Non-random distribution of vacuoles in Schizosaccharomyces pombe

Kinase Hog1 and Adr1 Opposingly Regulate Haploid Cell Morphology by Controlling Vacuole Size in Sporisorium scitamineum

Morphogenesis is a strictly regulated efficient system in eukaryotes for adapting to environmental changes. However, the morphogenesis regulatory mechanism in smut fungi is not clear. This study reports a relationship between MAP kinase Hog1 and cAMP-dependent protein kinase A catalytic subunit (Adr1) for the morphological regulation in the sugarcane pathogen Sporisorium scitamineum. The results demonstrated that MAP kinase Hog1 and cAMP/PKA signaling pathways are essential for the morphological development of S. scitamineum. Interestingly, MAP kinase Hog1 and cAMP/PKA signaling pathways’ defective mutants exhibit an opposite morphological phenotype. The morphology of cAMP/PKA defective mutants is recovered by deleting the SsHOG1 gene. However, MAP kinase Hog1 and cAMP-dependent protein kinase catalytic subunit Adr1 do not interfere with each other. Further investigations showed that kinase Hog1 and Adr1 antagonistically regulates the vacuolar size, which contributes to the cell size and determines the cellular elongation rates. Kinase Hog1 and Adr1 also antagonistically balanced the cell wall integrity and permeability. Taken together, kinase Hog1- and Adr1-based opposing morphogenesis regulation of S. scitamineum by controlling the vacuolar size and cell wall permeability is established during the study.

The PPIP5K Family Member Asp1 Controls Inorganic Polyphosphate Metabolism in S. pombe

Inorganic polyphosphate (polyP) which is ubiquitously present in both prokaryotic and eukaryotic cells, consists of up to hundreds of orthophosphate residues linked by phosphoanhydride bonds. The biological role of this polymer is manifold and diverse and in fungi ranges from cell cycle control, phosphate homeostasis and virulence to post-translational protein modification. Control of polyP metabolism has been studied extensively in the budding yeast Saccharomyces cerevisiae. In this yeast, a specific class of inositol pyrophosphates (IPPs), named IP₇, made by the IP6K family member Kcs1 regulate polyP synthesis by associating with the SPX domains of the vacuolar transporter chaperone (VTC) complex. To assess if this type of regulation was evolutionarily conserved, we determined the elements regulating polyP generation in the distantly related fission yeast Schizosaccharomyces pombe. Here, the VTC machinery is also essential for polyP generation. However, and in contrast to S. cerevisiae, a different IPP class generated by the bifunctional PPIP5K family member Asp1 control polyP metabolism. The analysis of Asp1 variant S. pombe strains revealed that cellular polyP levels directly correlate with Asp1-made IP₈ levels, demonstrating a dose-dependent regulation. Thus, while the mechanism of polyP synthesis in yeasts is conserved, the IPP player regulating polyP metabolism is diverse.