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Health Of Crops Depends On ’Protein Wars’

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04.11.2005

Interesting facts have been discovered in phytoimmunity sphere by the Russian-Belorus group of biochemists in the framework of the Russian Foundation for Basic Research and Belorus Foundation for Basic Research projects. To protect themselves from pathogenic fungi, which penetrate plant tissues with the help of proteinase proteins, vegetables produce inhibitors to these proteinases. A peculiar “arms race” is taking place between them.

Animals’ immune system cells are aimed at resistance within the organism but phytoimmunity is mainly based on preventing the pathogen from “drilling a hole” in the integuments and defending itself from a vegetable antibiotic. Fungi penetrate plant tissues with the help of proteinase enzymes which decompose proteins of cellular walls and antimicrobial proteins.

Researchers have assumed that a plant organism should produce appropriate inhibitors to protect itself from these enzymes.

Specialists of the Lomonosov Moscow State University, Bach Institute of Bioorganic Chemistry, Russian Academy of Sciences and the Belorus Institute of Experimental Botany decided to check if plants’ resistance to parasitic fungi is connected with inhibitor proteins’ activity.

Biochemists investigated to what extent vegetal matters are capable of “turning off” various proteinases as bovine trypsin and similar enzymes complexes used by microbes and pathogenic fungi.

It has turned out that phytoimmunity is connected with synthesis of proteins inhibiting trypsin, chymotrypsin and subtilysine action, as well as with synthesis of complicated enzymatic mixtures excreted by phytopathogens.

For experiments biologists selected several kinds of cereals, legumes and buckwheat. Proteinases’ inhibitors were extracted from their seeds and proteinases were extracted from laboratory cultures of these fungi (having removed mycelium from culture broth). After the mixtures of substances were obtained they were allowed to react. Inhibitory activity of seeds’ extracts can be judged by the change of reaction mixture transparency. This is measured by chemists with a special device.

It has turned out that different cultures and sorts specialize in inhibiting different enzymes: Wheat mainly inhibits subtilysine. Triticale (wheat and rye hybrid) inhibits trypsin. Sorts that are low susceptible to fungus diseases turn out to have more protease inhibitors at their disposal than highly susceptible ones.

Biologists have discovered that abundance of chymotrypsin and subtilysine inhibitors block way to covered smut and root rot, and substances inhibiting trypsin activity impede downy mildew.

Fermentative relation between a plant and parasites may be presented as arms race: a parasite produces a destructive enzyme, and the plant – produces its inhibitor. Health of green plantations and crops depends on the “arms race” outcome.

Sergey Komarov | Quelle: alphagalileo
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