Infections mediated by broad host range entomopathogenic fungi represent seminal observations that led to one of the first germ theories of disease and are a classic example of a co-evolutionary arms ...race between a pathogen and target hosts. These fungi are able to parasitize susceptible hosts via direct penetration of the cuticle with the initial and potentially determining interaction occurring between the fungal spore and the insect epicuticle. Entomogenous fungi have evolved mechanisms for adhesion and recognition of host surface cues that help direct an adaptive response that includes the production of: (a) hydrolytic, assimilatory, and/or detoxifying enzymes including lipase/esterases, catalases, cytochrome P450s, proteases, and chitinases; (b) specialized infectious structures, e.g., appressoria or penetrant tubes; and (c) secondary and other metabolites that facilitate infection. Aside from immune responses, insects have evolved a number of mechanisms to keep pathogens at bay that include: (a) the production of (epi) cuticular antimicrobial lipids, proteins, and metabolites; (b) shedding of the cuticle during development; and (c) behavioral-environmental adaptations such as induced fever, burrowing, and grooming, as well as potentially enlisting the help of other microbes, all intended to stop the pathogen before it can breach the cuticle. Virulence and host-defense can be considered to be under constant reciprocal selective pressure, and the action on the surface likely contributes to phenomena such as strain variation, host range, and the increased virulence often noted once a (low) virulent strain is "passaged" through an insect host. Since the cuticle represents the first point of contact and barrier between the fungus and the insect, the "action on the surface" may represent the defining interactions that ultimately can lead either to successful mycosis by the pathogen or successful defense by the host. Knowledge concerning the molecular mechanisms underlying this interaction can shed light on the ecology and evolution of virulence and can be used for rational design strategies at increasing the effectiveness of entomopathogenic fungi for pest control in field applications.
Broad host range insect pathogenic fungi penetrate through the host cuticle, necessitating an ability to confront and overcome surface lipids and other molecules that often include antimicrobial ...compounds. In this context, induction of lipid assimilatory pathways by exogenous substrates is crucial for successful infection to occur, and lipid growth substrates can have significant effects on the virulence of fungal infectious propagules, e.g. conidia. The production of lipases is a critical part of the cuticle-degrading repertoire and pathways involved in triglyceride metabolism and phospholipid homeostasis have been shown to contribute to host invasion. Mobilization of endogenous lipid stores via the activities of the caleosin and perilipin lipid storage-turnover proteins, have been linked to diverse processes including formation of penetration structures, e.g. germ tubes and appressoria, spore properties and dispersal, and the ability to respond to lipid growth substrates and virulence. Here, we summarize recent advances in our understanding of lipid assimilation and mobilization pathways in the ability of entomogenous fungi to infect and use host substrates. Host surface and internal lipids can alternatively act as antifungal barriers, inducers of pathogenesis-related pathways, and/or as fungal growth substrates. Lipids and lipid assimilation can be considered as forming a co-evolutionary web between the insect host and entomogenous fungi.
Doping bismuth oxychloride (BiOCl) with other elements can help improve its photocatalytic performance. The present study used a simple one-step hydrothermal method to synthesize tungsten-doped BiOCl ...nanosheets. The results showed the negligible effects of W-doping on the crystal structure, morphology and specific surface area of BiOCl. Diffuse reflectance spectroscopy (DRS), however, showed increases in light absorption and a shift in the absorption edge towards higher wavelengths in the presence of W. Measuring the photocatalytic performance of the samples in decomposing an aqueous solution of rhodamine B (RhB) under light irradiation showed that doping BiOCl with W preserves photocatalytic performance under both UV irradiation and visible-light irradiation, whereas pure BiOCl showed negligible photocatalytic activities under visible-light irradiation. The high photocatalytic activity of BiOCl doped with W compared to that of pure BiOCl is explained by the reduction in band gap and increase in light absorption due to the formation of W energy bands in the forbidden energy gap of BiOCl. A plausible mechanism was proposed for the photocatalytic activity of W-doped BiOCl in decomposing RhB under visible light.
W-doped BiOCl nanoplates were synthesized by a one-step hydrothermal method.W-doped BiOCl displays excellent photocatalytic activity under visible light.The W energy level in band gap enhances the photocatalytic activity.The possible mechanism for photocatalytic degradation was proposed.
Ambrosia beetles and their microbial communities, housed in specialized structures termed mycangia, represent one of the oldest and most diverse systems of mutualism and parasitism described thus ...far. Comprised of core filamentous fungal members, but also including bacteria and yeasts, the mycangia represent a unique adaptation that allows beetles to store and transport their source of nutrition. Although perhaps the most ancient of “farmers,” the nature of these interactions remains largely understudied, with the exception of a handful of emerging pathosystems, where the fungal partner acts as a potentially devastating tree pathogen. Such virulence is often seen during “invasions,” where (invasive) beetles carrying the fungal symbiont/plant pathogen expand into new territories and presumably “naïve” trees. Here, we summarize recent findings on the phylogenetic relationships between beetles and their symbionts and advances in the developmental and genetic characterization of the mechanisms that underlie insect-fungal-plant interactions. Results on genomic, transcriptomic, and metabolomic aspects of these relationships are described. Although many members of the fungal
Raffaelea
-beetle symbiont genera are relatively harmless to host trees, specialized pathosystems including wilt diseases of laurel and oak, caused by specific subspecies (
R. lauricola
and
R. quercus
, in the USA and East Asia, respectively), have emerged as potent plant pathogens capable of killing healthy trees. With the development of genetic tools, coupled to biochemical and microscopic techniques, the ambrosia beetle-fungal symbiont is establishing itself as a unique model system to study the molecular determinants and mechanisms that underlie the convergences of symbioses, mutualism, parasitism, and virulence.
Key points
• Fungal-beetle symbioses are diverse and ancient examples of microbial farming.
• The mycangium is a specialized structure on insects that houses microbial symbionts.
• Some beetle symbiotic fungi are potent plant pathogens vectored by the insect.
Seven-day-old maize seedlings were subjected to NaCl (150 mM) without or with the presence of equimolar concentrations of urea, potassium nitrate or ammonium sulfate (at 60 kg N ha
−1
) for the ...subsequent 15 days. The results show that NaCl significantly decreased photosynthetic activity parameters (Hill reaction, Pn, Ci and Gs), shoot fresh and dry weights, chlorophylls, protein, GSH and AsA. The activities of ALA-D, Rubisco, PEP-C, MDH, PPDK, SOD, CAT and APX were significantly inhibited. On the contrary, NaCl significantly elevated MDA, O
2
∙−
, H
2
O
2
, soluble sugars and proline. The application of the nitrogenous sources mostly ameliorated the photosynthetic activity synchronous with counterbalancing the decreases in growth, protein and pigments. The activities of ALA-D, Rubisco, PEP-C, MDH and PPDK enhanced remarkably with N applied under salinity. Furthermore, enhancements were detected in GSH and AsA contents and SOD, CAT and APX activities, which decreased free radicals, soluble sugars and proline. These effects reveal that maize was vulnerable to NaCl stress; however, N overcame the stress status and ameliorated the plant tolerance to salinity concomitant with repairing photosynthetic activity and maintaining higher antioxidants and ROS homeostasis; urea seemed to be the most efficient. Taken together, these findings conclude that N enhanced the capability of maize to tolerate NaCl via protecting photosynthetic apparatus for normal photochemical functioning and improving antioxidants and ROS homeostasis as effective salt tolerance mechanisms.
Ambrosia beetles require their fungal symbiotic partner as their cultivated (farmed) food source in tree galleries. While most fungal-beetle partners do not kill the host trees they inhabit, since ...their introduction (invasion) into the United states around ~2002, the invasive beetle Xyleborus glabratus has vectored its mutualist partner (but plant pathogenic) fungus, Harringtonia lauricola, resulting in the deaths of over 300 million trees. Concerningly, indigenous beetles have been caught bearing H. lauricola. Here, we show colonization of the mycangia of the indigenous X. affinis ambrosia beetle by H. lauricola. Mycangial colonization occurred within 1 h of feeding, with similar levels seen for H. lauricola as found for the native X. affinis-R. arxii fungal partner. Fungal mycangial occupancy was stable over time and after removal of the fungal source, but showed rapid turnover when additional fungal cells were available. Microscopic visualization revealed two pre-oral mycangial pouches of ~100-200 × 25-50 μm/each, with narrow entry channels of 25-50 × 3-10 μm. Fungi within the mycangia underwent a dimorphic transition from filamentous/blastospore growth to yeast-like budding with alterations to membrane structures. These data identify the characteristics of ambrosia beetle mycangial colonization, implicating turnover as a mechanism for host switching of H. lauricola to other ambrosia beetle species.
Entropy generation for the steady two-dimensional laminar forced convection flow and heat transfer of an incompressible Jeffrey non-Newtonian fluid over a linearly stretching, impermeable and ...isothermal sheet is numerically investigated. The governing differential equations of continuity, momentum and energy are transformed using suitable similarity transformations to two nonlinear coupled ordinary differential equations (ODEs). Then the ODEs are solved by applying the numerical implicit Keller’s box method. The effects of various parameters of the flow and heat transfer including Deborah number, ratio of relaxation to retardation times, Prandtl number, Eckert number, Reynolds number and Brinkman number on dimensionless velocity, temperature and entropy generation number profiles are analyzed. The results reveal that the entropy generation number increases with the increase of Deborah number while the increase of ratio of relaxation to retardation times causes the entropy generation number to reduce. A comparative study of the numerical results with the results from an exact solution for the dimensionless velocity gradient at the sheet surface is also performed. The comparison shows excellent agreement within 0.05% error.
The present study aimed at alleviating the impacts of alachlor (Ala) or atrazine (Atr) on maize growth by seed-dressing with naphthalic anhydride (NA, 0.4% w/w by seed weight). The dressed and ...undressed seeds were germinated for 10 days and treated with Ala or Atr at 3.2 or 1.8 kg ha−1, respectively, then the herbicide residues were determined in shoots one day after treatment. Atr residues were higher than Ala and remained in the same level for the 2nd day then retracted consistently up to 12 days. Meanwhile, GSH and GST were significantly induced while growth parameters were reduced; the effect of Atr was higher than Ala. Nonetheless, ABA, phenolics and anthocyanins as well as PAL, TAL and CI were increased but IAA was decreased coincidently with enhanced IAA-O and peroxidase. The immediate detection of the herbicide residues could conclude that growth reduction as elucidated from the decreased IAA concomitant with elevating ABA, phenolics and anthocyanin contents and enzyme activities are consequences of the herbicide persistence. The drop of IAA was preceded by the stimulation of IAA-O and peroxidase while the increased phenolics and anthocyanins followed PAL, TAL and CI stimulation confirming the regulatory roles of these enzymes. The application of NA greatly lowered the herbicide residues concurrently with ameliorations in growth parameters, GSH, GST, and maintained the balancing of secondary metabolites and plant growth regulators. Lowering Ala and Atr residues by NA in synchronization with enhanced GSH and GST could conclude that NA encouraged the detoxification of the herbicide. Moreover, the balances of IAA, ABA, phenolics and anthocyanins were mostly maintained in normal levels concomitantly with growth ameliorations suggesting that phytohormones and secondary metabolites are involved in the elevation of maize tolerance to Ala and Atr.
Maize; Naphthalic Anhydride; Herbicides; Persistence; tolerance; Agricultural Science; Agricultural Policy; Agronomy; Environmental Science; Plant Biology.
Abstract
Severe Acute Respiratory Syndrome Corona Virus Type-2 (SARS-COV-2) was first detected in China and created a global pandemic rapidly. Subsequently after serious efforts different types of ...vaccines produced against the virus and recommended for all people including pregnant women. The aim of this study was to realize the willingness of pregnant women to accept the COVID-19 vaccine in Kabul Afghanistan. For this purpose, a cross-sectional study was conducted in gynecology wards of several hospitals in Kabul, Afghanistan from 10th of July to 20th of August 2021 through direct interview with the pregnant women who had come for prenatal care to the healthcare centers. The collected data were analyzed through Statistical Package for Social Studies (SPSS) version 25. Simple descriptive analysis computed for demographic characteristics and bi-variable (Chi-square) analysis was carried out to find out the associations of taking vaccine with demographic variables. A p-value of < 0.05 was considered significant at 95% confidence interval. A total of 491 who were completed the inclusion criteria included in the analysis. A small portion of pregnant women (8.6%) illustrated the intent to get the COVID-19 vaccine if it is recommended by the health authorities in Afghanistan. Our study found a high rate of COVID-19 vaccine refusal among pregnant women in Kabul, Afghanistan. They showed the concern on adverse effects of the vaccine as the main reason for refusal, emphasizing the need to reduce the misconception on vaccine efficacy and campaigns to enhance awareness on the vaccine safety and benefits for mothers and babies.
The Ascomycete fungal insect pathogens, Beauveria and Metarhizium spp. have emerged as model systems with which to probe diverse aspects of fungal growth, stress response, and pathogenesis. Due to ...the availability of genomic resources and the development of robust methods for genetic manipulation, the last 5 years have witnessed a rapid increase in the molecular characterization of genes and their pathways involved in stress response and signal transduction in these fungi. These studies have been performed mainly via characterization of gene deletion/knockout mutants and have included the targeting of general proteins involved in stress response and/or virulence, e.g. catalases, superoxide dismutases, and osmolyte balance maintenance enzymes, membrane proteins and signaling pathways including GPI anchored proteins and G-protein coupled membrane receptors, MAPK pathways, e.g. (i) the pheromone/nutrient sensing, Fus3/Kss1, (ii) the cell wall integrity, Mpk1, and (iii) the high osmolarity, Hog1, the PKA/adenyl cyclase pathway, and various downstream transcription factors, e.g. Msn2, CreA and Pac1. Here, we will discuss current research that strongly suggests extensive underlying contributions of these biochemical and signaling pathways to both abiotic stress response and virulence.
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