Learned early
A good immune response is important to quickly overpower incoming pathogens. Now researchers show in Plant Cell that that basis of this response stems from 500 million years ago.
Immune receptors are important for the recognition of pathogens. Plants have multiple types of immune receptors. One of those are the NLR immune receptors located inside the cell. A fair amount is known about the NLR-proteins of flowering plants. But researchers don’t know that much of NLR-proteins of non-flowering plants. That he researchers decided to investigate in more detail.
Firstly they fished for 33 different plants, from algae to flowering plants, all NLR genes from their genome. Using the gene sequence, the researchers studied the different modules those NLR genes contained. They came across known modules, like TIR and CC. But the noticed also modules that did not occur often in NLRs of flowering plants.
The big variety of NLR immune receptors illustrates that there are many ways to get an immune response
Subsequently the researchers analysed how much the NLRs of non-flowering plants contributed to the immunity of plants. First they studied this for NLRs with TIR and CC modules. Mostly because lots is known about those modules. The researchers selected 20 TIR modules and 5 CC modules from non-flowering plants. Those they placed in plants of the tabaco family. Followed up by analysing the immune response in the form of cell death. For 11 of the TIR modules and 3 of the CC modules they observed a strong immune response. In a similar way the researchers analysed two modules that did not occur in NLRs of flowering plants. Also for these modules the researchers observed a strong immune response in the form of cell death.
Lastly the researchers analysed the CC modules in more detail. They noticed that the CC modules of non-flowering plants have a MEAPL motif where CC modules of flowering plants have a MADA motif. For the MADA motif it is known that it is essential for the functionality of the NLR protein. For the MEAPL motif this also appears to be the case. Changed the researchers the motif a little bit, then the resulting NLR protein did no longer work. In addition, the NLR protein kept its functionality when the researchers swopped the MEAPL motif for the MADA motif.
It appears that NLR immune receptors originated long for the origin of flowering plants. Probably contributing to the immunity of plants. The big variety of NLR immune receptors illustrates that there are many ways for this. Even the same functionality can be gained in multiple ways, like the CC module illustrates. Better knowledge about how those not that well known NLR modules work, can in time contribute to a better immunity of crops.
Literature
Khong-Sam Chia, Jiorgos Kourelis, Albin Teulet, Martin Vickers, Toshiyuki Sakai, Joseph F Walker, Sebastian Schornack, Sophien Kamoun, Philip Carella, The N-terminal domains of NLR immune receptors exhibit structural and functional similarities across divergent plant lineages, The Plant Cell, 2024;, koae113, https://doi.org/10.1093/plcell/koae113
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