Ustilago maydis, corn smut

Taxonomic lineage

cellular organisms - Eukaryota - Fungi/Metazoa group - Fungi - Dikarya - Basidiomycota - Ustilaginomycotina - Ustilaginomycetes - Ustilaginales - Ustilaginaceae - Ustilago - Ustilago maydis

Brief facts

Ustilago maydis (corn smut) is dimorphic filamentous fungus that together with mushrooms and many other fungi belongs to phylum Basidiomycota. Dimorphic means that the fungus exists in two forms: saprotrophic yeast-like form that lives on dead organic material and is non-pathogenic and parasitic filamentous form that derives nutrients from its host. Filamentous means that unlike yeasts, which cells do not have polarity and proliferate by simple budding U. maydis expands its mycelium by polar tip hyphal growth.

Order Ustilaginales contains many important plant pathogens such as Ustilago hordei, Ustilago nuda, Ustilago nigra (oat pathogens), Tilletia indica, Tilletia caries, and Tilletia controversa (wheat pathogens). Of all Ustilaginales, U. maydis is best known and has rather narrow specificity - it can parazitize only on corn (Zea mays) and on its ancestor teozinte (Zea mexicana).

U. maydis causes stunting, chlorosis, and above all, induces formation of galls, or tumors, on infested corn palnt, primarily on ears.

Corn invaded by U. maydis is considered a delicacy in Mexico. Traditional Mexican dishes such as Quesadillas de huitlacoche or Sopa de huitlacoche have been recently introduced into the high-end restaurants with success. The cooking of U. maydis infested corn is believed to exist since pre-Columbus era.

U. maydis is used extensively in biological research and is considered a very valuable model system not only in molecular plant pathology but also in studies of eukaryotic cell's signaling pathways, molecular transport, cell division mechanisms, and many other areas.