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.
Park
Gyungsoon
G
Department of Plant Pathology and Microbiology, 1415 Boyce Hall, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA.
Pan
Songqin
S
Borkovich
Katherine A
KA
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