Immune Cell Death Zonation Regulated by Protein Hubs in Plants

Project Information

ImmunoZoneHubs

Grant agreement ID: 101068121

DOI

10.3030/101068121

Project terminated on 30 October 2025

EC signature date 26 July 2022

Start date 1 September 2023

End date 31 March 2026

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 165 312,96

Coordinated by

CENTRE DE RECERCA EN AGRIGENOMICA CSIC-IRTA-UAB-UB
Spain

Periodic Reporting for period 1 - ImmunoZoneHubs (Immune Cell Death Zonation Regulated by Protein Hubs in Plants)

Reporting period: 2023-09-01 to 2026-03-31

Summary of the context and overall objectives of the project

Global agriculture faces the dual challenge of a growing population and escalating threats from plant pathogens migrating due to climate change. Fungal and bacterial infections destroy up to 40% of global crop yields annually, resulting in billions of euros in losses and threatening food stability. Historically, the primary solution has been chemical pesticides. However, the European Green Deal and the "Farm to Fork" strategy aim to reduce pesticide use by 50% by 2030, necessitating a shift toward biological, "built-in" plant immunity.
This project addressed a critical gap in understanding how plants manage Immunity-related Cell Death (ICD). When a plant recognizes a pathogen, it triggers a localized "suicide" of infected cells to halt the infection. For this to be effective, the plant must precisely control the death zone and ensure surrounding cells are "primed" to survive. Without strict control, runaway tissue damage can kill the entire plant. The project addressed the lack of knowledge regarding the molecular "boundaries" of this process and the protein machinery triggering it.
The project pursued two primary objectives:
Objective 1: Defining Spatial Boundaries and marker genes in Arabidopsis. We sought to resolve the spatiotemporal dynamics of the immune response by identifying "marker genes" that distinguish between cells undergoing suicide and healthy surrounding tissue. This provides the first high-resolution mapping of cellular boundaries that confine infection.
Objective 2: Characterizing protease-containing protein hubs. We focused on the Metacaspase 1 (MC1) protease to decipher how signaling platforms (hubs) are assembled at the cell surface to transduce the detection of a pathogen into a coordinated cellular response.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The work combined cell biology, biochemistry, and molecular genetics to decode the lifecycle of immune signaling hubs.
Mapping the Spatial Boundaries of Immunity: Using transcriptomic data, we isolated a panel of candidate marker genes through RT-qPCR validation. The gene AT5G17760 was confirmed as a robust marker for cells committed to death, and its function was further characterized in the context of stress responses. We isolated homozygous mutant lines and generated fluorescent reporter constructs (Promoter:GFP) for selected markers. These tools allow the scientific community to visualize the "border control" mechanisms plants use to prevent pathogen spread while maintaining surrounding tissue health.
Discovery of the Autophagic "Off-Switch": We characterized the Metacaspase 1 (MC1) signaling complex, discovering that upon pathogen recognition, MC1 associates with the plasma membrane and also organizes into biomolecular condensates to amplify the immune signal. Crucially, the research revealed that these protein hubs are subsequently targeted by the cell’s internal recycling machinery, autophagy. By demonstrating that autophagy acts as a selective "off-switch" to dismantle the MC1 complex, we identified a novel homeostatic mechanism to terminate the death signal once the threat is contained. These findings were published in Salguero-Linares et al. (2025), a major contribution to plant protease and immunity fields.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Prior to this project, plant cell death was viewed as a linear "on/off" pathway. This project advanced the state of the art in several ways:
A New Regulatory Paradigm: We discovered that immune hubs are actively sequestered into condensates and cleared via autophagy, introducing a previously unrecognized layer of "off-switch" regulation.
Spatial Mapping Tools: By validating marker genes for different immune zones, we provided a high-resolution molecular toolkit. This allows researchers to study plant-pathogen interactions at a local level rather than using "bulk" tissue samples.
Career Leadership: A major impact was the professional development of the researcher, who secured a tenure-track position at the university, ensuring the expertise gained is institutionalized within the European Research Area.
Agricultural Impact: Identifying natural "off-switches" provides potential targets for future crop breeding. Optimizing these mechanisms could lead to "smarter" crops that defend themselves with minimal collateral damage, supporting a pesticide-free economy.