Activation of the cAMP pathway in Ustilago maydis reduces fungal proliferation and teliospore formation in plant tumors

Mol Plant Microbe Interact. 2000 Oct;13(10):1034-40. doi: 10.1094/MPMI.2000.13.10.1034.


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 Galpha 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Cyclic AMP / metabolism*
  • Cyclic AMP-Dependent Protein Kinases / genetics
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Fungal Proteins*
  • GTP-Binding Protein alpha Subunits*
  • Genes, Fungal
  • Heterotrimeric GTP-Binding Proteins / genetics
  • Heterotrimeric GTP-Binding Proteins / metabolism
  • Microscopy, Electron
  • Mutation
  • Plant Tumors / microbiology*
  • Signal Transduction
  • Spores, Fungal / physiology
  • Surface Properties
  • Ustilago / cytology
  • Ustilago / genetics
  • Ustilago / physiology*


  • Fungal Proteins
  • GTP-Binding Protein alpha Subunits
  • Gpa3 protein, Ustilago maydis
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases
  • Heterotrimeric GTP-Binding Proteins