Ustilago maydis, model system for analysis of the
molecular basis of fungal pathogenicity
Christoph W. Basse and Gero Steinberg
Max-Planck-Institute for Terrestrial Microbiology, Department of
Organismic Interactions, Karl-von-Frisch Strasse, 35043 Marburg, Germany
||Ustilago maydis, a
facultative biotrophic basidiomycete fungus, causes smut disease in maize.
A hallmark of this disease is the induction of large plant tumours that
are filled with masses of black-pigmented teliospores. During the last
15 years U. maydis has become an important model system
to unravel molecular mechanisms of fungal phytopathogenicity. This review
highlights recent insights into molecular mechanisms of complex signalling
pathways that are involved in the transition from budding to filamentous
growth and operate during the pathogenic growth phase. In addition, we
describe recent progress in understanding the structural basis of
morphogenesis and polar growth in different stages of U. maydis
development. Finally, we present an overview of recently identified genes
related to pathogenic development and summarize novel molecular and
genomic approaches that are powerful tools to explore the genetic base of
||Ustilago maydis (DC) Corda
(synonymous with Ustilago zeae Ung.)-Kingdom Eukaryota, Phylum
Fungi, Order Basidiomycota, Family Ustilaginomycetes, Genus Ustilago.
||Infects aerial parts of corn plants
(Zea mays) and its progenitor teosinte (Zea mays ssp. parviglumis).
Maize smut is distributed throughout the world.
||U. maydis causes
chlorotic lesions in infected areas, the formation of anthocyanin
pigments, necrosis, hyperplasia and hypertrophy of infected organs.
Infection by U. maydis can inhibit development and lead to
stunting of infected plants. A few days after infection plant tumours
develop in which massive fungal proliferation and the formation of the
black-pigmented, diploid teliospores occurs. Under natural conditions
tumours predominantly develop on sexual organs (tassels and ears), stems
and nodal shoots. Tumours may vary in size from minute pustules to several
centimetres in diameter and contain up to 200 billion spores.
U. maydis induced maize tumours. (A) Leaf tumours 10 days after
inoculation of a compatible mixture of sporidia into 7-day-old maize
plants. (B) Tumors caused by U. maydis in a maize field. Tumors developed
in individual kernels and are partially burst, releasing black
teliospores. Photograph kindly provided by Jörg Kämper.
the full article