15.11.2017 change 15.11.2017

Study of the delay gene. Why plants wait to sprout?

Photo: Fotolia Photo: Fotolia

Why do seeds not germinate in the last hot summer day? How do they "know" they should still wait? This is one of the plant genes\' doing. It is being studied by researchers from the Institute of Biochemistry and Biophysics PAS. On the example of this gene they draw important conclusions about information processing in the cell.

Warmth, humidity, sufficient light... It would seem that such conditions should suffice for the plant to sprout. But food weather does not always mean that the seed should be immediately awakened to life. That could be fatal. That is why plants have their own genetic brakes, timers that temporarily suppress seed germination, even if the conditions appear to be perfect. This gene is being investigated by Dr. Szymon Świeżewski from the Institute of Biochemistry and Biophysics PAS in Warsaw, winner of this year\'s National Science Centre Award.

"Sometimes it is enough to have one warm day at the end of summer for the seeds to start to germinate - in extreme situations even on the parent plant\'s ear. This phenomenon - so-called overgrowth - is a big problem in agriculture. Such seeds cannot be used to make flour or planted in the following year. They are only suitable for feed" - said Dr. Szymon Świeżewski in an interview with PAP. The scientist explained that in case of overgrowth, this genetic brake does not work as it should.

"Resting time is a very valuable ability of a plant - it\'s the ability not to sprout despite favourable conditions. Resting time depends on only one gene - DOG1 - chosen by evolution" - said Świeżewski. His team attempts to figure out exactly how this gene works. And on the example of this gene, understand the more universal mechanisms of information processing in the cell.

Trash DNA? !hsart taht ton s\'tI

Researchers from the Institute of Biochemistry and Biophysics PAS have, for example, explained the function of the non-coding part of the DOG1 gene. In the genome of bacteria over 90% nucleotides in DNA encode proteins. And in people only ... 2 percent. It is unclear why DNA in complex organisms is so long. Why do we need all these nucleotides that do not make proteins? Dr. Świeżewski\'s team\'s research sheds some light on the functions of such "junk" DNA fragments.

Dr. Świeżewski explained how DNA is processed. An enzyme - polymerase - is attached to DNA. And at some point it encounters a promoter. And that means that there is a message written for the enzyme in the genome: "HEY! START MAKING RNA!". And then the DNA polymerase begins to weave RNA (no proteins are produced without RNA).

Sense of antisense

DOG1 gene has a promoter in front and back. This is comparable to the situation when in the DNA at the end we find: "ANR GNIKAM TRATS !YEH". It seems to be a mistake. Until we read these characters backwards. A polymerase that is moving along the DNA strand in the opposite direction will understand this message. It will treat it as a gene promoter and make second RNA from the same gene, going backwards. That is the case with the DOG1 gene. Two strands of RNA are formed: sense RNA and antisense RNA.

In the case of the DOG1 gene only sense RNA encodes the protein. The antisense RNA does not. "And since that RNA does not encode the protein, it may seem to be junk. But we\'ve found that antisense transcription regulates an important biological phenomenon" - said Dr Świeżewski. He explained that removing the antisense non-coding RNA from the cells results in a very strong resting time of the seeds. And that means that in spite of great conditions seeds do not enter the germination phase for a long time.

"We found that in this case the antisense is a regulator of sense RNA" - concluded the researcher. It is one of the first studies in the world that have shown that RNA "woven backwards" functions in the body. Earlier it was only a theory.

"In subsequent studies we have shown that this phenomenon is more universal. There are more genes, in the case of which the >>tail wails a dog<<, in which an antisense transcript is generated from the other end of the gene and that transcript regulates the activity of the gene" - said Dr. Świeżewski.

By studying a model plant - Arabidopsis - biologists have already discovered about 1800 genes that are transcribed in two directions, and the antisense transcript has a function. "We only show the scale of this phenomenon. There are very, very many such genes" - said Dr Świeżewski.

Studies of the team from the Institute of Biochemistry and Biophysics PAS show that if you want to understand gene function and regulation, antisense transcription cannot be ignored. It turns out that antisense makes a lot of sense after all.

Author: Ludwika Tomala

editor: Anna Ślązak

PAP - Science in Poland

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