Researchers show where and how plants find nutrients potassium

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Potassium is an essential nutrient for all living things. Plants need it in large quantities, especially for growth and to better withstand stress. For this reason, they absorb a lot of potassium from the soil. In agriculture, this leads to a lack of available potassium in the soil – which is why the mineral is an important component of fertilizer. A team of German and Chinese researchers has now shown, for the first time, where and how plants detect potassium deficiency in the roots, and what signaling pathways coordinate growth change. root and potassium uptake to support plant potassium supply.

Background: Potassium uptake and transport at the level of individual cells is largely unspecified, and many of the molecular structures and mechanisms involved in these processes are known. Also, researchers have shown decades ago that plants adapt particularly to potassium deficiency. One puzzle that remains, however, is how plants discover the presence of potassium in the soil and what are the mechanisms behind the changing reactions in an organism that ‘plant. The new study sheds light on these issues. The results were published in the journal Cell development

Comments go against the textbooks

The researchers studied thale wax plants (Arabidopsis thaliana) that were transformed with the newly developed GEPII potassium reporter protein. This reporter protein enables microscopic detection of potassium ion density and circulation in cells and cigarettes. Even in the absence of potassium deficiency, the research team made a very remarkable finding: the density of this nutrient in the cytoplasm of the cells increased with all cell coverings inside the root, from the outside to the inside.

“Those comments were surprising,” said Dr. Jörg Kudla from the Institute of Plant Biology and Biotechnology at the University of Münster (Germany). “They go against the textbooks, which claim that the nutrients are distributed evenly, from the outside to the inside, towards the tightness of the root canal – not the not only from cell to cell but also through the intercellular spaces.”

will be “potassium sensitive niche” dealing with potassium deficiency

The team of researchers subsequently studied how roots deal with potassium deficiency. In doing so, they showed for the first time that if plants are deficient in potassium, potassium density is reduced just within certain cells in the root canal. The “postmeristematic cells” that just above the working stem cells in the root canal reacts very quickly to potassium deficiency; the density of potassium within the cell (in the cytoplasm) decreases within seconds. It was not previously known that a specific group of cells located centrally within the root crop responds to potassium deficiency in its surroundings. The researchers described this group of cells as a “potassium-sensitive niche”.

“Those ideas, too, were very surprising,” Kudla said. “If plants are depleted of potassium, only the cells in the potassium-sensitive area show a reaction; potassium concentrations in the other stem cells remain unchanged. Previously it was naturally assumed that the cells in the outermost cell stage, the epidermis, would initially respond to a decrease in potassium concentration in the soil. “

Looking at the potassium pathway

Simultaneously with the decrease in potassium concentration in the potassium-sensitive area, calcium signals occur in these cells and spread out in the root. As a messenger substance, calcium controls many processes in living organisms – just as it does here: the calcium signals begin with the inhibition of complex molecular signals. This sequence of signals, which the researchers were the first to explain in detail, ultimately causes not only the increased production of potassium transport proteins, but also changes in it. the font difference in the root. This enables the absorption of potassium ions more efficiently and maintains their dispersal in the plant. “For the first time, “arsa Kudla,” using imaging techniques, we have observed the pathway of potassium in an organism.”

The results provide a basic insight into where plants find the essential nutrient potassium available and how they adapt to it. Understanding these processes in the future could help to better breed plants for agricultural purposes and use fertilizers more appropriately.

The approach

To show the circulation of potassium in the roots of the plant, the researchers used special microscopic methods (e.g., Förster regenerative energy transfer, FRET), in combination with sensitizing proteins for potassium, calcium and hydrogen peroxide. To study the molecular mechanisms, the researchers compared and compared transgenic Arabidopsis plants that, as a result of various genetic mutations, showed signs of potassium deficiency. They used a number of genetic, molecular-biological and biochemical methods to identify and identify the proteins and mechanisms involved in the release of the potassium and calcium signals.