Transcriptional activator Cat8 is involved in regulation of xylose alcoholic fermentation in the thermotolerant yeast Ogataea (Hansenula) polymorpha

Additional file 5. List of primers used in this study (restriction sites are underlined)

Functional characterization of zinc cluster transcriptional regulators in Saccharomyces cerevisiae and Candida albicans

Zinc cluster proteins form a major class of fungal-specific transcriptional regulators in Saccharmyces cerevisiae. They are characterized by a well-conserved zinc cluster motif essential for DNA recognition. These regulators are implicated in transcriptional control of genes involved in various cellular processes such in sugar metabolism, biosynthesis of amino acids, gluconeogenesis, ergosterol biosynthesis and pleiotropic drug resistance (PDR)/stress response. A classic example of zinc cluster protein is Gal4, a regulator of galactose catabolism. However, a number of zinc cluster genes encode putative regulators with unknown function. A phenotypic analysis of zinc cluster deletion strains has implicated them in certain pathways. Rds2 was identified as a regulator of PDR in Saccharomyces cerevisiae as it confers resistance to an antifungal agent. A genomewide location approach (ChIP-chip) was employed to assign roles for Rds2. Results showed that Rds2 plays a major role in glucose metabolism. It functions as an activator and a repressor of gluconeogenic genes during the diauxic shift. It also mediates sensitivity to the antifungal drug azoles by regulating the expression of genes in the ergosterol biosynthetic pathway. Its ortholog in the pathogenic yeast Candida albicans, Cwt1, is also involved in glucose metabolism but not in PDR. Functional relationship among known PDR regulators in S. cerevisiae was uncovered in a phenotypic analysis of double deletion of zinc cluster genes. Altogether, this study provides new insight regarding the roles of zinc cluster regulators in transcriptional control of genes involved in multiple physiological process

Reprogramming of the Ethanol Stress Response in Saccharomyces cerevisiae by the Transcription Factor Znf1 and Its Effect on the Biosynthesis of Glycerol and Ethanol

The yeast S. cerevisiae is a major microbe that is widely used in food and nonfood industries. However, accumulation of ethanol has a negative effect on its growth and limits ethanol production. </jats:p

Actin cytoskeletal inhibitor 19,20-epoxycytochalasin Q sensitizes yeast cells lacking ERG6 through actin-targeting and secondarily through disruption of lipid homeostasis

AbstractRepetitive uses of antifungals result in a worldwide crisis of drug resistance; therefore, natural fungicides with minimal side-effects are currently sought after. This study aimed to investigate antifungal property of 19, 20-epoxycytochalasin Q (ECQ), derived from medicinal mushroom Xylaria sp. BCC 1067 of tropical forests. In a model yeast Saccharomyces cerevisiae, ECQ is more toxic in the erg6∆ strain, which has previously been shown to allow higher uptake of many hydrophilic toxins. We selected one pathway to study the effects of ECQ at very high levels on transcription: the ergosterol biosynthesis pathway, which is unlikely to be the primary target of ECQ. Ergosterol serves many functions that cholesterol does in human cells. ECQ’s transcriptional effects were correlated with altered sterol and triacylglycerol levels. In the ECQ-treated Δerg6 strain, which presumably takes up far more ECQ than the wild-type strain, there was cell rupture. Increased actin aggregation and lipid droplets assembly were also found in the erg6∆ mutant. Thereby, ECQ is suggested to sensitize yeast cells lacking ERG6 through actin-targeting and consequently but not primarily led to disruption of lipid homeostasis. Investigation of cytochalasins may provide valuable insight with potential biopharmaceutical applications in treatments of fungal infection, cancer or metabolic disorder.</jats:p

Regulation of Gluconeogenesis in Saccharomyces cerevisiae Is Mediated by Activator and Repressor Functions of Rds2▿

In Saccharomyces cerevisiae, RDS2 encodes a zinc cluster transcription factor with unknown function. Here, we unravel a key function of Rds2 in gluconeogenesis using chromatin immunoprecipitation-chip technology. While we observed that Rds2 binds to only a few promoters in glucose-containing medium, it binds many additional genes when the medium is shifted to ethanol, a nonfermentable carbon source. Interestingly, many of these genes are involved in gluconeogenesis, the tricarboxylic acid cycle, and the glyoxylate cycle. Importantly, we show that Rds2 has a dual function: it directly activates the expression of gluconeogenic structural genes while it represses the expression of negative regulators of this pathway. We also show that the purified DNA binding domain of Rds2 binds in vitro to carbon source response elements found in the promoters of target genes. Finally, we show that upon a shift to ethanol, Rds2 activation is correlated with its hyperphosphorylation by the Snf1 kinase. In summary, we have characterized Rds2 as a novel major regulator of gluconeogenesis

Selection of Potential Yeast Probiotics and a Cell Factory for Xylitol or Acid Production from Honeybee Samples

Excessive use of antibiotics has detrimental consequences, including antibiotic resistance and gut microbiome destruction. Probiotic-rich diets help to restore good microbes, keeping the body healthy and preventing the onset of chronic diseases. Honey contains not only prebiotic oligosaccharides but, like yogurt and fermented foods, is an innovative natural source for probiotic discovery. Here, a collection of three honeybee samples was screened for yeast strains, aiming to characterize their potential in vitro probiotic properties and the ability to produce valuable metabolites. Ninety-four isolates out of one-hundred and four were able to grow at temperatures of 30 °C and 37 °C, while twelve isolates could grow at 42 °C. Fifty-eight and four isolates displayed the ability to grow under stimulated gastrointestinal condition, at pH 2.0–2.5, 0.3% (w/v) bile salt, and 37 °C. Twenty-four isolates showed high autoaggregation of 80–100% and could utilize various sugars, including galactose and xylose. The cell count of these isolates (7–9 log cfu/mL) was recorded and stable during 6 months of storage. Genomic characterization based on the internal transcribed spacer region (ITS) also identified four isolates of Saccharomyces cerevisiae displayed good ability to produce antimicrobial acids. These results provided the basis for selecting four natural yeast isolates as starter cultures for potential probiotic application in functional foods and animal feed. Additionally, these S. cerevisiae isolates also produced high levels of acids from fermented sugarcane molasses, an abundant agricultural waste product from the sugar industry. Furthermore, one of ten identified isolates of Meyerozyma guilliermondiii displayed an excellent ability to produce a pentose sugar xylitol at a yield of 0.490 g/g of consumed xylose. Potentially, yeast isolates of honeybee samples may offer various biotechnological advantages as probiotics or metabolite producers of multiproduct-based lignocellulosic biorefinery.</jats:p

Trypsin hydrolysed protein fractions as radical scavengers and anti-bacterial agents from ficus deltoidea

Different molecular sizes of protein hydrolysates were prepared from the crude protein extract of Ficus deltoidea using the technique of membrane ultrafiltration after trypsin hydrolysis. Gel electrophoretic images shows the presence of 12, 8, 7 and 7 protein bands for the protein fractions prepared from the molecular weight cut-off of 3, 10, 30 and 100 kDa, respectively. The protein hydrolysates were found to have higher radical scavenging activity than those unhydrolysed fractions at the similar molecular size. They exhibited significant differences in the radical scavenging activities based on one-way analysis of variance, except for the protein hydrolysates of 30 and 100 kDa. The smallest protein hydrolysates, 3 kDa appeared to have the comparable activity (30%) with bovine serum albumin as a positive control in this study. Similarly, the 3 kDa protein hydrolysates achieved the highest inhibitory activity (87.5%) against Pseudomonas aeruginosa at the concentration of 128 µg/mL. The protein hydrolysates were found to be more effective against gram negative bacteria (P. aeruginosa and Escherichia coli) because of lower minimum inhibitory concentration (MIC) and effective inhibitory concentration at 50% (EC50) than gram positive bacterium (Staphylococcus aureus). Trypsin catalysed hydrolysis seemed to improve the anti-bacterial activity of protein hydrolysates in a bacterial strain dependent manner. The MIC could achieve 1–55 µg/mL at different molecular sizes of protein fractions. Mass spectra matching revealed that 26% of 226 identified proteins belonged to the category of plant defensive proteins in stress management and metal handling

Life-span extension by pigmented rice bran in the model yeast Saccharomyces cerevisiae

Benefits of whole grains as dietary supplements and active ingredients in health products have been promoted. Despite being neglected as an agricultural byproduct of polished rice, pigmented rice bran has emerged as a promising source of natural anti-aging compounds. Indeed, the extract of red rice bran Hom Dang cultivar contained rich phenolic acids and flavonoids. It displayed high antioxidant activities in vitro and in vivo assays. Using yeast model, extract and bioactive compounds, quercetin and protocatechuic acid found in the rice bran pericarp, effectively reduced levels of intracellular reactive oxygen species (ROS), restored plasma membrane damages and prolonged life-span of pre-treated wild-yeast cells. Importantly, these molecules modulated life span-extension through a mechanism of ROS reduction that resembles to that operated under the highly conserved Tor1- and Sir2-dependent signaling pathways, with the human homologs TORC1 and SIRT1, respectively. The key longevity factors Sch9 and Rim15 kinases, Msn2/4 regulators and a novel transcription factor Asg1, the antioxidant enzymes superoxide dismutases and glutathione peroxidases played important role in mediating longevity. Yeast clearly provides an instrumental platform for rapid screening of compounds with anti-aging efficacies and advances knowledge in the molecular study of ageing