Potato blight desease (Photo from: pixabay.com)
Publish Date: 30.03.2022
Category: Interdisciplinary research, Our contribution to sustainable development goals
Sustainable development goals: 1 No poverty, 2 Zero hunger, 3 Good health and well-being, 9 Industry, innovation and infrastructure, 10 Reduced inequalities, 15 Life on land, 17 Partnerships for the goals (Indicators)
Plant diseases have far-reaching consequences affecting crops and reliability of food supply, but for many of these diseases the causes and underlying mechanisms are not yet explained. In a recent study published in Science Advances, the researchers thus focused on a family of Necrosis and ethylene-inducing peptide 1-like proteins (NLPs), which are produced by numerous phytopathogenic microbes and cause damage to important crops such as potatoes, tomatoes, soy, tobacco, cocoa... Research on the mechanisms of action of NLP proteins is a result of a cooperation between the National Institute of Chemistry, the University of Ljubljana and research institutions from Great Britain, Japan, Italy, Finland and Germany and led to a discovery of an unique multi-step mechanism of damaging plant-cell membranes.
Plant diseases can cause extensive damage to crops, posing a serious threat to a stable global food supply. One example is potato blight desease, which caused severe famine in Ireland in the 19th century and is still not fully understood. Many of these diseases are caused by various pathogenic microbes, such as bacteria, fungi and oomycetes, which all secrete NLP proteins that damage plant-cell membranes and in addition to potatoes also affect tomatoes, soybeans, tobacco, vines and other economically important crops. The researchers analyzed the interactions between NLP proteins from oomycete Pythium aphanidermatum and model membranes containing plant lipids glycosylinositol phosphorylceramides (GIPC), to which NLP proteins attach when binding to the plant cell membrane. Using biochemical and biophysical methods and computer simulations, NLP proteins have been shown to damage the membrane in a multistage process involving the initial binding of NLP proteins to GIPC containing membranes, surface aggregation of proteins and consequent formation of small, transient pores in the membrane (Figure right below), through which small molecules from the plant cytoplasm are released, serving as nutrients for pathogens.
Figure left: Consequences of the potato blight desease, caused by NLP proteins. (Source: pixabay.com) Figure right: A scheme of NLP proteins (violet ovals) binding to the outer side of a lipid membrane, and a consequent pore formation. (Author: Katja Pirc)
The first author of the study Katja Pirc, the head of the entire research team Gregor Anderluh and the majority of the slovenian part of the research group Tina Snoj, Marija Srnko, Jure Borišek and Marjetka Podobnik come from the National Institute of Chemistry in Ljubljana. Mojca Mally and Jure Derganc are the researchers from the Institute of Biophysics, Faculty of Medicine, University of Ljubljana, which have contributed to the discovery and understanding of the specific NLP protein damaging mechanism by developing a new microfluidics method for analyzing the interactions of toxins with model membranes (Figure 1 and 2). Nada Žnidaršič works at the Department of Biology at the Biotechnical Faculty, University of Ljubljana and in this study applied transmission electron microscopy to analyze liposomes with bound NLP proteins, which helped elucidate the interactions of protein clusters with model membranes (Figure 3).
Figure 1 (left): A schematical presentation of a microfluidics system that enables the analysis of the interactions between the model plant cell membranes (depicted as white circles inside the experimental chamber) and the NLP proteins, diffusing into the chamber from the solution in the main channel (Author: Jure Derganc). Figure 2 (middle): Brightfield and fluorescence microscopy snapshots of a model plant cell membrane in dependence on time. NLP proteins (green) bind to the membrane, which becomes permeable for small molecules of fluorescent marker (red). (Authors: Jure Derganc and Mojca Mally). Figure 3 (right): Analysis of the ultrastructural organization of protein clusters on model membranes in a transmission electron microscopy lab (Author: Nada Žnidaršič).
The discovered mechanism of NLP proteins for plant cell damage differs from the known mechanisms that damage animal cells, where damaging protein formations have an ordered trans-membrane structure. Regarding the prevalence of NLP proteins, the understanding of the mechanisms of their action is crucial for developing specific and targeted strategies to inhibit NLP proteins without causing damage to other organisms.