Function follows form in plant immunity

The University of Cologne, Germany, and the Max Planck Institute for Plant Breeding Research have discovered a novel biochemical mechanism explaining how immune proteins defend plants against invading microorganisms. The journal Cell contains their findings.

Humans rely on our immune systems to fight diseases. Plants also have immune responses when invaded by harmful microbes. Key players in the plant immune responses are the immune receptors, which detect the presence of foreign organisms and set in motion protective responses to repel them.

The toll-Interleukin-1receptor (TIR) domain is one of the specialized regions of the immune receptors that is used to break down the molecule nicotinamide adenine dinucleotide (NAD + ). A protective mechanism that leads to the death of plant cells at sites of attempted infections is an effective way to protect the plant as a whole. Studies have shown that the breakdown of NAD + is not enough for plant protection.

Jijie Chai is affiliated with the University of Cologne and Tsinghua University in Beijing, China, as well as with the School of Biological Sciences.

The authors used structural analysis to show how TIR proteins form different structures for the breakdown of NAD + orRNA/DNA. The ability to form two alternative molecular complexes is a characteristic of the immune system. The shape of the TIR proteins is what determines the activity.

The authors suggested that specific small molecules generated by the breakdown of RNA and DNA were responsible for cell death. The scientists were able to identify the molecule as cAMP/cGMP using analytical chemistry. The authors analysis showed that the TIR domains were triggering the production of non-canonical 2. Cell death activity was impaired when they reduced TIR-mediated production.

It stands to reason that their levels would be kept in check if 2 and 3 promote cell death in plants. The authors discovered that a known negative regulator of TIR function in plants, NUDT7, acts bydepleting. The scientists could show that the pathogen proteins also have negative regulators released by them. This suggests that invading microorganisms have evolved clever strategies to disarm the plant defense mechanism for their own benefit.

Dongli Yu, one of three co-first authors of this study, sums up the significance of his study thus: "We have identified a new role for the TIR domain of immune receptors in protecting plants against infections." Novel strategies for making plants more resistant to harmful microbes and in this way contribute to food security will be suggested.

More information: Dongli Yu et al, TIR domains of plant immune receptors are 2′,3′-cAMP/cGMP synthetases mediating cell death, Cell (2022). DOI: 10.1016/j.cell.2022.04.032 Journal information: Cell Citation: Function follows form in plant immunity (2022, May 20) retrieved 20 May 2022 from https://phys.org/news/2022-05-function-immunity.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.