The so-called "junk" DNA is essential and plays a key role in speciation

More than 10% of our genome is composed of repetitive, seemingly meaningless genetic material called satellite DNA, which does not code for any protein

In the years since a series of documents were generated, however, Mr.

Now, in the latest issue of the study published online on July 24 in the journal Molecular Biology and Evolution, Yamashita and former postdoctoral researcher Madhav Jagannathan, currently an assistant professor at the Swiss Federal Institute of Technology Zurich, have further advanced these studies.

"Seven or eight years ago, when we decided to study satellite DNA, we had no plans to study evolution," Yamashita said

Origin of Species: DNA version

Researchers have known for many years that satellite DNA varies greatly among different species

"These are the fastest evolving sequences in the genome, but the previous view was,'Well, these are junk sequences.

But when they investigated the importance of satellite DNA for the reproduction and survival of pure species, Yamashita and Jagannathan discovered for the first time clues that these repetitive sequences might play a role in speciation

When the researchers deleted a protein called Prod in Drosophila melanogaster that was combined with a specific satellite DNA sequence, the chromosomes of Drosophila melanogaster would spread out of the cell nucleus to form a small cell mass called micronucleus.

If this part of the satellite DNA is essential for the survival of one species but is missing for another species, it may mean that over time, the two species of fruit flies have evolved different satellite DNA sequences to play the same role.

Yamashita said: "When we realize the function of (satellite DNA in cells), the difference in satellite DNA between different species is as shocking as lightning

The story of two fruit flies

In order to study how satellite DNA differences lead to reproductive incompatibility, the researchers decided to focus on two branches of the Drosophila family tree: the classic laboratory model Drosophila melanogaster and its closest relative, Drosophila mimics

Researchers can mate female Drosophila melanogaster and male Drosophila, "but the offspring of this hybridization are very unhappy," Yamashita said

Yamashita and Jagannathan raised fruit flies together, and then studied the tissues of the offspring to see what caused these "unhappy" hybrid offspring to fall like flies

In addition, researchers can also create healthy hybrid fruit flies by changing certain genes in the mother of fruit flies called "hybrid incompatibility genes"

Taken together, these findings indicate that because satellite DNA mutations are relatively frequent, proteins that bind satellite DNA and hold chromosomes together must evolve to keep up.

In future research, Mr.

This feat of bioengineering may take several years
.
Yamashita said: "Now this is just a pure concept
.
" "In the process of making this repair, many details may need to be resolved
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"

At present, the researchers plan to continue to study the role of satellite DNA in cells, and they have a new understanding of the role of satellite DNA in speciation
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"For me, the surprising part of this paper is that our assumptions are correct," Jagannathan said
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"I mean, in retrospect, there are many things that may not be consistent with our assumptions, so we were able to draw a clear path from beginning to end, which is a bit surprising
.
"

references:

 “Defective Satellite DNA Clustering into Chromocenters Underlies Hybrid Incompatibility in Drosophila ”by Madhav Jagannathan and Yukiko M Yamashita, 24 July 2021, Molecular Biology and Evolution .

DOI: 10.
1093/molbev/msab221