An international team of researchers fr om NSU, the Institute of Cytology and Genetics SB RAS, and the National University of Singapore discovered and explored a unique mechanism for plants to adapt to cold. To survive low temperatures and conserve their stem cells, plants sacrifice the roots of newly born cells. The article has been published in the high-ranking scientific journal CELL.
The unexpected effect of low temperatures (4 ° C), lasting from 16 to 72 hours, was first discovered by Professor Chen Xu’s group from Singapore. When plants "freeze", the DNA damage begins in the stem cells of the root. It is reversible, but dividing the cell with broken DNA can lead to the death of its offspring. When plants are stressed by cold, this role is often taken by the stem cell of the root cap (the tip of the root) and one of its daughter cells dies immediately after "birth." It is interesting that the plant as a whole, benefits from this cell death. It is more quickly restored after the cold and becomes less susceptible to subsequent stresses such as drought.
All plants have two main stem cell niches, in the tip of the root and on the top of the shoot, and the remaining plant cells are formed from them. In the stem cell niche, the root is isolated from the resting center which ensures its maintenance. Its cells rarely divide, but signal the remaining to stay stem cells, that is, to preserve the ability to turn into cells of any type. For the successful development of the root, it is important that the resting center and the surrounding stem cell niche are not disturbed. This is achieved due to the high concentration of auxin, the main plant hormone, in the resting center. “Our colleagues have discovered a mechanism for protecting the root, about which nothing was known before. This has a kind of "hardening" effect in the plant. Low temperatures are harmful to the plant, but short-term treatment with lower temperatures, on the contrary, can be an advantage. In this case, only the cells of the root tip die, and their life was already short, while the remaining tissues stay intact ", explained Victoria Mironova, Head of the NSU Laboratory of Computer Transcriptomics and Evolutionary Bioinformatics, Head of the System Biology of Plant Morphogenesis at the Institute of Cytology and Genetics SB RAS, Candidate of Biological Sciences.
To understand the mechanism of root cap cells suicidal tendencies, Novosibirsk bioinformatics created a mathematical model, in fact a system, with a large number of equations. The mechanism is regulated at the genetic level by activating the work of several groups of genes and the proteins encoded by them that are responsible for auxin transport. “Our model allows us to talk about what happens with phytohormone auxin and its transport, the so-called PIN-proteins. Modeling showed that in cold conditions, when the cells in the central part of the root cap are dividing, the concentration of the hormone in the resting center falls and this poses a threat to the further life of the plant. When these cells die, the concentration of the hormone is restored and this helps to preserve the stem cell niche. Our prediction was checked by researchers from Singapore and they found that the expression of the WOX5 gene, one of the main regulators of maintaining the stem cell niche, is reduced in the absence of the death of daughter cells, compared to the roots wh ere cell death took place, " reported Maria Savina, lead engineer at the NSU Laboratory of Computer Transcriptomics and Evolutionary Bioinformatics, Junior Research Associate at the Institute of Cytology and Genetics.
Scientists have created a simple tool for studying the behavior of the stem cell niche in response to abiotic stress and the widespread distribution of plants, like the rezuchovidka Tal in the Northern Hemisphere, will allow us to understand the genetic mechanisms for plants adapting to cold. This is possible because the lines of this plant differ in their fitness for cold stress and most likely carry mutations in key genes of cold stress.
Continuation of these studies will bring tangible benefits to agriculture. It is already clear that auxin treatment of plants before it gets cold can help them survive and resume rapid growth when it gets warmer. A mathematical model will also prove useful in the future, because it can be used to study the effects of other stresses and identify ways to reduce their negative consequences. It is also possible the authors results will be useful for studying methods of adaptation of mammals to the cold. The organization of stem cell niches functioning and sensitivity to stress are similar in animals and plants.
Scientists from the Laboratory of Computer Transcriptomics and Evolutionary Bioinformatics teach courses for students at the NSU Department of Natural Sciences.
