- The plant pathogen U. maydis enters meiosis only during growth in its host, Zea mays.
- we have identified a gene, kpp2, which encodes a putative MAP kinase related to Pmk1 of Magnaporthe grisea and Fus3p of Saccharomyces cerevisiae.
- In the phytopathogenic fungus Ustilago maydis, pheromone-mediated cell fusion is a prerequisite for the generation of the infectious dikaryon.
- The MAPK cascade is presumed to be composed of:
- Kpp4/Ubc4 (MAPK kinase kinase)
- Fuz7 (MAPK kinase)
- Ubc3/Kpp2 (MAPK).
- Strains lacking components of this signaling pathway, such as the G-subunit Gpa3 or the adenylyl cyclase Uac1, are nonpathogenic and grow filamentously.
- Alternatively, Ras2 in U. maydis may act on the MAPK cascade composed of Ubc4, Fuz7, and Kpp2/Ubc3, since this cascade is a positive regulator of filamentous growth. Moreover, the farthest-upstream component, Kpp4/Ubc4, contains a RA domain that is conserved in proteins interacting with Ras proteins (3; Müller et al., submitted). In S. pombe, Ras1 regulates the Ubc4 homologue, Byr2, by interacting with the RA domain of Byr2 MAPKK kinase, and this interaction leads to the translocation of Byr2 to the plasma membrane (8, 45, 63). Recently, the ras2 gene of U. maydis was found to act upstream of kpp2/ubc3. 
- Banuett F. Ustilago maydis, the delightful blight. Trends Genet. 1992 May;8(5):174-80.
- Müller P, Aichinger C, Feldbrügge M, and Kahmann R. The MAP kinase kpp2 regulates mating and pathogenic development in Ustilago maydis. Mol Microbiol. 1999 Dec;34(5):1007-17.
- Müller P, Weinzierl G, Brachmann A, Feldbrügge M, and Kahmann R. Mating and pathogenic development of the Smut fungus Ustilago maydis are regulated by one mitogen-activated protein kinase cascade. Eukaryot Cell. 2003 Dec;2(6):1187-99.
- Müller P, Katzenberger JD, Loubradou G, and Kahmann R. Guanyl nucleotide exchange factor Sql2 and Ras2 regulate filamentous growth in Ustilago maydis. Eukaryot Cell. 2003 Jun;2(3):609-17.