Plant immunity-boosting molecule identified
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Two studies published in the journal Science by researchers at the Max Planck Institute for Plant Breeding Research in Cologne, Germany in collaboration with colleagues in China have discovered natural cellular molecules that drive critical plant immune responses. This compound has all the advantages of being a small messenger designed by plants to activate the main defense control center. Harnessing this insight allows scientists and plant breeders to design molecules that make plants, including many important plant species, more resistant to disease.
World food production must double by 2050 to feed the additional 2 billion people living on Earth by that time. Increasing food production requires increasing yields of many of our staple crops. To do so, there needs to be strategies to ensure that we can make crops more resistant to microscopic infectious agents, while also ensuring that food production is environmentally safe. Achieving this, in turn, requires a detailed understanding of the plant’s immune system—the defenses plants put up against invading microorganisms.
Now, in two studies, scientists led by Jijie Chai and Jane Parker of the Max Planck Institute for Plant Breeding Research in Cologne and the University of Cologne, Germany, collaborated with Junbiao Chang’s group at Zhengzhou University in Zhengzhou and Zhifu Han and his colleagues at Tsinghua University in Beijing, China, has identified two classes of molecules and determined how they work in mediating immune responses in plant cells. Their findings pave the way for the design of bioactive small molecules that allow researchers and plant growers to manipulate—and thereby increase—plant resistance to harmful microbes.
At the molecular level, the primary immune strategy employed by plants involves proteins called nucleotide-binding leucine-rich repeat receptors, or NLRs for short. NLRs are activated by attacking microorganisms and triggering a protective immune response. This immune response culminates in a so-called hypersensitivity response, which involves limiting the growth of the pathogen and often tightly curtailed cell death at the site of infection—similar to amputating a toe to ensure the body’s survival.
One class of NLR proteins, called toll/interleukin-1 (TIR) receptor domains, called TIR-NLRs (or TNLs), have been shown to relay signals to downstream immune protein Enhanced Disease Susceptibility 1 (EDS1). ). The smaller TIR-containing protein also signals to EDS1 to potentiate disease resistance. EDS1 functions as a control center that, depending on the type of other protein it interacts with, induces plant cells to limit the growth of pathogens or causes cell death. Previous work demonstrated that the TNL receptor and TIR protein are actually pathogen-induced enzymes. Evidence suggests that this TIR enzyme produces small messengers or messengers that signal EDS1 in cells. However, the identity of the precise molecules produced by TNL or TIR that stimulate various immune responses remains elusive.
Parker and colleagues determined that two functional EDS1 modules leading to immunity or cell death could be triggered by the pathogen-activated enzyme TNL in plant cells. To identify small molecules produced by TNL or TIR and acting on EDS1, Chai’s group rearranged a key component of the signaling pathway in insect cells, a system that allows the production and purification of a large number of molecules that can then be isolated and characterized. Using this approach, the authors discovered two distinct classes of modified nucleotide molecules produced by TNL and TIR. These compounds preferentially bind to and activate distinct EDS1 sub-complexes. Therefore, the authors demonstrated that the distinct EDS1 sub-complex recognizes certain TIR-produced molecules, which function as information-carrying chemicals, to enhance immune responses.
TIR immune receptors and the EDS1 hub protein are present in many important plant species, such as rice and wheat, and Jijie Chai demonstrated that “the identified TIR-catalyzed small molecules can be used as general and natural immunostimulants for controlling plant diseases.” Jane Parker further states that “knowing the biochemical modes of action of these small molecules opens a new chapter in plant immune signaling and disease management.”
Linking sensing to signaling during plant immunity
Shijia Huang et al, Identification and mechanism of TIR-catalyzed small molecule receptors in plant immunity, Science (2022). DOI: 10.1126/science.abq3297
Aolin Jia et al, TIR-catalyzed ADP ribosylation reaction generates signaling molecules for plant immunity, Science (2022). DOI: 10.1126/science.abq8180
Provided by Max Planck Society
Quote: Plant immunity enhancing molecules identified (2022, 7 July) retrieved 7 July 2022 from https://phys.org/news/2022-07-molecules-boosting-immunity.html
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