The interplay between electron transport chain function and iron regulatory factors influences melanin formation in Cryptococcus neoformans.

Mitochondrial functions are critical for the ability of the fungal pathogen Cryptococcus neoformans to cause disease. However, mechanistic connections between key functions such as the mitochondrial electron transport chain (ETC) and virulence factor elaboration have yet to be thoroughly characterized. Here, we observed that inhibition of ETC complex III suppressed melanin formation, a major virulence factor. This inhibition was partially overcome by defects in Cir1 or HapX, two transcription factors that regulate iron acquisition and use. In this regard, loss of Cir1 derepresses the expression of laccase genes as a potential mechanism to restore melanin, while HapX may condition melanin formation by controlling oxidative stress. We hypothesize that ETC dysfunction alters redox homeostasis to influence melanin formation. Consistent with this idea, inhibition of growth by hydrogen peroxide was exacerbated in the presence of the melanin substrate L-DOPA. In addition, loss of the mitochondrial chaperone Mrj1, which influences the activity of ETC complex III and reduces ROS accumulation, also partially overcame antimycin A inhibition of melanin. The phenotypic impact of mitochondrial dysfunction was consistent with RNA-Seq analyses of WT cells treated with antimycin A or L-DOPA, or cells lacking Cir1 that revealed influences on transcripts encoding mitochondrial functions (e.g., ETC components and proteins for Fe-S cluster assembly). Overall, these findings reveal mitochondria-nuclear communication via ROS and iron regulators to control virulence factor production in C. neoformans.IMPORTANCEThere is a growing appreciation of the importance of mitochondrial functions and iron homeostasis in the ability of fungal pathogens to sense the vertebrate host environment and cause disease. Many mitochondrial functions such as heme and iron-sulfur cluster biosynthesis, and the electron transport chain (ETC), are dependent on iron. Connections between factors that regulate iron homeostasis and mitochondrial activities are known in model yeasts and are emerging for fungal pathogens. In this study, we identified connections between iron regulatory transcription factors (e.g., Cir1 and HapX) and the activity of complex III of the ETC that influence the formation of melanin, a key virulence factor in the pathogenic fungus Cryptococcus neoformans. This fungus causes meningoencephalitis in immunocompromised people and is a major threat to the HIV/AIDS population. Thus, understanding how mitochondrial functions influence virulence may support new therapeutic approaches to combat diseases caused by C. neoformans and other fungi.

The interplay between electron transport chain function and iron regulatory factors influences melanin formation in Cryptococcus neoformans.

Mitochondrial functions are critical for the ability of the fungal pathogen Cryptococcus neoformans to cause disease. However, mechanistic connections between key functions such as the mitochondrial electron transport chain (ETC) and virulence factor elaboration have yet to be thoroughly characterized. Here, we observed that inhibition of ETC complex III suppressed melanin formation, a major virulence factor. This inhibition was partially blocked upon loss of Cir1 or HapX, two transcription factors that regulate iron acquisition and use. In this regard, loss of Cir1 derepresses the expression of laccase genes as a potential mechanism to restore melanin, while HapX may condition melanin formation by controlling oxidative stress. We hypothesize that ETC dysfunction alters redox homeostasis to influence melanin formation. Consistent with this idea, inhibition of growth by hydrogen peroxide was exacerbated in the presence of the melanin substrate L-DOPA. Additionally, loss of the mitochondrial chaperone Mrj1, which influences the activity of ETC complex III and reduces ROS accumulation, also partially blocked antimycin A inhibition of melanin. The phenotypic impact of mitochondrial dysfunction was consistent with RNA-Seq analyses of WT cells treated with antimycin A or L-DOPA, or cells lacking Cir1 that revealed influences on transcripts encoding mitochondrial functions (e.g., ETC components and proteins for Fe-S cluster assembly). Overall, these findings reveal mitochondria-nuclear communication via ROS and iron regulators to control virulence factor production in C. neoformans.

High Detectivity of PbS Films Deposited on Quartz Substrates: The Role of Enhanced Photogenerated Carrier Separation.

PbS films grown on quartz substrates by the chemical bath deposition method were annealed in an O2 atmosphere to investigate the role of oxygen in the sensitization process at different annealing temperatures. The average grain size of the PbS films gradually increased as the annealing temperature increased from 400 °C to 700 °C. At an annealing temperature of 650 °C, the photoresponsivity and detectivity reached 1.67 A W-1 and 1.22 × 1010 cm Hz1/2 W-1, respectively. The role of oxides in the sensitization process was analyzed in combination with X-ray diffraction and scanning electron microscopy results, and a three-dimensional network model of the sensitization mechanism of PbS films was proposed. During the annealing process, O functioned as a p-type impurity, forming p+-type PbS layers with high hole concentrations on the surface and between the PbS grains. As annealing proceeds, the p+-type PbS layers at the grain boundaries interconnect to form a three-dimensional network structure of hole transport channels, while the unoxidized p-type PbS layers act as electron transport channels. Under bias, photogenerated electron-hole pairs were efficiently separated by the formed p+-p charge separation junction, thereby reducing electron-hole recombination and facilitating a higher infrared response.

Phase separation in viral infections.

Viruses rely on the reprogramming of cellular processes to enable efficient viral replication; this often requires subcompartmentalization within the host cell. Liquid-liquid phase separation (LLPS) has emerged as a fundamental principle to organize and subdivide cellular processes, and plays an important role in viral life cycles. Despite substantial advances in the field, elucidating the exact organization and function of these organelles remains a major challenge. In this review, we summarize the biochemical basis of condensate formation, the role of LLPS during viral infection, and interplay of LLPS with innate immune responses. Finally, we discuss possible strategies and molecules to modulate LLPS during viral infections.

The excavation of novel toxin-resistance proteins against trichothecenes toxins in Paramyrothecium roridum.

Trichothecene toxins cause serious hazard towards human health and economical crops. However, there are no sufficient molecular strategies to reduce the hazard of trichothecene toxins. Thus it is urgent to exploit novel approaches to control the hazard of trichothecenes. In this study, four trichothecene toxin-resistance genes including mfs1, GNAT1, TRP1 and tri12 in Paramyrothecium roridum were excavated based on genome sequencing results, and then expressed in toxin-sensitive Saccharomyces cerevisiae BJ5464, the toxin resistance genes pdr5, pdr10 and pdr15 of which were firstly knocked out simultaneously by the introduction of TAA stop codon employing CRISPR/Cas9 system. Therefore, three novel hazardous toxin-resistance genes mfs1, GNAT1, TRP1 in P. roridum were firstly excavated by the co-incubation of DON toxin and toxin resistant genes-containing BJ5464 strains. The in vitro function and properties of novel toxin-resistance genes coding proteins including GNAT1, MFS1 and TRP1 were identified by heterologous expression and cellular location analysis as well as in vitro biochemical reaction. The excavation of novel trichothecene toxin-resistance genes provide novel molecular clues for controlling the harm of trichothecenes, meanwhile, this study will also pave a new way for the yield improvement of trichothecenes by heterologous expression to facilitate the development of trichothecenes as anti-tumor lead compounds.

Lithocaldehydes A and B, polyketones from the deep sea-derived fungus Phomopsis lithocarpus FS508.

Lithocaldehydes A (1) and B (2), a pair of novel diastereoisomers possessing an unprecedented 6/6/5/5/6 highly-fused ring system forming an earring-like skeleton, were isolated from the deep sea-derived fungus Phomopsis lithocarpus FS508. The structures of 1 and 2 were fully characterized and established through extensive spectroscopic interpretations and ECD calculations. Moreover, compounds 1 and 2 were shown to be promising antibiotics, exhibiting potent antifungal activities that are comparable to those of the positive control nystatin.

Cytotoxic triquinane-type sesquiterpenoids from the endophytic fungus Cerrena sp. A593.

The culture broth of Cerrena sp. A593, which was isolated from Pogostemon cablin, showed potent cytotoxicity against several human tumor cell lines. The following chemical study resulted in the isolation of two new triquinane-type sesquiterpenoids, named cerrenins D (1) and E (2), along with two known compounds plerocybellone A (3) and chloriolin B (4). Their structures were fully assigned with the aid of extensive spectroscopic analysis (1H and 13C NMR, HSQC, HMBC, 1H-1H COSY, HRESIMS, and IR) and data from the literature. Moreover, cytotoxic activity in vitro of compounds 1-4 were evaluated against SF-268, MCF-7, NCI-H460, and HepG-2 tumor cell lines. The new compound 1 exhibited weak growth inhibitory activity against all the four tumor cell lines with IC50 values of 41.01, 14.43, 29.67, 44.32 µM.

Disclosure of the Molecular Mechanism of Wheat Leaf Spot Disease Caused by Bipolaris sorokiniana through Comparative Transcriptome and Metabolomics Analysis.

Wheat yield is greatly reduced because of the occurrence of leaf spot diseases. Bipolaris sorokiniana is the main pathogenic fungus in leaf spot disease. In this study, B. sorokiniana from wheat leaf (W-B. sorokiniana) showed much stronger pathogenicity toward wheat than endophytic B. sorokiniana from Pogostemon cablin (P-B. sorokiniana). The transcriptomes and metabolomics of the two B. sorokiniana strains and transcriptomes of B. sorokiniana-infected wheat leaves were comparatively analyzed. In addition, the expression levels of unigenes related to pathogenicity, toxicity, and cell wall degradation were predicted and validated by quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis. Results indicated that pathogenicity-related genes, especially the gene encoding loss-of-pathogenicity B (LopB) protein, cell wall-degrading enzymes (particularly glycosyl hydrolase-related genes), and killer and Ptr necrosis toxin-producing related unigenes in the W-B. sorokiniana played important roles in the pathogenicity of W-B. sorokiniana toward wheat. The down-regulation of cell wall protein, photosystem peptide, and rubisco protein suggested impairment of the phytosynthetic system and cell wall of B. sorokiniana-infected wheat. The up-regulation of hydrolase inhibitor, NAC (including NAM, ATAF1 and CUC2) transcriptional factor, and peroxidase in infected wheat tissues suggests their important roles in the defensive response of wheat to W-B. sorokiniana. This is the first report providing a comparison of the transcriptome and metabolome between the pathogenic and endophytic B. sorokiniana strains, thus providing a molecular clue for the pathogenic mechanism of W-B. sorokiniana toward wheat and wheat's defensive response mechanism to W-B. sorokiniana. Our study could offer molecular clues for controlling the hazard of leaf spot and root rot diseases in wheat, thus improving wheat yield in the future.

Cytotoxic Polyketides from a Deep-Sea Sediment Derived Fungus Diaporthe phaseolorum FS431.

Two new chromone-derived polyketides phaseolorins, G and H (1 and 2), and one new anthraquinone derivative, phaseolorin I (3), together with three known compounds (4-6), were isolated from the deep-sea sediment-derived fungus Diaporthe phaseolorum FS431. The structures of the new compounds were determined by comprehensive analysis of their spectroscopic data, and the absolute configuration of 1 was established by quantum chemical calculations of electron capture detection (ECD). All the isolated compounds (1-6) were tested for their in vitro cytotoxic activities against four human tumor cell lines, of which compound 4 exhibited significant effect against MCF-7, HepG-2, and A549 tumor cell lines with IC50 values of 2.60, 2.55, and 4.64 µM, respectively.

Tersone A-G, New Pyridone Alkaloids from the Deep-Sea Fungus Phomopsis tersa.

Four phenylfuropyridone racemates, (±)-tersones A-C and E (1-3, 5), one phenylpyridone racemate, (±)-tersone D (4), one new pyridine alkaloid, tersone F (6), single new phenylfuropyridone, tersone G (7) and two known analogs 8 and 9 were isolated from the deep-sea fungus Phomopsis tersa. Their structures and absolute configurations were characterized on the basis of comprehensive spectroscopic analyses, single-crystal X-ray diffraction experiments, and electronic circular dichroism (ECD) calculations. Moreover, compounds 1-9 were evaluated for in vitro antimicrobial and cytotoxic activity. Compounds 5b and 8b exhibited antibacterial activity against S. aureus with the MIC value of 31.5 µg/mL, while compound 5b showed cytoxic activities against SF-268, MCF-7, HepG-2 and A549 cell lines with IC50 values of 32.0, 29.5, 39.5 and 33.2 µM, respectively.

Four new metabolites from the endophytic fungus Diaporthe lithocarpus A740.

One new benzophenone derivative, named tenllone I (1), two new eremophilane derivatives lithocarins B (2) and C (3), and a new monoterpentoid lithocarin D (4), together with two know compounds (5 and 6) were isolated from the endophytic fungus Diaporthe lithocarpus A740. All of the structures for these new compounds were fully characterized and established on the basis of extensive spectroscopic interpretation. In addition, all the isolated compounds were evaluated in vitro for their cytotoxic activity. Compounds 2, 3, and 5 showed weak inhibitory activities against tumor cell lines.

Lithocarols A-F, six tenellone derivatives from the deep-sea derived fungus Phomopsis lithocarpus FS508.

Lithocarols A-F (1-6) possessing novel highly-oxygenated isobenzofuran core, together with a related known compound isoprenylisobenzofuran A (7) were isolated from the marine-derived fungus Phomopsis lithocarpus FS508. Among them, lithocarols A-E (1-5) represent the first examples of poly-ketal derivatives in tenellone family. The structures for all these compounds were fully elucidated by spectroscopic analysis, X-ray diffraction, and electronic circular dichroism calculations. Their cytotoxic assay disclosed that compounds 1-4 displayed moderate growth inhibitory effect against four human tumor cell lines with the IC50 values ranging from 10.5 to 38.7 µM.

Asymmetric Transmission in a Mie-Based Dielectric Metamaterial with Fano Resonance.

Chiral metamaterials with asymmetric transmission can be applied as polarization-controlled devices. Here, a Mie-based dielectric metamaterial with a spacer exhibiting asymmetric transmission of linearly polarized waves at microwave frequencies was designed and demonstrated numerically. The unidirectional characteristic is attributed to the chirality of the metamolecule and the mutual excitation of the Mie resonances. Field distributions are simulated to investigate the underlying physical mechanism. Fano-type resonances emerge near the Mie resonances of the constituents and come from the destructive interference inside the structure. The near-field coupling further contributes to the asymmetric transmission. The influences of the lattice constant and the spacer thickness on the asymmetric characteristics were also analyzed by parameter sweeps. The proposed Mie-based metamaterial is of a simple structure, and it has the potential for applications in dielectric metadevices, such as high-performance polarization rotators.

Chromone-Derived Polyketides from the Deep-Sea Fungus Diaporthe phaseolorum FS431.

Five new chromone-derived polyketides phaseolorins A-F (1⁻5), together with nine known compounds, were isolated from the deep-sea derived fungus Diaporthe phaseolorum FS431. The structures of new compounds were determined by analysis of their NMR and high-resolution electrospray ionization mass spectroscopy (HRESIMS) spectroscopic data. The absolute configurations were confirmed by chemical transformations, extensively experimental electron capture detection (ECD) calculations, or X-ray crystallography. Among them, compound 2 represented the first example for a new family of chromone derivative possessing an unprecedented recombined five-member γ-lactone ring. Moreover, the new compounds (1⁻5) were evaluated for in vitro cytotoxic activities against a panel of human cancer cell lines.

Cytosporins A-D, novel benzophenone derivatives from the endophytic fungus Cytospora rhizophorae A761.

Four novel benzophenone derivatives, cytosporins A-D (1-4), hemiterpene-conjugated phenolics with an unprecedented benzo[b][1,5]dioxocane skeleton, were isolated from Cytospora rhizophorae A761. The structures of the new compounds were fully characterized on the basis of extensive spectroscopic analysis. The deduced structure represents the first example of natural meroterpenoids which bear a benzo[b][1,5]dioxocane framework embodying hemiterpene and benzophenone moieties. Moreover, compounds 1-4 were evaluated for in vitro antimicrobial activity.

Three new diterpenes and two new sesquiterpenoids from the endophytic fungus Trichoderma koningiopsis A729.

Three new diterpenes koninginols A-C (1-3) and two new sesquiterpenoids 11-hydroxy-15-drimeneoic acid (4), koninginol D (5), together with twelve known compounds (6-17) were isolated from the endophytic fungus Trichoderma koningiopsis A729 derived from Morinda officinalis. Their structures were fully assigned with the aid of extensive spectroscopic analysis and reported data from the previous literatures. Koninginols A and B were disclosed as intriguing diterpene alkaloids, whereas the koninginol C was disclosed as one of the two examples of harziandione diterpene. All the isolates were evaluated for their antitumor activity, and compounds 1-2, 4-6, 11-13, 16-17 were evaluated for their antibacterial activity, wherein the new compounds 1 and 2 exhibited significant antibacterial activity against Bacillus subtilis with MIC values of 10 and 2 µg/mL, respectively.

A Mechanical Sensor Using Hybridized Metamolecules.

Hybridized metamaterials with collective mode resonance are usually applied as sensors. In this paper, we make use of one Mie-based hybridized metamolecule comprising of dielectric meta-atoms and an elastic bonding layer in order to detect the distances and applied forces. The hybridization induced splitting results in two new collective resonance modes, of which the red-shifted mode behaves as the in-phase oscillation of two meta-atoms. Owing to the synergy of the oscillation, the in-phase resonance appears as a deep dip with a relatively high Q-factor and figure of merit (FoM). By exerting an external force, namely by adjusting the thickness of the bonding layer, the coupling strength of the metamolecule is changed. As the coupling strength increases, the first collective mode dip red-shifts increasingly toward lower frequencies. By fitting the relationship of the distance⁻frequency shift and the force⁻frequency shift, the metamolecule can be used as a sensor to characterize tiny displacement and a relatively wide range of applied force in civil engineering and biological engineering.

Two new 12-membered macrolides from the endophytic fungal strain Cladosprium colocasiae A801 of Callistemon viminalis.

Two new polyketide metabolites, the 12-membered macrolides 4-hydroxy-12-methyloxacyclododecane-2,5,6-trione (1) and 12-methyloxacyclododecane-2,5,6-trione (2), were isolated from the endophytic fungal strain Cladosprium colocasiae A801 of the plant Callistemon viminalis, together with five known derivatives. Their structures were fully characterized by means of detailed spectroscopic analysis for new structures, and in comparison with published data for known compounds. The antibacterial, cytotoxic, and α-glucosidase inhibitory activities of the new compounds 1 and 2 were evaluated.

Two new metabolites from Daldinia eschscholtzii, an endophytic fungus derived from Pogostemon cablin.

The chemical investigation of the mycelia of endophytic fungus Daldinia eschscholtzii A630, which was isolated from the medicinal plant Pogostemon cablin, resulted in the isolation of two new compounds, named eschscholin A (1), 3-ene-2-methyl-2H-1-benzopyran-5-ol (2), and one new natural product 3,5-dihydroxy-2-methyl-4H-chromen-4-one (3), along with seven known compounds. Their structures were fully characterized by means of detailed spectroscopic analysis, and in comparison with published data for known compounds. All of the isolated compounds (1-10) were evaluated for their antibacterial activities.

An Easy and Efficient Strategy for the Enhancement of Epothilone Production Mediated by TALE-TF and CRISPR/dcas9 Systems in Sorangium cellulosum.

Epothilones are a kind of macrolides with strong cytotoxicity toward cancer cells and relatively lower side effects compared with taxol. Epothilone B derivate ixabepilone has been used for the clinical treatment of advanced breast cancer. However, the low yield of epothilones and the difficulty in the genetic manipulation of Sorangium cellulosum limited their wider application. Transcription activator-like effectors-Trancriptional factor (TALE-TF)-VP64 and clustered regularly interspaced short palindromic repeats (CRISPR)/dCas9-VP64 have been demonstrated as effective systems for the transcriptional improvement. In this study, a promoter for the epothilone biosynthesis cluster was obtained and the function has been verified. The TALE-TF-VP64 and CRISPR/dcas9-VP64 target P3 promoter were electroporated into S. cellulosum strain So ce M4, and the transcriptional levels of epothilone biosynthesis-related genes were significantly upregulated. The yield of epothilone B was improved by 2.89- and 1.53-fold by the introduction of recombinant TALE-TF-VP64-P3 and dCas9-VP64-P3 elements into So ce M4, respectively. The epothilone D yield was also improved by 1.12- and 2.18-fold in recombinant dCas9-So ce M4 and TALE-VP64 strains, respectively. The transcriptional regulation mechanism of TALE-TF-VP64 and the competition mechanism with endogenous transcriptional factor were investigated by electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP), demonstrating the combination of the P3 promoter and TALE-TF element and the competition between TALE-TF and endogenous transcriptional protein. This is the first report on the transcriptional regulation of the epothilone biosynthetic gene cluster in S. cellulosum using the TALE-TF and dCas9-VP64 systems, and the regulatory mechanism of the TALE-TF system for epothilone biosynthesis in S. cellulosum was also firstly revealed, thus shedding light on the metabolic engineering of S. cellulosum to improve epothilone yields substantially and promoting the application of epothilones in the biomedical industry.