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MUT9: The gene behind all genes

DNA: The life code that can program visible and invisible features on the outside of your body. It is a complex molecule that contains secrets that have never been known, so there are many ways to approach it when conducting research. Epigenetics is the study of how gene expression has been maintained in the long term. It is closely linked to the regulation of chromatin: a protein complex and nucleic acids that lie within DNA preventing some genes to be represented. Epigenetics also studies modifications on how inherited genes are featured throughout various generations without affecting DNA sequence. There’s some sort of genetic memory that generates changes in the long term. For instance, whenever a plant is going through a rough drought it has to learn how to adapt itself to survive, so in that sense, if the plant goes through another drought it will know how to react faster than others. Armando Casas, a professor at Yachay Tech School of Biological Sciences and Engineering is working on genes from this perspective.

DNA lies not only within the cell, but it is formed of chromatin, a complex system with other proteins called histones. These proteins contain DNA and allow the information contained to be arranged inside the nucleus. But this means that for a gene to be featured, you have to unpack it. This is why the cell created a control system on dispersion that controls the packing and unpacking gene system. Then, if the cell “does not want” a gene to be featured, it is packed right back. If the cell “wants” the gene to be constantly featured, then it does not pack it. When Armando studied his postdoc at Nebraska University (US), the lab worked with gene silencing at chromatin level, studying mechanisms that were in charge of packing and unpacking genes.

At that time his team was investigating these mechanisms. For that, they use a green alga called Chlamydomas as a model. In order to study it, they got an alga that contained a transgene resistant to an antibiotic. This gene was packaged, therefore, it was not featured. So they decided to find mutants that have flaws in DNA packaging. They found them and on those, the gene was featured, making the alga resistant to the antibiotic. Using this system they cloned several genes; every one of them related to chromatin regulation, thus related to DNA packing.

There’s a variety of modifications that occur within the chromatin. Simply put, we can say that DNA is organized in chromatin, an enzyme that acts by modifying chromatin and its packing or unpacking. While trying to understand how it happens, Armando and his team discovered a gene: MUT9. This gene produces a protein that transmits messages to modify other proteins: a kinase. It acts causing chromatin condensation. It was discovered in Chlamydomonas, but, like we said before, it is a green alga, thus a unicellular organism. The team could not help but wonder how this gene had evolved into a multicellular organism, in a more advanced plant with a complex development.

They chose Arabidopsis, a flower plant native to the Iberian Peninsula and a model organism for genetic studies. It is special because its genetic “map” is already known, which means that its genome is already sequenced. Besides, due to the existence of collections of mutants previously gathered, it is easy to obtain modifications on the Arabidopsis. The differences appeared right away.

In Chlamydomas, the MUT9, is only a gene, a single kinase. In Arabidopsis, it has turned into 4 because the genes normally duplicate themselves and this species kept them all. These four genes have different roles. For example, one has the role of regulating the flowering of the plant; therefore a plant with the mutant gene MUT9 blooms later due to a failure to repress another gene which in turn represses flowering. This is how it works: flowering cannot occur until the plant is well developed, then there is a repressor gene that blocks it up to that point. By featuring the repressor gene of appropriate flowering, the plant grows and is ready when the gene is silenced and the plant flowers. With the mutation, the repressor gene is not silenced and the plant keeps growing without flowering.

The other two kinases work more or less the same, silencing genes related to the development of the plant. When kinases are not silencing other genes, due to the mutation, it is possible to see strange behaviors on the plant development. These genes also appear to be involved with stress response. When a plant is under stress (drought, for instance) it stops growing. This is because the silencing genes increase phosphorylation in chromatin, making it pack other genes responsible for the growth of the plant. In simpler words, it is responsible for slowing down its entire metabolism in order to cope with stress. Therefore, if these silencing genes are blocked, the plant does not endure stress because it keeps growing and using up its last resources quickly.

Casas mentioned that one of his goals is to continue researching MUT9 genes, however not on Arabidopsis, but trying to understand how it behaves similarly way on crops. He expects to have the ability to control flowering in these crops in the future. What he hopes to achieve is, rather than manipulate each gene, to manipulate this gene to make some plants flower before or after, depending on the needs of each crop. For example, making fruit trees bloom faster, or making lettuce flourish later because we care about is the leaf, not the flower.

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