Pathogenic Development in Ustilago maydis A Progression of Morphological Transitions That Results in Tumor Formation and Teliospore Production

The PTEN/PI3K/mTOR signal transduction pathway is involved in the regulation of biological processes such as metabolism, cell growth, cell proliferation, and apoptosis. This pathway has been extensively studied in mammals, leading to the conclusion that PTEN is a major tumor suppressor gene. PTEN orthologues have been characterized in a variety of organisms, both vertebrates and non-vertebrates, and studies of the associated PTEN/PI3K/mTOR pathway indicate that it is widely conserved. Studies in fungal systems indicated a role of PTEN in fungal defense mechanisms in Candida albicans, and in the developmental process of sporulation in Saccharomyces cerevisiae. The present study was aimed at investigating the role of the PTEN ortholog, ptn1, in Ustilago maydis, the pathogen of maize. U. maydis ptn1 mutant strains where ptn1 gene is deleted or overexpressed were examined for phenotypes associate with mating, virulence and spore formation. While the overexpression of ptn1 had no substantial effects on virulence, ptn1 deletion strains showed slight reductions in mating efficiency and significant reductions in virulence; tumor formation on stem and/or leaves were severely reduced. Moreover, tumors, when present, had significantly lower levels of mature teliospores, and the percent germination of such spores was similarly reduced. Thus, ptn1 is required for these important aspects of virulence in this fungus.

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Cell type specific transcriptional reprogramming of maize leaves during Ustilago maydis induced tumor formation

10.1101/552562 ◽

2019 ◽

Author(s):

Mitzi Villajuana-Bonequi ◽

Alexandra Matei ◽

Corinna Ernst ◽

Asis Hallab ◽

Björn Usadel ◽

...

Keyword(s):

Cell Division ◽

Genetic Model ◽

Ustilago Maydis ◽

Tumor Formation ◽

Bundle Sheath ◽

Cell Type ◽

Transcriptional Reprogramming ◽

Maize Leaves ◽

Maize Cell ◽

Cell Type Specific

SummaryUstilago maydis is a biotrophic pathogen and well-established genetic model to understand the molecular basis of biotrophic interactions. U. maydis suppresses plant defense and induces tumors on all aerial parts of its host plant maize. In a previous study we found that U. maydis induced leaf tumor formation builds on two major processes: the induction of hypertrophy in the mesophyll and the induction of cell division (hyperplasia) in the bundle sheath. In this study we analyzed the cell-type specific transcriptome of maize leaves 4 days post infection. This analysis allowed identification of key features underlying the hypertrophic and hyperplasic cell identities derived from mesophyll and bundle sheath cells, respectively. We examined the differentially expressed (DE) genes with particular focus on maize cell cycle genes and found that three A-type cyclins, one B-, D- and T-type are upregulated in the hyperplasic tumorous cells, in which the U. maydis effector protein See1 promotes cell division. Additionally, most of the proteins involved in the formation of the pre-replication complex (pre-RC, that assure that each daughter cell receives identic DNA copies), the transcription factors E2Fand DPa as well as several D-type cyclins are deregulated in the hypertrophic cells.

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Dissecting Defense-Related and Developmental Transcriptional Responses of Maize during Ustilago maydis Infection and Subsequent Tumor Formation

PLANT PHYSIOLOGY ◽

10.1104/pp.105.061200 ◽

2005 ◽

Vol 138 (3) ◽

pp. 1774-1784 ◽

Cited By ~ 69

Author(s):

Christoph W. Basse

Keyword(s):

Ustilago Maydis ◽

Tumor Formation ◽

Transcriptional Responses

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Identification of cis-Active Elements in Ustilago maydis mig2 Promoters Conferring High-Level Activity During Pathogenic Growth in Maize

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-18-0075 ◽

2005 ◽

Vol 18 (1) ◽

pp. 75-87 ◽

Cited By ~ 21

Author(s):

Jan W. Farfsing ◽

Kathrin Auffarth ◽

Christoph W. Basse

Keyword(s):

Expression Profile ◽

Promoter Activity ◽

Fluorescent Protein ◽

Mutational Analysis ◽

Core Promoter ◽

Ustilago Maydis ◽

Tumor Formation ◽

Homologous Gene ◽

Specific Expression ◽

High Level

The Ustilago maydis mig2 cluster comprises five highly homologous genes that display a pronounced plant-specific expression profile. A 350-bp mig2-5 promoter fragment contained all elements sufficient to confer differential promoter activity. Mutational analysis of this region, fused to the green fluorescent protein reporter gene, allowed dissecting core promoter elements required for high-level promoter activity from elements conferring inducible expression in planta. In particular, the presence of several 5′-CCA-3′ motifs within a short stretch of the mig2-5 promoter was decisive for inducible promoter activity. On this basis, we reconstituted an artificial promoter whose inducible activity specifically relied on multiple CCA motifs. In addition, we identified a novel mig2 homologous gene, mig2-6, that is not part of the mig2 cluster, but displayed the strongest differential expression profile among mig2 genes. The deletion of all six mig2 genes did not compromise the ability to induce tumor formation in infected maize plants. Comparative sequence analysis including the mig2-6 promoter revealed an over-representation of the consensus motif 5′-MNMNWNCCAMM-3′. We discuss putative transcriptional activators involved in mig2 regulation.

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Complementation of Ustilago maydis MAPK Mutants by a Wheat Leaf Rust, Puccinia triticina Homolog: Potential for Functional Analyses of Rust Genes

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-20-6-0637 ◽

2007 ◽

Vol 20 (6) ◽

pp. 637-647 ◽

Cited By ~ 32

Author(s):

Guanggan Hu ◽

Andrena Kamp ◽

Rob Linning ◽

Suresh Naik ◽

Guus Bakkeren

Keyword(s):

Deletion Mutant ◽

Plant Pathogens ◽

Developmental Stages ◽

Expressed Sequence Tag ◽

Expression System ◽

Puccinia Triticina ◽

Ustilago Maydis ◽

Tumor Formation ◽

Mitogen Activated Protein Kinase ◽

Double Deletion

From a large expressed sequence tag (EST) database representing several developmental stages of Puccinia triticina, we discovered a mitogen-activated protein kinase (MAPK) with homology to kinases with known pathogenic functions in other fungi. This PtMAPK1 is similar to the Ustilago maydis MAPK, Ubc3/Kpp2, but has a longer N-terminal extension of 43 amino acids (aa) with identities to U. maydis Kpp6, a homolog of Ubc3/Kpp2 with a 170-aa N-terminal extension. Ubc3/Kpp2 is involved in mating and subsequent pathogenic development, whereas Kpp6 functions during invasive growth in corn tissue. PtMAPK1, expressed from a Ustilago sp.-specific promoter, was able to complement a ubc3/kpp2 deletion mutant and restore mating. It also substantially increased virulence on corn, measured as tumor formation, of a kpp6 deletion mutant. Moreover, this construct restored to near-full pathogenicity a ubc3/kpp2 kpp6 nonpathogenic double deletion mutant. Complementation of the ubc3/kpp2 mutant with the complete PtMAPK gene and verification of expression by reverse-transcription polymerase chain reaction indicated that the rust promoter is recognized in U. maydis. Phylogenetically, these basidiomycete plant pathogens are related, which was reflected in comparison of P. triticina ESTs to U. maydis gene sequences. The U. maydis heterologous expression system allows functional analysis of rust genes, currently frustrated by the lack of efficient transformation and selection procedures.

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Morphological Transitions in the Life Cycle of Ustilago maydis and Their Genetic Control by the a and b Loci

Experimental Mycology ◽

10.1006/emyc.1994.1024 ◽

1994 ◽

Vol 18 (3) ◽

pp. 247-266 ◽

Cited By ~ 58

Author(s):

Flora Banuett ◽

Ira Herskowitz

Keyword(s):

Life Cycle ◽

Genetic Control ◽

Ustilago Maydis ◽

Morphological Transitions

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Regulation of Ustilago maydis Dimorphism, Sporulation, and Pathogenic Development by a Transcription Factor with a Highly Conserved APSES Domain

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-23-2-0211 ◽

2010 ◽

Vol 23 (2) ◽

pp. 211-222 ◽

Cited By ~ 32

Author(s):

María D. García-Pedrajas ◽

Lourdes Baeza-Montañez ◽

Scott E. Gold

Keyword(s):

Transcription Factor ◽

Morphological Changes ◽

Ustilago Maydis ◽

Filamentous Growth ◽

Tumor Formation ◽

Regulatory Sequences ◽

In Planta ◽

Consensus Binding Site ◽

Filamentous Form ◽

Null Mutants

In Ustilago maydis, the causal agent of corn smut, the morphological transition from yeast to filamentous growth is inextricably linked to pathogenicity; budding haploid cells are saprobic and, upon mating of compatible strains, the fungus converts to dikaryotic filamentous growth and obligate parasitism. The filamentous dikaryon proliferates in the host plant, inducing tumor formation and undergoing additional morphological changes that eventually result in the production of melanized diploid teliospores. In an attempt to identify new trans-acting factors that regulate morphogenesis in U. maydis, we searched for the presence of common binding sequences in the promoter region of a set of 37 genes downregulated in the filamentous form. Putative cis-acting regulatory sequences fitting the consensus binding site for the Aspergillus nidulans transcription factor StuA were identified in 13 of these genes. StuA is a member of the APSES transcription factors which contain a highly conserved DNA-binding domain with a basic helix-loop-helix (bHLH)-like structure. This class of proteins comprises critical regulators of developmental processes in ascomycete fungi such as dimorphic growth, mating, and sporulation but has not been studied in any fungus of the phylum Basidiomycota. A search for StuA orthologs in the U. maydis genome identified a single closely related protein that we designated Ust1. Deletion of ust1 in budding haploid wild-type and solopathogenic strains led to filamentous growth and abolished mating, gall induction, and, consequently, in planta teliosporogenesis. Furthermore, cultures of ust1 null mutants produced abundant thick-walled, highly pigmented cells resembling teliospores which are normally produced only in planta. We showed that ssp1, a gene highly induced in teliospores produced in the host, is also abundantly expressed in cultures of ust1 null mutants containing these pigmented cells. Our results are consistent with a major role for ust1 in regulating dimorphism, virulence, and the sporulation program in U. maydis.

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