Reversible phosphorylation of a lectin-receptor-like kinase controls xylem immunity

Between Host and Invaders: The Subcellular Cell Wall Dynamics at the Plant-Pathogen Interface

Plant-pathogen interactions have profound ecological implications and are crucial for food security. Usually studied at the two extreme scales of plant organ symptomatology and host-microbe molecules, they are a cell-cell event mainly occurring at the subcellular level of the plant apoplast. Here, the cell walls of both organisms suffer an intense alteration as a consequence of active degradation by the opponent and self-protection mechanisms to survive and continue growing. The plant cell wall modifications and their role in defense as danger signals and activators of signaling cascades have been studied for a few decades, mainly at the organ plane. Still, much remains unknown about this process, including cellular and subcellular minority decorations, proteins, and mechanical cues. Comparatively, the microbial cell wall changes in planta are virtually unexplored. By investigating the interface between plant and microbial cell walls biochemically, structurally, and mechanically, we aim to highlight the dynamic interplay in these subcellular areas and its significance for the host-invader interaction.

Control of H2S synthesis by the monomer-oligomer transition of OsCBSX3 for modulating rice growth-immunity balance

Hydrogen sulfide (H2S) is recognized as an important gaseous signaling molecule, similar to nitric oxide and carbon monoxide. However, less is known about the biosynthetic mechanism of H2S in plants and its role in plant-pathogen interactions. Here, we show that H2S induces the bursts of reactive oxygen species and upregulates the expression of defense-related genes in rice. However, excessive H2S concentrations inhibit rice growth. We found that the cystathionine β-synthase OsCBSX3 regulates rice growth and resistance to bacteria pathogens, Xanthomonas oryzae pv. oryzicola (Xoc) and X. oryzae pv. oryzae (Xoo), by modulating H2S biosynthesis. OsCBSX3 exists in both oligomeric and monomeric forms in rice. Compared with wild-type OsCBSX3, an oligomerization-disrupted mutant exhibits the reduced capacity for H2S synthesis, diminished resistance to X. oryzae, and inability to localize to the chloroplast. Upon pathogen infection, rice triggers PsbO-dependent oligomerization of OsCBSX3, leading to increased H2S production and enhanced defense responses. However, excessive concentrations of H2S reduce the oligomerized form of OsCBSX3, facilitating its dissociation from PsbO, an important subunit of photosystem II, and its binding to OsTrxZ, a member of the thioredoxin family. We further demonstrated that OsTrxZ can directly convert OsCBSX3 into monomers, thereby mitigating the excessive H2S synthesis and its negative effects on rice growth and development. Overexpression of PsbO enhances rice resistance to both Xoc and Xoo, whereas overexpression of OsTrxZ exerts the opposite effect. Taken together, these findings suggest that PsbO and OsTrxZ antagonistically modulate the interconversion between oligomeric and monomeric forms of OsCBSX3, thereby balancing rice resistance and developmental processes.

PP2C Phosphatase Pic6 Suppresses MAPK Activation and Disease Resistance in Tomato

Type 2C protein phosphatases (PP2Cs) are essential for regulating plant immune responses to pathogens. Our study focuses on the tomato PP2C-immunity associated candidate 6 (Pic6), elucidating its role in negatively regulating pattern-triggered immunity (PTI) signaling pathways in tomato. Using reverse-transcription quantitative polymerase chain reaction (RT-qPCR), we observed that treatment with microbe-associated molecular patterns (MAMPs)-flg22 and flgII-28-significantly increased Pic6 mRNA levels in wild-type (RG-PtoR) tomato plants. Pic6 features a conserved N-terminal kinase-interacting motif (KIM) and a C-terminal PP2C domain. We produced variants of Pic6 with mutations in these regions, demonstrating their involvements in negatively regulating tomato immunity. Agrobacterium-mediated transient overexpression of Pic6 resulted in enhanced growth of the bacterial pathogen Pseudomonas syringae pathovar tomato (Pst) strain DC3000ΔhopQ1-1 compared with a yellow fluorescent protein (YFP) control. Additionally, Pic6 overexpression inhibited mitogen-activated protein kinase (MAPK) activation in response to flg22 and flgII-28 treatments. Importantly, Pic6 exhibited phosphatase activity and interacted with tomato Mkk1/Mkk2 proteins and dephosphorylated them in a KIM-dependent manner. Furthermore, we generated RG-pic6 loss-of-function mutants by CRISPR/Cas9, revealing that the absence of Pic6 heightened MAPK activity and increased resistance to Xanthomonas euvesicatoria strain 85-10 (Xe 85-10) when compared with the wild-type (RG-PtoR) plants. Transcript analyses showed that after flg22/flgII-28 treatment, PTI-reporter genes NAC and Osmotin were significantly upregulated in RG-pic6 mutants in comparison to the wild-type (RG-PtoR) plants. Overall, our findings indicate that Pic6 acts as a negative regulator of MAPK signaling and plays a pivotal role in modulating tomato immunity against bacterial pathogens. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

The miR172a-SNB module orchestrates both induced and adult-plant resistance to multiple diseases via MYB30-mediated lignin accumulation in rice

Plants mount induced resistance and adult-plant resistance against different pathogens throughout the whole growth period. Rice production faces threats from multiple major diseases, including rice blast, sheath blight, and bacterial leaf blight. Here, we report that the miR172a-SNB-MYB30 module regulates both induced and adult-plant resistance to these three major diseases via lignification in rice. Mechanistically, pathogen infections induce the expression of miR172a, which downregulates the transcription factor SNB to release its suppression of MYB30, leading to an increase in lignin biosynthesis and disease resistance throughout the whole growth period. Moreover, expression levels of miR172a and MYB30 gradually increase and are consistently correlated with lignin contents and disease resistance during rice development, reaching a peak at full maturity, whereas SNB RNA levels are negatively correlated with lignin contents and disease resistance, indicating the involvement of the miR172a-SNB-MYB30 module in adult-plant resistance. The functional domain of SNB protein and its binding sites in the MYB30 promoter are highly conserved among more than 4000 rice accessions, while abnormal expression of miR172a, SNB, or MYB30 compromises yield traits, suggesting artificial selection of the miR172a-SNB-MYB30 module during rice domestication. Taken together, these results reveal a novel role for a conserved miRNA-regulated module that contributes significantly to induced and adult-plant resistance against multiple pathogens by increasing lignin accumulation, deepening our understanding of broad-spectrum resistance and adult-plant resistance.

Engineering a conserved immune coreceptor into a primed state enhances fungal resistance in crops without growth penalty

Plants must tactically balance immunity and growth when combating lethal pathogens like fungi. CHITIN ELICITOR RECEPTOR KINASE 1 (CERK1), a conserved cell-surface co-receptor for the fungal elicitor chitin, enables plants to induce chitin-triggered immunity to counteract fungal invasion. Previously, we reported that bacterial infection can prime CERK1 through juxtamembrane (JM) phosphorylation to enhance fungal resistance, which only occurs in Arabidopsis (Arabidopsis thaliana) and its close relatives in Brassicaceae. Here, we aim to transfer the priming mechanism of Arabidopsis CERK1 (AtCERK1) to crop CERK1 via JM substitution. We revealed in protoplasts that the entire AtCERK1 JM variable region (AtJM) is essential for imparting the bacterial elicitor flg22-induced primed state to the Nicotiana benthamiana CERK1 (NbCERK1). The NbCERK1 chimera containing AtJM (NbCERK1AtJM) and similarly constructed rice (Oryza sativa) OsCERK1AtJM could undergo flg22-induced JM phosphorylation and confer enhanced antifungal immunity upon bacterial coinfection. Moreover, the NbCERK1AtJM+3D derivative with AtJM phosphomimetic mutations to mimic a constant primed state and similarly constructed OsCERK1AtJM+3D were sufficient to mediate strengthened chitin responses and fungal resistance in transgenic plants independent of bacterial infection. Importantly, no growth and reproduction defects were observed in these plants. Taken together, this study demonstrates that manipulating the primed state of a cell-surface immune receptor offers an effective approach to improve disease resistance in crops without compromising growth and yield and showcases how fundamental insights in plant biology can be translated into crop breeding applications.

Natural variations of maize ZmLecRK1 determine its interaction with ZmBAK1 and resistance patterns to multiple pathogens

Maize (Zea mays) is one of the most important crops in the world, but its yield and quality are seriously affected by diverse diseases. Identifying broad-spectrum resistance genes is crucial for developing effective strategies to control the disease in maize. In a genome-wide study in maize, we identified a G-type lectin receptor kinase ZmLecRK1, as a new resistance protein against Pythium aphanidermatum, one of the causal pathogens of stalk rot in maize. Genetic analysis showed that the specific ZmLecRK1 allele can confer resistance to multiple pathogens in maize. The cell death and disease resistance phenotype mediated by the resistant variant of ZmLecRK1 requires the co-receptor ZmBAK1. A naturally occurring A404S variant in the extracellular domain of ZmLecRK1 determines the ZmLecRK1-ZmBAK1 interaction and the formation of ZmLecRK1-related protein complexes. Interestingly, the ZmLecRK1 susceptible variant was found to possess the amino acid S404 that is present in the ancestral variants of ZmLecRK1 and conserved among the majority of grass species, while the resistance variant of ZmLecRK1 with A404 is only present in a few maize inbred lines. Substitution of S by A at position 404 in ZmLecRK1-like proteins of sorghum and rice greatly enhances their ability to induce cell death. Further transcriptomic analysis reveals that ZmLecRK1 likely regulates gene expression related to the pathways in cell wall organization or biogenesis in response to pathogen infection. Taken together, these results suggest that the ZmLecRK1 resistance variant enhances its binding affinity to the co-receptor ZmBAK1, thereby enhancing the formation of active complexes for defense in maize. Our work highlights the biotechnological potential for generating disease-resistant crops by precisely modulating the activity of ZmLecRK1 and its homologs through targeted base editing.

Role of ROS signaling in the plant defense against vascular pathogens

Reactive oxygen species (ROS) is a collective term for highly reactive oxygen derivatives, including singlet oxygen, hydroxyl radicals, superoxide anions, and hydrogen peroxide. In plants, ROS are produced in apoplasts, chloroplasts, mitochondria, and peroxisomes. Although ROS are toxic when their levels exceed a certain threshold, low-concentration ROS can serve as essential signaling molecules for plant growth and development, as well as plant responses to abiotic and biotic stresses. Various aspects of the role of ROS in plants have been discussed in previous reviews. In this review, we first summarize recent progress in the regulatory mechanisms of apoplastic ROS signaling and then propose its potential roles in plant defense against vascular pathogens to provide new ideas for the prevention and control of vascular diseases.

Cross-family transfer of the Arabidopsis cell-surface immune receptor LORE to tomato confers sensing of 3-hydroxylated fatty acids and enhanced disease resistance

Plant pathogens pose a high risk of yield losses and threaten food security. Technological and scientific advances have improved our understanding of the molecular processes underlying host-pathogen interactions, which paves the way for new strategies in crop disease management beyond the limits of conventional breeding. Cross-family transfer of immune receptor genes is one such strategy that takes advantage of common plant immune signalling pathways to improve disease resistance in crops. Sensing of microbe- or host damage-associated molecular patterns (MAMPs/DAMPs) by plasma membrane-resident pattern recognition receptors (PRR) activates pattern-triggered immunity (PTI) and restricts the spread of a broad spectrum of pathogens in the host plant. In the model plant Arabidopsis thaliana, the S-domain receptor-like kinase LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION (AtLORE, SD1-29) functions as a PRR, which senses medium-chain-length 3-hydroxylated fatty acids (mc-3-OH-FAs), such as 3-OH-C10:0, and 3-hydroxyalkanoates (HAAs) of microbial origin to activate PTI. In this study, we show that ectopic expression of the Brassicaceae-specific PRR AtLORE in the solanaceous crop species Solanum lycopersicum leads to the gain of 3-OH-C10:0 immune sensing without altering plant development. AtLORE-transgenic tomato shows enhanced resistance against Pseudomonas syringae pv. tomato DC3000 and Alternaria solani NL03003. Applying 3-OH-C10:0 to the soil before infection induces resistance against the oomycete pathogen Phytophthora infestans Pi100 and further enhances resistance to A. solani NL03003. Our study proposes a potential application of AtLORE-transgenic crop plants and mc-3-OH-FAs as resistance-inducing biostimulants in disease management.

LORE receptor homomerization is required for 3-hydroxydecanoic acid-induced immune signaling and determines the natural variation of immunosensitivity within the Arabidopsis genus

The S-domain-type receptor-like kinase (SD-RLK) LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION (LORE) from Arabidopsis thaliana is a pattern recognition receptor that senses medium-chain 3-hydroxy fatty acids, such as 3-hydroxydecanoic acid (3-OH-C10:0), to activate pattern-triggered immunity. Here, we show that LORE homomerization is required to activate 3-OH-C10:0-induced immune signaling. Fluorescence lifetime imaging in Nicotiana benthamiana demonstrates that AtLORE homomerizes via the extracellular and transmembrane domains. Co-expression of AtLORE truncations lacking the intracellular domain exerts a dominant negative effect on AtLORE signaling in both N. benthamiana and A. thaliana, highlighting that homomerization is essential for signaling. Screening for 3-OH-C10:0-induced reactive oxygen species production revealed natural variation within the Arabidopsis genus. Arabidopsis lyrata and Arabidopsis halleri do not respond to 3-OH-C10:0, although both possess a putative LORE ortholog. Both LORE orthologs have defective extracellular domains that bind 3-OH-C10:0 to a similar level as AtLORE, but lack the ability to homomerize. Thus, ligand binding is independent of LORE homomerization. Analysis of AtLORE and AlyrLORE chimera suggests that the loss of AlyrLORE homomerization is caused by several amino acid polymorphisms across the extracellular domain. Our findings shed light on the activation mechanism of LORE and the loss of 3-OH-C10:0 perception within the Arabidopsis genus.

Walking down the phosphorylation path to root immunity

Pathogen perception in plant roots is under-explored compared to that in shoots. In this issue of Cell Host & Microbe, Wang et al. characterize the phosphorylation-mediated signaling pathway that positively and negatively regulates plant resistance to bacterial wilt disease upon perception of a metabolite from the soil-borne vascular pathogen Ralstonia solanacearum.