DISRUPTION OF 2 GENES FOR CHITIN SYNTHASE IN THE PHYTOPATHOGENIC FUNGUS USTILAGO-MAYDIS

The phytopathogenic fungus Ustilago maydis exhibits a dimorphic transi tion in which non-pathogenic, yeast-like cells mate to form a pathogen ic, filamentous dikaryon. Northern analysis indicated that two chitin synthase genes, chs1 and chs2, from U. maydis are expressed at similar levels in yeast-like cells and in cells undergoing the mating reactio n leading to the filamentous cell type. A mutation was constructed in each of the chitin synthase genes by targeted gene disruption. Each mu tant showed a reduction in the level of trypsin-activated enzyme activ ity, compared with a wild-type strain, but retained the wild-type morp hology, the ability to mate and the ability to form the filamentous pa thogenic cell type.