Deletion of the MBP1 Gene, Involved in the Cell Cycle, Affects Respiration and Pseudohyphal Differentiation in Saccharomyces cerevisiae

Role of putative APSES family transcription factor Swi6 in cell wall synthesis regulation in the agaricomycete Pleurotus ostreatus

Clade A APSES family transcription factor Swi6 functions alongside Mbp1 to form the MBF (MluI cell cycle box-binding factor) complex in ascomycetes. In the agaricomycete Pleurotus ostreatus, Mbp1 plays a crucial role in regulating β-glucan and chitin synthesis; however, the role of Swi6 has not been explored in this fungus. In this study, its involvement in cell wall synthesis regulation was analysed using swi6 disruption strains in P. ostreatus. The Δswi6 strains exhibited reduced growth rates and shorter aerial hyphae formation in both agar and liquid media, suggesting an essential role of Swi6 in normal vegetative growth. Furthermore, swi6 disruption affected cell wall thickness distribution, the expression of specific chitin synthase genes, the relative percentage of chitin, and sensitivity to calcofluor white, suggesting that Swi6 is required for normal chitin synthesis regulation in P. ostreatus. In contrast, no significant differences were observed between the wild-type and Δswi6 strains in the relative percentage of α- and β-glucan and the expression of α- and β-glucan synthase genes, suggesting its unimportant role in α- and β-glucan synthesis regulation. In conclusion, Swi6 is necessary for normal mycelial growth and chitin synthesis regulation in P. ostreatus. To the best of our knowledge, this study is the first report on the functional differences and overlaps between Mbp1 and Swi6 in the regulation of cell wall synthesis in agaricomycetes.

Putative APSES family transcription factor mbp1 plays an essential role in regulating cell wall synthesis in the agaricomycete Pleurotus ostreatus

The clade A APSES family transcription factors (Mbp1, Swi4, and Swi6) contribute to cell wall synthesis regulation in fungi. Herein, evolutionary relationships among these proteins were clarified by phylogenetic analysis using various ascomycetes and basidiomycetes, and then the detailed function of Mbp1 in cell wall synthesis regulation was analyzed in Pleurotus ostreatus. Our phylogenetic analysis revealed that Mbp1 and Swi6 are widely conserved among various fungi, whereas Swi4 is a protein specific for Saccharomycotina. In P. ostreatus, two putative clade A APSES family transcription factors, protein ID 83192 and 134090, were found and identified as Mbp1 and Swi6, respectively. The mbp1 gene was then disrupted through homologous recombination using P. ostreatus 20b strain (Δku80) as a host to obtain mbp1 disruption strains (Δmbp1). Disruption of mbp1 significantly decreased the growth rate and shortened aerial hyphae, suggesting that Mbp1 is involved in mycelial growth, especially aerial hyphal growth. Furthermore, thinner cell walls, decreased relative percentage of β-glucan, and downregulation of all β-glucan synthase genes were observed in Δmbp1 strains. Therefore, Mbp1 plays an essential role in β-glucan synthesis regulation in P. ostreatus. Disruption of mbp1 also impacted the expression profiles of chitin synthase genes, septum formation, and sensitivity to a chitin synthesis inhibitor, suggesting that Mbp1 also regulates chitin synthesis. In conclusion, Mbp1 is responsible for normal mycelial growth and regulates β-glucan and chitin synthesis in P. ostreatus. To the best of our knowledge, this is the first report on the detailed function of Mbp1 in cell wall synthesis regulation in fungi.

FvMbp1-Swi6 complex regulates vegetative growth, stress tolerance, and virulence in Fusarium verticillioides

The mycotoxigenic fungus Fusarium verticillioides is a common pathogen of grain and medicine that contaminates the host with fumonisin B1 (FB1) mycotoxin, poses serious threats to human and animal health. Therefore, it is crucial to unravel the regulatory mechanisms of growth, and pathogenicity of F. verticillioides. Mbp1 is a component of the MluI cell cycle box binding factor complex and acts as an APSES-type transcription factor that regulates cell cycle progression. However, no information is available regarding its role in F. verticillioides. In this study, we demonstrate that FvMbp1 interacts with FvSwi6 that acts as the cell cycle transcription factor, to form the heteromeric transcription factor complexes in F. verticillioides. Our results show that ΔFvMbp1 and ΔFvSwi6 both cause a severe reduction of vegetative growth, conidiation, and increase tolerance to diverse environmental stresses. Moreover, ΔFvMbp1 and ΔFvSwi6 dramatically decrease the virulence of the pathogen on the stalk and ear of maize. Transcriptome profiling show that FvMbp1-Swi6 complex co-regulates the expression of genes associated with multiple stress responses. These results indicate the functional importance of the FvMbp1-Swi6 complex in the filamentous fungi F. verticillioides and reveal a potential target for the effective prevention and control of Fusarium diseases.

Measuring effect of mutations & conditions on microbial respiratory rates

Cellular respiration is central to a wide range of cellular processes. In microorganisms, the effect of a mutation or an environmental condition on the rate of respiration is usually determined by measuring oxygen consumption in the media. We describe this method and discuss caveats and controls for the method.

Alpha-enolase 1 knockdown facilitates the proliferation and invasion of villous trophoblasts by upregulating COX-2

BACKGROUND

Enolase 1 (ENO1) is a metabolic enzyme which participates in pyruvate synthesis and ATP production in cells. Previously, differential expression of ENO1 was discovered in villous tissues between recurrent miscarriage and induced abortion. This study was designed to explore whether ENO1 influences the proliferation and invasion of villous trophoblasts and the related molecular mechanisms.

METHODS

First, ENO1 expression in placental villus tissues collected from recurrent miscarriage (RM) patients and women for induced abortion as well as in trophoblast-derived cell lines was detected by RT-qPCR and western blotting. ENO1 localization and expression in villus tissues were further confirmed through immunohistochemistry staining. Then, the effects of ENO1 downregulation on trophoblast Bewo cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) process were evaluated by CCK-8 assay, transwell assay, and western blotting. As for the regulatory mechanism of ENO1, the expression of COX-2, c-Myc and cyclin D1 in Bewo cells after ENO1 knockdown was finally evaluated by RT-qPCR and western blotting.

RESULTS

ENO1 was mainly localized in the cytoplasm, with very small amounts in the nucleus of trophoblast cells. ENO1 expression in the villi tissues of RM patients was significantly increased, when compared with the villous tissues of healthy controls. Furthermore, Bewo cells, a trophoblast cell line with relatively higher expression of ENO1, was used to downregulate the ENO1 expression by ENO1-siRNA transfection. ENO1 knockdown significantly facilitated Bewo cell growth, EMT process, migration, and invasion. ENO1 silencing markedly elevated COX-2, c-Myc, and cyclin D1 expression.

CONCLUSION

ENO1 may participate in the development of RM via suppressing the growth and invasion of villous trophoblasts via reducing the expression of COX-2, c-Myc, and cyclin D1.