- 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. . pmid:1369743.
- Müller P, Aichinger C, Feldbrügge M, and Kahmann R. . pmid:10594825.
- Müller P, Weinzierl G, Brachmann A, Feldbrügge M, and Kahmann R. . pmid:14665454.
- Müller P, Katzenberger JD, Loubradou G, and Kahmann R. . pmid:12796306.