Tube anemone has the largest animal mitochondrial genotype ever sequenced

Publicado em 11 junho 2019

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

Flower Anemones (Ceriantharia) focus on the article recently released in Scientific Reports describing the results of the study led by Sérgio Nascimento Stampar, a professor at the School of Science and Letters of the State University of Sao Paulo (FCL-UNESP) in Assisi, Brazil.

The study was supported by FAPESP through regular grants for the project "Evolution and Variety of Ceriantharia (Cnidaria) and through its São Paulo International Research Program (SPRINT) under the Cooperative Agreement with the University of North Carolina (UNC) in Charlotte US.

Mitogen is simpler than the nuclear genome, which in the case of I. nocturnus has not yet been sequenced, explained Stampar. The human nuclear genome contains about 3 billion pairs of bases, for example. Another discovery reported in the article is that I. nocturnus and Pachycerianthus magnus (the other species studied by the Stampar group, 77,828 pairs of bases) have linear genomes such as those in Medusozoa, while other species in their class (Anthozoa) and most animals have a circular genome.

I. nocturnus is located in the Atlantic from the coast of Patagonia in Argentina to the north as the east coast of the United States. P. Magnus lives in the marine environment around the island of Taiwan in Asia. They both inhabit water up to 15 m deep.

"Mitogen I. nocturnusa is almost five times greater than human mythogenic," said Stampar. "We believe we are more molecularly complex, but in fact our genome is more" filtered "during our evolution. Preservation of this genome is probably more expensive in terms of energy consumption."

The form of mitogens in these two types of anemone tubes and the sequences of the genes they contained were more surprising than their size.

Since they are related species, their gene sequences should be similar, but I. nocturnus has five chromosomes, while P. magnus has eight, each having a different composition in the sense of a gene. Such variations were previously found only in the medusa, sponges and some crabs.

"People and types of bone fish are similar to these two tubular anemones in terms of the structure of mitochondrial DNA," said Stampar.

Sao Paulo Coast and South Sea Sea

To reach these results, researchers have picked up specimens in São Sebastião, located on the coast of Sao Paulo State Brazil, and in Taiwan in the South China Sea. Small bits of animal pips were used for sequencing of mycogenomas.

The genomes of the two types available to date from the database were incomplete due to difficulties in their determination. After completing the study, researchers published the genome by donating them to GenBan, a database that was hosted by the National Center for Biotechnical Information (NCBI) at the National Institute of Health (NIH) in the United States.

Another sequencing hurdle was the difficulty in collecting these animals due to their unobtrusive behavior. In response to any potential threat, the pipe anemone is hidden in a long leather tube that differentiates it from true ocean anemones, making capture impossible.

"You have to dig a hole around it, sometimes as deep as a meter, and stop the part of the pipes buried in the sand." All this has to be done under the water while you are carrying diving equipment. Otherwise, it hides in the buried part of the pipe and you simply can not catch it, "he said. is Stampar.

Thanks to the support of FAPESP's SPRINT program, Stampar and Marymegan Daly, a research associate at Ohio State University in the United States, have partnered with Adam Reitzel and Jason Macrander at UNC Charlotte. Macrander, then Postdoctoral Researcher under Reitzel, is a professor at Florida Southern College.

Reitzel and Macrander specialize in the use of bioinformatics for filtering genomic data and collecting millions of mitochondrial DNA fragments in one sequence. They used this technique to get full mitochondrial genomes for both species.

"In this technique, you sequitate the genome bits and connect them to a circle. The problem is that it works only with the circular genome. Since we could not find the part that would close the circuit, we realized that the genome must be linear, Medusozoa, "said Stampar.

This discovery is a way of possible reclassification of species of fire (hydras, medus, polyps, corals and sea anemones). The studied tubular anemones seem to form a separate group of corals and marine anemones and show some similarities with honey.

However, more data will be needed before a final conclusion can be drawn. The necessary data could be derived from the sequencing of the nuclear genomes of these species, which Stampar and his group intend to complete by the end of 2019.

Simple sea anemones are not that simple yet

More information:
Sérgio N. Stampar et al., Linear Mitochondrial Genome in Anthozo (Cnidaria): Case Study in Ceriantharia, Scientific Reports (2019). DOI: 10,1038 / s41598-019-42621-z
Tube anemone has the largest genetics of animal mitochondria ever sequenced (2019, June 11)
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