The Experts below are selected from a list of 345 Experts worldwide ranked by ideXlab platform

Guoxiong Peng - One of the best experts on this subject based on the ideXlab platform.

  • disruption of an adenylate forming reductase required for conidiation increases virulence of the insect pathogenic fungus Metarhizium acridum by enhancing cuticle invasion
    Pest Management Science, 2020
    Co-Authors: Hongjuan Wang, Nemat O Keyhani, Guoxiong Peng
    Abstract:

    BACKGROUND: Metarhizium acridum, is a specific acridid pathogen developed for use against the migratory locust (Locusta migratoria manilensis). Adenylate-forming reductases (AFRs) include enzymes that are involved in natural product biosynthesis. Here, we genetically characterize the functions of a class IV AFR in M. acridum (MaAfrIV ) on fungal development and virulence. RESULTS: Gene expression analyses indicated MaAfrIV was induced on locust wings early during the infection process. Surprisingly, loss of MaAfrIV increased virulence (25.20% decrease in the median lethal time) against the locust in topical bioassays but was no different than the wild type when the cuticle was bypassed by direct infection of conidia into the insect hemocoel. Virulence markers including protease (Pr1) expression and appressorial turgor pressure were higher in the mutant than the parent strain. No difference was seen in the expression of host immune genes (Toll pathway) or in polyphenol oxidase (PPO) activity in locusts infected by the ΔMaAfrIV or wild type strains. However, the ΔMaAfrIV strain was unable to successfully sporulate on dead cadavers. CONCLUSION: Disruption of MaAfrIV increased fungal virulence by promoting insect cuticle invasion without altering host immune response or fungal immune evasion. Although loss of MaAfrIV conferred an apparent benefit to the fungus in terms of enhanced virulence, a significant trade-off was seen in the inability of the fungus to sporulate on the cadaver. As conidiation on the cadaver is essential for subsequent propagation in the environment, loss of MaAfrIV can reduce the engineering strains survivability in the field and improve the safety. © 2019 Society of Chemical Industry.

  • the macrea gene regulates normal conidiation and microcycle conidiation in Metarhizium acridum
    Frontiers in Microbiology, 2019
    Co-Authors: Dongxu Song, Hengqing Ji, Guoxiong Peng
    Abstract:

    As a C2H2 type zinc finger transcription factor, CreA is the key in Carbon Catabolism Repression (CCR) pathway, which negatively regulates the genes in carbon sources utilization. As conidiation in filamentous fungi is affected by nutritional conditions, CreA may contribute to fungal conidiation, which has been well studied in filamentous fungi, especially Aspergillus spp., but researches on entomopathogenic fungi are not enough. In this study, we found a homologous gene MaCreA in Metarhizium acridum, and the MaCreA deletion strain showed delayed conidiation, significant decrease in conidial yield, and 98.88% lower conidial production, when compared with the wild-type strain, and the normal conidiation and microcycle conidiation pattern shift was blocked. RT-qPCR showed that the transcription levels of the genes FlbD and LaeA (related to asexual development) were significantly altered, and those of most of the conidiation-related genes were higher in ΔMaCreA strain. The results of RNA-Seq revealed that MaCreA regulated the two conidiation patterns by mediating genes related to cell cycle, cell division, cell wall, and cell polarity. In conclusion, CreA, as a core regulatory gene in conidiation, provides new insight into the mechanism of conidiation in entomopathogenic fungi.

  • the protein phosphatase gene mappt1 acts as a programmer of microcycle conidiation and a negative regulator of uv b tolerance in Metarhizium acridum
    Applied Microbiology and Biotechnology, 2019
    Co-Authors: Jie Zhang, Nemat O Keyhani, Zhenglong Wang, Guoxiong Peng
    Abstract:

    : The Ser/Thr protein phosphatase Ppt1 (yeast)/PP5 (humans) has been implicated in signal transduction-mediated growth and differentiation, DNA damage/repair, cell cycle progression, and heat shock responses. Little, however, is known concerning the functions of Ppt1/PP5 in filamentous fungi. In this study, the Ppt1 gene MaPpt1 was characterized in the insect pathogenic fungus, Metarhizium acridum. The MaPpt1 protein features a three-tandem tetratricopeptide repeat (TPR) domain and a peptidyl-prolyl cis-trans isomerase-like (PP2Ac) domain. Subcellular localization using an MaPpt1::eGFP fusion protein revealed that MaPpt1 was localized in the cytoplasm of spores, but gathered at the septa in growing hyphae. Targeted gene inactivation of MaPpt1 in M. acridum resulted in unexpected reprogramming of normal aerial conidiation to microcycle conidiation. Although overall vegetative growth was unaffected, a significant increase in conidial yield was noted in ΔMaPpt1. Stress-responsive phenotypes and virulence were largely unaffected in ΔMaPpt1. Exceptionally, ΔMaPpt1 displayed increased UV tolerance compared to wild type. Digital gene expression data revealed that MaPpt1 mediates transcription of sets of genes involved in conidiation, polarized growth, cell cycle, cell proliferation, DNA replication and repair, and some important signaling pathways. These data indicate a unique role for Ppt1 in filamentous fungal development and differentiation.

  • a bifunctional catalase peroxidase makatg1 contributes to virulence of Metarhizium acridum by overcoming oxidative stress on the host insect cuticle
    Environmental Microbiology, 2017
    Co-Authors: Guohong Li, Guoxiong Peng, Nemat O Keyhani
    Abstract:

    Summary Microbial pathogens are exposed to damaging reactive oxygen species (ROS) produced from a variety of sources including chemical reactions due to exposure to stress (UV, heat) or by hosts as a defense response. Here we demonstrate that a bifunctional catalase-peroxidase, MakatG1, in the locust-specific fungal pathogen, Metarhizium acridum, functions as a ROS detoxification mechanism during host cuticle penetration. MakatG1 expression was highly induced during on-cuticle appressoria development as compared to vegetative (mycelia) growth or during in vivo growth in the insect hemocoel. A MakatG1 deletion mutant strain (ΔMakatG1) showed decreased catalase and peroxidase activities and significantly increased susceptibility to oxidative (H2O2 and menadione) and UV stress as compared to wild type and complemented strains. Insect bioassays revealed significantly reduced virulence of the ΔMakatG1 mutant when topically inoculated, but no impairment when the insect cuticle was bypassed. Germination and appressoria formation rates for the ΔMakatG1 mutant were decreased on locust wings and quinone/phenolic compounds derived from locust wings, but were not affected on plastic surfaces compared with the wild type strain. These data indicate that MakatG1 plays a pivotal role in penetration, reacting to and detoxifying specific cuticular compounds present on the host cuticle during the early stages of fungal infection. This article is protected by copyright. All rights reserved.

  • an ena atpase maena1 of Metarhizium acridum influences the na thermo and uv tolerances of conidia and is involved in multiple mechanisms of stress tolerance
    Fungal Genetics and Biology, 2015
    Co-Authors: Guoxiong Peng
    Abstract:

    Abstract In fungi, ENA ATPases play key roles in osmotic and alkaline pH tolerance, although their functions in thermo- and UV-tolerances have not been explored. Entomopathogenic fungi are naturally widespread and have considerable potential in pest control. An ENA ATPase gene, MaENA1 , from the entomopathogenic fungus Metarhizium acridum was functionally analyzed by deletion. MaENA1 -disruption strain (Δ MaENA1 ) was less tolerant to NaCl, heat, and UV radiation than a wild-type strain (WT). Digital Gene Expression profiling of conidial RNAs resulted in 281 differentially expressed genes (DEGs) between the WT and Δ MaENA1 strains. Eighty-five DEGs, 56 of which were down-regulated in the Δ MaENA1 strain, were shown to be associated with heat/UV tolerance, including six cytochrome P450 superfamily genes, 35 oxidoreductase genes, 24 ion-binding genes, seven DNA repair genes, and five other genes. In addition, eight genes were components of stress responsive pathways, including the Ras-cAMP PKA pathway, the RIM101 pathway, the Ca 2+ /calmodulin pathway, the TOR pathway, and the HOG/Spc1/Sty1/JNK pathway. These results demonstrated that MaENA1 influences fungal tolerances to Na + , heat, and UV radiation in M . acridum , and is involved in multiple mechanisms of stress tolerance. Therefore, MaENA1 is required for the adaptation and survival of entomopathogenic fungi in stressful conditions in the environment and in their hosts.

Nemat O Keyhani - One of the best experts on this subject based on the ideXlab platform.

  • spatial and temporal transcriptomic analyses reveal locust initiation of immune responses to Metarhizium acridum at the pre penetration stage
    Developmental and Comparative Immunology, 2020
    Co-Authors: Wei Zhang, Xiaoli Zheng, Jianhong Chen, Nemat O Keyhani
    Abstract:

    Abstract Insect hemocyte and fat body tissues play critical functional roles in insect immunity. Little, however, is known concerning the dynamic responses of these tissues to fungal infection. Here, we report on a time course of locust hemocyte and fat body transcriptomic responses to infection by the acridid specific fungal pathogen, Metarhizium acridum. Fat body responses were more pronounced at all infection stages as compared to hemocytes. Immune and other related genes were induced far earlier than previously considered including at pre-penetration stages. Differential expression in hemocyte and fat body tissues persisted throughout the course of infection up until host death. Our data indicate selective pressure on the host to recognize the infection as early as possible in order to limit its spread. Overall, fat body and hemocyte tissues launch a robust multi-tiered response to combat the fungal pathogen, with our data providing potential host targets for exploitation in pest control.

  • disruption of an adenylate forming reductase required for conidiation increases virulence of the insect pathogenic fungus Metarhizium acridum by enhancing cuticle invasion
    Pest Management Science, 2020
    Co-Authors: Hongjuan Wang, Nemat O Keyhani, Guoxiong Peng
    Abstract:

    BACKGROUND: Metarhizium acridum, is a specific acridid pathogen developed for use against the migratory locust (Locusta migratoria manilensis). Adenylate-forming reductases (AFRs) include enzymes that are involved in natural product biosynthesis. Here, we genetically characterize the functions of a class IV AFR in M. acridum (MaAfrIV ) on fungal development and virulence. RESULTS: Gene expression analyses indicated MaAfrIV was induced on locust wings early during the infection process. Surprisingly, loss of MaAfrIV increased virulence (25.20% decrease in the median lethal time) against the locust in topical bioassays but was no different than the wild type when the cuticle was bypassed by direct infection of conidia into the insect hemocoel. Virulence markers including protease (Pr1) expression and appressorial turgor pressure were higher in the mutant than the parent strain. No difference was seen in the expression of host immune genes (Toll pathway) or in polyphenol oxidase (PPO) activity in locusts infected by the ΔMaAfrIV or wild type strains. However, the ΔMaAfrIV strain was unable to successfully sporulate on dead cadavers. CONCLUSION: Disruption of MaAfrIV increased fungal virulence by promoting insect cuticle invasion without altering host immune response or fungal immune evasion. Although loss of MaAfrIV conferred an apparent benefit to the fungus in terms of enhanced virulence, a significant trade-off was seen in the inability of the fungus to sporulate on the cadaver. As conidiation on the cadaver is essential for subsequent propagation in the environment, loss of MaAfrIV can reduce the engineering strains survivability in the field and improve the safety. © 2019 Society of Chemical Industry.

  • Inhibitor of apoptosis-1 gene as a potential target for pest control and its involvement in immune regulation during fungal infection.
    Pest Management Science, 2020
    Co-Authors: Wei Zhang, Nemat O Keyhani, Hao Zhang
    Abstract:

    BACKGROUND: Environmentally friendly insect management technologies, including RNAi and entomopathogenic fungi, have attracted increasing attention as options for pest control. Here, we sought to extend RNAi directed targeting of the inhibitor of apoptosis protein 1 (IAP1) gene to the locust, and to examine its relationship to immune responses and susceptibility to Metarhizium acridum, a locust specific fungal pathogen. RESULTS: Expression of the locust LmIAP gene was induced in the hemolymph and fat body after M. acridum infection. RNAi directed silencing of locust LmIAP1 resulted in increased Caspase 3 activity, degeneration of the gut, and dose dependent mortality. Synergistic mortality was seen in RNAi-LmIAP/fungal co-infection experiments with the median survival time (MST) values decreasing from ~5 d for RNAi and M. acridum treatments alone, to 2.6 d for co-treatments. Reduced haemocyte numbers and antimicrobial peptide levels were seen in co-treated locusts, with changes in gut opportunistic pathogenic bacteria were seen between treatments. Enhanced fungal sporulation on co-treated insect cadavers was also compared with fungal infection alone. CONCLUSIONS: Silencing of the locust LmIAP1 gene results in direct mortality and increases insect susceptibility to insect fungal pathogens in part by decreasing immunity and altering the gut microbiome. This article is protected by copyright. All rights reserved.

  • members of chitin synthase family in Metarhizium acridum differentially affect fungal growth stress tolerances cell wall integrity and virulence
    PLOS Pathogens, 2019
    Co-Authors: Junjie Zhang, Yanru Du, Nemat O Keyhani, Hui Jiang
    Abstract:

    Chitin is an important component of the fungal cell wall with a family of chitin synthases mediating its synthesis. Here, we report on the genetic characterization of the full suite of seven chitin synthases (MaChsI-VII) identified in the insect pathogenic fungus, Metarhizium acridum. Aberrant distribution of chitin was most evident in targeted gene knockouts of MaChsV and MaChsVII. Mutants of MaChsI, MaChsIII, MaChsIV showed delayed conidial germination, whereas ΔMaChsII and ΔMaChsV mutants germinated more rapidly when compared to the wild-type parent. All MaChs genes impacted conidial yield, but differentially affected stress tolerances. Inactivation of MaChsIII, MaChsV, MaChsVII resulted in cell wall fragility, and ΔMaChsV and ΔMaChsVII mutants showed high sensitivity to Congo red and calcofluor white, suggesting that the three genes are required for cell wall integrity. In addition, ΔMaChsIII and ΔMaChsVII mutants showed the highest sensitivities to heat and UV-B stress. Three of seven chitin synthase genes, MaChsIII, MaChsV, MaChsVII, were found to contribute to fungal virulence. Compared with the wild-type strain, ΔMaChsIII and ΔMaChsV mutants were reduced in virulence by topical inoculation, while the ΔMaChsVII mutant showed more severe virulence defects. Inactivation of MaChsIII, MaChsV, or MaChsVII impaired appressorium formation, affected growth of in insecta produced hyphal bodies, and altered the surface properties of conidia and hyphal bodies, resulting in defects in the ability of the mutant strains to evade insect immune responses. These data provide important links between the physiology of the cell wall and the ability of the fungus to parasitize insects and reveal differential functional consequences of the chitin synthase family in M. acridum growth, stress tolerances, cell wall integrity and virulence.

  • the protein phosphatase gene mappt1 acts as a programmer of microcycle conidiation and a negative regulator of uv b tolerance in Metarhizium acridum
    Applied Microbiology and Biotechnology, 2019
    Co-Authors: Jie Zhang, Nemat O Keyhani, Zhenglong Wang, Guoxiong Peng
    Abstract:

    : The Ser/Thr protein phosphatase Ppt1 (yeast)/PP5 (humans) has been implicated in signal transduction-mediated growth and differentiation, DNA damage/repair, cell cycle progression, and heat shock responses. Little, however, is known concerning the functions of Ppt1/PP5 in filamentous fungi. In this study, the Ppt1 gene MaPpt1 was characterized in the insect pathogenic fungus, Metarhizium acridum. The MaPpt1 protein features a three-tandem tetratricopeptide repeat (TPR) domain and a peptidyl-prolyl cis-trans isomerase-like (PP2Ac) domain. Subcellular localization using an MaPpt1::eGFP fusion protein revealed that MaPpt1 was localized in the cytoplasm of spores, but gathered at the septa in growing hyphae. Targeted gene inactivation of MaPpt1 in M. acridum resulted in unexpected reprogramming of normal aerial conidiation to microcycle conidiation. Although overall vegetative growth was unaffected, a significant increase in conidial yield was noted in ΔMaPpt1. Stress-responsive phenotypes and virulence were largely unaffected in ΔMaPpt1. Exceptionally, ΔMaPpt1 displayed increased UV tolerance compared to wild type. Digital gene expression data revealed that MaPpt1 mediates transcription of sets of genes involved in conidiation, polarized growth, cell cycle, cell proliferation, DNA replication and repair, and some important signaling pathways. These data indicate a unique role for Ppt1 in filamentous fungal development and differentiation.

Raymond J St Leger - One of the best experts on this subject based on the ideXlab platform.

  • horizontal gene transfer allowed the emergence of broad host range entomopathogens
    Proceedings of the National Academy of Sciences of the United States of America, 2019
    Co-Authors: Qiangqiang Zhang, Xiaoxuan Chen, Chuan Xu, Hong Zhao, Xing Zhang, Guohong Zeng, Ying Qian, Wubin Mi, Yamin Meng, Raymond J St Leger
    Abstract:

    The emergence of new pathogenic fungi has profoundly impacted global biota, but the underlying mechanisms behind host shifts remain largely unknown. The endophytic insect pathogen Metarhizium robertsii evolved from fungi that were plant associates, and entomopathogenicity is a more recently acquired adaptation. Here we report that the broad host-range entomopathogen M. robertsii has 18 genes that are derived via horizontal gene transfer (HGT). The necessity of degrading insect cuticle served as a major selective pressure to retain these genes, as 12 are up-regulated during penetration; 6 were confirmed to have a role in penetration, and their collective actions are indispensable for infection. Two lipid-carrier genes are involved in utilizing epicuticular lipids, and a third (MrNPC2a) facilitates hemocoel colonization. Three proteases degraded the procuticular protein matrix, which facilitated up-regulation of other cuticle-degrading enzymes. The three lipid carriers and one of the proteases are present in all analyzed Metarhizium species and are essential for entomopathogenicity. Acquisition of another protease (MAA_01413) in an ancestor of broad host-range lineages contributed to their host-range expansion, as heterologous expression in the locust specialist Metarhizium acridum enabled it to kill caterpillars. Our work reveals that HGT was a key mechanism in the emergence of entomopathogenicity in Metarhizium from a plant-associated ancestor and in subsequent host-range expansion by some Metarhizium lineages.

  • Construction of a Hypervirulent and Specific Mycoinsecticide for Locust Control
    Scientific Reports, 2014
    Co-Authors: Weiguo Fang, Hsiao-ling Lu, Glenn F. King, Raymond J St Leger
    Abstract:

    Locusts and grasshoppers (acridids) are among the worst pests of crops and grasslands worldwide. Metarhizium acridum, a fungal pathogen that specifically infects acridids, has been developed as a control agent but its utility is limited by slow kill time and greater expense than chemical insecticides. We found that expression of four insect specific neurotoxins improved the efficacy of M. acridum against acridids by reducing lethal dose, time to kill and food consumption. Coinoculating recombinant strains expressing AaIT1(a sodium channel blocker) and hybrid-toxin (a blocker of both potassium and calcium channels), produced synergistic effects, including an 11.5-fold reduction in LC50, 43% reduction in LT50 and a 78% reduction in food consumption. However, specificity was retained as the recombinant strains did not cause disease in non-acridids. Our results identify a repertoire of toxins with different modes of action that improve the utility of fungi as specific control agents of insects.

  • New perspectives on insect pathogens
    Fungal Biology Reviews, 2011
    Co-Authors: Raymond J St Leger, Chengshu Wang, Weiguo Fang
    Abstract:

    Recent research on entomopathogenic fungi suggests that many of them have a multifactorial influence on plant growth and soil ecology by also being endophytes, pathogens of protozoans, antagonists of plant pathogens and associates with the rhizosphere. There is very little data as to the ecological consequences of these interactions, but a deeper understanding of the mechanisms by which entomopathogens interact with other microbes, as well as with insects and plants could be used to develop the potential of these fungi as comprehensive plant symbionts. The genome sequences of the specific locust pathogen Metarhizium acridum and the broad host range Metarhizium robertsii have been used to investigate adaptations to insect parasitism and determine the identity, origin and evolution of traits needed for diverse lifestyles and host switching. Functional genomic approaches confirmed that M. robertsii up-regulates different genes in the presence of plants and insects, demonstrating that it has specialist genes for a bifunctional lifestyle. The more versatile life history pattern of M. robertsii is also reflected in a larger genome encoding more toxins and extracellular enzymes than M. acridum. However, secreted proteins are markedly more numerous in both Metarhizium spp. than in plant pathogens and nonpathogenic fungi, pointing to a greater complexity in the interactions between Metarhizium spp. and their environments. Commercial development of entomopathogenic fungi for pest control has been hindered by poor performance relative to chemical insecticides. We have demonstrated that the expression of genes encoding arthropod neurotoxins in M. robertsii can greatly improve virulence. We have also produced a Metarhizium anisopliae strain that expresses a single-chain antibody fragment that blocks transmission of malaria. Recombinant antibodies provide a vast array of potential anti-insect effectors that would allow construction of highly specific biopesticides with minimal additional negative environmental impact relative to parental wild type strains.

  • insertion of an esterase gene into a specific locust pathogen Metarhizium acridum enables it to infect caterpillars
    PLOS Pathogens, 2011
    Co-Authors: Sibao Wang, Weiguo Fang, Chengshu Wang, Raymond J St Leger
    Abstract:

    An enduring theme in pathogenic microbiology is poor understanding of the mechanisms of host specificity. Metarhizium is a cosmopolitan genus of invertebrate pathogens that contains generalist species with broad host ranges such as M. robertsii (formerly known as M. anisopliae var. anisopliae) as well as specialists such as the acridid-specific grasshopper pathogen M. acridum. During growth on caterpillar (Manduca sexta) cuticle, M. robertsii up-regulates a gene (Mest1) that is absent in M. acridum and most other fungi. Disrupting M. robertsii Mest1 reduced virulence and overexpression increased virulence to caterpillars (Galleria mellonella and M. sexta), while virulence to grasshoppers (Melanoplus femurrubrum) was unaffected. When Mest1 was transferred to M. acridum under control of its native M. robertsii promoter, the transformants killed and colonized caterpillars in a similar fashion to M. robertsii. MEST1 localized exclusively to lipid droplets in M. robertsii conidia and infection structures was up-regulated during nutrient deprivation and had esterase activity against lipids with short chain fatty acids. The mobilization of stored lipids was delayed in the Mest1 disruptant mutant. Overall, our results suggest that expression of Mest1 allows rapid hydrolysis of stored lipids, and promotes germination and infection structure formation by M. robertsii during nutrient deprivation and invasion, while Mest1 expression in M. acridum broadens its host range by bypassing the regulatory signals found on natural hosts that trigger the mobilization of endogenous nutrient reserves. This study suggests that speciation in an insect pathogen could potentially be driven by host shifts resulting from changes in a single gene.

  • the rhizosphere competent entomopathogen Metarhizium anisopliae expresses a specific subset of genes in plant root exudate
    Microbiology, 2011
    Co-Authors: Monica Pavaripoll, Claudia Angelini, Weiguo Fang, Sibao Wang, Francisco J Posada, Raymond J St Leger
    Abstract:

    Metarhizium anisopliae and Beauveria bassiana are ubiquitous insect pathogens and possible plant symbionts, as some strains are endophytic or colonize the rhizosphere. We evaluated 11 strains of M. anisopliae and B. bassiana, and two soil saprophytes (the non-rhizospheric Aspergillus niger and the rhizosphere-competent Trichoderma harzianum) for their ability to germinate in bean root exudates (REs). Our results showed that some generalist strains of M. anisopliae were as good at germinating in RE as T. harzianum, although germination rates of the specialized acridid pathogen Metarhizium acridum and the B. bassiana strains were significantly lower. At RE concentrations of <1 mg ml−1, M. anisopliae strain ARSEF 2575 showed higher germination rates than T. harzianum. Microarrays showed that strain 2575 upregulated 29 genes over a 12 h period in RE. A similar number of genes (21) were downregulated. Upregulated genes were involved in carbohydrate metabolism, lipid metabolism, cofactors and vitamins, energy metabolism, proteolysis, extracellular matrix/cell wall proteins, transport proteins, DNA synthesis, the sexual cycle and stress response. However, 41.3 % of the upregulated genes were hypothetical or orphan sequences, indicating that many previously uncharacterized genes have functions related to saprophytic survival. Genes upregulated in response to RE included the subtilisin Pr1A, which is also involved in pathogenicity to insects. However, the upregulated Mad2 adhesin specifically mediates adhesion to plant surfaces, demonstrating that M. anisopliae has genes for rhizosphere competence that are induced by RE.

Donald W Roberts - One of the best experts on this subject based on the ideXlab platform.

  • possible source of the high uv b and heat tolerance of Metarhizium acridum isolate arsef 324
    Journal of Invertebrate Pathology, 2018
    Co-Authors: Drauzio E N Rangel, Donald W Roberts
    Abstract:

    Abstract The isolate ARSEF 324 of Metarhizium acridum is very tolerant to UV-B radiation and heat, but the intrinsic traits behind the extreme tolerance of this isolate to both stress conditions have not been elucidated. Because trehalose and mannitol are documented stress reducers in fungi, we investigated the accumulation of these compounds in conidia of ARSEF 324 compared with the accumulation of these two compounds in conidia of M. robertsii (ARSEF 23 and ARSEF 2575), which are considerably more susceptible to UV-B radiation and heat than ARSEF 324. Conidia of ARSEF 324 produced on potato dextrose agar plus yeast extract accumulated two-fold more trehalose and mannitol than conidia of ARSEF 23 and ARSEF 2575 produced on the same medium. The high accumulation of trehalose and mannitol in conidia of ARSEF 324 suggests one mechanism that it uses to attain its high tolerance to UV-B radiation and heat.

  • Riboflavin induces Metarhizium spp. to produce conidia with elevated tolerance to UV-B, and upregulates photolyases, laccases and polyketide synthases genes.
    Journal of Applied Microbiology, 2018
    Co-Authors: R.a. Pereira‐junior, Donald W Roberts, Carla Huarte-bonnet, Flávia R. S. Paixão, Nicolás Pedrini, Everton K K Fernandes
    Abstract:

    AIMS: The effect of nutritional supplementation of two Metarhizium species with riboflavin (Rb) during production of conidia was evaluated on (i) conidial tolerance (based on germination) to UV-B radiation and on (ii) conidial expression following UV-B irradiation, of enzymes known to be active in photoreactivation, viz., photolyase (Phr), laccase (Lac) and polyketide synthase (Pks). METHODS AND RESULTS: Metarhizium acridum (ARSEF 324) and Metarhizium robertsii (ARSEF 2575) were grown either on (i) potato dextrose agar medium (PDA), (ii) PDA supplemented with 1% yeast extract (PDAY), (iii) PDA supplemented with Rb (PDA+Rb), or (iv) PDAY supplemented with Rb (PDAY+Rb). Resulting conidia were exposed to 866·7 mW m-2 of UV-B Quaite-weighted irradiance to total doses of 3·9 or 6·24 kJ m-2 . Some conidia also were exposed to 16 klux of white light (WL) after being irradiated, or not, with UV-B to investigate the role of possible photoreactivation. Relative germination of conidia produced on PDA+Rb (regardless Rb concentration) or on PDAY and exposed to UV-B was higher compared to conidia cultivated on PDA without Rb supplement, or to conidia suspended in Rb solution immediately prior to UV-B exposure. The expression of MaLac3 and MaPks2 for M. acridum, as well as MrPhr2, MrLac1, MrLac2 and MrLac3 for M. robertsii was higher when the isolates were cultivated on PDA+Rb and exposed to UV-B followed by exposure to WL, or exposed to WL only. CONCLUSIONS: Rb in culture medium increases the UV-B tolerance of M. robertsii and M. acridum conidia, and which may be related to increased expression of Phr, Lac and Pks genes in these conidia. SIGNIFICANCE AND IMPACT OF THE STUDY: The enhanced UV-B tolerance of Metarhizium spp. conidia produced on Rb-enriched media may improve the effectiveness of these fungi in biological control programs.

  • Species of the Metarhizium anisopliae complex with diverse ecological niches display different susceptibilities to antifungal agents.
    Fungal Biology, 2017
    Co-Authors: Guilherme T P Brancini, Drauzio E N Rangel, Donald W Roberts, Ludmilla Tonani, Gilberto U L Braga
    Abstract:

    Abstract Species of the Metarhizium anisopliae complex are globally ubiquitous soil-inhabiting and predominantly insect-pathogenic fungi. The Metarhizium genus contains species ranging from specialists, such as Metarhizium acridum that only infects acridids, to generalists, such as M. anisopliae, Metarhizium brunneum, and Metarhizium robertsii that infect a broad range of insects and can also colonize plant roots. There is little information available about the susceptibility of Metarhizium species to clinical and non-clinical antifungal agents. We determined the susceptibility of 16 isolates comprising four Metarhizium species with different ecological niches to seven clinical (amphotericin B, ciclopirox olamine, fluconazole, griseofulvin, itraconazole, tebinafine, and voriconazole) and one non-clinical (benomyl) antifungal agents. All isolates of the specialist M. acridum were clearly more susceptible to most antifungals than the isolates of the generalists M. anisopliae sensu lato, M. brunneum, and M. robertsii. All isolates of M. anisopliae, M. brunneum, and M. robertsii were resistant to fluconazole and some were also resistant to amphotericin B. The marked differences in susceptibility between the specialist M. acridum and the generalist Metarhizium species suggest that this characteristic is associated with their different ecological niches, and may assist in devising rational antifungal treatments for the rare cases of mycoses caused by Metarhizium species.

  • quantification of cyclobutane pyrimidine dimers induced by uvb radiation in conidia of the fungi aspergillus fumigatus aspergillus nidulans Metarhizium acridum and Metarhizium robertsii
    Photochemistry and Photobiology, 2010
    Co-Authors: Erika Nascimento, Sergio Henrique Da Silva, Donald W Roberts, Everaldo Dos Reis Marques, Gilberto U L Braga
    Abstract:

    : Conidia are responsible for reproduction, dispersal, environmental persistence and host infection of many fungal species. One of the main environmental factors that can kill and/or damage conidia is solar UV radiation. Cyclobutane pyrimidine dimers (CPD) are the major DNA photoproducts induced by UVB. We examined the conidial germination kinetics and the occurrence of CPD in DNA of conidia exposed to different doses of UVB radiation. Conidia of Aspergillus fumigatus, Aspergillus nidulans and Metarhizium acridum were exposed to UVB doses of 0.9, 1.8, 3.6 and 5.4 kJ m(-2). CPD were quantified using T4 endonuclease V and alkaline agarose gel electrophoresis. Most of the doses were sublethal for all three species. Exposures to UVB delayed conidial germination and the delays were directly related both to UVB doses and CPD frequencies. The frequencies of dimers also were linear and directly proportional to the UVB doses, but the CPD yields differed among species. We also evaluated the impact of conidial pigmentation on germination and CPD induction on Metarhizium robertsii. The frequency of dimers in an albino mutant was approximately 10 times higher than of its green wild-type parent strain after exposure to a sublethal dose (1.8 kJ m(-2)) of UVB radiation.

  • ctc medium a novel dodine free selective medium for isolating entomopathogenic fungi especially Metarhizium acridum from soil
    Biological Control, 2010
    Co-Authors: Everton K K Fernandes, Drauzio E N Rangel, Chad A Keyser, Nelson R Foster, Donald W Roberts
    Abstract:

    The selective media most commonly used for isolating hyphomycetous species of entomopathogenic fungi from non-sterile substrates rely on N-dodecylguanidine monoacetate (dodine) as the selective fungicide. Although these media are effective for isolating many species of Metarhizium and Beauveria from soil, they are inefficient media for isolation of an important Metarhizium species, Metarhizium acridum, from non-sterile soil. Our current study was directed to formulating a dodine-free selective medium that is efficient for isolating naturally occurring Beauveria spp. and Metarhizium spp., especially M. acridum, from soil. The selective medium (designated CTC medium) consists of potato dextrose agar plus yeast extract (PDAY) supplemented with chloramphenicol, thiabendazole and cycloheximide. In comparisons with selective media previously reported in the literature, the CTC medium afforded colonies that were larger and had both earlier and more abundant conidiation of entomopathogenic fungi, features which greatly facilitated identification of the emerging entomopathogenic fungi. In addition to efficient re-isolation of M. acridum, this medium also is an effective tool for selective isolation of Metarhizium brunneum, Metarhizium robertsii, Beauveria bassiana and Beauveria brongniartii from non-sterile field-collected soil samples inoculated (spiked) with fresh conidia in the laboratory.

Gilberto U L Braga - One of the best experts on this subject based on the ideXlab platform.

  • combining transcriptomics and proteomics reveals potential post transcriptional control of gene expression after light exposure in Metarhizium acridum
    G3: Genes Genomes Genetics, 2019
    Co-Authors: Guilherme T P Brancini, Marcia Eliana Da Silva Ferreira, Drauzio E N Rangel, Gilberto U L Braga
    Abstract:

    Light is an important stimulus for fungi as it regulates many diverse and important biological processes. Metarhizium acridum is an entomopathogenic fungus currently used for the biological control of insect pests. The success of this approach is heavily dependent on tolerance to environmental stresses. It was previously reported that light exposure increases tolerance to ultraviolet radiation in M. acridum. There is no information in the literature about how light globally influences gene expression in this fungus. We employed a combination of mRNA-Sequencing and high-throughput proteomics to study how light regulates gene expression both transcriptionally and post-transcriptionally. Mycelium was exposed to light for 5 min and changes at the mRNA and protein levels were followed in time-course experiments for two and four hours, respectively. After light exposure, changes in mRNA abundance were observed for as much as 1128 genes or 11.3% of the genome. However, only 57 proteins changed in abundance and at least 347 significant changes at the mRNA level were not translated to the protein level. We observed that light downregulated subunits of the eukaryotic translation initiation factor 3, the eIF5A-activating enzyme deoxyhypusine hydroxylase, and ribosomal proteins. We hypothesize that light is perceived as a stress by the cell that responds to it by reducing translational activity. Overall, our results indicate that light acts both as a signal and a stressor to M. acridum and highlight the importance of measuring protein levels in order to fully understand light responses in fungi.

  • Responses of entomopathogenic fungi to the mutagen 4-nitroquinoline 1-oxide
    Fungal Biology, 2018
    Co-Authors: Claudinéia A.s. Araújo, Guilherme T P Brancini, Gilberto U L Braga, Luciana P. Dias, Breno Pupin, Paulo C. Ferreira, Josane Mittmann, Drauzio E N Rangel
    Abstract:

    Abstract Survival of entomopathogenic fungi under solar ultraviolet (UV) radiation is paramount to the success of biological control of insect pests and disease vectors. The mutagenic compound 4-nitroquinoline 1-oxide (4-NQO) is often used to mimic the biological effects of UV radiation on organisms. Therefore, we asked whether tolerance to 4-NQO could predict tolerance to UV radiation in thirty isolates of entomopathogenic fungi and one isolate of a xerophilic fungus. A dendrogram obtained from cluster analyses based on the 50 and 90% inhibitory concentrations (IC 50 and IC 90 , respectively), calculated by Probit analysis, divided the fungal isolates into six clusters numbered consecutively based on their tolerance to 4-NQO. Cluster 6 contained isolates of the species with the highest tolerance to 4-NQO (IC 50 > 4.7 μM), including Mariannaea pruinosa , Lecanicillium aphanocladii , and Torrubiella homopterorum . Cluster 1 contained isolates least tolerant to 4-NQO (IC 50 Metarhizium acridum (ARSEF 324), Tolypocladium geodes , and Metarhizium brunneum (ARSEF 7711). With few exceptions, the majority of Metarhizium species showed moderate to low tolerances (IC 50 between 0.4 and 0.9 μM) and were placed in cluster 2. Cluster 3 consisted of two Metarhizium robertsii isolates with moderate tolerance (IC 50 between 1.0 and 1.2 μM). Cluster 5 contained the species with high tolerance (IC 50 between 1.9 and 4.0 μM), including one Metarhizium anisopliae (ARSEF 4343) isolate. The most UV tolerant isolate of M. acridum , ARSEF 324, was the least tolerant to 4-NQO. Also, L. aphanocladii , which is very susceptible to UV radiation, showed high tolerance to 4-NQO. Our results indicate that tolerance to 4-NQO does not correlate with tolerance to UV radiation. Therefore this chemical compound is not a predictor of UV tolerance in entomopathogenic fungi.

  • The Xenon Test Chamber Q-SUN® for testing realistic tolerances of fungi exposed to simulated full spectrum solar radiation.
    Fungal Biology, 2018
    Co-Authors: Luciana P. Dias, Gilberto U L Braga, Claudinéia A.s. Araújo, Breno Pupin, Paulo C. Ferreira, Drauzio E N Rangel
    Abstract:

    Abstract The low survival of insect-pathogenic fungi when used for insect control in agriculture is mainly due to the deleterious effects of ultraviolet radiation and heat from solar irradiation. In this study, conidia of 15 species of entomopathogenic fungi were exposed to simulated full-spectrum solar radiation emitted by a Xenon Test Chamber Q-SUN XE-3-HC 340S (Q-LAB® Corporation, Westlake, OH, USA), which very closely simulates full-spectrum solar radiation. A dendrogram obtained from cluster analyses, based on lethal time 50 % and 90 % calculated by Probit analyses, separated the fungi into three clusters: cluster 3 contains species with highest tolerance to simulated full-spectrum solar radiation, included Metarhizium acridum, Cladosporium herbarum, and Trichothecium roseum with LT50 > 200 min irradiation. Cluster 2 contains eight species with moderate UV tolerance: Aschersonia aleyrodis, Isaria fumosorosea, Mariannaea pruinosa, Metarhizium anisopliae, Metarhizium brunneum, Metarhizium robertsii, Simplicillium lanosoniveum, and Torrubiella homopterorum with LT50 between 120 and 150 min irradiation. The four species in cluster 1 had the lowest UV tolerance: Lecanicillium aphanocladii, Beauveria bassiana, Tolypocladium cylindrosporum, and Tolypocladium inflatum with LT50

  • exposing Metarhizium acridum mycelium to visible light up regulates a photolyase gene and increases photoreactivating ability
    Journal of Invertebrate Pathology, 2018
    Co-Authors: Guilherme T P Brancini, Luciano Bachmann, Marcia Eliana Da Silva Ferreira, Drauzio E N Rangel, Gilberto U L Braga
    Abstract:

    Abstract Metarhizium acridum is an entomopathogen currently used against acridids. We have previously reported that exposing mycelium to visible light increases M. acridum tolerance to ultraviolet-B (UV-B) radiation. Here we evaluated if light could also increase tolerance to ultraviolet-C (UV-C) radiation. We observed that, as opposed to UV-B radiation, light did not increase tolerance to UV-C radiation under dark repair conditions. However, light did increase tolerance to UV-C radiation if photoreactivating light was present after UV-C exposure. Quantitative PCR experiments revealed that light up-regulates a photolyase gene. This is the first report showing that light regulates photoreactivating ability in M. acridum .

  • Species of the Metarhizium anisopliae complex with diverse ecological niches display different susceptibilities to antifungal agents.
    Fungal Biology, 2017
    Co-Authors: Guilherme T P Brancini, Drauzio E N Rangel, Donald W Roberts, Ludmilla Tonani, Gilberto U L Braga
    Abstract:

    Abstract Species of the Metarhizium anisopliae complex are globally ubiquitous soil-inhabiting and predominantly insect-pathogenic fungi. The Metarhizium genus contains species ranging from specialists, such as Metarhizium acridum that only infects acridids, to generalists, such as M. anisopliae, Metarhizium brunneum, and Metarhizium robertsii that infect a broad range of insects and can also colonize plant roots. There is little information available about the susceptibility of Metarhizium species to clinical and non-clinical antifungal agents. We determined the susceptibility of 16 isolates comprising four Metarhizium species with different ecological niches to seven clinical (amphotericin B, ciclopirox olamine, fluconazole, griseofulvin, itraconazole, tebinafine, and voriconazole) and one non-clinical (benomyl) antifungal agents. All isolates of the specialist M. acridum were clearly more susceptible to most antifungals than the isolates of the generalists M. anisopliae sensu lato, M. brunneum, and M. robertsii. All isolates of M. anisopliae, M. brunneum, and M. robertsii were resistant to fluconazole and some were also resistant to amphotericin B. The marked differences in susceptibility between the specialist M. acridum and the generalist Metarhizium species suggest that this characteristic is associated with their different ecological niches, and may assist in devising rational antifungal treatments for the rare cases of mycoses caused by Metarhizium species.