Abstract
BackgroundThe Saccharomyces cerevisiae MYO1 gene encodes the myosin II heavy chain (Myo1p), a protein required for normal cytokinesis in budding yeast. Myo1p deficiency in yeast (myo1Δ) causes a cell separation defect characterized by the formation of attached cells, yet it also causes abnormal budding patterns, formation of enlarged and elongated cells, increased osmotic sensitivity, delocalized chitin deposition, increased chitin synthesis, and hypersensitivity to the chitin synthase III inhibitor Nikkomycin Z. To determine how differential expression of genes is related to these diverse cell wall phenotypes, we analyzed the global mRNA expression profile of myo1Δ strains.ResultsGlobal mRNA expression profiles of myo1Δ strains and their corresponding wild type controls were obtained by hybridization to yeast oligonucleotide microarrays. Results for selected genes were confirmed by real time RT-PCR. A total of 547 differentially expressed genes (p ≤ 0.01) were identified with 263 up regulated and 284 down regulated genes in the myo1Δ strains. Gene set enrichment analysis revealed the significant over-representation of genes in the protein biosynthesis and stress response categories. The SLT2/MPK1 gene was up regulated in the microarray, and a myo1Δslt2Δ double mutant was non-viable. Overexpression of ribosomal protein genes RPL30 and RPS31 suppressed the hypersensitivity to Nikkomycin Z and increased the levels of phosphorylated Slt2p in myo1Δ strains. Increased levels of phosphorylated Slt2p were also observed in wild type strains under these conditions.ConclusionFollowing this analysis of global mRNA expression in yeast myo1Δ strains, we conclude that 547 genes were differentially regulated in myo1Δ strains and that the stress response and protein biosynthesis gene categories were coordinately regulated in this mutant. The SLT2/MPK1 gene was confirmed to be essential for myo1Δ strain viability, supporting that the up regulated stress response genes are regulated by the PKC1 cell integrity pathway. Suppression of Nikkomycin Z hypersensitivity together with Slt2p phosphorylation was caused by the overexpression of ribosomal protein genes RPL30 and RPS31. These ribosomal protein mRNAs were down regulated in the myo1Δ arrays, suggesting that down regulation of ribosomal biogenesis may affect cell integrity in myo1Δ strains.
Highlights
The Saccharomyces cerevisiae MYO1 gene encodes the myosin II heavy chain (Myo1p), a protein required for normal cytokinesis in budding yeast
The functional categories of the up regulated genes that were represented as listed in the Saccharomyces Genome Database (SGD) were: cell organization and biogenesis (17/263), metabolism (25/263), transport (9/ 263), carbohydrate metabolism (23/263), stress response (17/263), protein biosynthesis (2/263), cell cycle (3/ 263), signal transduction (7/263), transcription (1/263), sporulation (4/263), budding (4/263), RNA processing (4/263), protein transport (6/263), protein amino acid phosphorylation (2/263), protein amino acid dephosphorylation (1/263), autophagy (2/263), DNA repair (5/ 263), cell growth and maintenance (1/263), and unknown functions (130/263) (Additional file 1)
Following our analysis of the global mRNA expression profile in myo1∆ strains of Saccharomyces cerevisiae we found that there were 547 differentially regulated genes
Summary
The Saccharomyces cerevisiae MYO1 gene encodes the myosin II heavy chain (Myo1p), a protein required for normal cytokinesis in budding yeast. In addition to the loss of normal cytokinesis function, myo1∆ strains present phenotypes such as the formation of attached cells, loss of axial budding pattern, cell enlargement, osmotic hypersensitivity, delocalized chitin deposition [5], increased chitin synthesis[6,7], and hypersensitivity to Nikkomycin Z [8]. The diversity of these phenotypes, many of which can be associated with cell wall organization, suggests that myosin II may affect cellular functions other than cytokinesis. The purpose of this study was to generate a global mRNA expression profile of myo1∆ strains using yeast oligonucleotide microarrays to identify potential relationships between the multiple myo1∆ phenotypes mentioned and changes in the transcription profile of specific genes that can be functionally related to these phenotypes
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