"Nature": Chinese scholars reveal the key mechanism of plant immunity enhancement

▎Editor of WuXi AppTec's content team Like us, plants are often in contact with various fungi, bacteria, viruses, etc.
, and may get sick as a result
.

Similarly, plants have evolved sophisticated immune systems to maintain health
.

 A few days ago, Professor Zhang Yuelin and Professor Li Xin, a plant immunologist working at the University of British Columbia (UBC) in Canada, published a paper in the top academic journal "Nature", revealing an important signaling mechanism when the plant immune system strengthens its defenses
.

 ▲This new study was recently launched in the journal Nature.
According to the researchers, the immune response of plants is mainly triggered by two types of receptor molecules
.

One type is the pattern recognition receptor PRR located in the cell membrane, which recognizes the pattern molecules specific to plant pathogens to trigger the first layer of the immune system, namely "Pattern-Triggered Immunity" (abbreviated as PTI, Pattern-Triggered Immunity); the other type is located in Nucleotide in the cell binds to the receptor NLR to directly or indirectly recognize the pathogen’s effector, thereby triggering the second layer of the immune system, which is called "Effector-triggered immunity" (ETI for short), to prevent the pathogen from spreading to Healthy organization
.

 These two immune pathways were usually studied separately in the past, but this study points out an important connection between them
.

Researchers have found that when plants respond to pathogens, the activation of NLR's TIR signal plays a vital role in enhancing the defense response during the PRR-mediated pattern triggering immune process
.

 ▲Professor Zhang Yuelin and Professor Li Xin (picture source: UBC official website), the two corresponding authors of this study, previous studies have shown that many NLRs have N-terminal TIR (Toll/interleukin-1 receptor) domains, this type of NLR With the help of the NADase activity of the TIR domain, two parallel signal pathways are activated through different modules
.

 Researchers knocked out different module components in the model organism Arabidopsis to block the TIR signal, and found that all of them would lead to the weakening of the plant’s pattern-triggered immune response, such as reducing the level of the plant hormone salicylic acid and the expression of defense genes, and weakening the response Resistance to pathogens
.

Correspondingly, in transgenic plants that inhibit NLR accumulation, the immune response triggered by pathogen model molecules will also be weakened
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 In addition, the researchers used flg22 polypeptide or nlp20 to treat plants, these substances trigger patterns to trigger immunity
.

However, they found that many genes encoding proteins containing TIR domains are rapidly overexpressed, indicating that once the pattern-triggered immunity is activated, the inducible expression of a large number of TIR genes is probably the way to activate TIR signals
.

Experiments have shown that overexpression of these TIR genes will promote Arabidopsis to synthesize salicylic acid to resist pathogens
.

In summary, this study found that in addition to recognizing pathogen effectors, some TLR receptors also play an important role in the process of triggering immune responses in amplifying modes
.

 Reference: [1] Hainan Tian et al.
, (2021) Activation of TIR signalling boosts pattern-triggered immunity.
Nature.
Doi: https://doi.
org/10.
1038/s41586-021-03987-1