Identification and characterization of PDC1, a novel protein involved in the epigenetic cell degeneration Crippled Growth in Podospora anserina

Tinh-Suong Nguyen Hervé Lalucque Philippe Silar
Paris Interdisciplinary Energy Research Institute (LIED-PIERI), Université Paris 7 Diderot, Paris, France

Many fungi display epigenetic instability. In Podospora anserina, the epigenetic cell degeneration “Crippled Growth” (CG) is characterized by slow growth, alteration of pigmentation and inability to differentiate fructifications and aerial hyphae (Silar,1999). CG is due to a cytoplasmic and infectious element called C produced during stationary phase. Two types of CG mutants were isolated: IDC mutants impaired in the development of CG and PDC mutants promoting the development of CG (Haedens et al., 2005). The former have been well studied and all mutants are affected in the MAPK1 pathway (Kicka & Silar, 2004 ; Kicka et al., 2006), the MAPK2 pathway (Lalucque et al., 2012), the Nox1 NADPH oxidase complex (Malagnac et al., 2004 ; Lacaze et al., 2014), or in small cysteine-containing proteins probably involved in signal transduction (Lalucque et al., 2017). Here, we present for the first time an analysis of a PDC mutant, the PDC2205 strain mutated in the pdc1 gene coding the PDC1 protein. This 290 amino acids protein is present in most Ascomycota. All the proteins homologous to PDC1 show a conservation of six amino acids: four cysteines, one histidine and one tryptophan. Site directed mutagenesis revealed that each of these amino acids plays an important role in PDC1 activity. Moreover, epistasis analyses have been conducted with available IDC mutants to place PDC1 with respect to the other actors of CG. Cytological observations, in progress, should reveal the cellular localization of PDC1.

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