Cell Wall Thickness Research Articles

Mechanical strategies supporting growth and size diversity in Filamentous Fungi.

The stereotypical tip growth of filamentous fungi supports their lifestyles and functions. It relies on the polarized remodeling and expansion of a protective elastic cell wall (CW) driven by large cytoplasmic turgor pressure. Remarkably, hyphal filament diameters and cell elongation rates can vary extensively among different fungi. To date, however, how fungal cell mechanics may be adapted to support these morphological diversities while ensuring surface integrity remains unknown. Here, we combined super-resolution imaging and deflation assays to measure local CW thickness, elasticity and turgor in a set of fungal species spread on the evolutionary tree that spans a large range in cell size and growth speeds. While CW elasticity exhibited dispersed values, presumably reflecting differences in CW composition, both thickness and turgor scaled in dose-dependence with cell diameter and growth speeds. Notably, larger cells exhibited thinner lateral CWs, and faster cells thinner apical CWs. Counterintuitively, turgor pressure was also inversely scaled with cell diameter and tip growth speed, challenging the idea that turgor is the primary factor dictating tip elongation rates. We propose that fast-growing cells with rapid CW turnover have evolved strategies based on a less turgid cytoplasm and thin walls to safeguard surface integrity and survival.

Polystyrene nanoplastics induce cell type-dependent secondary wall reinforcement in rice (Oryza sativa) roots and reduce root hydraulic conductivity

Nanoplastics (NPs) have been demonstrated the ability to penetrate plant roots and cause stress. However, the extent of NPs penetration into various root tissues and the corresponding plant defense mechanisms remain unclear. This study examined the penetration and accumulation patterns of polystyrene nanoplastics (PS-NPs) in different cell types within rice roots, and explored how the roots quickly modify their cell wall structure in response. The findings showed that fully developed sclerenchyma cells in rice roots effectively prevented the invasion of PS-NPs. Meanwhile, PS-NPs triggered the accumulation of lignin and suberin in specific cells such as the exodermis, sclerenchyma, and xylem vessels. PS-NPs at a concentration of 50 mg L−1 increased cell wall thickness by 18.6 %, 21.1 %, and 22.4 % in epidermis, exodermis, and sclerenchyma cells, respectively, and decreased root hydraulic conductivity by 14.8 %. qPCR analysis revealed that PS-NPs influenced the cell wall synthesis pathway, promoting the deposition of lignin and suberin monomers on the secondary wall through the up-regulation of genes such as OsLAC and OsABCG. These results demonstrate that PS-NPs can induce cell type-specific strengthening of secondary walls and barrier formation in rice roots, suggesting the potential role of plant secondary wall development in mitigating NPs contamination risks in crops.

Roles of α-1,3-glucosyltransferase in growth and polysaccharides biosynthesis of Ganoderma lucidum

Ganoderma lucidum polysaccharides are valuable natural compounds possessing significant biological activity, with glycosyltransferases playing a crucial role in their biosynthesis. Although the function of β-1,3-glucosyltransferase in polysaccharides production is well understood, the role of α-1,3-glucosyltransferase in edible fungi remains unclear. In this study, over-expression of the α-1,3-glucosyltransferase gene in G. lucidum (glagt) was found to suppress the growth, with the maximum biomass and mycelial growth rate decreasing by 21.78 % and 79.61 %, respectively, a behavior distinct from β-1,3-glucosyltransferase. The fungal pellet diameter decreased by 38 % and the cell-wall thickness by 32.44 %, whereas intracellular and extracellular polysaccharides production increased by 27.58 % and 66.08 %, respectively. In the transcription level, overexpressing the glagt gene i) downregulated the citrate synthase and isocitrate dehydrogenase gene in the TCA cycle, disrupting energy metabolism and fungal growth; ii) upregulated key enzymes involved in UDP-glucose synthesis and glycosyltransferases (gl24465, gl24971, and gl22535); and iii) universally increased the transcriptional level of glucosidases gl21451, gl30087, and gl24581 by 22 %–397 %, contributing to cell-wall thinning to facilitate polysaccharides export. Conversely, the glagt gene downregulation promoted G. lucidum growth and decreased polysaccharides production. The results elucidate the roles of GLAGT and are expected to inspire in-depth exploration of polysaccharides biosynthesis pathways.

Fibre morphological characteristics, chemical composition and fuel properties of paulownia COTEVISA-2 wood

AbstractThe aim of this study was to determine the elemental composition and the fibre morphological characteristics, chemical and fuel properties of wood from paulownia COTEVISA-2 clone growing on a plantation near Granada, Spain. The research was carried out on five boards representing five 5-year-old trees, taken from a height of approximately 2–3 m. Morphologically, COTEVISA-2 wood has fibres with mean length 0.923 mm, diameter 0.029 mm, lumen width 0.026 mm, and cell wall thickness 0.0015 mm. The slenderness ratio ranged between 19.27 and 64.31, the Runkel ratio between 0.060 and 0.4259, the rigidity index between 2.83 and 19.94, Mühsteph’s index between 0.1099 and 0.5082, and the flexibility coefficient between 0.701 and 0.943. Significant differences between trees were found for the values of morphological characteristics of fibres and the derived indices, apart from the solids index. Mean values of chemical properties obtained from two parallel determinations for each sample showed that the wood contains on average 48.15% cellulose, 27.48% lignin, 7.38% pentosans and substances soluble in cold water (2.38%), hot water (3.87%), ethanol (5.51%) and 1% NaOH (19.64%). The elemental composition of paulownia COTEVISA-2 wood is as follows: C – 49.06%, H – 6.19%, N – 0.43%, S – 0.021%, Cl – 0.05%. The wood contained 0.4% ash. The heat of combustion of paulownia COTEVISA-2 wood is 18.58 MJ/kg, and the calorific value is 17.18 MJ/kg. The results suggest that paulownia COTEVISA-2 is a promising wood for energy and paper production.

Fossils can reveal a long-vanished combination of character states: Evidence from a mysterious foliicolous anamorphic fungus from the Middle Siwalik (Late Miocene) of Himachal Pradesh, India

ABSTRACT Fossils can unveil a long-vanished combination of character states that inform inferences about the timing and patterns of diversification of modern fungi. By examining the well-preserved stacked chained vesicular conidiophores developed in clusters from the basal stroma, we describe a new taxon of fossil Zygosporiaceae with a combination of characters unknown among extant taxa on compressed serrated-margined dicot leaf (cf. Fagaceae) recovered from the Siwalik sediments (Late Miocene; ca. 12–8 Ma) of Himachal Pradesh, western Himalaya. Based upon conidiophore morphology, our Siwalik fungal remains, similar to Zygosporium Mont. (Zygosporiaceae: Xylariales: Sordariomycetes), are recognized as a new fossil species, Z. stromaticum Kundu & Khan, sp. nov. Zygosporium stromaticum is the only known fossil anamorphic fungus that occurs on plant cuticles and has a cluster of stacked chained vesicular conidiophores arising from a poorly preserved basal stroma formed by irregular, thick-walled cells. Its combination of morphological characteristics is unknown in extant fungal taxa, so Z. stromaticum likely represents a new anamorphic foliicolous fungus that may now be extinct. This unique evidence may be essential for the calibration of divergence time estimations of fungal lineages.

Low-Temperature Regulates the Cell Structure and Chlorophyll in Addition to Cellulose Metabolism of Postharvest Red Toona sinensis Buds across Different Seasons.

Postharvest fibrosis and greening of Toona sinensis buds significantly affect their quality during storage. This study aimed to clarify the effects of low-temperature storage on postharvest red TSB quality harvested in different seasons. Red TSB samples were collected from Guizhou province, China, 21 days after the beginning of spring (Lichun), summer (Lixia), and autumn (Liqiu), and stored at 4 °C in dark conditions. We compared and analyzed the appearance, microstructure, chlorophyll and cellulose content, and expression levels of related genes across different seasons. The results indicated that TSB harvested in spring had a bright, purple-red color, whereas those harvested in summer and autumn were green. All samples lost water and darkened after 1 day of storage. Severe greening occurred in spring-harvested TSB within 3 days, a phenomenon not observed in summer and autumn samples. Microstructural analysis revealed that the cells in the palisade and spongy tissues of spring and autumn TSB settled closely during storage, while summer TSB cells remained loosely aligned. Xylem cells were smallest in spring-harvested TSB and largest in autumn. Prolonged storage led to thickening of the secondary cell walls and pith cell autolysis in the petioles, enlarging the cavity area. Chlorophyll content was higher in leaves than in petioles, while cellulose content was lower in petioles across all seasons. Both chlorophyll and cellulose content increased with storage time. Gene expression analysis showed season-dependent variations and significant increases in the expression of over half of the chlorophyll-related and cellulose-related genes during refrigeration, correlating with the observed changes in chlorophyll and cellulose content. This research provides valuable insights for improving postharvest storage and freshness preservation strategies for red TSB across different seasons.

Assessing Structural Traits in Triticum aestivum and Zea mays for C3 and C4 Photosynthetic Differentiation Using Free-hand and Semi-thin Sections.

The enhanced efficiency of C4 photosynthesis, compared to the C3 mechanism, arises from its ability to concentrate CO2 in bundle sheath cells. The effectiveness of C4 photosynthesis and intrinsic water use efficiency are directly linked to the share of mesophyll and bundle leaf cells,size and density of bundle sheaths, and size, density, and cell wall thickness of bundle sheath cells. Rapid microscopical analysis of these traits can be performed on free-hand and semi-thin sections using conventional light microscopy, providing valuable information about photosynthetic efficiency in C4 crops by means of identifying and examining specific cell types. Additionally, errors in freehand and semi-thin section preparation that affect anatomical measurements and cell type diagnoses are shown, as well as how to avoid these errors. This microscopical approach offers an efficient means of gathering insights into photosynthetic acclimation to environmental variation and aids in the rapid screening of crops for future climates.

Effect of girdling on phloem and xylem formation in a range of gymnosperms and angiosperms

Summary Girdling is often used as an experimental method to study source/sink controls of cambial growth. However, the phloem responses to girdling have not been well investigated. The aim of this research was to characterize the anatomical changes in the phloem and xylem of different species following trunk girdling. Different species of gymnosperm (Abies sibirica, Pinus sylvestris) and angiosperm (Alnus incana, Populus tremula) woody plants were selected. We girdled trunks during active growth and sampled tissues at two levels (1 cm and 35 cm) above the girdle at the end of the growing season. General responses to girdling were recorded for the studied species, such as increased phloem increments, parenchymatization of conducting tissues, reduction in the size of conducting elements, and an increase in the size of axial parenchyma cells in the phloem and xylem. We observed the suppression of xylogenesis in 3 out of 4 species. Differences in the structure of conducting tissues were found, which are due to species differences in the initial tissue structure. In gymnosperms, noticeable differences in the number of resin ducts in the xylem were observed between control and girdled trees. In angiosperms, we found the formation of cells with thickened cell walls in girdled trees (i.e., the formation of phloem and xylem fibers with thickened cell walls in aspen and sclereids in the phloem of alder). Based on the literature data, the observed responses may be due to both the wounding effect and the influence of the high sugar content above the girdle.

Influencing Factors for the Growth of Cladophora and Its Cell Damage and Destruction Mechanism: Implication for Prevention and Treatment

Cladophora is commonly found in marine and freshwater around the globe and provides productivity for littoral zone microorganisms and invertebrates. The eutrophication of the water body has led to the abnormal proliferation of Cladophora in some water, often in river coast channel outbreaks. Even under the nutritional deficiency systems, such as the central trunk canal of the South-to-North Water Diversion in China, Cladophora’s blooms affect water quality and seriously jeopardize human health. Thus, the structural characteristics of Cladophora cells and spores, the factors affecting the growth of Cladophora cells, and the mechanisms of damage and destruction of Cladophora cells and spores were investigated. Cladophora cells are cylindrical with very thick cell walls. The inner layer of the spore wall is a thin membrane which contains the nucleus of the spore. The growth and spreading of Cladophora cells are affected by various environmental factors such as light, temperature, water depth, water level, nutrient salts, pH, etc. Some physical treatment measures, such as ultrasounds, would destroy the cell walls and membranes of Cladophora by its high-intensity mechanical action. Chemicals and aquatic plant measures can destroy Cladophora cells’ photosynthesis system, antioxidant enzyme systems, proteins, and ultrastructure. Based on the mechanisms for these cell damage and destruction, a combination of measures that are likely to inhibit the growth of Cladophora cells effectively was suggested. Furthermore, the damaged cells of Cladophora could provide some environmental benefits. Aggregated results could provide a scientific basis for further research on the control of blooms of Cladophora or the reuse of Cladophora cells as a natural resource.

The functions of laccase gene GhLAC15 in fiber colouration and development in brown-colored cotton.

The monotonicity of color type in naturally colored cottons (NCCs) has become the main limiting factor to their widespread use, simultaneously coexisting with poor fiber quality. The synchronous improvement of fiber quality and color become more urgent and crucial as the demand for sustainable development increases. The homologous gene of wild cotton Gossypium stocksii LAC15 in G. hirsutum, GhLAC15, was also dominantly expressed in the developing fibers of brown cotton XC20 from 5 DPA (day post anthesis) to 25 DPA, especially at the secondary cell wall thickening stage (20 DPA and 25 DPA). In XC20 plants with downregulated GhLAC15 (GhLAC15i), a remarkable reduction in proanthocyanidins (PAs) and lignin contents was observed. Some of the key genes in the phenylpropane and flavonoid biosynthesis pathway were down-regulated in GhLAC15i plants. Notably, the fiber length of GhLAC15i plants showed an obvious increase and the fiber color was lightened. Moreover, we found that the thickness of cotton fiber cell wall was decreased in GhLAC15i plants and the fiber surface became smoother compared to that of WT. Taken together, this study revealed that GhLAC15 played an important role in PAs and lignin biosynthesis in naturally colored cotton fibers. It might mediate fiber color and fiber quality by catalyzing PAs oxidation and lignin polymerization, ultimately regulating fiber colouration and development.

Sound transmission loss analysis of novel sandwich plate with star-shaped auxetic cellular cores

A star-shaped auxetic cellular metamaterial with a negative Poisson’s ratio (NPR) was employed in this study to model lightweight sandwich panels, and an analysis of its sound transmission characteristics was conducted. Utilizing the first-order shear deformation theory (FSDT) and the Hamiltonian principle, the free vibration equation for the sandwich plate is derived. Subsequently, leveraging the fluid-structure coupling condition and incorporating the Navier method, the sound transmission loss (STL) is analytically described. The efficacy of the proposed method is validated through numerical analysis and an acoustic insulation experiment using an impedance tube. Based on the theoretical modeling, it is calculated that the sound insulation effect of the star-shaped cellular core exceeds that of the traditional reentrant cellular with NPR. A systematic analysis is subsequently conducted to explore the impact of star-shaped cellular structure parameters on the STL of the sandwich panel. It can be obtained that the increase in core layer thickness leads to a reduction in the first-order resonance frequency of the sandwich panel, but concurrently diminishing its sound insulation performance. The change of the connecting rib length exerts a more considerable influence on the structure’s STL compared to the side rib length. While as the cell wall thickness reduces from 2.0 to 1.0 mm, the average STL of the sandwich plate across the analysis band decreases by 8.43%, from 46.3 to 42.7 dB.

CELLULOSE SYNTHASE-LIKE C proteins modulate cell wall establishment during ethylene-mediated root growth inhibition in rice.

The cell wall shapes plant cell morphogenesis and affects the plasticity of organ growth. However, the way in which cell wall establishment is regulated by ethylene remains largely elusive. Here, by analyzing cell wall patterns, cell wall composition and gene expression in rice (Oryza sativa, L.) roots, we found that ethylene induces cell wall thickening and the expression of cell wall synthesis-related genes, including CELLULOSE SYNTHASE-LIKE C1, 2, 7, 9, 10 (OsCSLC1, 2, 7, 9, 10) and CELLULOSE SYNTHASE A3, 4, 7, 9 (OsCESA3, 4, 7, 9). Overexpression and mutant analyses revealed that OsCSLC2 and its homologs function in ethylene-mediated induction of xyloglucan biosynthesis mainly in the cell wall of root epidermal cells. Moreover, OsCESA-catalyzed cellulose deposition in the cell wall was enhanced by ethylene. OsCSLC-mediated xyloglucan biosynthesis likely plays an important role in restricting cell wall extension and cell elongation during the ethylene response in rice roots. Genetically, OsCSLC2 acts downstream of ETHYLENE-INSENSITIVE3-LIKE1 (OsEIL1)-mediated ethylene signaling, and OsCSLC1, 2, 7, 9 are directly activated by OsEIL1. Furthermore, the auxin signaling pathway is synergistically involved in these regulatory processes. These findings link plant hormone signaling with cell wall establishment, broadening our understanding of root growth plasticity in rice and other crops.

Responses of Physiological Traits and Soil Properties in Pinus thunbergia and Euonymus japonicus Saplings under Drought and Cadmium (Cd) Stress

Pinus thunbergii and Euonymus japonicus are two species commonly found in arid and semi-arid areas; however, their responses in terms of physiological traits and soil properties under drought and cadmium (Cd) stress are not clear. In this study, we carried out single and combined stress treatments consisting of drought and Cd on saplings of P. thunbergii and E. japonicus and investigated the responses in terms of the physiological traits and soil properties of both species. For both species, under single Cd stress, Cd was observed in both the xylem and phloem, while the root Cd2+ flow rate fluctuated at different levels of Cd stress. Under both single and combined stress, as the stress level increased, the abscisic acid (ABA) content of the leaves and roots increased significantly, while the indole-3-acetic acid (IAA) content of the leaves and roots decreased significantly. Moreover, the non-structural carbohydrate (NSC) content of the leaves, stems, and roots, as well as the leaf chlorophyll content, decreased significantly. Under drought stress, the xylem water potential and hydraulic conductivity significantly decreased, which was exacerbated by Cd stress; this led to a more significant decrease in water potential and hydraulic conductivity under the combined stresses. Meanwhile, no significant changes in the conduit lumen diameter and double-wall thickness were observed, except for the double cell wall thickness of the P. thunbergii tracheid, which increased. In addition, both the single stresses and the combined stress of drought and Cd induced significant changes in the soil properties of the two species, i.e., the ammonium nitrogen, nitrate nitrogen, and effective phosphorus of the soil increased significantly, and the increase in content was more significant under combined stress. The diversity of the soil microbial community of P. thunbergii saplings significantly increased, while no change was found in its microbial community abundance under the single stresses and combined stress; however, the diversity and abundance of the soil microbial community in E. japonicus saplings showed the opposite pattern, which indicates that the effect of Cd on soil microorganisms is more significant than the effect of drought. The activity of sucrase and catalase in P. thunbergii soil fluctuated under the single stress and combined stress when compared, and the activity of sucrase in the soil of the E. japonicus species decreased. However, its catalase activity increased significantly under the single drought and Cd stress and combined stress when compared. We found that the combined stresses exacerbated the effects of the single stress in both species. Our study provides more detailed information on the responses in terms of the physiological traits and soil properties of the two species under single and combined stress consisting of drought and Cd.

Morphological diversity of the velamen radicum in the genus Anthurium (Araceae).

Epiphytes develop anatomical features to improve efficiency of the uptake of water and nutrients, such as absorptive foliar scales or a velamen radicum. Despite substantial studies on the occurrence, morphology, development and phylogeny of the velamen, most of the available literature is focused on Orchidaceae, making current knowledge on velamen clearly biased. A recent publication firmly established that velamina are common in Anthurium species. Thus, this study provides further insights by describing velamen morphological characteristics of Anthurium species and classifying them into different velamen types. Furthermore, we investigate if the different velamen morphological traits are clade-specific and phylogenetically conserved within the genus. Using SEM, we performed a morphological study on 89 Anthurium species, describing six micromorphological traits of velamen and exodermis, following traits used to classify Orchidaceae velamen by Porembski & Barthlott (1988). We distinguished nine velamen types, including two that are unique to Anthurium and not similar to any type found in Orchidaceae. Comparing velamen morphology within the phylogenetic tree of Anthurium revealed clear phylogenetic signals. This study provides detailed morphological descriptions among 89 species of Anthurium from the Araceae, and substantially broadens our knowledge of this tissue. However, velamen function has been even less studied, with hardly anything known about functional significance of having secondary cell wall thickening and perforations on velamen cell walls. Therefore, a logical next step would be to connect these anatomical features to their functions.

Experimental and numerical study of drop hammer test on honeycomb sandwich panel resistant to rock burst in coal mine roadway

This study addresses the ubiquitous issue of effective support resistant to the rock bursts within coal mine roadways and introduces an innovative solution in the form of a steel honeycomb sandwich panel (HSP). It is designed for installation on traditional metal supports in coal mine roadways, serves as an integral element of an energy-absorption support system tailored to withstand rock burst impacts. The investigation incorporates drop hammer impact tests conducted on eight HSP specimens, varying in cell wall thickness and core height. A comprehensive three-dimensional finite element model, inclusive of mesh considerations, was constructed and subsequently validated. Combining experimental and numerical approaches, the drop hammer impact response and energy absorption characteristics of HSP structures were analyzed. The findings reveal good energy absorption capabilities, with HSPs dissipating over 90 % of impact energy, over 85 % attributed to the core layer. Thinner core cell walls reduce peak impact loads, mitigating structural impact effects. In the experimental parameters delineated in the present study, it is observed that core layers with thicknesses of 1.0 mm and 1.5 mm demonstrate enhanced energy absorption capabilities. Variations in core height minimally affect peak impact forces, with only a 7.41 % distinction between 60 mm and 140 mm core layers. However, it is worth noting that higher core layers can achieve an enhanced energy absorption capacity. Thinner facesheets enhance energy absorption, and alterations in impactor mass have minimal effects under constant impact energy conditions. Additionally, a predictive equation for estimating indentation depth was proposed, closely aligned with finite element results. This equation holds potential for informing future HSP designs, offering valuable insights for diverse engineering applications.

Defective pgsA contributes to increased membrane fluidity and cell wall thickening in Staphylococcus aureus with high-level daptomycin resistance.

The cationic lipopeptide antimicrobial daptomycin has become an essential tool for combating infections with Staphylococcus aureus that display reduced susceptibility to β-lactams or vancomycin. Since daptomycin's activity is based on interaction with the negatively charged membrane of S. aureus, routes to daptomycin-resistance occur through mutations in the lipid biosynthetic pathway surrounding phosphatidylglycerols and the regulatory systems that control cell envelope homeostasis. Therefore, there are many avenues to achieve daptomycin resistance and several different, and sometimes contradictory, phenotypes of daptomycin-resistant S. aureus, including both increased and decreased cell wall thickness and membrane fluidity. This study is significant because it demonstrates the unexpected influence of a lipid biosynthesis gene, pgsA, on membrane fluidity and cell wall thickness in S. aureus with high-level daptomycin resistance.

Insights into the molecular basis of reduced vancomycin susceptibility among three prominent Staphylococcus aureus clonal complexes.

Our understanding of the mechanisms that underlie the development of vancomycin-intermediate Staphylococcus aureus (VISA) is incomplete. To provide a more comprehensive view of this process, we compared genome sequences of clonal complex (CC) 5, CC8, and CC45 VISA clinical isolates and measured changes in the transcriptomes of these isolates during culture with a subtherapeutic concentration of vancomycin. Notably, we identified differentially expressed genes that were lineage-specific or common to the lineages tested, including genes that have not been previously reported to contribute to a VISA phenotype. Changes in gene expression were accompanied by reduced growth rate, increased cell wall thickness, and reduced susceptibility to daptomycin, televancin, tigecycline, and vancomycin. Our results provide support to the idea that changes in gene expression contribute to the development of VISA among three CCs that are a prominent cause of human infections.

Colonization by the endophytic fungus Phyllosticta fallopiae combined with the element Si promotes the growth of Dendrobium nobile

Endophytic fungi can promote plant growth and development, particularly of Orchidaceae species. Previously, we found that the endophytic fungus Phyllosticta fallopiae DN14, collected from Dendrobium nobile growing on rocks in a wild habitat, significantly promoted growth of its host plant D. nobile, an important herb in Chinese traditional medicine that contains the bioactive component dendrobine. Phyllosticta was positively correlated with FW and dendrobine content of D. nobile and with Si content of the epiphytic matrix. Si is also highly beneficial for the growth and productivity of many plants. Here, we co-cultured D. nobile with P. fallopiae DN14 in half-strength Murashige and Skoog medium with and without various concentrations of Si to investigate the effects of DN14 and Si on plant fresh weight and dendrobine content. We also explored the effects of DN14 infection and colonization on host plant growth, Si accumulation and transport, and expression of key genes, as well as the interaction between DN14 and Si. The combination of DN14 and Si promoted the lignification of D. nobile roots, stems, and leaves and markedly increased the thickening of xylem cell walls. Co-culture with DN14 increased transport of Si from roots to stems and from stems to leaves. Transcriptome sequencing and qRT–PCR analyses showed that enhancement of D. nobile growth by DN14 and Si may involve upregulation of plant hormone-related genes (AUX/IAA and MYC) and lignin biosynthesis genes (HCT, PAL1, and PAL2). Insoluble Si promoted the growth of DN14, perhaps through downregulation of genes (e.g., FBP, MPI, RPIAD) related to carbohydrate metabolism, and DN14 in turn promoted the transformation of insoluble Si into soluble Si for plant uptake. These findings demonstrate that endophytic fungi and Si can improve the growth of D. nobile and therefore show promise as organic amendments for commercial cultivation.

Fighting Emerging Caspofungin-Resistant Candida Species: Mitigating Fks1-Mediated Resistance and Enhancing Caspofungin Efficacy by Chitosan.

Invasive candidiasis poses a worldwide threat because of the rising prevalence of antifungal resistance, resulting in higher rates of morbidity and mortality. Additionally, Candida species, which are opportunistic infections, have significant medical and economic consequences for immunocompromised individuals. This study explores the antifungal potential of chitosan to mitigate caspofungin resistance in caspofungin-resistant Candida albicans, C. krusei, and C. tropicalis isolates originating from human and animal sources using agar well diffusion, broth microdilution tests, and transmission electron microscope (TEM) analysis of treated Candida cells. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) was performed to assess the expression of SAGA complex genes (GCN5 and ADA2) and the caspofungin resistance gene (FKS) in Candida species isolates after chitosan treatment. The highest resistance rate was observed to ketoconazole (80%) followed by clotrimazole (62.7%), fluconazole (60%), terbinafine (58%), itraconazole (57%), miconazole (54.2%), amphotericin B (51.4%), voriconazole (34.28%), and caspofungin (25.7%). Nine unique FKS mutations were detected, including S645P (n = 3 isolates), S645F, L644F, S645Y, L688M, E663G, and F641S (one isolate in each). The caspofungin minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values before chitosan treatment ranged from 2 to 8 µg/mL and 4 to 16 µg/mL, respectively. However, the MIC and MFC values were decreased after chitosan treatment (0.0625-1 µg/mL) and (0.125-2 µg/mL), respectively. Caspofungin MIC was significantly decreased (p = 0.0007) threefold following chitosan treatment compared with the MIC values before treatment. TEM analysis revealed that 0.5% chitosan disrupted the integrity of the cell surface, causing irregular morphologies and obvious aberrant changes in cell wall thickness in caspofungin-resistant and sensitive Candida isolates. The cell wall thickness of untreated isolates was 0.145 μm in caspofungin-resistant isolate and 0.125 μm in sensitive isolate, while it was significantly lower in chitosan-treated isolates, ranging from 0.05 to 0.08 μm when compared with the cell wall thickness of sensitive isolate (0.03 to 0.06 μm). Moreover, RT-qPCR demonstrated a significant (p < 0.05) decrease in the expression levels of histone acetyltransferase genes (GCN5 and ADA2) and FKS gene of caspofungin-resistant Candida species isolates treated with 0.5% chitosan when compared with before treatment (fold change values ranged from 0.001 to 0.0473 for GCN5, 1.028 to 4.856 for ADA2, and 2.713 to 12.38 for FKS gene). A comparison of the expression levels of cell wall-related genes (ADA2 and GCN5) between caspofungin-resistant and -sensitive isolates demonstrated a significant decrease following chitosan treatment (p < 0.001). The antifungal potential of chitosan enhances the efficacy of caspofungin against various caspofungin-resistant Candida species isolates and prevents the development of further antifungal resistance. The results of this study contribute to the progress in repurposing caspofungin and inform a development strategy to enhance its efficacy, appropriate antifungal activity against Candida species, and mitigate resistance. Consequently, chitosan could be used in combination with caspofungin for the treatment of candidiasis.

Genetic engineering of Haematococcus pluvialis microalgae for the enhancement of astaxanthin production: A review

Haematococcus pluvialis (H. pluvialis) is a significant natural source of astaxanthin, garnering interest in the pharmaceutical and nutraceutical industries. However, astaxanthin production from H. pluvialis is constrained by factors such as a lengthy cultivation period and thick cell walls. Recent research has explored different strategies, such as optimising cultivation conditions, to enhance astaxanthin biosynthesis. This review paper aims to summarise the recent advancement of metabolic and genetic engineering in astaxanthin biosynthesis from H. pluvialis. The review would provide a comprehensive analysis of the molecular components and mechanism involved in the biosynthesis pathway of astaxanthin in H. pluvialis, revealing the specific genes responsible for governing its biosynthesis. Numerous metabolic methodologies are investigated, including manipulating light intensity, salinity, nutrient deficiency, and temperature to enhance microalgae biomass and astaxanthin accumulation. Genetic engineering strategies have recently been studied to manipulate specific genes (e.g. bkt, CrtR-b, pds) to increase astaxanthin production. However, the limitation of genetic engineering is still unclear due to its mechanism of astaxanthin esterification and the transport of secondary β-carotenoids from the chloroplast to the cytosol. This lack of understanding has posed a challenge to maximise astaxanthin production through genetic engineering. This review also provides recent insights and future research directions for genetic engineering by providing a holistic approach to the complex interplay of genetics, metabolism, and biotechnological strategies to maximise astaxanthin production.