According to the researchers, it is a hormone, a small signal molecule, which controls the growth of plants. The decoding may help a lot in expanding agricultural crops and dealing with the global food crisis
International and multidisciplinary research led by Prof. Elon Shani and PhD student Jania Binenbaum from the School of Plant Sciences and Food Security At Tel Aviv University, he revealed the mechanism of action and movement in the plant of the hormone gibberellin - a substance of enormous importance for the growth of agricultural crops. The complex research included dozens of experiments in a wide variety of fields: physiology, molecular biology, biochemistry, mathematical models, fluorescence microscopy, genetics, and more. The experiments were carried out over the course of 7 years by several research groups around the world - at Tel Aviv University, the Weizmann Institute of Science and the Volcanic Institute in Israel, as well as in Denmark, France, England, Germany and Spain. The groundbreaking research was published in the prestigious journal Nature Plants.
A small hormone with enormous importance
"Few people outside the scientific community have heard of the gibberellin hormone, but in fact it is one of the substances with the greatest impact on humanity," says Prof. Shani. "It is a hormone, a small signal molecule, which controls the growth of plants, and is directly related to the Green Revolution of the 60s and 70s, which made agricultural work more efficient and significantly increased grain yields - wheat, barley, corn and rice. In fact, gibberellin manipulation techniques in plants are one of the main reasons why we have enough food in the world today. But despite its importance, very little was known until recently about the mechanism of action and movement of gibberellin in the plant space. In the current study, we embarked on a comprehensive journey in order to answer some fundamental questions: How does the gibberellin move inside the plant? Where does it accumulate? And how exactly does it work in specific cells in the plant?"
The study was carried out on the Arabidopsis plant (white sedum), which is used as a model plant in many studies. In the first step, the researchers sought to identify the mechanism that transports the gibberellin from the leaves where it is formed, through the transport system known as Shifa, to the root. For this purpose, they created various mutations in the plants and performed genetic scans on them, thus discovering three carrier proteins (transporters) without which the gibberellin does not reach its destination. These are proteins that are found in the shoot cells, and work together to move the gibberellin molecule from one side of the cell membrane to the other, thus enabling its long journey throughout the entire plant. In other words: the function of these proteins is to charge the gibberellin from the leaf to the transport tissues, where it flows down the plant to the root.
In the next step, the researchers used an advanced method of fluorescence microscopy with single-cell resolution to examine the effect of gibberellin - or its absence - on cells in the root. They found that gibberellin accumulates in a layer of cells in the root known as the endodermis - which separates the transport tissue from the rest of the root cells. It is known that one of the functions of the endodermis is to control the passage of substances absorbed by the root from the soil (water, salts, gases and various nutrients) to the transport tissues that carry these substances to the rest of the plant. This control is done by producing a control layer - a cork-like sealant called suberin. In this study, the researchers discovered that in the absence of the gibberellin hormone, the production of suberin was impaired. Bottom line: the gibberellin is responsible for controlling the production of suberin in the endodermis, and thus it directly affects the nutrition of the plant and its growth.
Nourishing humanity under changing climate conditions
"Until now, it was known that the movement of the gibberellin hormone in the plant is necessary for the normal development of the plant, but the mechanism that enables this movement was not known," explains Dr. Bienenbaum. "In our research, we deciphered the system that allows the transition of gibberellin between the different parts of the plant, and we also discovered a new role of gibberellin: control of the production of suberin, a substance of great importance for plant development. Understanding the mechanisms of gibberellin movement in the plant may form the basis for applied research in the future, with a significant impact on nutritional security and the development of the plant in a changing environment.'
Prof. Shani concludes: "In a long and complex multidisciplinary study, we managed to reveal the mechanisms of movement and action of one of the most important substances for the nutrition of humanity: the hormone gibberellin. We found how the gibberellin gets from the leaves to the root, where it accumulates in the root, and how it affects the plant's nutrition mechanisms from there. We hope and believe that the insights emerging from the research will help the development of innovative methods for improving and increasing crops, especially cereals, in order to face one of the biggest challenges of the current era: feeding increasing numbers of people in changing climate conditions."
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