome had to be linear, as well for Medusozoa, "Stampar said.

The discovery allows for possible reclassification of small species (hydrates, jellyfish, polyps, corals and marine anemones). The investigated tubular anemones form a separate group of corals and marine anemones and show some resemblance to the jellyfish.

However, more data will be needed before a final conclusion can be reached. Necessary data can be obtained from the sequence of nuclear genomes of these species that Stampar and his group intend to complete by the end of 2019.

Sea anemones are usually not so simple after all

More information:
Sergei N. Stampar et al., Linear mitochondrial genome in Anthozoa (Cnidaria): case study in Ceriantharia, Scientific reports (2019). DOI: 10.1038 / s41598-019-42621-z

The Tube Anemone has the largest animal mitochondrial genome that has ever been sequenced (2019, 11 June)
restored 11 June 2019

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