Project description:The maize smut fungi Ustilago maydis and Sporisorium reilianum are closely related and have similar genomes in terms of size and synteny. While U. maydis induces tumors locally at sites of infection, S. reilianum systemically colonizes the host and causes symptoms in the inflorescences. To investigate the genetic basis of these differences, an interspecific recombinant hybrid (rUSH) with the mating type system of S. reilianum was generated. rUSH exhibited extensive in-planta proliferation, showing a S. reilianum-like phenotype at all developmental stages except teliospore formation. Transcriptome profiling revealed that expression of pathogenicity-related effector gene orthologs was induced in rUSH, but not in a wild-type hybrid control. Multiple transcriptome comparisons identified 253 differentially expressed one-to-one effector orthologs with distinct regulatory patterns, including cis-, trans-, and rUSH-specific regulation. Functional analysis via CRISPR/Cas9 mutagenesis uncovered three novel virulence factors among the rUSH-specific regulated effectors. Ultimately, rUSH facilitated to identify the transcription factor UmHdp2 as key regulator of U. maydis-induced tumorigenesis. Together, these findings highlight the utility of a recombinant, interspecific hybrid in unraveling the molecular mechanisms underlying pathogenic differences in closely related fungal pathogens.
Project description:The maize smut fungi Ustilago maydis and Sporisorium reilianum are closely related and have similar genomes in terms of size and synteny. While U. maydis induces tumors locally at sites of infection, S. reilianum systemically colonizes the host and causes symptoms in the inflorescences. To investigate the genetic basis of these differences, an interspecific recombinant hybrid (rUSH) with the mating type system of S. reilianum was generated. rUSH exhibited extensive in-planta proliferation, showing a S. reilianum-like phenotype at all developmental stages except teliospore formation. Transcriptome profiling revealed that expression of pathogenicity-related effector gene orthologs was induced in rUSH, but not in a wild-type hybrid control. Multiple transcriptome comparisons identified 253 differentially expressed one-to-one effector orthologs with distinct regulatory patterns, including cis-, trans-, and rUSH-specific regulation. Functional analysis via CRISPR/Cas9 mutagenesis uncovered three novel virulence factors among the rUSH-specific regulated effectors. Ultimately, rUSH facilitated to identify the transcription factor UmHdp2 as key regulator of U. maydis-induced tumorigenesis. Together, these findings highlight the utility of a recombinant, interspecific hybrid in unraveling the molecular mechanisms underlying pathogenic differences in closely related fungal pathogens.
Project description:Dimorphic fungi have the ability to change morphology during their lifecycle, a crucial feature for the establishment of infection and fungal growth and development in planta. Life cycle of the dimorphic sugarcane smut fungi, Sporisorium scitamineum, involves recognition and mating of compatible saprophytic yeast-like haploid sporidia (MAT-1 and MAT-2) that upon fusion, develop into infective dikaryotic mycelia. Although the dimorphic transition is intrinsically linked with the pathogenicity and virulence of S. scitamineum, it has never been studied using a proteomics approach. In the present study, an iTRAQ-based comparative proteomic analysis of three distinct stages covering the dimorphic transition period - haploid sporidial stage (MAT-1 and MAT-2) to the transition phase (24 hours post co-culturing (hpc)) and dikaryotic mycelial stage (48 hpc) was carried out. Functional categorization showed that the most altered biological processes were energy production, primary metabolism especially carbohydrate, amino acid, fatty acid, followed by translation, post-translation and protein turnover. The identified proteins could be grouped into 8 distinct clusters with different trends in abundance. Enrichment analysis of the clusters showed that biological processes related to energy production through oxidative phosphorylation, citrate cycle, and β-oxidation, transcription, translation and redox homeostasis were specifically altered. In addition, an overall downregulation of carbohydrate metabolism and reprogrammed amino acid metabolism were observed. Several differentially abundant proteins (DAPs), especially in the dikaryotic mycelial stage were predicted as effectors. Taken together, key molecular mechanisms underpinning the dimorphic transition in S. scitamineum at the proteome level were highlighted. A catalogue of stage-specific and dimorphic transition-associated -proteins and potential effectors identified herein are potential candidates for defective mutant screening to elucidate their functional role in the dimorphic transition and pathogenicity in S. scitamineum.
Project description:In opportunistic human pathogenic fungi, changes in gene expression play a crucial role in the evolution of growth stages from early spore germination through host infection. Comparative transcriptomics from diverse fungal pathogens along closely related non-pathogenic model provided insights of regulatory mechanisms behind the initiation of infectious processes by different fungi. We examined the gene expression patterns of 3,845 single-copy orthologous genes (SCOGs) across five phylogenetically distinct species, including the opportunistic human pathogens Fusarium oxysporum, Aspergillus fumigatus, and A. nidulans, and nonpathogenic species Neurospora crassa and Trichoderma asperelloides, at four sequential stages spore germination.