Biology subjects

Langen, G.

Publications and source records attributed to Langen, G..

10 recordsLinked to original sources

bioRxiv2026

A fungal effector hijacks conserved plant GSK3-like kinases to reprogram host cell identity

Stable developmental programs normally resist reprogramming, yet pathogens can override these constraints to induce profound tissue and cellular remodeling. How microbial pathogens access conserved developmental signaling networks to reprogram host growth and differentiation remains poorly understood. Here, we show that the maize smut fungus Ustilago maydis deploys the effector Iag1 to reprogram host cell fate by targeting the conserved GSK3-like kinase BIN2. Iag1 contains a PPNT short interaction motif found also in plant viral effectors that mediates its association with BIN2 and related maize GSK3-like kinases and is essential for effector activity and full fungal virulence. This interaction attenuates BIN2-dependent signaling, reduces phosphorylation of the BIN2 substrate BES1, and triggers extensive transcriptional reprogramming consistent with coordinated perturbation of brassinosteroid, auxin, and other BIN2-regulated developmental pathways. These changes result in extensive epidermal developmental reprogramming, including loss of stomatal identity, altered cell division orientation, and aberrant cell expansion. Together, our findings identify GSK3-like kinases as conserved developmental signaling hubs that pathogens can exploit to unlock host developmental plasticity and suggest that short motifs provide an evolutionarily flexible strategy for targeting these central regulatory nodes.

plant biology↗

bioRxiv2026

Low intra-microbiota antagonism underlies stable and protective barley root microbiota

Plants rely on root-associated microbiota for growth and pathogen protection, yet the community properties underlying stable beneficial functions remain unclear. Here, we show that low intra-microbiota antagonism is associated with stability and pathogen protection in the barley root microbiota. Using a comprehensive culture collection of barley root endophytes, we reconstructed bacterial synthetic communities (SynComs) and compared a core SynCom resembling the natural microbiota with a trait-prioritized SynCom assembled from strains selected for predicted host benefits. Although strains from both communities exhibited broad pathogen-inhibitory potential, the communities behaved differently in planta. The core SynCom showed low internal antagonism, remained stable, and protected barley roots against fungal pathogens without impairing growth. In contrast, the trait-prioritized SynCom exhibited strong internal antagonism, unstable assembly, loss of protection, and reduced root growth. Together, our findings indicate that microbiota function cannot be predicted from individual strain traits alone. Rather, low intra-microbiota antagonism promotes community stability and enables protective functions to emerge in barley roots. Significance statementPlants rely on root microbiota for disease protection, yet the principles governing community stability and protective function remain poorly understood. Here, we show that low intra-microbiota antagonism is associated with a stable and protective barley root microbiota, whereas strong internal antagonism destabilizes communities, impairs root growth, and abolishes pathogen protection. These findings show that microbiota function depends not only on beneficial traits of individual strains, but also on compatibility among community members. HighlightsO_LILow intra-microbiota antagonism is associated with stable and protective barley root microbiota. C_LIO_LITrait-prioritized SynCom assembly with higher intra-microbiota antagonism can lead to dysbiosis. C_LIO_LIA highly antagonistic Pseudomonas strain is buffered by the core SynCom but detrimental in an unstable community. C_LIO_LICommunity compatibility better explains protection than individual strain traits. C_LIO_LIStable bacterial communities support fungal endophyte-mediated protection and maintain pathogen protection across barley genotypes. C_LI

plant biology↗

bioRxiv2026

Prion-like domains control plastid targeting of PEPSI effectors and PEPSI6-mediated modulation of DXR during root symbiosis

Microbial effectors often act in the apoplast or cytosol, but how they reach host organelles during beneficial plant-fungal interactions remains poorly understood. Here, we identify a class of secreted prion-like effector proteins from the mutualistic root endophyte Serendipita indica, termed PEPSIs. These proteins contain prion-like domains (PrLDs) embedded within intrinsically disordered regions, and three tested PEPSIs require these domains for plastid localization. Focusing on PEPSI6, we show that plastid targeting depends on its PrLD and is associated with engagement of plastid import and proteostasis machinery. In plastids, PEPSI6 associates with 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR), promotes DXR accumulation, alters methylerythritol phosphate pathway metabolites, and enhances tolerance to the DXR inhibitor fosmidomycin. PEPSI6 also undergoes apoplastic C-terminal CAP-domain processing, and its colonization-promoting activity persists after PrLD deletion, indicating a plastid-targeting-independent function. Overall, this work identifies PrLDs as noncanonical plastid-targeting elements in PEPSI effectors and reveals DXR as a target of fungal manipulation during root symbiosis. HighlightsO_LIPrion-like domains control plastid targeting of selected PEPSI effectors. C_LIO_LIPEPSI6 associates with DXR and promotes its accumulation in plastids. C_LIO_LIPEPSI6 alters MEP-pathway metabolites and increases tolerance to fosmidomycin. C_LIO_LIApoplastic processing reveals a plastid-independent PEPSI6 activity during root symbiosis. C_LI

plant biology↗

bioRxiv2026

The transcription factor SiROCX controls a monocot-specific CAZyme program for host cell wall remodeling during symbiotic root colonization

Intracellular accommodation of beneficial fungi requires controlled remodeling of host cell walls while avoiding activation of plant immune responses. During colonization of monocot roots, the endophytic fungus Serendipita indica induces a suite of carbohydrate-active enzymes (CAZymes) targeting xylan and cellulose. Weighted gene co-expression network analysis identified the basidiomycete-specific transcription factor SiROCX as a key regulator of this monocot-adapted program. DNA affinity purification sequencing (DAP-seq) defined the SiROCX binding motif and revealed a CAZyme-enriched target regulon. Inducible SiROCX overexpression selectively activated motif-containing CAZyme genes and markedly enhanced xylanase and cellulase activities on xylan and native barley root cell walls. Premature activation of this program triggered expression of a plant immune marker despite comparable fungal biomass, indicating that precise temporal control of CAZyme deployment is required to maintain symbiotic compatibility. Together, these findings identify SiROCX as a central regulator of a monocot-adapted cell wall-degrading secretome and reveal a basidiomycete-specific regulatory module that coordinates host cell wall remodeling with immune-compatible symbiotic colonization. SignificanceBeneficial fungi colonize living plant cells, requiring host cell wall remodeling while avoiding immune activation. However, the key transcriptional regulators coordinating this process in basidiomycetes during symbiotic root colonization remain unknown. We identify SiROCX, a conserved basidiomycete-specific transcription factor, as a master activator of a monocot-adapted xylan/cellulose degradation program in the root endophyte Serendipita indica. By integrating in planta co-expression networks, DAP-seq, secretome proteomics, and enzymatic assays, we show that SiROCX overexpression markedly enhances secretion and activity of xylan- and cellulose-degrading enzymes, boosting sugar release from monocot cell walls. These findings reveal a basidiomycete-specific regulatory module for immune-compatible host cell wall remodeling, providing a framework to engineer fungal CAZyme programs for crop symbiosis and biomass conversion.

microbiology↗

bioRxiv2025

A fungal root endophyte functionally complements host immunity and mitigates natural immune variation in Arabidopsis

Beneficial root-associated microbes can enhance plant resilience by complementing aspects of host immunity. The fungal root endophyte Serendipita indica (Si) is known to promote plant growth and confer broad stress tolerance. To assess how natural host genetic variation influences Si-mediated protection, we screened 47 Arabidopsis thaliana accessions for susceptibility to the fungal pathogen Bipolaris sorokiniana (Bs) with and without Si colonization. All accessions benefited from Si, indicating that endophyte-mediated disease mitigation occurs broadly across diverse host genotypes. A focused comparison of two genetically and geographically proximate Swedish accessions, T510 and T530, which displayed the most divergent protection scores, revealed substantial differences in Bs susceptibility. Transcriptome profiling under bi- and tripartite colonization showed conserved defense responses in both accessions. Bs infection downregulated growth- and development-related genes, consistent with a growth-immunity trade-off, with T530 exhibiting higher Bs colonization and a stronger transcriptional response than T510. Co-colonization with Si effectively suppressed pathogen growth and disease symptoms in both accessions. Comparative genomic and transcriptomic analyses identified four immune receptor genes, including the TIR-NLR ISI, present in T510 but absent in T530. An isi T-DNA insertion mutant phenocopied the heightened Bs susceptibility of T530, confirming that ISI contributes to root immunity, while Si-mediated protection remained intact despite increased pathogen susceptibility. Together, these findings demonstrate that fungal endophytes can mitigate the functional consequences of natural immune variation and enhance the resilience of genetically diverse plant populations. HighlightsO_LIS. indica confers broad protection against B. sorokiniana largely independent of host genotype or pathogen susceptibility. C_LIO_LIThe TIR-NLR immune receptor ISI contributes to root immunity but is not essential for S. indica-mediated protection. C_LIO_LIBeneficial endophytes can mitigate natural immune variation effects and support overall plant health. C_LI

ecology↗

bioRxiv2023

Time-resolved transcriptomics reveal a mechanism of host niche defense: beneficial root endophytes deploy a host-protective antimicrobial GH18-CBM5 chitinase

Associations between plants and beneficial root-endophytic fungi enhance plant performance by improving nutrient uptake, abiotic stress tolerance and disease resistance. To successfully colonize different host plants and defend their host niche against competing microbes, but also to cooperate with beneficial bacterial members of the microbiota, root endophytes such as Sebacinales secrete a multitude of tightly regulated effector-proteins and carbohydrate-active enzymes. However, the functions, specificity, and regulation of these proteins remain poorly understood. In this study, we employ time-resolved transcriptomics to analyse the gene expression profiles of two Sebacinales members interacting with organisms from different kingdoms of life. We identified crucial genes for plant colonization and intermicrobial competition, including a fungal GH18-CBM5 chitinase specifically upregulated in response to the phytopathogenic fungus Bipolaris sorokiniana. This chitinase protects the plant hosts against the pathogen, reducing fungal biomass and disease symptoms in barley and Arabidopsis thaliana. Our findings shed light on interaction partner specific gene expression in Sebacinales endophytes, with potential applications in enhancing plant health and resilience. Bullet pointsO_LIBoth Serendipita indica (Si) and Serendipita vermifera (Sv) show similar transcriptional responses to three host species and the phytopathogen Bipolaris sorokiniana (Bs), indicating common interaction principles between Sebacinales and plant hosts or fungi. C_LIO_LIThese shared mechanisms involve the activation of effector genes like small secreted proteins and carbohydrate-active enzymes. C_LIO_LICooperation with beneficial bacteria elicits only minimal transcriptomic alterations in Sebacinales compared to plants and Bs. C_LIO_LISebacinales respond to Bs by upregulating a specific GH18-CBM5 chitinase unique to Basidiomycota within the fungal kingdom, inhibiting Bs growth and reducing disease symptoms in Arabidopsis thaliana and barley. C_LI

microbiology↗

bioRxiv2023

Autophagy restricts fungal accommodation in the roots ofArabidopsis thaliana

Endophytic colonization of Arabidopsis thaliana by the beneficial root endophyte Serendipita indica is characterized by an initial biotrophic phase followed by a restricted host cell death-associated phase. This latter phase involves regulated cell death (RCD) for fungal accommodation. However, the host molecular pathways that limit S. indica colonization and govern symbiosis remain largely unknown. Our study demonstrates that autophagy, a major cellular degradation pathway, is activated during S. indica colonization and is required to restrict fungal colonization in Arabidopsis. Independent Arabidopsis knockout (KO) mutants deficient in autophagosome formation are more susceptible to deoxyadenosine (dAdo), a cell death inducer produced by two secreted S. indica effectors at the onset of the cell death-associated phase. In the atg5 autophagy mutant background, impaired dAdo uptake prevents dAdo-induced and symbiosis-mediated cell death. Based on our data, we propose that autophagy-mediated pro-survival responses in the host are crucial for maintaining a balanced symbiotic interaction between S. indica and Arabidopsis. In a NutshellOur study reveals that during colonization of Arabidopsis thaliana roots by the beneficial root endophyte Serendipita indica, autophagy, a key cellular degradation pathway, is activated to limit fungal colonization. Autophagy-deficient Arabidopsis mutants are more susceptible to deoxyadenosine (dAdo), a cell death inducer produced by S. indica. We propose that autophagy-mediated pro-survival responses are essential for maintaining a balanced symbiotic interaction between S. indica and Arabidopsis.

microbiology↗

bioRxiv2022

A fungal endophyte-generated nucleoside signal regulates host cell death and promotes root colonization

The intracellular colonization of plant roots by the beneficial fungal endophyte Serendipita indica follows a biphasic strategy. After an early biotrophic phase, the interaction transitions to a host cell death phase restricted to the epidermal and cortex layers of the root. Host cell death contributes to the successful accommodation of the fungus during the beneficial interaction in Arabidopsis thaliana. How host cell death is initiated and controlled is largely unknown. Here we show that two fungal enzymes, the ecto-5-nucleotidase SiE5NT and the nuclease SiNucA, act synergistically in the plant apoplast at the onset of cell death to produce deoxyadenosine (dAdo), a potent cell death inducer in animal systems. The uptake of extracellular dAdo, but not the structurally related adenosine (Ado), activates a previously undescribed cell death mechanism in A. thaliana. Mutation of the equilibrative nucleoside transporter ENT3 in A. thaliana results in resistance to cell death triggered by extracellular dAdo and reduced fungal-mediated cell death during root colonization. A library screen of A. thaliana T-DNA insertion lines identified a toll/interleukin-1 receptor nucleotide-binding leucine-rich repeat (TIR-NLR) protein as an additional intracellular component in dAdo-triggered cell death. Mutation of this previously uncharacterised TIR-NLR, which we have named ISI (induced by S. indica), affects host cell death, fungal colonization and growth promotion, suggesting a key role in the regulation of root cell death and plant-microbe interaction. Our data show that the combined activity of two fungal apoplastic enzymes leads to the production of a metabolite that, upon uptake, triggers TIR-NLR-modulated plant cell death, providing a link to immunometabolism in plants. Short summaryEfficient intraradical colonization by the beneficial fungal endophyte Serendipita indica requires restricted host cell death. How this symbiotic host cell death is initiated and controlled is largely unknown. Here we show that two fungal enzymes, the ecto-5-nucleotidase SiE5NT and the nuclease SiNucA, act synergistically in the apoplast at the onset of cell death to produce deoxyadenosine (dAdo), a potent cell death inducer in animal systems. Uptake of extracellular dAdo activates a previously undescribed cell death mechanism in plants. Mutation of the A. thaliana equilibrative nucleoside transporter ENT3 leads to resistance to cell death triggered by uptake of extracellular dAdo and to reduced fungal-mediated cell death during colonization. A library screen of A. thaliana T-DNA insertion lines identified a TIR-NLR protein as an additional intracellular component in dAdo-triggered cell death, providing a link to immunometabolism in plants. In a nutshellRegulated host cell death is part of the plant defense strategy against pathogens, but it is also involved in the accommodation of certain beneficial microbes in the roots. We have identified extracellular metabolites and intracellular metabolic signals that contribute to colonization by beneficial root fungal endophytes and uncovered a conserved cell death mechanism likely co-opted for establishing plant-endophyte symbiosis.

plant biology↗

bioRxiv2021

The fungal root endophyte Serendipita vermifera displays inter-kingdom synergistic beneficial effects with the microbiota in Arabidopsis thaliana and barley

Plant root-associated bacteria can confer protection against pathogen infection. By contrast, the beneficial effects of root endophytic fungi and their synergistic interactions with bacteria remain poorly defined. We demonstrate that the combined action of a fungal root endophyte from a widespread taxon with core bacterial microbiota members provides synergistic protection against an aggressive soil-borne pathogen in Arabidopsis thaliana and barley. We additionally show early inter-kingdom growth promotion benefits which are host and microbiota composition dependent. HighlightsO_LIThe root endophytic fungus Serendipita vermifera can functionally replace core bacterial microbiota members in mitigating pathogen infection and disease symptoms. C_LIO_LIS. vermifera additionally stabilizes and potentiates the protective activities of root-associated bacteria and mitigates the negative effects of a non-native bacterial community in A. thaliana. C_LIO_LIInter-kingdom synergistic beneficial effects do not require extensive host transcriptional reprogramming nor high levels of S. vermifera colonisation. C_LIO_LIInter-kingdom protective benefits are largely independent of the host while synergism leading to early inter-kingdom growth promotion is driven by host species and microbiota composition. C_LI

plant biology↗

bioRxiv2018

The fungal root endophyte Serendipita indica modifies extracellular nucleotides to subvert plant immunity

One sentence abstractImmune modulation by metabolites in plant fungus interaction\n\nAbstractExtracellular adenosine 5'-triphosphate (eATP) is an essential signaling molecule that mediates different cellular processes through its interaction with membrane-associated receptor proteins in animals and plants. eATP regulates plant growth, development and responses to biotic and abiotic stresses. Its accumulation in the apoplast induces ROS production and cytoplasmic calcium increase mediating a defense response to invading microbes. We demonstrate that perception of eATP is important in plant-fungus interaction and that during colonization by the beneficial root endophyte Serendipita indica accumulation of eATP in the apoplast occurs at early symbiotic stages. We show by liquid chromatography-tandem mass spectrometry, cytological and functional analysis that S. indica subvert eATP host response by secreting SiE5NT, an enzymatically active ecto-5'nucleotidase capable of hydrolyzing eATP to adenosine. A. thaliana lines producing extracellular SiE5NT are signi?cantly better colonized and have reduced eATP levels and defense signaling, indicating that SiE5NT functions as a compatibility factor. Our data show that extracellular bioactive nucleotides play an important role in fungus-root interactions and that fungi can modify plant derived metabolites in the apoplast to modulate host immunity.

plant biology↗