Mitogen-activated protein kinase cascade required for regulation of development and secondary metabolism in Neurospora crassa.
Mitogen-activated protein kinase (MAPK) signaling cascades are composed of MAPK kinase kinases (MAPKKKs), MAPK kinases (MAPKKs), and MAPKs. In this study, we characterize components of a MAPK cascade in Neurospora crassa (mik-1, MAPKKK; mek-1, MAPKK; and mak-1, MAPK) homologous to that controlling cell wall integrity in Saccharomyces cerevisiae. Growth of basal hyphae is significantly reduced in mik-1, mek-1, and mak-1 deletion mutants on solid medium. All three mutants formed short aerial hyphae and the formation of asexual macroconidia was reduced in Deltamik-1 mutants and almost abolished in Deltamek-1 and Deltamak-1 strains. In contrast, the normally rare asexual spores, arthroconidia, were abundant in cultures of the three mutants. Deltamik-1, Deltamek-1, and Deltamak-1 mutants were unable to form protoperithecia or perithecia when used as females in a sexual cross. The MAK-1 MAPK was not phosphorylated in Deltamik-1 and Deltamek-1 mutants, consistent with the involvement of MIK-1, MEK-1, and MAK-1 in the same signaling cascade. Interestingly, we observed increased levels of mRNA and protein for tyrosinase in the mutants under nitrogen starvation, a condition favoring sexual differentiation. Tyrosinase is an enzyme that catalyzes production of the secondary metabolite l-DOPA melanin. These results implicate the MAK-1 pathway in regulation of development and secondary metabolism in filamentous fungi.
Department of Plant Pathology and Microbiology, 1415 Boyce Hall, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA.
Gyungsoon
G
Park
Songqin
S
Pan
Katherine A
KA
Borkovich
D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D015966:Gene Expression Regulation, Fungal; D025301:Hyphae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008543:Melanins / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000378:metabolism; D009492:Neurospora crassa / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D010766:Phosphorylation
D005656:Fungal Proteins; D008543:Melanins; D014442:Monophenol Monooxygenase; D020928:Mitogen-Activated Protein Kinases