Project description:The high osmolarity glycerol response (HOG) pathway plays a pivotal role in the stress response, virulence regulation, and differentiation of fungi, including Cryptococcus neoformans that causes fatal meningoencephalitis. Core signaling components of in the HOG pathway, including the Tco-Ypd1-Ssk1 phosphorelay system and the Ssk2-Pbs2-Hog1 MAPK module, have been elucidated but its downstream transcription factors remain unclear. Here we demonstrated that Atf1 with a basic leucine zipper domain is the transcription factor downstream of Hog1 in C. neoformans. We found that ATF1 expression was differentially regulated by oxidative damaging agents, mainly in a Hog1-dependent, but Mpk1-independent, manner. Interestingly, Atf1 not only promoted oxidative stress response and adaptation, but also played an opposing role to Hog1 in the process. Atf1 primarily localized to the nucleus under both unstressed and oxidative stress conditions in a Hog1-independent manner. Our data demonstrated that Atf1 promoted pheromone production and sexual differentiation under negative control by Hog1. Finally, a DNA microarray-based transcriptome analysis of the atf1M-bM-^HM-^F mutant under unstressed and oxidative stress conditions revealed that Atf1 regulated oxidative stress response genes, including a sulfiredoxin gene (SRX1). Intriguing, the array data further demonstrated that Atf1 modulated basal expression of genes involved in DNA repair and genotoxic stress response. Supporting this, we found that the atf1M-bM-^HM-^F mutant was highly sensitive to genotoxic agents. In conclusion, this study provided a further insight into the Hog1-dependent oxidative and genotoxic stress response and differentiation mechanism of C. neoformans. There are more than 95% of genome homology between JEC21 and H99. Therefore 6 slides of JEC21 (Cryptococcus neoformans var. neoformans serotype D) 70-mer oligo are used in this analysis, 3 biological replicate experiments are performed, total RNAs are extracted 2 conditions (with or without treatment of Hydroten peroxide) from H99 (H99 Wild type strain (Cryptococcus neoformans var. grubii serotype A), and atf1M-NM-^T). We use the mixed all of total RNAs from this experiment as a control RNA. We use Cy3 as Sample dye and Cy5 as a control dye.

Project description:Carbon dioxide (CO2) sensing, transport, and metabolism play a pivotal role in survival and proliferation of pathogenic microbes infecting human host from natural environments due to the drastic difference of CO2 levels. Carbonic anhydrases (CAs) are not only key CO2-metabolic enzymes catalyzing reversible interconversion between CO2 and bicarbonate (HCO3-), but also important CO2-signaling modulators. Cryptococcus neoformans that causes fatal fungal meningitis contains two functional CAs, Can1 and Can2, among which Can2 plays essential roles for growth and sexual differentiation of the pathogen. However, downstream genes and signaling network regulated by CAs have not been studied thus far. In this study, we constructed a C. neoformans strain where CAN2 expression is controlled by the CTR4 (copper transporter) promoter and elucidated its transcriptome patterns by using DNA microarray analysis to elucidate downstream target genes of Can2. Expectedly, the CAN2 promoter replacement strain showed growth defects in a CO2-dependent manner when CAN2 is repressed. The CA-transcriptome analysis discovered a number of Can2-dependent genes, including those involved in fatty acid biosynthesis (FAS1), sexual differentiation (GPB1), capsule structure organization (CAS3), iron-metabolism (CFO2), and a number of stress-regulated genes, including an oxidative stress-responsive Atf1 transcription factor, although a majority of them do not have any orthologs in other fungi. The present study revealed other roles of Atf1 in capsule and melanin production and diverse stress responses, including thermotolerance and antifungal drug resistance, of C. neoformans. This study provides further insights into the signaling network of CA/CO2-sensing pathway in pathogenic fungi. 17 slides are used in this analysis, 3 or 2 biological replicate experiments are performed, total RNAs are extracted from 2 strains (H99 Wild type strain, CTR4::CAN2) at 2 time points (0hr time, 12hr time) in 2 conditions (BCS, CuSO4). We use the mixed all of total RNAs from this experiment as a control RNA. We use Cy5 as Sample dye and Cy3 as a control dye. Several experiment samples are dye swaped.

Project description:The ability to sense and adapt to a hostile host environment is a crucial element for virulence of pathogenic fungi, including Cryptococcus neoformans. These cellular responses are evoked by diverse signaling cascades, including the stress-activated HOG pathway. Despite previous analysis of central components of the HOG pathway, its downstream signaling network is poorly characterized in C. neoformans. Here we performed comparative transcriptome analysis with HOG signaling mutants to explore stress-regulated genes and their correlation with the HOG pathway in C. neoformans. In this study we not only provide important insights into remodeling patterns of global gene expression for counteracting external stresses, but also elucidated novel characteristics of the HOG pathway in C. neoformans. First, inhibition of the HOG pathway increases expression of ergosterol biosynthesis genes and cellular ergosterol content, conferring a striking synergistic antifungal activity with amphotericin B and providing an excellent opportunity to develop a novel therapeutic method for treatment of cryptococcosis. Second, a number of cadmium-sensitive genes are differentially regulated by the HOG pathway, and their mutation causes resistance to cadmium. Finally, we have discovered novel stress-defense and HOG-dependent genes, which encodes a sodium/potassium efflux pump, protein kinase, multidrug transporter system, and elements of the ubiquitin-dependent system. There is more than 95% genome homology between JEC21 (Cryptococcus neoformans var. neoformans serotype D) and H99 (Cryptococcus neoformans var. grubii serotype A). Therefore, 100 slides of JEC21 70-mer oligo arrays are used in this analysis. 3 biological replicate experiments are performed. Total RNAs are extracted under 3 conditions (1M NaCl, 20ug/ul Fludioxonil, 2.5mM Hydrogen peroxide) at 3 time points (0time, 30min, 60min) with 4 strains from H99 (wild type, hog1Î , ssk1Î , skn7Î). We use a mix of all the total RNAs from this experiment as the control RNA. We use Cy5 as the sample dye and Cy3 as the control dye. Several samples are dye swapped.

Project description:The target of rapamycin (TOR) pathway is an evolutionarily conserved signal transduction system that is activated by varying nutrient and environmental signals and governs a plethora of eukaryotic biological processes. Nevertheless, its role in the human fungal pathogen Cryptococcus neoformans remains elusive. In this study, we investigated the TOR pathway by functionally characterizing two Tor-like kinases, Tor1 and Tlk1, in C. neoformans. We successfully deleted TLK1, but not TOR1. TLK1 deletion did not result in any evident in vitro phenotypes, except for a minor role in diamide and polyene resistance, suggesting that Tlk1 is mainly dispensable for the growth of C. neoformans. We further demonstrated that Tor1, but not Tlk1, is essential and the target of rapamycin by constructing and analyzing conditionally regulated strains and sporulation analysis of heterozygous mutants in the diploid strain background. To analyze the functions of Tor1 in more detail, we constructed constitutive TOR1 overexpression strains. Tor1 negatively regulated thermotolerance and the DNA damage response, which are two important virulence factors of C. neoformans. We also found that TOR1 overexpression reduced Mpk1 phosphorylation, which is required for cell wall integrity and thermoresistance, and Rad53 phosphorylation, which governs the DNA damage response pathway. Tor1 is localized to the cytoplasm but enriched in the vacuole membrane. Phosphoproteomics and transcriptomics revealed that Tor1 regulates a variety of biological processes, including metabolic processes, cytoskeleton organization, ribosome biogenesis, autophagy, and stress response. Finally, screening rapamycin-sensitive and -resistant kinase and transcription factor mutants revealed that the TOR pathway may crosstalk with a number of signaling pathways, including the Hog1 pathway. In conclusion, our study demonstrates that a single Tor1 kinase plays a variety of roles in the fungal meningitis pathogen C. neoformans.

Dataset Information

Cryptococcus neoformans var. grubii

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