The more social the shrimp, the larger its genome


A team of researchers from Columbia university discovered that eusocial shrimp have larger genomes than their less social parents. The larger genome includes an accumulation of transposable elements – moving DNA sequences – providing new information on the relationship between social and genomic evolution. The research is published in PNAS.1

Eusociality in sea creatures

Professor Dustin Rubenstein from Columbia University has been studying serpentine shrimp for many years. Crustaceans are so called because of the distinct “snap” sound their claws make when they close quickly. This is a defense mechanism that can deter predators and stun prey. Sometimes large gatherings of serpentine shrimp are therefore strong that they are known to disrupt underwater research and communications.

Rubenstein, professor of ecology, evolution and environmental biology, is particularly interested in the Synalpheus kind of serpentine shrimp, because it contains the only eusocial species.

What is a genre?

The genus is a biological classification classification that falls between family and species.

If an organism is eusocial, it demonstrates advanced social behaviors including: living together in groups, cooperating to care for offspring, division of labor, and overlapping of generations so that younger populations can help older generations. It is a phenomenon well recognized and studied in certain species of insects, such as ants.

Rubenstein and his team accidentally discovered that shrimp possess another interesting characteristic: the size of their genome varies considerably and seems to be linked to their social organization. This contradicts what we know about eusociality in the insect world. Genomic studies have shown that eusocial insects generally have smaller genomes than their less social parents.

Bigger genome, greater accumulation of transposable elements

The researchers – including collaborators from the University of Seattle and the Bedford Institute of Oceanography – decided to dig deeper to understand the larger genome of the social shrimp. Applying new genomic research techniques, the group analyzed the genomes of Synalpheus crunchy shrimp and found that the largest genome size identified in the eusocial shrimp contained an accumulation of transposable elements.

Transposable elements are sometimes called “jumping genes” – these are DNA sequences that travel through the genome. This movement can create and / or reverse mutations that alter the genetic identity of a cell, thus contributing to evolution.

“We have developed a method to extract information on transposable elements from low coverage sequencing data. This approach allowed us to compare a large number of shrimp species efficiently and cost effectively without first having to sequence and assemble the genomes of each species. »Rubenstein said Technological networks.

“We found that eusocial species had more transposable elements in their genome than non-eusocial species,” he added. “We used evolutionary modeling to explore why such a relationship exists and found that they seem to accumulate in the genomes of eusocial species.”

The researchers hypothesize that the increase in transposable elements in the genome is due to the unique social organization of the shrimp. Being an eusocial species, the majority of shrimp will never reproduce in their lifetime. The small effective size of the population means that it is difficult to “purge” transposable elements from the genome; therefore, they accumulate over time. “Interestingly, each eusocial species appears to accumulate a different type of transposable element in its genome,” Rubenstein added.

The relationship between the genome and social evolution

In the publication, the authors say their research highlights a fluid relationship between the genome and social evolution, demonstrating how social organization might influence genome architecture. “This is one of the first studies to link transposable elements to different forms of social life, opening up a whole series of questions about how the unique demography of the population of social species influences the evolution of the genome,” said commented Rubenstein.

The incredible size of shrimp genomes posed a challenge for researchers – it prevented them from applying next-generation sequencing techniques to the entire shrimp genome, a method known as whole genome sequencing, or WGS. “We have developed a new way to study transposable elements from limited amounts of sequence data,” explained Rubenstein. In a next step, the team hopes to go back and sequence the entire genome to collect even more data and learn as much as possible about the relationship between social evolution and genome evolution. They also intend to analyze – in more detail – where transposons occur to determine whether they play a role in the evolution of eusociality. “We also hope to examine elements transposable in other social organisms, such as birds and mammals, to see if these same relationships exist in vertebrates,” Rubenstein concluded.

Dustin Rubenstein was speaking to Molly Campbell, science writer for Technology Networks.

Reference: Chak STC, Harris SE, Hultgren KM, Jeffery NW, Rubenstein DR. Eusociality in crunchy shrimp is associated with larger genomes and an accumulation of transposable elements. Proc Natl Acad Sci United States. 2021; 118 (24): e2025051118. doi: 10.1073 / pnas.2025051118.

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