title: A non-Mendelian MAPK-generated hereditary unit controlled by a second MAPK pathway in Podospora anserina.
abstract: The Podospora anserina PaMpk1 MAP kinase (MAPK) signaling pathway can generate a cytoplasmic and infectious element resembling prions. When present in the cells, this C element causes the crippled growth (CG) cell degeneration. CG results from the inappropriate autocatalytic activation of the PaMpk1 MAPK pathway during growth, whereas this cascade normally signals stationary phase. Little is known about the control of such prion-like hereditary units involved in regulatory inheritance. Here, we show that another MAPK pathway, PaMpk2, is crucial at every stage of the fungus life cycle, in particular those controlled by PaMpk1 during stationary phase, which includes the generation of C. Inactivation of the third P. anserina MAPK pathway, PaMpk3, has no effect on the development of the fungus. Mutants of MAPK, MAPK kinase, and MAPK kinase kinase of the PaMpk2 pathway are unable to present CG. This inability likely relies upon an incorrect activation of PaMpk1, although this MAPK is normally phosphorylated in the mutants. In PaMpk2 null mutants, hyphae are abnormal and PaMpk1 is mislocalized. Correspondingly, stationary phase differentiations controlled by PaMpk1 are defective in the mutants of the PaMpk2 cascade. Constitutive activation of the PaMpk2 pathway mimics in many ways its inactivation, including an effect on PaMpk1 localization. Analysis of double and triple mutants inactivated for two or all three MAPK genes undercover new growth and differentiation phenotypes, suggesting overlapping roles. Our data underscore the complex regulation of a prion-like element in a model organism.
authors.affiliation: Université Paris Sud 11, Institut de Génétique et Microbiologie, Unité Mixte de Recherche Centre National de la Recherche Scientifique, 91405 Orsay Cedex, France.
authors.forename: Hervé
authors.initials: H
authors.lastname: Lalucque
authors.forename: Fabienne
authors.initials: F
authors.lastname: Malagnac
authors.forename: Sylvain
authors.initials: S
authors.lastname: Brun
authors.forename: Sébastien
authors.initials: S
authors.lastname: Kicka
authors.forename: Philippe
authors.initials: P
authors.lastname: Silar
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D004789:Enzyme Activation / Q000235:genetics; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D025282:Mycelium / Q000235:genetics / Q000254:growth & development; D010641:Phenotype; D010766:Phosphorylation; D048468:Podospora / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D021381:Protein Transport
chemical_list: D020928:Mitogen-Activated Protein Kinases