Research interests

Our group investigates plant immunity with a focus on the role of cell wall-derived glycans (oligosaccharides) as key molecular signals in plant-pathogen interactions. We study how carbohydrate fragments from plant cell walls, which are released during pathogen attack or cell wall remodeling, are perceived by plant Pattern Recognition Receptors (PRRs) at the cell surface, and how this specific recognition activates Pattern-Triggered Immunity (PTI) and disease resistance.

We combine genetics, biochemistry, structural biology, and glycomics to: 

• Decipher the structural bases of glycan recognition by PRR receptors.
• Identify the signaling complexes and downstream components that mediate glycan-triggered immunity.
• Explore and structurally characterize the diversity of Damage-Associated Molecular Patterns (DAMPs) released from plant cell walls during infection.
• Translate this knowledge into agrobiological applications, developing glycan-based biostimulants and biopesticides as sustainable agriculture solutions to replace chemical pesticides.
  
  

Thus, our research provides fundamental insights into plant cell wall biology, receptor-ligand interactions, and immune signaling, while contributing to the development of biotechnological solutions for sustainable crop protection.

Our current research lines are: 

• Identification of molecular components involved in glycan perception (IPs: Antonio Molina, Lucía Jorda)
• Characterization of plant cell wall-derived immune-active oligosaccharides (IPs: Antonio Molina, Lucía Jorda)
• Harnessing glycan-based biostimulants for enhanced crop protection (IPs: Antonio Molina, Lucía Jorda, Miguel Angel Torres)
• Transition metal homeostasis in plant-pathogen interactions (IP: Lucía Jorda)
• Ecological and molecular factors involved in fungal endophytism and pathogenesis (IP: Soledad Sacristán), More information

Identification of molecular components involved in glycan perception

To dissect glycan-triggered immunity, we established a multi-tiered screening platform that combines complementary readouts of early immune activation. Using aequorin luminescence system, we monitor rapid cytosolic calcium fluxes upon DAMPs perception by PRRs. Determination of ROS production, MAP kinase activation, and transcriptional reprogramming provide additional layers of resolution on the defense signaling outputs triggered by these DAMPs. This integrative system enables us to identify novel glycans triggering immune responses, to test their activity as elicitors and systematically identify mutant plants with altered responses to these DAMPs, as proxy to characterize novel molecular components (e.g. PRRs) required for glycan-mediated immunity.

Forward genetic screening using Ca2+ cytosolic measurements as a tool to identify PRRs and other proteins involved in oligosaccharide perception and PTI activation (Martín-Dacal et al., 2022).

Applying this approach, we uncovered a specific subgroup of Leucine-Rich Repeat-Malectin receptor kinases (LRR-MAL RK) called IGP1, IGP3, and IGP4, for impaired in glycan perception, as essential components of glycan-triggered immunity (Martín-Dacal et al., 2022). These receptors were shown to be required for immune responses triggered by cellulose-derived oligosaccharides (β-1,4-D-glucose glucans), as well as other glycans like mixed-linked-glucans (β-1,3/1,4-glucans, e.g. MLG43 trisaccharide), and xylotetraose and arabinoxylan oligosaccharides. These functions of IGP1/IGP3/IGP4 in the perception of these glycans positioning LRR-MAL RKs as key molecular sentinels of cell wall integrity and disease resistance activation (Martín-Dacal et al., 2022; Fernández-Calvo et al., 2024).

Characterization of the IGP family and proposed model for its role in sensing cell wall-derived glycans

Biochemical analyses, conducted in collaboration with Julia Santiago (University of Lausanne), demonstrated that Extracellular domain (ECD) of IGP1 directly binds the cellulose-derived trisaccharide CEL3. This discovery represents one of the first direct demonstrations of glycan-DAMP perception at the molecular level in plants and aligns with computational predictions of receptor-glycoligand interactions in plant immunity (del Hierro et al., 2020). These computational and molecular approaches establish a powerful framework for anticipating the molecular principles of carbohydrate recognition and reveal a dedicated receptor network for carbohydrate sensing, paving the way to dissect the downstream signaling modules, co-receptors, and transcriptional regulators that mediate glycan-induced immunity.

Identification of plant cell wall-derived immune-active oligosaccharides

The plant cell wall has emerged as a major source of carbohydrate-based DAMPs (Molina et al., 2024). Its remarkably structural complexity, determined by the diversity of monosaccharides, glycosidic linkages, branching patterns, and chemical modifications of wall polysaccharides, gives rise to a vast array of compounds able of triggering plant immune responses. However, only few of these molecules have been characterized to date. Our work aims to identify novel cell wall-derived danger signals and define the structural signatures of cell wall-derived DAMPs that plants recognize as immune elicitors.

To address this, we apply environmentally friendly methodologies such as subcritical water extraction to recover bioactive cell wall fractions from plant biomass (Rebaque et al., 2023). These approaches avoid harsh chemical treatments, generating sustainable bioextracts and biofractions that retain immunogenic glycans capable of priming plant immunity and enhancing resistance.

Our work has revealed that cellulose-derived oligomers (CEL3), mixed-linked β-1,3/1,4-glucans (e.g., MLG43), and other hemicellulose-derived oligosaccharides act as potent DAMPs recognized by these IGPs, each activating distinct but convergent immune signaling pathways (Rebaque et al., 2021; Martín-Dacal et al., 2022; Fernández-Calvo et al., 2024).

Pathogen-induced cell wall remodeling releases a broad spectrum of glycan signals, underscoring the diversity and specificity of glycan perception in plants. Importantly, these discoveries are consistent with recent evidence that Arabidopsis cell wall composition itself determines disease resistance specificity and plant fitness (Molina et al., 2021), placing glycan recognition at the crossroads of immunity, adaptation, and growth. By linking chemical structure, extraction method, and bioactivity, we are building a molecular framework to exploit glycans as natural elicitors and to develop sustainable, glycan-based biostimulants for crop protection.

Protective effect of cell wall-derived biofractions against different pathogens

Harnessing glycan-based biostimulants for enhanced crop protection

To translate mechanistic insights into biological relevance, we test cell wall fractions enriched in specific glycan structures in plant-pathogen assays. Exogenous application of these biofractions primes plants for enhanced resistance against pathogens, including necrotrophic fungi such as Botrytis cinerea or hemibiotrophic bacteria as Pseudomonas syringae pv. tomato DC3000. These treatments mimic the natural release of oligosaccharides during infection, establishing glycans as bona fide immune-activating signals with agronomic potential. Building on this, we are exploring how such glycans, alone or in defined mixtures, can be used as biostimulants and resistance inducers, a concept we outlined in our recent perspective (Molina et al., 2024 Mol Plant). This translational approach bridges cell wall glycobiology with sustainable crop protection strategies.

We are implementing this translational biology strategy in several collaborative projects. For example, in the EU-funded CITRUSBUSTERS we aim to develop innovative and sustainable solutions based in glycan-triggered disease resistance in citrus to prevent the introduction and limit the spread of two major devastating citrus diseases caused by the bacterium Candidatus Liberibacter and the fungus Phyllosticta citricarpa. The project involves researchers from CBGP and partners across Europe and Brasil and focus on protecting citrus through three main strategies: i) early detection of outbreaks; ii) enhancing citrus plant resilience; and iii) delivering safe and effective biocontrol tools. Our research specifically targets the use of natural bioproducts as biotechnological tools to control these diseases. This innovative approach seeks to activate citrus immunity using biofractions enriched in cell wall-derived oligosaccharides.

Transition metal homeostasis in plant-pathogen interactions

We discovered for the first time that zinc is a fundamental element in the immune response of Arabidopsis thaliana against the necrotrophic fungus Plectosphaerella cucumerina BMM (PcBMM), as plants use zinc-toxicity as a defence mechanism to fend-off invading microbes (Escudero et al., 2021). The overall goal of this research line is to unveil the molecular bases of this new, yet uncharacterized, layer of zinc-mediated immunity, ZiMI, in plants.

Role of HMA2 and HMA4 in zinc mediated immunity

Ecological and molecular factors involved in fungal endophytism and pathogenesis

This research line focuses on elucidating the mechanisms that govern interactions between fungal endophytes and plants, with the ultimate goal of applying them effectively to improve crop productivity.