Genome-wide transcriptional profiling and enrichment mapping reveal divergent and conserved roles of Sko1 in the Candida albicans osmotic stress response

Candida albicans maintains both commensal and pathogenic states in humans. Here, we have defined the genomic response to osmotic stress mediated by transcription factor Sko1. We performed microarray analysis of a sko1\u3b4/\u3b4 mutant strain subjected to osmotic stress, and we utilized gene sequence enrichment analysis and enrichment mapping to identify Sko1-dependent osmotic stress-response genes. We found that Sko1 regulates distinct gene classes with functions in ribosomal synthesis, mitochondrial function, and vacuolar transport. Our in silico analysis suggests that Sko1 may recognize two unique DNA binding motifs. Our C. albicans genomic analyses and complementation studies in Saccharomyces cerevisiae showed that Sko1 is conserved as a regulator of carbohydrate metabolism, redox metabolism, and glycerol synthesis. Further, our real time-qPCR results showed that osmotic stress-response genes that are dependent on the kinase Hog1 also require Sko1 for full expression. Our findings reveal divergent and conserved aspects of Sko1-dependent osmotic stress signaling. \ua9 2013 Elsevier Inc.Peer reviewed: YesNRC publication: Ye

Nanomechanics of yeast surfaces revealed by AFM

Despite the large and well-documented characterization of the microbial cell wall in terms of chemical composition, the determination of the mechanical properties of surface molecules in relation to their function remains a key challenge in cell biology.The emergence of powerful tools allowing molecular manipulations has already revolutionized our understanding of the surface properties of fungal cells. At the frontier between nanophysics and molecular biology, atomic force microscopy (AFM), and more specifically single-molecule force spectroscopy (SMFS), has strongly contributed to our current knowledge of the cell wall organization and nanomechanical properties. However, due to the complexity of the technique, measurements on live cells are still at their infancy.In this chapter, we describe the cell wall composition and recapitulate the principles of AFM as well as the main current methodologies used to perform AFM measurements on live cells, including sample immobilization and tip functionalization.The current status of the progress in probing nanomechanics of the yeast surface is illustrated through three recent breakthrough studies. Determination of the cell wall nanostructure and elasticity is presented through two examples: the mechanical response of mannoproteins from brewing yeasts and elasticity measurements on lacking polysaccharide mutant strains. Additionally, an elegant study on force-induced unfolding and clustering of adhesion proteins located at the cell surface is also presented