Tracing evolution in Plants’ Transition to Land
A study from the group of Hirofumi Nagakami at the Max Planck Institute for Plant Breeding Research has shown how a versatile protein family may have helped plants colonize land. We sat down with Dr. Nagakami to learn more about this study and the work of his group in general. This interview has been edited for length and clarity.
Dear Hiro, congratulations on your paper in Current Biology! Your study is concerned with a subfamily of plant proteins called the SERKs. What are the major findings of your work?
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Thank you! The major finding of this study is that we discovered that a protein called SERK (SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE) interacts and functions alongside BIR (BAK1-INTERACTING RECEPTOR-LIKE KINASE) to regulate development and defence against bacterial pathogens in the liverwort Marchantia polymorpha, similar to its role in flowering plants. Liverworts belong to bryophytes (non-vascular plants), which are a sister lineage to vascular plants, including flowering plants. Our findings suggest that the SERK-BIR functional module was established after plant terrestrialization, before the diversification of bryophytes and vascular plants, and the function of the SERK-BIR has been maintained for over 450 million years across diverse plant lineages. This is significant because it implies that balancing development and immunity was a key factor for plant survival on land.
I very much appreciate the heroic efforts of first author Cate(Yijia)’s in finalising this study. It is also important to mention that this work would not have been possible without the invaluable support of both our external and internal collaborators, who are listed as co-authors of this article.
Why are the SERKs so important?
Plants generally lack mobility and instead adapt their growth, development, and life cycle by sensing both environmental and internal cues. To achieve this, they possess a large number of receptors, primarily located on the cell surface. In flowering plants, SERKs function as co-receptors for various cell surface receptors, playing key roles in regulating development and defending against pathogens. This highlights the critical role of SERKs as signalling hubs that help balance plant development and immunity, essential for plant survival.
How does this latest study fit with the overall aims of the work in your lab?
The focus of my research group is to understand how immune systems are conserved or diversified throughout the evolution of land plants. In our previous study, we discovered that the first line of plant defence—known as pattern-triggered immunity (PTI)—is conserved in bryophytes (https://www.mpipz.mpg.de/pr-hiro-2023-en). Knowing that SERKs are involved in immunity in flowering plants led us to question whether they might also be doing the same in bryophytes. We could take advantage of the fact that Marchantia polymorpha possesses only a single SERK. So, although we cannot yet say for sure that SERK plays a role in PTI or immunity in bryophytes, we are excited by our finding that BIR, which interacts with SERK, contributes to defence against bacterial pathogens. This may be a key first finding that could allow us to unravel the mechanisms of immunity in bryophytes, which may differ from those in flowering plants.
What questions in your research do you find most exciting and interesting right now?
Studies using the premier model plant Arabidopsis thaliana have provided valuable insights into the molecular mechanisms underlying the plant immune system. However, recent studies supported by extensive genomic data and the establishment of various plant models across different lineages have begun to reveal that species within the Brassicaceae family have uniquely evolved certain immunity-related components. We also observed this while investigating the immune system of Marchantia polymorpha. Personally, I am excited by the opportunity to discover novel immunity-related components or mechanisms through the use of diverse plant models, which may have been overlooked due to the predominant reliance on Arabidopsis thaliana as a model system.
