Specific Functional Features of the Cell Integrity MAP Kinase Pathway in the Dimorphic Fission Yeast Schizosaccharomyces japonicus

Abstract

Mitogen activated protein kinase (MAPK) signaling pathways execute essential functions in eukaryotic organisms by transducing extracellular stimuli into adaptive cellular responses. In the fission yeast model Schizosaccharomyces pombe the cell integrity pathway (CIP) and its core effector, MAPK Pmk1, play a key role during regulation of cell integrity, cytokinesis, and ionic homeostasis. Schizosaccharomyces japonicus, another fission yeast species, shows remarkable differences with respect to S. pombe, including a robust yeast to hyphae dimorphism in response to environmental changes. We show that the CIP MAPK module architecture and its upstream regulators, PKC orthologs Pck1 and Pck2, are conserved in both fission yeast species. However, some of S. pombe’s CIP-related functions, such as cytokinetic control and response to glucose availability, are regulated differently in S. japonicus. Moreover, Pck1 and Pck2 antagonistically regulate S. japonicus hyphal differentiation through fine-tuning of Pmk1 activity. Chimeric MAPK-swapping experiments revealed that S. japonicus Pmk1 is fully functional in S. pombe, whereas S. pombe Pmk1 shows a limited ability to execute CIP functions and promote S. japonicus mycelial development. Our findings also suggest that a modified N-lobe domain secondary structure within S. japonicus Pmk1 has a major influence on the CIP signaling features of this evolutionarily diverged fission yeast.

Special Issue “The Fungal Cell Wall Integrity Pathway”

“…In this line, the work of Navarro et al shows that the dimorphism-regulating histidine kinase (Drk1) of the pathogenic fungus Paracoccidioides brasiliensis plays an important role in cell wall homeostasis, in contrast to the involvement of histidine kinases in the response to high osmolarity in S. cerevisiae [ 21 ]. In turn, Gomez-Gil et al investigate the architecture and functionality of the CWI pathway (CIP pathway) of Schizosaccharomyces japonicus [ 22 ]. They prove that, while certain features of this pathway previously described in S. pombe are conserved in S. japonicus , others have evolved differently in both fission yeast species.…”