title: Absence of Yps7p, a putative glycosylphosphatidylinositol-linked aspartyl protease in Pichia pastoris, results in aberrant cell wall composition and increased osmotic stress resistance.
abstract: Recently, studies performed on Saccharomyces cerevisiae and Candida albicans have confirmed the importance of fungal glycosylphosphatidylinositol (GPI)-anchored aspartyl proteases (yapsins) for cell-wall integrity. Genome sequence annotation of Pichia pastoris also revealed seven putative GPI-anchored aspartyl protease genes. The five yapsin genes assigned as YPS1, YPS2, YPS3, YPS7 and MKC7 in P. pastoris were disrupted. Among these putative GPI-linked aspartyl proteases, disruption of PpYPS7 gene confers the Ppyps7Δ mutant cell increased resistance to cell wall perturbing reagents congo red, calcofluor white (CW) and sodium dodecyl sulfate. Quantitative analysis of cell wall components shows lower content of chitin and increased amounts of β-1,3-glucan. Further staining of the cell with CW demonstrates that disruption of PpYPS7 gene causes a reduction of the chitin content in lateral cell wall. Consistently, transmission electron micrographs show that the inner layer of mutant cell wall, mainly composed of chitin and β-1, 3-glucan, is much thicker than that in parental strain GS115. Additionally, Ppyps7Δ mutant also exhibits increased osmotic resistance compared with parental strain GS115. This could be due to the dramatically elevated intracellular glycerol level in Ppyps7Δ mutant. These results suggest that PpYPS7 is involved in cell wall integrity and response to osmotic stress.
authors.affiliation: Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Guan
authors.forename: Jianyong
authors.initials: J
authors.lastname: Lei
authors.forename: Shuai
authors.initials: S
authors.lastname: Su
authors.forename: Fengxiang
authors.initials: F
authors.lastname: Chen
authors.forename: Zuoying
authors.initials: Z
authors.lastname: Duan
authors.forename: Yun
authors.initials: Y
authors.lastname: Chen
authors.forename: Xiaohai
authors.initials: X
authors.lastname: Gong
authors.forename: Huazhong
authors.initials: H
authors.lastname: Li
authors.forename: Jian
authors.initials: J
authors.lastname: Jin
mesh_terms: D057055:Aspartic Acid Proteases / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000737:chemistry*; D002686:Chitin / Q000737:chemistry; D019295:Computational Biology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D009154:Mutation; D009995:Osmosis; D010641:Phenotype; D010843:Pichia / Q000166:cytology* / Q000201:enzymology / Q000235:genetics; D010957:Plasmids; D011509:Proteoglycans; D013312:Stress, Physiological; D047071:beta-Glucans / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D017261:Glycosylphosphatidylinositols; D011509:Proteoglycans; D047071:beta-Glucans; D002686:Chitin; C010770:polysaccharide-K; D057055:Aspartic Acid Proteases