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How do toxins from microbial pathogens damage plant membranes?

Publication of the results in the renowned scientific journal Science Advances

 

Ljubljana, March 14, 2022 – Researchers at the National Institute of Chemistry have coordinated an international research team that has discovered a new, unique mechanism by which proteins secreted by some of the most important plant disease pathogens damage the plant cell membrane. Clarification of the molecular mechanism of pore formation in the plant cell membrane will facilitate the design and development of new products for plant and crop protection. The study was published in one of the most prestigious scientific journals, Science Advances. It is the result of the collaboration of the National Institute of Chemistry with the University of Ljubljana and renowned foreign research institutions from Great Britain, Japan, Italy, Finland and Germany.

Plant diseases are widespread and can cause major damage to crops, posing a serious threat to a stable global food supply. These diseases are caused by pathogenic microbes such as bacteria, fungi, and oomycetes (which are fungi-like microorganisms, also called water molds) that secrete proteins that damage host plants. Understanding how these proteins interact with plant cells is critical for developing new crop protection agents against disease. One such disease, for example, is potato blight, which caused severe famine in 19th century Ireland and is still a major global problem.

In a study designed and conducted at the National Institute of Chemistry, an international team of researchers focused on Nep-1-like proteins. These proteins, which cause plant tissue necrosis, are secreted by some of the most important plant pathogens, that attack tomatoes, soybeans, tobacco and grapevines, in addition to potatoes. The researchers used a range of biochemical, biophysical and computational approaches to investigate how NLP proteins act on the plant cell membrane, the part of the plant cell that forms a selective barrier between the cell interior and the external environment. They focused on the interaction of the NLPPya protein from the oomycete Pythium aphanidermatum, which causes seed death in several crops, with a model membrane containing the lipids glycosylinositol phosphorylceramides (GIPC), which had been shown in a previous study to bind the protein to the membrane.

NLPPya was found to damage the membrane in a unique multistep process involving initial binding of the protein to the GIPC receptor in the membrane, protein aggregation, and formation of small pores in the membrane. Computer modeling and neutron reflectometry results have shown that the NLPPya protein does not penetrate deeper into the membrane, unlike to previously known bacterial or mammalian pore-forming proteins that form ordered structures that penetrate the membrane. NLP proteins can interact with multiple molecules of GIPC lipids in the membrane, resulting in membrane destabilization and the formation of pores through which small molecules are released from the plant cytoplasm, serving as nutrients for pathogens. Such a mechanism of membrane damage is adapted to the plant cell environment.

The authors of the study believe that knowledge of the mechanism by which microbial pathogens damage the membrane will open the door to new, more specific methods of protecting major crops.

First author of the study, dr. Katja Pirc, a researcher at the Department of Molecular Biology and Nanobiotechnology, said: "Plant membranedamage by NLP proteins is a highly damaging process that we want to understand as precisely as possible. In the future, the National Institute of Chemistry will focus on studying the interaction of several NLP proteins with the plant membrane, as we want to determine if they damage the membrane in a similar way. Determining the structure of the pores using cryo-electron microscopy will also be a big challenge. "

"NLP proteins are widely distributed in microbial pathogens that attack plants and are therefore an important target for designing strategies to prevent damage to plant cells. Understanding how these proteins damage cell membranes is a necessary prerequisite for the further development of such strategies," says Prof. dr. Gregor Anderluh, study leader and director of the National Institute of Chemistry. Anderluh emphasizes that the development of strategies targeting key microbial effector molecules can make an important contribution to plant protection and to maintaining the safety of global food production for future generations.

Dr. Luke Clifton of the U.K.’s ISIS Pulsed Neutron and Muon Source research institute, one of the world's leading centers for research in the physical and life sciences, said in a statement: »The use of neutron reflectometry for studying the interaction of NLP toxins with plant membrane models is a very nice example of how this technique can provide unique structural information which helps us gain a precision understanding how toxins function.

 

Link to article: https://www.science.org/doi/10.1126/sciadv.abj9406

For further information please contact: katja.pirc[at]ki.si

 

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