Expression of terpene synthase-related genes in parents and offspring of Flammulina filiformis based on differences in volatile aroma components.

Flammulina filiformis (F. filiformis) is one of the four major edible types of fungus in the world and has been cultivated in China since 800 CE (Anno Domini). Some of the most essential criteria for evaluating the quality of F. filiformis are the types and contents of volatile components present. A focused study on screened the terpene synthase genes involved in the aroma of offspring and compared key terpenoids between parents and offspring, which is helpful for the development and application of F. filiformis. Firstly, the volatile aroma components of parent and offspring F. filiformis were extracted using two pretreatment procedures, and then were semi-quantified by an internal standard. Forty-eight, fifty-eight, and forty-eight volatile compounds were identified in parents and offspring of three different strains, and 15, 22, and 12 aroma compounds (OAVs ≥ 1) were further screened out via calculating their odor activity values (OAVs). Terpenoids, in particular linalool and eucalyptol, which contribute more to the aroma, result in the unique green and grassy aroma of the offspring. At last, the F. filiformis genome was resequenced and the coordinates of genes related to terpenoid synthase were determined. The results showed that Scaffolds, including scaffold3.t874 and scaffold9.t157 were connected to terpenoid synthesis of offspring (No. 61523). The variant genes g269 and g61 were related to terpenoid synthase sequences. This study provides a theoretical foundation for the cultivation of more diverse and unique varieties of F. filiformis.

A simple transmission dynamics model for predicting the evolution of COVID-19 under control measures in China.

Epidemic forecasting provides an opportunity to predict geographic disease spread and counts when an outbreak occurs and plays a key role in preventing or controlling their adverse impact. However, conventional prediction models based on complex mathematical modelling rely on the estimation of model parameters, which yields unreliable and unsustainable results. Herein, we proposed a simple model for predicting the epidemic transmission dynamics based on nonlinear regression of the epidemic growth rate and iterative methods, which is applicable to the progression of the COVID-19 outbreak under the strict control measures of the Chinese government. Our model yields reliable and accurate results as confirmed by the available data: we predicted that the total number of infections in mainland China would be 91 253, and the maximum number of beds required for hospitalised patients would be 62 794. We inferred that the inflection point (when the growth rate turns from positive to negative) of the epidemic across China would be mid-February, and the end of the epidemic would be in late March. This model is expected to contribute to resource allocation and planning in the health sector while providing a theoretical basis for governments to respond to future global health crises or epidemics.

Assessment of fine-scale parameterizations at low latitudes of the North Pacific.

Fine-scale parameterizations based on shear and stratification are widely used to study the intensity and spatial distribution of turbulent diapycnal mixing in the ocean. Two well-known fine-scale parameterizations, Gregg-Henyey-Polzin (GHP) parameterization and MacKinnon-Gregg (MG) parameterization, are assessed with the full-depth microstructure data obtained in the North Pacific. The GHP parameterization commonly used in the open ocean succeeds in reproducing the dissipation rates over smooth topography but fails to predict the turbulence over rough topography. Failure of GHP parameterization over rough topography is attributed to the deviation of internal wave spectrum from the Garrett-Munk (GM) spectrum. The internal wave field over rough topography is characterized by energetic intermediate-scale and small-scale internal waves that are not described well by the GM model. The MG parameterization that is widely used in coastal environments is found to be successful in reproducing the dissipation rates over both smooth and rough topographies. The efficacy of GHP and MG parameterizations in evaluating the dissipation rates has been assessed. The result indicates that MG parameterization predicts the magnitude and variability of the dissipation rates better than the GHP parameterization.

Changes in trehalose content, enzyme activity and gene expression related to trehalose metabolism in Flammulina velutipes under heat shock.

Trehalose plays important roles in the protection of organisms against adverse environmental conditions. The growth and development of Flammulina velutipes is regulated and controlled under complex external conditions. This study investigated the effect of heat stress on trehalose metabolism in mycelia and fruiting bodies. The activities of enzymes involved in trehalose metabolism, the transcriptional levels of the corresponding genes and the trehalose content in the mycelia of Flammulina velutipes strain Dan3 under relatively high temperatures were investigated. The mycelia and fruiting bodies of a strain cultivated in a factory were collected at different stages to examine the trehalose content and expression levels of various genes. The results showed that intracellular trehalose significantly accumulated in the mycelia in response to 37 °C heat shock. Heat shock significantly stimulated the activities of trehalose-6-phosphate synthase and trehalose-6-phosphate phosphatase, thereby promoting the accumulation of trehalose for the first 2-6 h. The activity of neutral trehalase also decreased during this period. In addition, changes in the activities of trehalose-6-phosphate synthase, trehalose-6-phosphate phosphatase and neutral trehalase paralleled changes in the expression levels of the regulatory genes. As for the trehalose phosphorylase, the degradation of trehalose was stronger than its synthesis under heat stress. Heat shock can induce a stress response in the mycelia through the regulation of genes related to trehalose metabolism and the subsequent promotion and control of the transcription and translation of enzymes. The analysis of the trehalose and gene expression levels in the cultivated strain suggests that a substantial amount of trehalose had accumulated in the mycelia prior to induction of the primordia, and the fruiting bodies could possibly utilize degraded trehalose that translocated from the mycelia to maintain their growth.

Anti-Helicobacter pylori activity of bioactive components isolated from Hericium erinaceus.

ETHNOPHARMACOLOGICAL RELEVANCE: The fungus Hericium erinaceus (Bull.) Pers is used in Chinese traditional medicine to treat symptoms related to gastric ulcers. Different extracts from the fungus were assessed for anti-Helicobacter pylori activity to investigate the antibacterial activity of the ethanol extracts from H. erinaceus and verify the traditional indication of use. MATERIALS AND METHODS: The fruiting bodies of H. erinaceus were concentrated with ethanol by HPD-100 macroporous resin and the whole extract was partitioned by petroleum ether and chloroform to afford fractions with using a silica gel column. Several pure compounds of petroleum ether extracts were obtained and analyzed using nuclear magnetic resonance (NMR). The activity of the extracts and fractions towards H. pylori was assessed by the microdilution assay and by the disk diffusion assay in vitro. From the most active fraction, two pure compounds were isolated and identified as the main components with anti-H. pylori activity from the fungus H. erinaceus. The cytotoxicity of these two compounds against the human erythroleu-kemia cell line K562 was also evaluated. RESULTS: The crude ethanol extracts from the fungus H. erinaceus were inhibitory to H. pylori. The petroleum ether extracts (PE1s, PE2s) and the chloroform extracts (TEs) demonstrated strong inhibition to H. pylori. The inhibition of H. pylori was observed through an agar dilution test with minimal inhibition concentration (MIC) values from 400µg/mL to 12.5µg/mL. Two pure compounds, 1-(5-chloro-2-hydroxyphenyl)-3-methyl-1-butanone and 2,5-bis(methoxycarbonyl)terephthalic acid were isolated from the petroleum ether fractions and identified using (1)H NMR and (13)C NMR spectra analysis. The MIC value for 1-(5-chloro-2-hydroxyphenyl)-3-methyl-1-butanone was 12.5-50µg/mL and the MIC value for 2,5-bis(methoxycarbonyl)terephthalic acid was 6.25-25µg/mL. Both two compounds showed weak cytotoxicity against K562 with IC50<200mM. CONCLUSIONS: This study revealed that the extracts from petroleum ether contribute to the anti-H. pylori activity. The compounds obtained from petroleum ether extracts, 1-(5-chloro-2-hydroxyphenyl)-3-methyl-1-butanone and 2,5-bis(methoxycarbonyl)terephthalic acid, inhibit the growth of H. pylori.

Horizontal eddy energy flux in the world oceans diagnosed from altimetry data.

During the propagation of coherent mesoscale eddies, they directly or indirectly induce many effects and interactions at different scales, implying eddies are actually serving as a kind of energy carrier or energy source for these eddy-related dynamic processes. To quantify this dynamically significant energy flow, the multi-year averaged horizontal eddy energy fluxes (EEFs) were estimated by using satellite altimetry data and a two-layer model based on hydrographic climatology. There is a strong net westward transport of eddy energy estimated at the mean value of ~13.3 GW north of 5°N and ~14.6 GW at the band 5°S ~ 44°S in the Southern Hemisphere. However, poleward of 44°S east-propagating eddies carry their energy eastward with an averaged net flux of ~3.2 GW. If confirmed, it would signify that geostrophic eddies not only contain the most of oceanic kinetic energy (KE), but also carry and spread a significant amount of energy with them.

Transcriptome analysis of candidate genes and signaling pathways associated with light-induced brown film formation in Lentinula edodes.

High-throughput Illumina RNA-seq was used for deep sequencing analysis of the transcriptome of poly(A)+ RNA from mycelium grown under three different conditions: 30 days darkness (sample 118), 80 days darkness (313W), and 30 days darkness followed by 50 days in the light (313C), in order to gain insight into the molecular mechanisms underlying the process of light-induced brown film (BF) formation in the edible mushroom, Lentinula edodes. Of the three growth conditions, BF formation occurred in 313C samples only. Approximately 159.23 million reads were obtained, trimmed, and de novo assembled into 31,511 contigs with an average length of 1,746 bp and an N 50 of 2,480 bp. Based on sequence orientations determined by a BLASTX search against the NR, Swiss-Prot, COG, and KEGG databases, 24,246 (76.9 %) contigs were assigned putative descriptions. Comparison of 313C/118 and 313C/313W expression profiles revealed 3,958 and 5,651 significantly differentially expressed contigs (DECs), respectively. Annotation using the COG database revealed that candidate genes for light-induced BF formation encoded proteins linked to light reception (e.g., WC-1, WC-2, phytochrome), light signal transduction pathways (e.g., two-component phosphorelay system, mitogen-activated protein kinase pathway), and pigment formation (e.g., polyketide synthase, O-methyltransferase, laccase, P450 monooxygenase, oxidoreductase). Several DECs were validated using quantitative real-time polymerase chain reaction. Our report is the first to identify genes associated with light-induced BF formation in L. edodes and represents a valuable resource for future genomic studies on this commercially important mushroom.

An axenic culture system for fruiting body formation by an edible bolete phylogenetically related to culinary-medicinal penny bun mushroom, Boletus edulis Bull.:Fr. strains from China.

The ability of two freshly isolated Boletus stains to fruit under axenic conditions was tested using different solid and liquid nutrient media. One strain (YNCX04) produced numerous primordia from which fruiting bodies, 12 mm and 10 mm in length, with grey, convex pilei, and yellow-white, clavate stipes developed between 15 and 30 d after inoculation of fungal mycelium onto a solid medium consisting of mineral salts, thiamine, glucose, potato, an extract of Cunninghamia lanceolata root, and agar. The other strain (YNB200) produced numerous primordia but no sporophores. Strain YNCX04 lost the ability to form fruiting bodies in axenic culture 6 mo after initial isolation but retained the ability to form primordia for up to 18 mo. Based on internal transcribed spacer sequencing data, strains YNB200 and YNCX04 formed a sub-cluster together with four previously designated Boletus edulis strains from China. Phylogenetic analysis placed the Chinese strains closer to B. aestivalis than to European and North American strains of B. edulis, although a 29-bp fragment specific to all the B. aestivalis strains was absent from all the Chinese strains. Furthermore, partial 18S rDNA sequences from strains YNB200 and YNCX04 exhibited 98% similarity with an 18S rDNA sequence from B. edulis strain Be3. Further molecular studies are indicated to more accurately establish the taxonomic positions ofF3 and F4-3, as well as the Chinese strains designated as B. edulis.

Scaling of the local convective heat flux in turbulent Rayleigh-Bénard convection.

Local convective heat flux J(r) in turbulent thermal convection is obtained from simultaneous velocity and temperature measurements in a cylindrical cell filled with water. The measured J(r) in the bulk region shows a different scaling behavior with varying Rayleigh numbers compared with that measured in the plume-dominated regions near the sidewall and near the lower conducting plate. The local transport measurements thus allow us to disentangle boundary and bulk contributions to the total heat flux and directly check their respective scaling behavior against the theoretical predictions.

Extraction of plumes in turbulent thermal convection.

We present a scheme to extract the velocity of buoyant structures in turbulent thermal convection from simultaneous local velocity and temperature measurements. Applying this scheme to measurements taken at positions within the convection cell where the buoyant structures are dominated by plumes, we obtain the temperature dependence of the plume velocity and understand our results using the equations of motion. We further obtain the scaling behavior of the average local heat flux in the vertical direction at the cell center with the Rayleigh number and find that the scaling exponent is different from that measured for the Nusselt number. This difference leads to the conclusion that heat cannot be mainly transported through the central region of the convection cell.

Prandtl number dependence of the viscous boundary layer and the Reynolds numbers in Rayleigh-Bénard convection.

We report results from high Prandtl number turbulent thermal convection experiments. The viscous boundary layer and the Reynolds number are measured in four different fluids over wide ranges of the Prandtl number Pr and the Rayleigh number Ra, all in a single convection cell of unity aspect ratio. We find that the normalized viscous layer thickness may be represented as delta(v)/L=0.65Pr(0.24)Ra(-0.16). The Reynolds number based on the oscillation frequency of the large-scale flow is found as Re(o)(Ra,Pr)=1.1Ra(0.43)Pr(-0.76) and that based on the rms velocity Re(rms)(Ra,Pr)=0.84Ra(0.40)Pr-0.86. Both the Ra and the Pr exponents of Re(V(m))(Ra,Pr) based on the maximum velocity of the circulating wind appear to vary across the range of Pr covered, changing from 0.5 to 0.68 and -0.88 to -0.95, respectively, as Pr is increased from 6 to 1027.