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A step closer to durable plant-pathogen protection

Oct 19, 2018

A recent elegant study published in Proceedings of the National Academy of Sciences USA (PNAS) by Dr Jonathan Jones (Prof. at the University of East Anglia, UK), Dr. Panagiotis Sarris (IMBB-FORTH and elected Prof. at the University of Crete) and Dr. Panagiotis Moschou (IMBB-FORTH and Prof. at the University of Crete) sheds light on the defensive mechanisms of plants.

Plants are a major food, feed and biofuel source and the basis of a bio-based economy. However, plant products are in a constant threat especially nowadays. Climate change, shortage of arable land and the population increase exercise strong pressure on plant productivity. These three parameters will contribute to a continuous rise in plant diseases that will further exacerbate their effects. Therefore, plant diseases control is crucial to the reliable production of food, having also the added benefit of providing significant reductions in the agricultural use of land, water, fuel and other inputs.

Although plants, natural and cultivated populations, are endowed with disease resistance mechanisms, there are numerous examples of devastating plant disease impacts. Examples include the Irish potato famine (19th century), which was the result of an oomycete species that destroyed potato and enforced millions of Irish to migrate in order to survive. Other more recent examples include the chestnut blight, as well as recurrent severe plant diseases like rice blast, soybean cyst nematode, citrus canker and disease caused by the bacterium Xylella fastidiosa in Europe which infects a series of cultivated species including olive trees, vines and others. It is thus crucial the development of durable and environmentally friendly methods to battle plant diseases. Such methods could, for example, include engineering of the plant immune system in order to make plants tolerant to diseases.

To hijack defensive lines of plant cells, pathogens use many strategies. For example, the most common strategies are the delivery of toxins or of some pathogenic proteins known as “effectors”. To fight-off diseases, plants (and animals) carry nucleotide-binding leucine-rich repeat (NLR) immune receptors. In the published study, authors reveal the mechanism by which a pair of NLR immune receptors gets activated through a “decoy” region on the surface of NLR immune receptors that mimics the target of pathogenic effector proteins. In this way, plants can detect invading pathogens and trigger immune responses that lead to successful defence and disease resistance. The same immune receptors are inactivated when pathogens are not present to suppress autoimmunity that will lead to the self-destruction of the plant. This important discovery will allow in the future the selective introgression of NLR immune receptors in cultivated plant species for important pathogens. Furthermore, the suggested model in this work may apply also to other organisms, such as mammals and human.

Authors explain why this study on mechanisms of NLRs is important: “It is important to study in detail the mechanisms that underpin diseases and the defensive strategies of plants and animals. In this way, we can design durable and environmentally friendly solutions to fight-off pathogens threatening food security”.