Project description:The basidiomycete Ustilago maydis is the causal agent of corn smut disease and induces tumor formation during biotrophic growth in its host plant maize. The Usilago maydis genome harbors a homolog to the GATA transcription factors Nit2 and AreA that act as global regulators of nitrogen catabolite repression in filamentous model fungi Neurospora crassa and Aspergillus nidulans, respectively. We aimed at resolving the role of the Ustilago maydis Nit2 homolog for the utilization of complex nitrogen sources and pathogenicity.
Project description:• Ustilago maydis (U. maydis) is the causal agent of maize smut disease. During the colonization process, the fungus secretes effector proteins which suppress immune responses and redirect the host metabolism in favor of the pathogen. As effectors play a critical role during plant colonization, their identification and functional characterization is essential to understanding biotrophy and disease. • Using biochemical, molecular, and transcriptomic techniques, we performed a functional characterization of the U. maydis effector Jasmonate/Ethylene signaling inducer 1 (Jsi1). • Jsi1 interacts with several members of the plant co‐repressor family Topless/Topless related (TPL/TPR). Jsi1 expression in Zea mays (Z. mays) and Arabidopsis thaliana (A. thaliana) leads to transcriptional induction of the ethylene response factor (ERF) branch of the jasmonate/ethylene (JA/ET) signaling pathway. In A. thaliana, activation of the ERF‐branch leads to biotrophic susceptibility. Jsi1 likely activates the ERF‐branch via an EAR motif, which resembles EAR motifs from plant ERF transcription factors, that interacts with TPL/TPR proteins. • EAR motif‐containing effector candidates were identified from different fungal species including Magnaporthe oryzae, Sporisorium scitamineum, and Sporisorium reilianum. Interaction between plant TPL proteins and these effector candidates from biotrophic and hemibiotrophic fungi indicates the convergent evolution of effectors modulating the TPL/TPR co‐repressor hub.
Project description:The biotrophic fungal pathogen Ustilago maydis cause common smut in maize, and lead to gall formation on all aerial organs, especially on maize kernel thus reduce yield. The interaction of U. maydis with maize is a well-established model to study the interaction between maize and biotrophic pathogen. U. maydis infection could activate host immune responses including: ROS accumulation, protease activation, salicylic acid signaling. U. maydis employ several strategies to overcome maize immune response, thus initial the biotrophic interaction with host. It has been suggested that genetic factors of maize host affected the disease severity of U. maydis infection, here we investigated the transcriptome profile of resistance and susceptible maize lines upon U. maydis infection, thus propose candidate maize genes involved in the defense response in maize to corn smut cause by U. maydis.
Project description:The coding transcriptomes of filamentous cultures of the maize smut fungus Ustilago maydis and their extracellular vesicles (EVs) were compared. Protein-coding transcripts relatively enriched in EVs versus filament cells were identified and examined to identify potentially functional mRNA cargos of U. maydis EVs.
Project description:The basidiomycete Ustilago maydis is the causal agent of corn smut disease and induces tumor formation during biotrophic growth in its host plant maize. The Usilago maydis genome harbors a homolog to the GATA transcription factors Nit2 and AreA that act as global regulators of nitrogen catabolite repression in filamentous model fungi Neurospora crassa and Aspergillus nidulans. We aimed at resolving the role of the Ustilago maydis homolog Ncr1 for the utilization of complex nitrogen sources and pathogenicity. Sporidia of the indicated Ustilago maydis strains were grown overnight in ammonium minimal medium (Holliday, 1976) and samples for total RNA extraction were taken 2h after transfer to minimal medium lacking any nitrogen source (-N) during the exponential growth phase to assess those genes that are regulated in response to nitrogen starvation. The solopathogenic strain SG200 (control) and deletion mutants of (Nitrogen catabolite repression1) Ncr1 and (Target of Ncr1) Ton1, both being in the SG200 background, were studied in two independent experiments (one experiment for Ton1). Per strain and experiment, three biological replicate samples were analyzed (except for only biological replicates for Ncr1 in the second experiment).
Project description:Anthocyanin induction in plant is considered a general defense response against biotic and abiotic stresses. The infection by Ustilago maydis, the corn smut pathogen, is accompanied with anthocyanin induction in leaf tissue. We revealed that anthocyanin is intentionally induced by the virulence promoting secreted effector protein Tin2. Tin2 protein functions inside plant cells where it interacts with cytoplasmic maize protein kinase ZmTTK1. Tin2 masks an ubiquitin-proteasome degradation motif in ZmTTK1 leading to a more stable active kinase. Active ZmTTK1 controls transcriptional activation of genes in the anthocyanin biosynthesis pathway rerouting phenylalanine away from lignin biosynthesis. Therefore, we performed microarray analysis to understand how maize gene transcription in phenylpropanoid pathway is differentially changed after infection with Ustilago maydis SG200 (wild type) and SG200Dtin2 (anthocyanin-inducing effector mutant).
Project description:Ustilago maydis is a basidiomycete fungus that causes smut disease in maize. Most prominent symptoms of the disease are plant tumors, which can be induced by U. maydis on all aerial parts of the plant. We identified two linked genes, pit1 and pit2, which are specifically expressed during plant colonization. Deletion mutants for either pit1 or pit2 are unable to induce tumor development and elicit plant defense responses. We used the Affymetrix maize genome array to analyze the transcriptional responses of maize to deletion pit1 and pit2 mutants and found plant responses to both mutants being not significantly distinguishable.
Project description:Ustilago maydis is a biotrophic fungus causing corn smut disease in maize. To downregulate immune responses and promote host colonization, U. maydis secretes a set of effector proteins into the plant apoplast. An effector essential for U. maydis virulence is Pit2, an inhibitor of papain-like cysteine proteases (PLCPs). Pit2 virulence function relies on a 14 amino acids motif (PID14). While sequence of the Pit2 effector is highly diverse amongst related pathogen species, the PID14 motif is highly conserved. Interestingly, synthetic PID14 peptides act more efficiently as PLCP inhibitors than the full-length Pit2 effector. In line with this finding, mass spectrometry showed processing of Pit2 by maize PLCPs, which releases an inhibitory core motif of the PID14. Mutational analysis demonstrated that two residues of the released inhibitor peptide are essential for Pit2 function and, consequently, for U. maydis virulence. Based on these findings, we propose a model, in which the Pit2 effector functions as a decoy: Pit2 represents a favorable substrate for apoplastic PLCPs, which are central hubs of the maize immune system. Processing of Pit2 releases the inhibitor peptide, which in turn efficiently blocks PLCPs to modulate host immunity.
Project description:Ustilago maydis is a biotrophic fungus causing corn smut disease in maize. To downregulate immune responses and promote host colonization, U. maydis secretes a set of effector proteins into the plant apoplast. An effector essential for U. maydis virulence is Pit2, an inhibitor of papain-like cysteine proteases (PLCPs). Pit2 virulence function relies on a 14 amino acids motif (PID14). While sequence of the Pit2 effector is highly diverse amongst related pathogen species, the PID14 motif is highly conserved. Interestingly, synthetic PID14 peptides act more efficiently as PLCP inhibitors than the full-length Pit2 effector. In line with this finding, mass spectrometry showed processing of Pit2 by maize PLCPs, which releases an inhibitory core motif of the PID14. Mutational analysis demonstrated that two residues of the released inhibitor peptide are essential for Pit2 function and, consequently, for U. maydis virulence. Based on these findings, we propose a model, in which the Pit2 effector functions as a decoy: Pit2 represents a favorable substrate for apoplastic PLCPs, which are central hubs of the maize immune system. Processing of Pit2 releases the inhibitor peptide, which in turn efficiently blocks PLCPs to modulate host immunity.
Project description:Ustilago maydis is a biotrophic fungus causing corn smut disease in maize. To downregulate immune responses and promote host colonization, U. maydis secretes a set of effector proteins into the plant apoplast. An effector essential for U. maydis virulence is Pit2, an inhibitor of papain-like cysteine proteases (PLCPs). Pit2 virulence function relies on a 14 amino acids motif (PID14). While sequence of the Pit2 effector is highly diverse amongst related pathogen species, the PID14 motif is highly conserved. Interestingly, synthetic PID14 peptides act more efficiently as PLCP inhibitors than the full-length Pit2 effector. In line with this finding, mass spectrometry showed processing of Pit2 by maize PLCPs, which releases an inhibitory core motif of the PID14. Mutational analysis demonstrated that two residues of the released inhibitor peptide are essential for Pit2 function and, consequently, for U. maydis virulence. Based on these findings, we propose a model, in which the Pit2 effector functions as a decoy: Pit2 represents a favorable substrate for apoplastic PLCPs, which are central hubs of the maize immune system. Processing of Pit2 releases the inhibitor peptide, which in turn efficiently blocks PLCPs to modulate host immunity.