A small Ustilago maydis effector acts as a novel adhesin for hyphal aggregation in plant tumors

Activation of the cAMP Pathway in Ustilago maydis Reduces Fungal Proliferation and Teliospore Formation in Plant Tumors

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2000.13.10.1034 ◽

2000 ◽

Vol 13 (10) ◽

pp. 1034-1040 ◽

Cited By ~ 53

Author(s):

Julia Krüger ◽

Gabriel Loubradou ◽

Gerhard Wanner ◽

Erika Regenfelder ◽

Michael Feldbrügge ◽

...

Keyword(s):

Ustilago Maydis ◽

Regulatory Subunit ◽

In Planta ◽

Fungal Development ◽

Developmental Program ◽

Camp Pathway ◽

Induction Process ◽

Plant Tumors ◽

Null Mutants ◽

Corn Smut

In the corn smut fungus Ustilago maydis, mating of two haploid sporidia is a prerequisite for subsequent colonization of the host. Cyclic AMP (cAMP) and pheromone signals have been implicated in this developmental program. The cAMP pathway is also needed for subsequent fungal development in planta, as null mutants in any component of the pathway fail to form tumors. Here we show that moderate activation of the pathway conferred either by mutation in the Gα subunit or by mutation in the regulatory subunit of the protein kinase A influences tumor morphology. In the resulting tumors, the amount of fungal material is drastically reduced and fungal development is arrested at the stage of sporogenic hyphae. We conclude that tight regulation of the cAMP pathway is crucial for fungal development within the plant but does not interfere with the tumor induction process.

Download Full-text

Transcriptome Analysis of a Ustilago maydis ust1 Deletion Mutant Uncovers Involvement of Laccase and Polyketide Synthase Genes in Spore Development

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-05-14-0133-r ◽

2015 ◽

Vol 28 (1) ◽

pp. 42-54 ◽

Cited By ~ 13

Author(s):

Emir Islamovic ◽

María D. García-Pedrajas ◽

Nadia Chacko ◽

David L. Andrews ◽

Sarah F. Covert ◽

...

Keyword(s):

Deletion Mutant ◽

Polyketide Synthase ◽

Ustilago Maydis ◽

Adult Plant ◽

In Planta ◽

Dimorphic Fungus ◽

Melanin Biosynthesis ◽

Plant Tumors ◽

Vitro Model

Ustilago maydis, causal agent of corn smut disease, is a dimorphic fungus alternating between a saprobic budding haploid and an obligate pathogenic filamentous dikaryon. Maize responds to U. maydis colonization by producing tumorous structures, and only within these does the fungus sporulate, producing melanized sexual teliospores. Previously we identified Ust1, an APSES (Asm1p, Phd1p, Sok2p, Efg1p, and StuAp) transcription factor, whose deletion led to filamentous haploid growth and the production of highly pigmented teliospore-like structures in culture. In this study, we analyzed the transcriptome of a ust1 deletion mutant and functionally characterized two highly upregulated genes with potential roles in melanin biosynthesis: um05361, encoding a putative laccase (lac1), and um06414, encoding a polyketide synthase (pks1). The Δlac1 mutant strains showed dramatically reduced virulence on maize seedlings and fewer, less-pigmented teliospores in adult plants. The Δpks1 mutant was unaffected in seedling virulence but adult plant tumors generated hyaline, nonmelanized teliospores. Thus, whereas pks1 appeared to be restricted to the synthesis of melanin, lac1 showed a broader role in virulence. In conclusion, the ust1 deletion mutant provided an in vitro model for sporulation in U. maydis, and functional analysis supports the efficacy of this in vitro mutant analysis for identification of genes involved in in planta teliosporogenesis.

Download Full-text

The Gβ-Subunit-Encoding Gene bpp1 Controls Cyclic-AMP Signaling in Ustilago maydis

Eukaryotic Cell ◽

10.1128/ec.3.3.806-814.2004 ◽

2004 ◽

Vol 3 (3) ◽

pp. 806-814 ◽

Cited By ~ 31

Author(s):

Philip Müller ◽

Andreas Leibbrandt ◽

Hedwich Teunissen ◽

Stephanie Cubasch ◽

Christian Aichinger ◽

...

Keyword(s):

Gene Expression ◽

Cyclic Amp ◽

Ustilago Maydis ◽

Phytopathogenic Fungus ◽

Heterotrimeric G Proteins ◽

Receptor System ◽

Pheromone Signaling ◽

Active Allele ◽

Plant Tumors ◽

Signaling Activation

ABSTRACT In the phytopathogenic fungus Ustilago maydis, fusion of haploid cells is a prerequisite for infection. This process is controlled by a pheromone-receptor system. The receptors belong to the seven-transmembrane class that are coupled to heterotrimeric G proteins. Of four Gα subunits in U. maydis, only gpa3 has a function during mating and cyclic AMP (cAMP) signaling. Activation of the cAMP cascade induces pheromone gene expression; however, it does not lead to the induction of conjugation tubes seen after pheromone stimulation. To investigate the possibility that a Gβ subunit participates in pheromone signaling, we isolated the single β subunit gene, bpp1, from U. maydis. bpp1 deletion mutants grew filamentously and showed attenuated pheromone gene expression, phenotypes associated with Δgpa3 strains. In addition, a constitutively active allele of gpa3 suppressed the phenotype of the bpp1 deletion strains. We suggest that Bpp1 and Gpa3 are components of the same heterotrimeric G protein acting on adenylyl cyclase. Interestingly, while Δgpa3 strains are impaired in pathogenicity, Δbpp1 mutants are able to induce plant tumors. This could indicate that Gpa3 operates independently of Bpp1 during pathogenic development.

Download Full-text