ZAR1 is a special type of immune receptor known as an NLR, which helps plants defend against pathogens. What’s remarkable is that while most NLRs evolve rapidly, even within the same species, ZAR1 has been remarkably conserved for millions of years. It traces its origins back to the Jurassic period, around 220 to 150 million years ago, when flowering plants were just starting to emerge.
By analyzing the genetic sequences of various plant species, we found that ZAR1 has been passed down through generations, and we identified 120 similar versions of ZAR1 in 88 different species. These included plants like Colacasia esculenta, Cinnamomum micranthum, and Aquilegia coerulea. Interestingly, ZAR1 has kept essential features that allow it to recognize harmful pathogens and trigger cell death, a defense mechanism against invaders.
We also conducted experiments to better understand how ZAR1 works. We discovered that ZAR1 has evolved to partner with another protein called RLCK, which helps activate the immune response. RLCKs and ZAR1 have been working together effectively ever since the time of the dinosaurs.
In addition to its ancient roots, ZAR1 has undergone some interesting changes over time. For example, in cassava and cotton, ZAR1 carries an additional domain called thioredoxin-like, which may provide additional protective functions. We also found that ZAR1 has given rise to new versions with integrated domains and modified features in some plant species.
Overall, our study highlights the unique journey of ZAR1 throughout millions of years of plant evolution. While other immune receptors often duplicate and expand their genes, ZAR1 has remained relatively stable. However, it has also undergone fascinating adaptations, acquiring new functions and variations in certain plant lineages.
Understanding the evolutionary history of immune receptors like ZAR1 provides valuable insights into the intricate defense mechanisms of plants. It sheds light on how plants have been safeguarding themselves for millions of years and how they continue to adapt to changing environments. Studying these ancient guardians can help us develop strategies to enhance plant health and protect our crops in the face of ever-evolving pathogens.
So next time you look at a plant, remember that it carries within it a silent, ancient ninja warrior like ZAR1, standing tall and defending its kingdom against invisible invaders.
Read the paper: Hiroaki Adachi, Toshiyuki Sakai, Jiorgos Kourelis, Hsuan Pai, Jose L Gonzalez Hernandez, Yoshinori Utsumi, Motoaki Seki, Abbas Maqbool, Sophien Kamoun, Jurassic NLR: Conserved and dynamic evolutionary features of the atypically ancient immune receptor ZAR1, The Plant Cell, Volume 35, 3662–3685.
Read the commentary: Ching Chan, Tracing the evolution of the ZAR1 resistosome back to the Jurassic era, The Plant Cell, Volume 35, 3629–3630.
This article is available on a CC-BY license via Zenodo. Cite as: Adachi, H., Sakai, T., and Kamoun, S. (2023) The ancient guardian: ZAR1 evolutionary journey and adaptations. https://doi.org/10.5281/zenodo.8385521