The basidiomycete U. maydis provides an excellent model
system with which to study interactions between endophytic
and pathogenic fungi, as it is an obligate, biotrophic parasite
of maize (Zea mays L. ssp. mays) and the teosintes (e.g. Z.
mays L. ssp. parviglumis) (K¨amper et al., 2006). Like many
grass smut pathogens, U. maydis is host specific and likely
shares a long evolutionary history with Zea hosts predating
maize domestication (Munkacsi et al., 2008). Haploid cells
of U. maydis mate to form an infectious dikaryotic hypha,
which penetrates the plant epidermis and proliferates to
form large galls filled with a mass of diploid teliospores
(Banuett & Herskowitz, 1996). The unique tumor development
distinguishes smut disease symptoms from those
caused by other pathogens, and the distinct stages of disease progression provide a tool to estimate the disease severity
(Gold et al., 1997).