The Tissue Browning and Concomitant Toughening of Yellow Flammulina filiformis Stipes Is Caused by Oxidative Damage-Mediated Metabolic Disorder and Cell Wall Glycan Remodeling.

The browning and associated toughening of fruiting body stipes are the main causes of declines in the commercial production of yellow Flammulina filiformis. The dynamic metabolic changes from the top to bottom stipe sections of yellow F. filiformis fruiting bodies were investigated by integrating physiological, transcriptomic, and metabolomic analyses. The results indicated that oxidative stress levels gradually increased accompanying the degree of tissue browning and toughening from the top to bottom sections of F. filiformis stipes. In-depth analysis showed that there were remarkable changes in the expression of genes, and the content of metabolites correlated with the primary and secondary metabolism of F. filiformis stipes. Interestingly, the expression levels of genes participating in chitosan biosynthesis and the degree of deacetylation of chitosan increased from top to bottom in F. filiformis stipes, implying that cell wall glycan remodeling may contribute to concomitant toughening of the browning of F. filiformis stipes.

MAC Family Transcription Factors Enhance the Tolerance of Mycelia to Heat Stress and Promote the Primordial Formation Rate of Pleurotus ostreatus.

Pleurotus ostreatus is a typical tetrapolar heterologous edible mushroom, and its growth and development regulatory mechanism has become a research hotspot in recent years. The MAC1 protein is a transcription factor that perceives copper and can regulate the expression of multiple genes, thereby affecting the growth and development of organisms. However, its function in edible mushrooms is still unknown. In this study, two transcription factor genes, PoMCA1a and PoMAC1b, were identified. Afterwards, PoMAC1 overexpression (OE) and RNA interference (RNAi) strains were constructed to further explore gene function. The results showed that the PoMAC1 mutation had no significant effect on the growth rate of mycelia. Further research has shown that OE-PoMAC1a strains and RNAi-PoMAC1b strains exhibit strong tolerance under 32 °C heat stress. However, under 40 °C heat stress, the OE of PoMAC1a and PoMAC1b promoted the recovery of mycelial growth after heat stress. Second, the OE of PoMAC1a can promote the rapid formation of primordia and shorten the cultivation cycle. In summary, this study indicated that there are functional differences between PoMAC1a and PoMAC1b under different heat stresses during the vegetative growth stage, and PoMAC1a has a positive regulatory effect on the formation of primordia during the reproductive growth stage.

Transcription factor FfMYB15 regulates the expression of cellulase gene FfCEL6B during mycelial growth of Flammulina filiformis.

BACKGROUND: Cellulose degradation can determine mycelial growth rate and affect yield during the growth of Flammulina filiformis. The degradation of cellulose requires the joint action of a variety of cellulases, and some cellulase-related genes have been detected in mushrooms. However, little is known about the transcriptional regulatory mechanisms of cellulose degradation. RESULTS: In this study, FfMYB15 that may regulate the expression of cellulase gene FfCEL6B in F. filiformis was identified. RNA interference (RNAi) showed that FfCEL6B positively regulated mycelial growth. Gene expression analyses indicated that the expression patterns of FfCEL6B and FfMYB15 in mycelia cultured on the 0.9% cellulose medium for different times were similar with a correlation coefficient of 0.953. Subcellular localization and transcriptional activity analyses implied that FfMYB15 was located in the nucleus and was a transcriptional activator. Electrophoretic mobility shift assay (EMSA) and dual-luciferase assays demonstrated that FfMYB15 could bind and activate FfCEL6B promoter by recognizing MYB cis-acting element. CONCLUSIONS: This study indicated that FfCEL6B played an active role in mycelial growth of F. filiformis and was regulated by FfMYB15.

Use of Hierarchical Cascading Technique for FEM Analysis of Transverse Mode Behaviors in Surface Acoustic Wave Devices.

This paper describes application of the hierarchical cascading technique (HCT) to the 3D FEM analysis of transverse mode behaviors in surface acoustic wave (SAW) devices. Mirror cascading is proposed as a speed up technique for the HCT operation using the general purpose graphic processing unit (GPGPU). Two methods are implemented for the analysis; one is impedance calculation, and the other is calculation of SAW scattering coefficients at boundaries. It is demonstrated that HCT enables rapid calculation for successive simulation with scanning design parameters. Thus, techniques discussed in the paper are quite effective for optimization of device structures. It is also shown that GPGPU can accelerate HCT calculation dramatically, especially for 3D cases discussed in this paper.

Analysis of SAW Scattering With Discontinuous Periodic Gratings Using Travelling Wave Excitation and Hierarchical Cascading Technique.

This paper proposes a technique to analyze surface acoustic wave (SAW) scattering at discontinuity in grating structures using the hierarchical cascading technique. The traveling wave excitation is applied to generate a specific SAW mode. Then the displacement distribution is obtained for the passive regions. The incident, reflected, and transmitted components are selectively evaluated by the Fourier transform so as to determine the scattering coefficients at the discontinuity. Rayleigh SAWs on the SiO2/128°YX-LiNbO3 structure and SH SAWs on the 42°YX-LiTaO3 structure are used as examples, and the behavior of two kinds of discontinuity are analyzed, and the obtained results are compared with those obtained by the COM model.

Influence of Coupling Between Rayleigh and SH SAWs on Rotated -Cut LiNbO3 to Their Propagations.

This paper investigates the influence of coupling between Rayleigh and shear-horizontal (SH) surface acoustic waves (SAWs) on rotated Y-cut LiNbO3 to their electromechanical coupling. For the purpose, a coupling-of-mode (COM) model including the coupling between two SAWs is developed, and the coupling influences to their excitation in addition to electromechanical coupling factors are discussed. Then, its validity is confirmed by comparison of its results with the finite-element method analysis. Comparing with the conventional COM shows this extended COM model could fit the complex value area much better in the dispersion curve analysis. After that, variation of COM parameters with the device design is discussed. Then, all COM parameters are fit by polynomial equations and the procedures to find the optimal rotation angle are obtained in terms of the SH mode suppression. It indicates that the optimal angle changes rapidly at certain Cu thickness, which is due to decoupling between two SAW modes. At last, structure based on the low-cut LiNbO3 is discussed and the validity of this COM model is further confirmed.

Impact of Coupling Between Multiple SAW Modes on Piston Mode Operation of SAW Resonators.

This paper investigates piston mode operation (PMO) when two kinds of surface acoustic waves (SAWs) exist and are coupled to each other. The extended thin plate model is used for the analysis. First, a PMO condition is derived in a closed form. It is verified that PMO is possible without adding phase shifters by the use of two SAW coupling. It is also shown that this operation offers suppression of the transverse modes for a wider frequency range than the conventional PMO. Then, parameters defined in the model are extracted for various SiO2-overlay/Al-grating/128° YX-LiNbO3 substrate structures, and the structure satisfying the PMO condition is designed. Finally, the structure is also analyzed using the 3-D finite element method. The result agrees well with that calculated by the extended thin plate model.

Wavenumber domain analysis of surface acoustic wave scattering from localized gratings on layered piezoelectric substrate.

This paper proposes a general finite element method (FEM)-based wavenumber domain analysis (WDA) to calculate scattering characteristics of surface acoustic wave (SAW) on arbitrary piezoelectric substrates. We add a damping loss mechanism (DLM) to the SAW injection port to avoid interferences from the incident and backscattered modes. After checking the validity of the proposed method, we calculate and study Sezawa mode scattering using a small number of electrodes on the ScAlN/3CSiC structure for demonstration. The frequency dependences of reflection and transmission coefficients and that of the power dissipation ratio for different termination conditions and electrode thicknesses are calculated. Also, the influence of base substrate materials and that of gratings on scattering parameters are explored. Investigation results demonstrate that high reflectivity with suppressed mode conversion can be obtained for the ScAlN-based layer structure if a base substrate with an extremely large velocity is used and if proper grating design is applied.

Modeling and Analysis of Lateral Propagation of Surface Acoustic Waves Including Coupling Between Different Waves.

This paper discusses lateral propagation of surface acoustic waves (SAWs) in periodic grating structures when two types of SAWs exist simultaneously and are coupled. The thin plate model proposed by the authors is extended to include the coupling between two different SAW modes. First, lateral SAW propagation in an infinitely long periodic grating is modeled and discussed. Then, the model is applied to the Al-grating/42° YX-LiTaO3 (42-LT) substrate structure, and it is shown that the slowness curve shape changes from concave to convex with the Al grating thickness. The transverse responses are also analyzed on an infinitely long interdigital transducer on the structure, and good agreement is achieved between the present and the finite-element method analyses. Finally, SAW resonators are fabricated on the Cu grating/42-LT substrate structure, and it is experimentally verified that the slowness curve shape of the shear horizontal SAW changes with the Cu thickness.

[Medium optimization for antagonistic Streptomyces S24 and its inhibition on Aspergillus flavus].

Streptomyces S24 has broad spectrum against Aspergillus spp. in food and feed, such as Aspergillus flavus, Aspergillus niger and Asperegillus alutacells. The objective of this study was to improve the production of antifungal substances produced by S24 and to test their inhibitory effects on Aspergillus flavus. By using one-factor-at-a-time experiment and orthogonal design method, we optimized the fermentation medium. The composition of an optimized medium for the production of antifungal substances contained (g/L): starch soluble, 10; Glucose, 40; yeast extract, 8; soybean powder, 24; KH2PO4 4; and CaCO3 0.8. As a result, the productivity of antifungal substances could reach to 10 235.45 microg/mL, and this value was 2.81 times higher than that of initial medium before optimization. Additionally, inhibitory effects of the products on Aspergillus flavus were analyzed. Antagonistic tests indicated that the antifungal substances greatly inhibited mycelium growth and spores germination of Aspergillus flavus. We observed through microscope that the mycelia grew abnormally, such as contorting, bulging, vacuole increasing and the cytoplasmic contents inside effusing and the spores appeared unusual, such as gathering, deforming, cytoplasmic contents inside effusing and fracturing.

[Isolation, purification and characterization of antifungal substances from Streptomyces hygroscopicus BS-112].

OBJECTIVE: In order to provide the basis for application of Streptomyces hygroscopicus BS-112 and its antifungal active substances, we isolated and purified the active substances produced by strain BS-112, and then we examined their chemical structures and determined their inhibitory effects on Aspergillus flavus. METHODS: We extracted and purified the antifungal active substances from strain BS-112 using column chromatography with X-5 macroporous resin and 200 - 300 mesh silica gel respectively, and then purified them by preparative HPLC with Venusil XBP C18 column. The chemical structures of active components were identified by means of spectroscopic analysis, including mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR). Their minimum inhibitory concentration and minimum fungicidal concentration against Aspergillus flavus were determined by the standard broth microdilution method. RESULTS: We obtained four active components from the fermentation broth of strain BS-112 and their chemical structures were the same as Tetrins A and B, Tetramycins A and B. Assay using 96-well plate illustrated that the MIC of Tetrin A, Tetrin B, Tetramycin A and Tetramycin B against Aspergillus flavus were 3.13 microg/mL,12.56 microg/mL,1.56 microg/mL and 6.25 microg/mL respectively, and their MFC were 6.25 microg/mL, 25.0 microg/mL, 3.13 microg/mL and 12.56 microg/mL respectively. CONCLUSION: The antifungal active substances of strain BS-112 were composed of four compounds, Tetrins A and B, Tetramycins A and B. The four active compounds showed strong inhibitory against Aspergillus flavus.

[Extraction and characterization of antifungal substances produced by antagonistic Streptomyces S24].

Streptomyces S24 has broad spectrum resistance to the Aspergillus in food and feed, such as Aspergillus flavus, Aspergillus niger, Asperegillus alutacells and so on. We studied the adsorption and desorption properties of antifungal substance from Streptomyces S24 on macroporous resins, screened the best elution solution and also investigated some physical and chemical characters of antifungal substance by determining the antifugal activity using oxford plate assay system. According to the analysis results, AB-8 resin offered the best adsorption and desorption capacity for antifungal substance and its saturated absorption capacity was 7.0822 x 10(4) microg/g, the optimal elution solution was 85% acetone and the dynamic desorption rate could reach 93.82%. The antifungal substance was stable to heat and alkali, not sensitive to organic solvents, and sensitive to ultraviolet rays and acid. Based on its ultraviolet spectrometry, the antifungal substance was identified as heptaene macrolide antibiotic.