Researchers have uncovered a previously unknown mechanism by which plants detect hydrogen peroxide (H₂O₂), a key signaling molecule involved in stress responses and immunity.
Image Credit: Issey Takahashi
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Scientific Frontline: Extended "At a Glance" Summary: Copper-Dependent Signal Detection in Plants
The Core Concept: Plants utilize a specialized copper-dependent sensing system within their plasma membrane receptors to detect hydrogen peroxide (\(\ce{H2O2}\)), a vital signaling molecule involved in stress responses and plant immunity.
Key Distinction/Mechanism: Contrary to the previous assumption that plants rely on cysteine residues to sense reactive oxygen species (ROS), the CARD1 (or HPCA1) receptor relies on a copper ion bound to a cluster of surface histidine residues. Detection occurs through redox chemistry—specifically the oxidation of copper (\(\text{Cu}^+ \rightarrow \text{Cu}^{2+}\))—rather than structural changes in cysteine.
Major Frameworks/Components:
- CARD1 (HPCA1) Receptor: A leucine-rich repeat receptor-like kinase on the cell surface responsible for monitoring the external environment.
- Hydrogen Peroxide (\(\ce{H2O2}\)): A reactive oxygen species (ROS) that functions as a primary indicator of pathogen presence and environmental stress.
- Copper-Histidine Cluster: The specific molecular site on the CARD1 receptor where copper ions bind to facilitate ROS detection.
- Redox Chemistry: The electron transfer process (copper oxidation) that either directly triggers cellular signaling or generates secondary molecules to activate a downstream immune response.
Branch of Science: Plant Biology, Biochemistry, Molecular Biology, and Structural Biology.
Future Application: The discovery provides a new molecular target for agricultural biotechnology, offering potential pathways to engineer crops with enhanced resilience to environmental stress, improved pathogen resistance, and superior overall yield protection.
Why It Matters: This breakthrough fundamentally reshapes our understanding of how sessile organisms interact with and perceive their environment. By establishing the existence of a metal-based ROS signaling pathway, it establishes a new paradigm for investigating redox-dependent mechanisms across biological systems.
Breakthrough Reveals a New Way Plants Perceive Hydrogen Peroxide, Offering New Insights for Crop Protection and Plant Immunity
Researchers at the Institute of Transformative Bio-Molecules (WPI-ITbM) at Nagoya University, together with collaborators from the RIKEN Center for Sustainable Resource Science (RIKEN CSRS) and Osaka University, have uncovered a previously unknown mechanism by which plants detect hydrogen peroxide (\(\ce{H2O2}\)), a key signaling molecule involved in stress responses and immunity. Published in Nature Communications, the study reveals that plants rely on a copper-dependent sensing system, rather than the previously assumed cysteine-based mechanism, to perceive reactive oxygen species (ROS).
This work reshapes our understanding of how plants respond to environmental stress and pathogens and may pave the way for improving crop resilience. Quinones and hydrogen peroxide play central roles in plant responses to pathogens and environmental stress, and understanding how plants perceive these molecules could inform strategies to enhance crop protection and stress tolerance.
How Plants Detect Redox-Related Molecules in Their Environment
As sessile organisms, plants constantly monitor their environment using specialized receptors on the surfaces of their cells. Among these, a class known as leucine-rich repeat receptor-like kinases can sense a wide range of stimuli. One such receptor, CARD1 (also called HPCA1), was previously shown to detect both quinones and ROS, such as \(\ce{H2O2}\). However, how a single receptor distinguishes between these chemically distinct signals remained unclear.
The research team discovered that CARD1 contains a copper ion bound to a cluster of histidine residues on its surface. This copper site plays a critical role in detecting \(\ce{H2O2}\).
Surprisingly, cysteine residues—previously thought to be essential for \(\ce{H2O2}\) sensing—are not required for signal perception. Instead, the CARD1 receptor uses copper to detect \(\ce{H2O2}\) through redox chemistry.
“The results showed that when the copper-binding site is disrupted, plants lose their ability to respond to \(\ce{H2O2}\) signals,” said Anuphon Laohavisit, lead author and designated associate professor at the WPI-ITbM. “In contrast, mutations in cysteine residues had little effect on signaling, indicating that their primary role is structural rather than signaling.”
Through computational approaches, the team suggests that ROS sensing by CARD1 could occur through the oxidation of copper (\(\text{Cu}^+ \rightarrow \text{Cu}^{2+}\)) at the receptor surface. Such a redox change may either directly trigger signaling or generate secondary molecules that activate downstream responses. It is likely that a separate pathway exists for quinone perception and remains to be identified.
Conclusion and Future Perspective
The researchers provide the first structural evidence of a metal ion–based sensing mechanism in plant plasma membrane receptors, reshaping our understanding of ROS perception in plants and paving the way for exploring metal-based ROS signaling mechanisms across biology.
Funding: This work was supported by JSPS KAKENHI (grants JP22H00364 and JP24K01718), the JST GteX Program (grant JPMJGX23B2), the JST FOREST Program (grant JPMJFR220G), the MEXT Promotion of Development of a Joint Usage/Research System Project: Coalition of Universities for Research Excellence Program (CURE) (grant JPMXP1323015482), the MEXT Project for Promoting Public Utilization of Advanced Research Infrastructure: Program for Supporting Construction of Core Facilities (grant JPMXS04411024), the RIKEN TRIP Initiative Field Omics, and the Mitsubishi Foundation.
Published in journal: Nature Communications
Title: A copper-dependent redox-based hydrogen peroxide perception in plants
Authors: Nobuaki Ishihama, Yohta Fukuda, Yumiko Shirano, Kazuhiro J. Fujimoto, Kaori Takizawa, Ryoko Hiroyama, Hiroki Ito, Mayumi Nishimura, Takeshi Yanai, Tsuyoshi Inoue, Ken Shirasu, and Anuphon Laohavisit
Source/Credit: Nagoya University
Edited by: Scientific Frontline
Reference Number: bot052126_01