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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 cellularmolecules that drive critical plant immune responses. These compounds are tailor made by plants to turn on key defense-control hubs. Scientists and plant breeders may be able to design plants that are more resistant to disease with the help of these insights.

The world needs to double food production in order to feed more people by the year 2050. Increasing the yields of our staple crops is needed to boost food production. Strategies need to be put in place to ensure that plants are resistant to infectious agents and that food production is not harmful to the environment. It is necessary to understand the plant immune system in order to achieve this.

Scientists from the Max Planck Institute for Plant Breeding Research in Cologne and the University of Cologne, as well as Junbiao Chang's group at Zhengzhou University, collaborated with colleagues at Ts to conduct two studies. Their work paves the way for the design of small molecule compounds that can be used to boost plant resistance against harmful microbes.

A main immune strategy employed by plants is the use of leucine-rich repeatreceptors, or NLRs. The protective immune responses are set in motion by NLRs. The immune responses end with the so-called hypersensitive response, which involves restriction of pathogen growth and death of cells at the site of the infection.

TIR-NLRs, which are called toll/Interleukin-1 Receptors, have been shown to relay signals to Enhanced Disease susceptibility 1 The signals that are fed into EDS1 are smaller. Depending on the type of other proteins it interacts with, EDS1 pushes plant cells to restrict pathogen growth or commit to cell death The work shows that TIR and TNL are pathogen-inspired. Evidence showed that the TIR enzymes produce a small messenger that signals to the EDS1 inside the cells. The identities of the precise molecule that stimulates the different immune responses have been a mystery.

The two functional EDS1 modules that lead to immunity or cell death can be triggered by a pathogen. The Chai group reconstituted key components of the signaling pathway in insect cells so that they could be isolated and characterized. The authors used this approach to discover two different classes of modified nucleotides. The compounds preferentially bound to and activated different parts of the EDS1 complex. The authors show that different EDS1 sub-complexes recognize certain TIR-produced molecule which function as information-carrying chemicals to promote immune responses.

Jijie Chai points out that the TIR-catalyzed small molecule could be used to control crop diseases, such as rice and wheat. The new chapter on plant immunity signaling and disease management will be opened by knowing the biochemical modes of action of these small molecule.

More information: Shijia Huang et al, Identification and receptor mechanism of TIR-catalyzed small molecules in plant immunity, Science (2022). DOI: 10.1126/science.abq3297

The signaling molecule for plant immunity is produced by the TIR-catalyzedADP-ribosylation reaction. There is a science.abq8180.

Journal information: Science