New Insights into Plant Immunity: Discovery of PRIMER Cells
LA JOLLA (January 8, 2025) -- Human bodies utilize a diverse population of immune cells that circulate among organs, responding to various threats. In contrast, plants must rely on individual cells to manage their own immunity. New research from Salk Institute scientists reveals how plant cells adapt to protect themselves against pathogens.
Upon encountering a threat, plant cells transition into a specialized immune state, becoming PRimary IMmunE Responder (PRIMER) cells. This new cell population acts as a hub, initiating the immune response. Surrounding these PRIMER cells are bystander cells, which play a crucial role in transmitting the immune response throughout the plant.
The findings, published in Nature on January 8, 2025, enhance understanding of the plant immune system, which is increasingly vital in the context of antimicrobial resistance and climate change.
Professor Joseph Ecker, senior author of the study, states, "In nature, plants are constantly being attacked and require a well-functioning immune system. However, plants lack mobile, specialized immune cells and must develop a system where every cell can respond to immune threats without neglecting other functions. Until now, the mechanisms behind this were unclear."
Plants encounter various pathogens, such as bacteria and fungi. When these pathogens invade, the stationary plant cells assume responsibility for responding and alerting nearby cells. Different pathogens may enter through various locations and times, resulting in simultaneous immune response stages across the plant.
To investigate this complexity, the Salk team employed two advanced profiling techniques: time-resolved single-cell multiomics and spatial transcriptomics. This combination allowed the team to observe the plant immune response in each cell with unprecedented detail.
First author Tatsuya Nobori notes, "Discovering these rare PRIMER cells and their surrounding bystander cells provides significant insight into how plant cells communicate to survive external threats."
The research involved introducing bacterial pathogens to the leaves of Arabidopsis thaliana, a model organism in plant research. The team identified a novel immune response state, PRIMER, which emerged in cells located at specific immune hotspots. PRIMER cells expressed a new transcription factor, GT-3a, likely crucial for alerting other cells to an active immune response.
Additionally, the bystander cells adjacent to PRIMER cells were found to express genes that facilitate long-distance communication. Future research aims to further elucidate the interactions between PRIMER and bystander cells, which are suspected to be essential for propagating the immune response.
This new understanding of the plant immune response is now available as a reference database for researchers globally. As pathogens evolve amid climate change and rising antibiotic resistance, this database serves as a foundation for future research aimed at ensuring healthy plants and crops.
Professor Ecker states, "There is significant interest in detailed cell atlases, and we are excited to create a publicly available resource for researchers. Our atlas could lead to discoveries about how individual plant cells respond to environmental stressors, crucial for developing climate-resilient crops."
Other contributors to the study include Joseph Nery, Alexander Monell, Travis Lee, Yuka Sakata, Shoma Shirahama, and Akira Mine.
The research received support from the Howard Hughes Medical Institute and the Human Frontiers Science Program.
About the Salk Institute for Biological Studies: Founded by Jonas Salk, the Salk Institute is dedicated to unlocking the secrets of life through research in various fields, including plant biology and immunobiology. Learn more at www.salk.edu.