A team of scientists has developed a new chemical compound that inhibits photosynthesis in plant leaves: it inhibits the activity of a protein complex that carries out one of the key reactions of the process - the decomposition of water into oxygen. This substance can become the prototype of herbicides that fight weeds, while it is harmless to humans and animals. The results of the study, supported by a grant from the Russian Science Foundation (RNF), were published in the journal Cells, reports "Gazeta.ru".
Photosynthesis is the process by which plants synthesize organic compounds from carbon dioxide and water. It is carried out with the help of two large protein complexes - photosystems 1 and 2 (PS1 and PS2), each of which consists of a reaction center, surrounding proteins and pigments. Under the action of sunlight, the chlorophyll in the reaction center becomes excited and transfers its electrons to other molecules in the photosystem. Subsequent electron transitions are accompanied by the accumulation of high-energy molecules, such as ATP, involved in the synthesis of organic compounds. The lack of electrons left from chlorophyll is compensated by the decomposition of water molecules - it is during this process that oxygen is released as a by-product.
Scientists from the Institute of Fundamental Biological Problems of the Russian Academy of Sciences (Pushchino) with colleagues from Gazi University (Turkey) have synthesized a new compound based on copper and an organic fragment that suppresses photosynthesis in leaves. To determine the effect of the substance, the authors isolated PS2-enriched thylakoid membranes from leaves—structures inside chloroplasts—and added a solution of the new compound to the resulting suspension. The inhibitory effect was assessed by how much the oxygen release caused by illumination was reduced - for example, its rate was reduced by 69%. In addition, the effect of the substance was studied by a number of other reactions characterizing the activity of PS2: for example, the addition of an inhibitor reduced the luminescence of chlorophyll during photosynthesis. At the same time, the effectiveness of the drug did not change with time, but depended only on its concentration.
A decrease in oxygen release indicated that the photosystem worked less efficiently. It is assumed that the main target of the new herbicide is the reaction center of the protein complex: the substance binds to the PS2 core and changes its structure. As a result, according to scientists, the process of charge transfer between the components of the electron transport chain was disrupted.
The developed inhibitor can be used in the creation of a new herbicide, which will be used, for example, in the fight against fast-growing weeds that appear before the germination of crops. Since the water decomposition reaction is carried out only in the plant cell, the herbicide is likely to be completely safe for humans and animals.
“We have developed a compound that will effectively get rid of unwanted plant species, thus significantly increasing crop yields. These data can become a fundamental basis for the development of substances that are effective at the lowest possible concentrations,” says the first author of the work, Sergey Zharmukhamedov, Candidate of Biological Sciences, Leading Researcher at the Institute of Fundamental Biological Problems of the Russian Academy of Sciences.
Also, scientists from the Institute of Molecular Biology and Biotechnology of the National Academy of Sciences of Azerbaijan (Baku), the Institute of Plant Physiology named after K.A. Timiryazev (Moscow), King Saud University (Saudi Arabia) and Moscow State University named after M.V. Lomonosov (Moscow).