Biology subjects

Garrido-Arandia, M.

Publications and source records attributed to Garrido-Arandia, M..

5 recordsLinked to original sources

bioRxiv2026

A pathogen α-L-arabinofuranosidase degrades host-derived immunogenic oligosaccharides to suppress plant immunity

Plant cell wall fragments released during pathogen attack can act as signalling molecules that trigger immune responses. Successful pathogens have potentially evolved diverse strategies to evade host recognition, including minimizing the accumulation of cell wall-derived elicitors. However, the mechanisms underlying this process remain largely unknown. Here, we characterized ZtGH54, an -L-arabinofuranosidase from the wheat pathogen Zymoseptoria tritici, that is essential for the acquisition of sugar nutrients from arabinan and arabinoxylan wall polysaccharides. ZtGH54 also hydrolyzes immunogenic oligosaccharides derived from arabinoxylan to prevent host recognition. Remarkably, this strategy is effective only in a subset of wheat cultivars, as the contribution of ZtGH54 to virulence is cultivar-dependent. While a ZtGH54 substrate is broadly recognized in wheat, one of the products generated by ZtGH54, xylotetraose, is recognized only by specific wheat cultivars, revealing natural variation in the perception of xylan-derived oligosaccharides. These findings establish ZtGH54 as a key virulence factor that simultaneously exploits cell wall host resources and suppresses wheat immunity through the precise hydrolysis of plant cell wall-derived signals.

plant biology↗

bioRxiv2026

Structural and functional insights into the role of Cysteine-Rich Receptor-Like Kinase 18 (CRK18) in Arabidopsis

Plants perceive and integrate diverse environmental signals through receptor kinase (RK) networks at the plasma membrane. Within this, Cysteine-Rich Receptor-Like Kinases (CRKs) constitute a large but not well-understood subfamily characterised by extracellular domains (ECDs) enriched in cysteine residues. CRKs have been implicated in plant responses to biotic and abiotic stress, as well as in developmental processes. Additionally, several CRKs have been proposed to act as redox sensors. Here, we investigate the homodimerization mechanism of Arabidopsis CRK18 and its regulation by redox conditions. By modulating pH and redox state, we assessed the stability and binding dynamics of the CRK18 ECD and its cysteine mutants. We also tested the plasma membrane localisation of all the cysteine mutants involved in the predicted disulfide bonds, and only CRK18C227A, C228A-ECD resembled the plasma membrane localization of wild-type CRK18. We combine co-immunoprecipitation, Forster resonance energy transfer-fluorescence lifetime imaging microscopy and microscale thermophoresis to quantify CRK18 self-association in planta and in vitro. Furthermore, we place CRK18 dimerization in a broader signalling context by identifying CRK18 interaction partners and CRK18-dependent signalling outputs. Using Arabidopsis CRK18 overexpression lines, we perform (phospho)proteomic and immunoprecipitation-mass spectrometry (IP-MS) analyses to map CRK18-centred signalling networks associated with stress-related responses. The constitutive activation of the CRK18 kinase domain and its interaction with many putative (cell wall) glycan-sensing RKs, including PERK15, suggest a regulatory role for CRK18. The absence of significant changes in the proteome and phosphoproteome of CRK18 overexpression lines in the absence of any trigger, and its restricted mobility after elicitation, suggest that CRK18 requires a stimulus for activation and possibly induces membrane microdomain reorganisation. This is in line with the infection assay with the nematode Heterodera schachtii, which causes modification and targeted damage to plant cell walls during infection, revealing that CRK18 acts as negative regulator of this process.

biochemistry↗

bioRxiv2025

The structural disorder of Dsup and its interaction with the human nucleosome: A computational study

The known role of the tardigrade-unique protein Dsup in protecting DNA from damage produced by radiation and radicals has prompted great attention for its biomedical applications. While we reported before a computational study on the Dsup-free DNA interaction (Minguez-Toral et al., Sci. Rep. 2020, 10, 13424), our objective here is to help characterize the interaction of Dsup with nucleosomal DNA. We first address the disordered status of Dsup to prove that it is a completely disordered protein. With a proper 3D model of Dsup and by means of molecular modeling, all-atom molecular dynamics simulations and calculations of electrostatic potentials and electric fields, we then present results for several complexes of the human nucleosome with one and two Dsup molecules. Our findings complement and expand upon a recent cryoEM structural study (Alegrio-Louro et al., Genes Dev. 2025, 39, 1-7) which demonstrated that Dsup is recognized through a HMGN-like nucleosome binding motif and resolved the structure for the short 5-residue binding motif of Dsup. In addition to confirming this HMGN-like binding mode, our computational approach reveals dynamic details about the complete 445-residue Dsup in its interaction with the nucleosome. Since our study includes complete histone tails (missing in X-ray and cryoEM structures), it provides a complete picture of distinct possible conformations of Dsup around the nucleosome improving upon low-resolution cryoEM maps available for some Dsup segments. Electrostatic potentials and electric fields reveal in one complex that while the HMGN-like binding motif anchors Dsup at the nucleosome binding site, the conformational freedom of the disordered protein dynamically confers a possible electrostatic protective envelope. This shielding-like effect of Dsup on nucleosomal DNA would thus be similar to that suggested in our previous report on free DNA.

biophysics↗

bioRxiv2025

Microbial metabolism of food allergens determines the severity of IgE-mediated anaphylaxis

Anaphylaxis is an acute, potentially life-threatening reaction, often triggered by foods and largely mediated by IgE. Critically important to anaphylaxis are the factors that modulate its severity. The human microbiota is known to influence oral tolerance, but the microbial mechanisms directly involved in IgE-mediated anaphylaxis remain unknown. Here, we demonstrate that human saliva and jejunum harbor peanut-degrading bacteria that metabolize immunodominant allergens (Ara h 1 and 2) and alter IgE-binding. Additionally, we provide in vivo evidence that oral bacteria metabolize peanut allergens, influencing systemic allergen exposure and anaphylaxis severity. Finally, in clinical studies, we observe that common peanut-degrading bacteria, such as Rothia, from the oral cavity, are more abundant in peanut-allergic patients who exhibit better tolerance to allergen exposure. Altogether, these results demonstrate that human microbiota modulates IgE-mediated reactions through allergen metabolism. We reveal a novel microbial mechanism with potential to prevent, or reduce, the severity of IgE-mediated anaphylaxis.

immunology↗

bioRxiv2022

A group of Arabidopsis thaliana Leucine Rich Repeat-Malectin Receptor Kinases are required for the activation of immune responses triggered by cellulose and mixed-linked glucan oligosaccharides

Plant immune system perceives through the extracellular ectodomains (ECDs) of Pattern Recognition Receptors (PRRs) a diversity of carbohydrate ligands from plant and microbial cell walls, which activate Pattern-Triggered Immunity (PTI). Among these ligands are oligosaccharides derived from mixed-linked {beta}-1,3/{beta}-1,4-glucans (MLGs, e.g., {beta}-1,4-D-(Glc)2-{beta}-1,3-D-Glc, MLG43) and cellulose (e.g., {beta}-1,4-D-(Glc)3, CEL3). The mechanisms of perception of carbohydrates by plants are poorly characterized, with the exception of that determining recognition of fungal chitin oligosaccharides (e.g., {beta}-1,4-D(GlcNAc)6, CHI6) that involves several PRRs with LysM-ECDs that function as receptor or co-receptors. Here, we describe the isolation and characterization of Arabidopsis thaliana mutants impaired in glycan perception (igp), which are defective in PTI activation mediated by MLG43 and CEL3, but not CHI6. igp1-igp4 are altered in receptor-like kinases [RLKs: AT1G56145 (IGP1), AT1G56130 (IGP2/3), and AT1G56140 (IGP4)] with Leucine-Rich-Repeat (LRR) and Malectin (MAL) domains in their ECDs. igp4 is a T-DNA insertional, loss of function mutant whereas igp1 and the allelic igp2/igp3 harbour point mutations (E906K and G773E, respectively) in their kinase domains, which impact their structure and surface electrostatic potential as revealed by in silico structural analyses. Notably, Isothermal Titration Calorimetry assays with purified ECD-RLKs showed that AT1G56145 binds with high affinity CEL3 (Kd = 1.19 {+/-} 0.03 M) and cellopentaose (Kd = 1.40 {+/-} 0.01 M), but not MLG43, supporting AT1G56145 function as a plant PRR for cellulose oligosaccharides. Our data suggest that these LRR-MAL RLKs are receptor/co-receptors of a novel mechanism of perception of cellulose and MLG-derived oligosaccharides and PTI activation in Arabidopsis thaliana. Significance StatementNew oligosaccharides that trigger plant immunity have been described recently, but the mechanisms of perception of these glycans are unknown. We describe here three Arabidopsis thaliana receptor kinases (AT1G56130, AT1G56140, and AT1G56145) with Leucine Rich Repeat (LRR) and Malectin (MAL) domains in their extracellular ectodomains (ECDs), which function as Pattern Recognition Receptors (PRRs) triggering immune response mediated by oligosaccharides from cellulose ({beta}-1,4-glucan) and mixed-linked {beta}-1,3/1,4-glucans (MLGs) of plant and microbial cell walls. The ECD-AT1G56145 binds cellulose oligosaccharides, but not MLGs, supporting its function as a novel receptor of carbohydrate ligands in plants. Our data indicate that these LRR-MAL-PRRs control a complex mechanism of oligosaccharides perception and immune activation that differs from that of fungal chitin oligosaccharides recognition which involves LysM-PRRs.

plant biology↗