Potatoes are an important food crop around the world. Pests have always been associated with plants, however in the past, the diversity of species as well as large distances between different plants gave some natural protection from pests. If a pest could infect one species of potato, it may be harder for the same pest to infect a different species. Similarly, if plants were further apart, there was a lower chance of the pest spreading.
Today, intensive farming techniques have reduced the diversity of plants while bringing them in closer proximity to one another. This puts them at risk from pests. Researchers have been using different techniques at Diamond to understand the plant pathogen Phytophthora infestans which was responsible for the Irish potato blight and is still a problem in modern agriculture.
Using X-ray fluorescence imaging at Diamond’s Microfocus Spectroscopy beamline (I18), as well as optical emission spectroscopy, a team of researchers analysed the elemental composition, or the ionome, of different potato plants. They discovered that the elements in the potatoes were dynamic and were subject to strong rearrangements when the plant was infected by P. infestans. One of the strongest findings was that when a potato plant became infected, the researchers saw a decrease in the amount of potassium at the infection sites with an increase in the amount of iron and manganese. These findings were corroborated by a thorough literature search. The publication in The Plant Journal noted that adding potassium to fertiliser decreased the chance of an infection occurring.
The research team went on to test potato plants that were known to be resistant to infection by P. infestans. They discovered a remarkable difference in the elemental composition at the inoculation site with respect to the non-resistant plants. The distribution of calcium, magnesium and silicon were all unique and are a signature that the plants are resistant. The changes in the levels of these important elements could be a signal of an immune response in the potato plants.
Another study investigating the same pathogen looked at how P. infestans is able to digest the surface tissue and penetrate the plant during the infection process. Research published in the journal Science uncovered a new family of enzymes that the plant pathogen is able to use to break down plant tissue.
Researchers discovered copper-dependent lytic polysaccharide monooxygenases (LPMOs) which are a family of enzymes that are produced at high levels by P. infestans when it is invading plant tissue. Data collected using a variety of methods including X-ray crystallography at Diamond’s I04 Macromolecular Crystallography (MX) beamline showed that the LPMOs are able to efficiently degrade pectin, a charged polysaccharide that gives strength to the plant cell wall. The LPMOs were able to cleave the backbone of the pectin molecule which weakened the plant tissue enough to allow the pathogen to enter.
To confirm this finding, the researchers used double-stranded RNA as a genetic tool to prevent P. infestans from being able to produce the LPMOs. In this case, the pathogen could not invade the plant tissue, indicating that the LPMOs are an essential component in the destruction of crops.
Understanding the ways that food can spoil is essential for food security as well as reducing the environmental impact caused by food spoilage and waste. The research carried out at Diamond produced new insights that can directly impact on the way we cultivate crops and can be applied to the study of other pests.
To find out more about the I18 beamline or discuss potential applications, please contact Principal Beamline Scientist Konstantin Ignatyev: email@example.com. For further information on I04, contact Principal Beamline Scientist Ralf Flaig: firstname.lastname@example.org.
Brouwer S. M. et al. Visualising the ionome in resistant and susceptible plant‐pathogen interactions. The Plant Journal (2021). DOI: 10.1111/tpj.15469.
Sabbadin F. et al. Secreted pectin monooxygenases drive plant infection by pathogenic oomycetes. Science (2021). DOI: 10.1126/science.abj1342.
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