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IGP receptors act as redox sensors to mediate broad-spectrum disease resistance induced by cellooligomers

Guangzheng SuniD, Wei PeiiD, Jingjing DaiiD, Jinyu HeiD, Xuan MiiD, Xinrui LiiD, Qinsheng ZhuiD, Ning XuiD, Zhichao ZhangiD, Liangyu Guo, Yifei YangiD, Mingzhu FaniD, Yan Na ReniD, Feng CheniD, Ming ChangiD, Zhifu HaniD, Aolin JiaiD, Xiaoquan WangiD, Yuanchao WangiD, Yu XiaoiD

Abstract

Cys-oxidation is a well-established post-translational regulator of intracellular protein function, yet its role in extracellular receptor-mediated signaling remains poorly understood. Here, we investigate the LRR-Malectin receptor-like kinase IGP1, a key receptor for plant cell wall damage-associated molecular patterns (DAMPs). We demonstrate that IGP1 directly recognizes cellooligomers with a degree of polymerization [≥] 3 via a conserved binding groove in its LRR domain, not the malectin domain as anticipated. Strikingly, a pair of cysteines within the malectin domain functions as a redox sensor, undergoing hydrogen peroxide-induced oxidation that sterically reduces ligand binding affinity and attenuates immune signaling. Phylogenetic analyses reveal that IGP originated after the terrestrialization of plants, and is an evolutionarily conserved redox sensor in land plants. Functional studies in Arabidopsis (Arabidopsis thaliana), wheat (Triticum aestivum), and soybean (Glycine max) confirm that the IGP-cellooligomer module confers broad-spectrum disease resistance. Our work uncovers a unique mechanism where ligand perception and redox sensing are integrated into a single receptor to regulate DAMP-triggered immunity.

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Claude Opus 5.5 · xhigh effort · 2 Nov 2026 · from the full text of version 1 (6 Oct 2025)

Plant LRR-Malectin receptor kinase IGP1 binds cellooligomers via its leucine-rich repeat domain while a conserved cysteine pair in its malectin domain senses hydrogen peroxide to attenuate immune signaling.

Plant cell wall cellooligomers act as damage-associated molecular patterns recognized by LRR-Malectin receptor-like kinases (IGPs), where the malectin domain was previously assumed to bind glycans and extracellular redox regulation remained unclear. Crystal structures, biochemistry, and phylogenomics across 1,177 species show that IGP1 instead binds cellooligomers via its LRR domain while a malectin cysteine pair acts as an H2O2 sensor that sterically dampens binding, regulating broad-spectrum plant immunity.

Key results

  1. ShownCrystal structures and calorimetry show that the IGP1 ectodomain directly binds cellooligomers with a degree of polymerization >= 3 in a 1:1 complex via an LRR3-5 and N-loopout groove rather than the malectin domain, independently of BAK1.

    Isothermal titration calorimetry (ITC) measured IGP1^ECD binding to cellotriose (CEL3, Kd ~ 1.61 uM) and cellotetraose (CEL4, Kd ~ 1.48 uM) but not cellobiose (CEL2) or hemicelluloses; crystal structures (2.49/2.65/2.74/2.69 A) revealed a WYW triad (W146/Y196/W220) stabilizing Glc1-3, where W146A or Y196A abolished binding and W220A increased Kd to ~18.6 uM, failing to rescue immunity in igp1-2. · Cellooligomers with DP ≥ 3 activate IGP1; Recognition mechanism of cellooligomers by IGPs; Mutagenesis of the IGP1-cellooligomer complex; Figure legends

  2. ShownA conserved C591/C592 cysteine pair in the IGP1 malectin domain functions as an extracellular redox sensor whose H2O2-induced oxidation sterically hinders cellooligomer binding and attenuates immune signaling.

    LC-MS/MS of CEL4-treated Arabidopsis protoplasts identified S-sulfenylation, sulfinylation, sulfonylation, and nitrosylation at C591/C592; sulfinylation-mimic IGP1^(CC-DD) reduced CEL4 affinity (Kd ~ 17.9 uM vs 1.48 uM WT and ~2.25 uM for CC-AA) and charge-reversed CC-RR abolished binding, with neither CC-DD nor CC-RR rescuing CEL4-triggered ROS burst or MAPK activation in igp1-2. · Oxidation on C591/592 attenuates the function of…; Recognition mechanism of cellooligomers by IGPs; Mutagenesis of the IGP1-cellooligomer complex; Figure legends

  3. ShownPhylogenomic analysis across 1,177 plant species traces LRR-Malectin RLKs to the ancestor of Zygnematophyceae and embryophytes, while cellooligomer-binding IGPs originated in embryophytes during plant terrestrialization and conserve the redox-sensing CC motif.

    Screening 46,929,358 protein models identified 14,636 high-confidence LRR-Malectin RLKs (earliest in Spirogloea muscicola) across clades A-D and 4,558 IGP orthologs from 1,037 species (earliest in the moss Ceratodon purpureus); among 321 structurally intact IGPs with natural CC motif variations, only ~16.7% carried D/N/E/R mutations that impair oligosaccharide sensing. · Identification of a potential conserved redox…; Origin and evolution of IGPs: structural…; Identification of LRR-malectin RLKs; Figure legends

  4. ShownIGP orthologs in wheat and soybean positively regulate resistance to fungal and oomycete pathogens, and exogenous CEL4 pretreatment confers broad-spectrum disease resistance across five plant species.

    GWAS of 349 wheat accessions linked TaIGP1 to Fusarium crown rot and leaf rust resistance (P < 10^-3), and BSMV-VIGS knockdown reduced powdery mildew resistance; RNAi co-silencing of GmIGP1/GmIGP1L/GmIGP2 (~50% knockdown) in soybean hairy roots impaired CEL4-induced ROS, MAPK, and GmPR1 expression and increased Phytophthora sojae infection, while 10 uM CEL4 protected 5 species. · IGP-cellooligomer immune modules confer…; Genome-wide association study (GWAS) assays; Soybean hairy root transformation and Phy. sojae…; Figure legends

Methods, data and reproducibility

HMMER and InterProScan screened 1,177 plant genomes to build phylogenies of 14,636 LRR-Malectin RLKs. The authors solved X-ray crystal structures of Arabidopsis IGP1^ECD (apo, CEL3-bound, CEL4-bound) and apo-IGP4^ECD, measured glycan binding via isothermal titration calorimetry, mapped C591/C592 oxidation by MAL-PEG2000 and LC-MS/MS, and tested immunity via Arabidopsis mutants, wheat GWAS/VIGS, and soybean RNAi.

  • X-ray crystal structures of Arabidopsis apo-IGP1^ECD (2.49 A), apo-IGP4^ECD (2.65 A), IGP1^ECD-CEL3 (2.74 A), and IGP1^ECD-CEL4 (2.69 A) · Arabidopsis · n = 4 crystal structures · PDB: 9WT4, 9WT5, 9WT6, 9WT7
  • Plant genomic datasets (1,177 species, 46,929,358 primary protein gene models) and de novo transcriptome assemblies (97 species) screened for LRR-Malectin RLKs and IGPs · Arabidopsis, plant (other) · n = 14,636 LRR-Malectin RLKs and 4,558 IGPs across 1,037 species
  • Chinese wheat (Triticum aestivum) panel genotyped with the Wheat 660K SNP array for Fusarium crown rot and leaf rust GWAS, plus cultivar Zhengmai9023 for BSMV-VIGS powdery mildew assays · plant (other) · n = 349 wheat accessions
  • Arabidopsis Col-0 and T-DNA mutants (igp1-2, igp2/3-2, igp4-2, igp1l-2, bak1), complementation lines, soybean (Williams, Hefeng47), tomato, and N. benthamiana immunity assays · Arabidopsis, plant (other) · n = n = 4 to 6 biological replicates per assay · SALK_016280C, SALK_144609C, SALK_005808C, SALK_203752C
Methods & tools
HMMER, InterProScan, AlphaFold 3, Iqtree, V.PhyloMaker2, muscle, FastTree, HKL2000, PHASER, COOT, Phenix, GAPIT
Reagents & environment
HMMER 3.3.2, InterProScan 5.69, Iqtree 2.4.0, muscle 5.1, FastTree 2.1.11, R 4.0.3 (ggplot2, GAPIT), PLINK 1.9, ORIGIN 7
Reproducibility gaps
Custom scripts for phylogenetic screening, GWAS, and structural modeling are not deposited in a public code repository; raw LC-MS/MS proteomics and soybean RNA-seq accessions are not listed.
Limitations (3)
  • Because BAK1/SERK co-receptors are dispensable for CEL4-triggered immunity and CEL4 does not induce IGP1^ECD homodimerization in gel filtration, the structural mechanism by which cellooligomer binding activates intracellular kinase signaling remains unresolved. · stated by the authors
  • Whether IGP receptors cross-react with chitooligosaccharides or whether LysM receptors compensate in plant lineages that lost IGP orthologs remains untested. · stated by the authors
  • How reactive oxygen species transcriptionally upregulate IGP expression and protein accumulation remains mediated by an unidentified mechanism. · stated by the authors

Who should read:Read this if you study plant pattern-triggered immunity, cell wall oligosaccharide DAMP perception, receptor-like kinase structural biology, or extracellular cysteine redox regulation.

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