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Like many other fungal pathogens Metarhizium anisopliae is a facultative saprophyte with both soil-dwelling and insect pathogenic life-stages. In addition, as M. anisopliae traverses the cuticle and enters the hemolymph it must adapt to several different host environments. In this study, we used expressed sequence tags and cDNA microarray analyses...
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... 22 out of 1718 genes were isolated from all three libraries. These overlapping genes included, for example, the translation elongation factor 1a, the lone endocellu- lar subtilisin pr1H, b-glucosidase, ribosomal protein S16, DNase I, rRNA intron endonuclease, endoglucan- ase B, chitinase 3, and the homolog of Neurospora clock control gene ccg-6 (supplementary Table 1). ...
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... broad view of the nature of the adaptations made by M. anisopliae following transfer to these media was obtained by classifying the ESTs into nine groups of functionally related genes (Table 1). The expression of genes involved in energy metabolism and RNA metabo- lism, as well as expression of transposable elements, was largely unaffected by the growth conditions tested. ...
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... the cell metabolism category, more genes were expressed by the fungus when challenged with hemo- lymph than with cuticle or root exudate. The high per- centage of transcripts involved in lipid metabolism in the H-library (Table 1) was mainly due to the abundant expression of two C-4 methyl sterol oxidases paralogs CN808221 and CN808291 (Table 2). The number of ESTs involved in carbohydrate metabolism in the H- (11.29%) and R-libraries (10.18%) was significantly higher (P < 0.01) than those in the C-library (7.02%) (Table 1). ...
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... high per- centage of transcripts involved in lipid metabolism in the H-library (Table 1) was mainly due to the abundant expression of two C-4 methyl sterol oxidases paralogs CN808221 and CN808291 (Table 2). The number of ESTs involved in carbohydrate metabolism in the H- (11.29%) and R-libraries (10.18%) was significantly higher (P < 0.01) than those in the C-library (7.02%) (Table 1). Individual genes for carbohydrate metabolism were sharply altered in regulation, possibly indicative of pivotal enzymes involved in metabolic reprogramming. ...
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... dehydrogenase (CN809022) and alde- hyde dehydrogenase (CN808873), often involved in detoxification of toxins, were common in the R-and H-libraries. Cellulose-related protein (AJ272778) and b-glucosidase 5 (AJ274129) were abundant in the C-li- brary (supplementary Table 1). ...
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... the cell structure and function category, M. anisop- liae expressed more genes involved in cell wall reorgani- zation, the extracellular matrix, and signaling when growing in hemolymph than it did either on cuticle or in root exudates (Table 1 and supplementary Table 1). For the cell cycle, division, and growth category, signif- icantly fewer transcripts were detected in the R-library than in the C-and H-libraries. ...
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... the cell cycle, division, and growth category, signif- icantly fewer transcripts were detected in the R-library than in the C-and H-libraries. The C-library contained more ESTs involved in the cell cycle, while the H-library had a higher level of clock control genes (Table 1). In Neurospora crassa the circadian clock controls asexual spore development (Bell-Pedersen et al., 1996). ...
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... heat shock proteins were isolated from all three libraries (supplementary Table 1), the abundance of transcripts of stress response genes was very different comprising 10.76% of the R-library, 6.80% of the H-li- brary, and only 1.61% of the C-library (Table 1). The R-library contained a highly expressed transcript (CN809626, 91/1022) that is similar to a nitrogen starva- tion gene (Table 2) as well as two homologs of ice nucleation protein (CN809313 and CN809464). ...
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... heat shock proteins were isolated from all three libraries (supplementary Table 1), the abundance of transcripts of stress response genes was very different comprising 10.76% of the R-library, 6.80% of the H-li- brary, and only 1.61% of the C-library (Table 1). The R-library contained a highly expressed transcript (CN809626, 91/1022) that is similar to a nitrogen starva- tion gene (Table 2) as well as two homologs of ice nucleation protein (CN809313 and CN809464). ...
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... H-library contained significantly more tran- scripts encoding products involved in detoxification and the synthesis of toxic metabolites. ESTs with hypo- thetical or unknown functions comprised 26.6% (C-li- brary), 22.7% (H-library), and 29.9% (R-library) (Table 1). ...
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... microarray data supported EST analysis show- ing sharp upregulation of C-4 methyl sterol oxidases in hemolymph, but also showed downregulation (À1.3- fold) of a sterol reductase (AJ273501) similar (E = 1 · 10 À57 ) to an enzyme from Nectria hematococca. In addition it demonstrated that enzymes for polyunsat- urated fatty acid biosynthesis, such as several desatu- rases (CN808158, CN808272, AJ273890, CN808437, and CN808164) were induced by hemolymph, and to a lesser extent by cuticle, but not by root exudates (supple- mentary Table 1). Disruption of desaturase genes in Aspergillus spp. ...
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... two aspartic prote- ases (CN809214 and CN809604) and a few proteasome subunits were upregulated in hemolymph (Fig. 3A). Genes encoding ribosomal proteins and translational machinery such as elongation factors were coordinately up regulated in hemolymph compared to SDB, while the same genes were usually downregulated in root exudates (supplementary Table 1). ...
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... to the C-and R-libraries, the H-library contained more ESTs for genes involved in signal transduction (Table 1). While microarray analysis indi- cated that most of these genes (47 in total) were also up regulated when the fungus was grown on cuticle as compared to SDB, none of these genes were upregulated in the R-medium (Fig. 3C), suggesting that they play a particular role in adaptation to host-related media. ...
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... the proteases, M. anisopliae also expressed dif- ferent subsets of genes for utilizing carbohydrates in different media (Table 1). However, as some of these enzymes can use multiple carbon sources their precise functions and targets in insect hemolymph are un- known. ...
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... of signal transduction pathways have long been recognized as being involved in fungal devel- opment and virulence (e.g., Borges-Walmsley and Walmsley, 2000). Both EST and microarray analyses showed differential expression of transduction chains during growth in SDB, root exudates, and host media (Table 1; Fig. 3C). Pathways associated with infection structure differentiation and virulence in other fungal species include the cAMP and mitogen-activated protein (MAP) kinase signaling systems which are themselves regulated by upstream G and ras components (BorgesWalmsley and Walmsley, 2000;Leberer et al., 2001;Nishimura et al., 2003;Xu, 2000). ...
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Citations
... Similar interkingdom interactions have likely driven the evolution of other plant-associated soil fungi, which have acquired the ability to infect and kill insects, giving rise to new lineages of endophytic insect pathogens characterized by multifunctional lifestyles (73). In this context, the entomopathogenic Metarhizium is an excellent example of a fungus with genotypic plasticity allowing a multifunctional lifestyle, ranging from insect pathogen to plant colonizer or saprotroph depending upon exposure to different environmental conditions (74)(75)(76). ...
Plants generate energy flows through natural food webs, driven by competition for resources among organisms, which are part of a complex network of multitrophic interactions. Here, we demonstrate that the interaction between tomato plants and a phytophagous insect is driven by a hidden interplay between their respective microbiotas. Tomato plants colonized by the soil fungus Trichoderma afroharzianum, a beneficial microorganism widely used in agriculture as a biocontrol agent, negatively affects the development and survival of the lepidopteran pest Spodoptera littoralis by altering the larval gut microbiota and its nutritional support to the host. Indeed, experiments aimed to restore the functional microbial community in the gut allow a complete rescue. Our results shed light on a novel role played by a soil microorganism in the modulation of plant-insect interaction, setting the stage for a more comprehensive analysis of the impact that biocontrol agents may have on ecological sustainability of agricultural systems.
... For example, Metarhizium is a soil-inhabiting insect-pathogenic fungus worldwide and is currently used as a biocontrol agent against crop pests (Sasan & Bidochka, 2012). Other fungi known as insect pathogens include Acremonium, Beauveria, Cladosporium, Clonostachys, and Isaria (Wang et al., 2005). ...
... The rhizosphere is a highly competitive environment in which microbes exhibit different strategies for survival. Entomopathogenic fungi (EPF) are commonly found in the rhizosphere, using root exudates as a source of nutrition but switching to insects when the opportunity arises [1][2][3][4][5]. EPF form symbiotic relationships with plants, leading to improved plant growth and productivity [1,6]. ...
Abstract: Fungal volatile organic compounds (VOCs) represent promising candidates for biopesticide fumigants to control crop pests and pathogens. Herein, VOCs produced using three strains of the ento�mopathogenic fungus Metarhizium brunneum were identified via GC-MS and screened for antimicrobial activity. The VOC profiles varied with fungal strain, development state (mycelium, spores) and culture conditions. Selected VOCs were screened against a range of rhizosphere and non-rhizosphere microbes,
including three Gram-negative bacteria (Escherichia coli, Pantoea agglomerans, Pseudomonas aeruginosa), five Gram-positive bacteria (Micrococcus luteus, Staphylococcus aureus, Bacillus subtilis, B. megaterium, B. thuringiensis), two yeasts (Candida albicans, Candida glabrata) and three plant pathogenic fungi (Pythium ultimum, Botrytis cinerea, Fusarium graminearum). Microbes differed in their sensitivity to the test compounds, with 1-octen-3-ol and isovaleric acid showing broad-spectrum antimi�crobial activity. Yeasts and bacteria were inhibited by the same VOCs. Cryo-SEM showed that both yeasts and bacteria underwent some form of “autolysis”, where all components of the cell, including the cell wall, disintegrated with little evidence of their presence in the clear, inhibition zone. The oomycete (P. ultimum) and ascomycete fungi (F. graminearum, B. cinerea) were sensitive to a wider range of VOCs than the bacteria, suggesting that eukaryotic microbes are the main competitors to M. brunneum in the rhizosphere. The ability to alter the VOC profile in response to nutritional cues may assist M. brunneum
to survive among the roots of a wide range of plant species. Our VOC studies provided new insights as to how M. brunneum may protect plants from pathogenic microbes and correspondingly promote healthy growth.
... Entomopathogenic fungi were intended to develop in almost all groups of insects as inundative biocontrol agents of insects, mites, and ticks Goettel et al. 2005). These fungi's difference in pathogenicity from bacteria and viruses is that they infect insects by breaching the host cuticle and by secreting extracellular enzymes like chitinases, lipases, and proteases to degrade the major constituents of the cuticle (i.e., lipids, chitin, and protein) and permit hyphal penetration (Wang et al. 2005;Cho et al. 2006). Many toxic substances such as small secondary metabolites, cyclic peptides, and macromolecular proteins are recorded from entomopathogenic fungi. ...
The impact of increasing human population, rising food demand, and adverse effects of climate change, viz., changing rainfall pattern, rising temperature, biotic-abiotic stresses, etc., has tremendously affected global food security. In addition, increased anthropogenic inputs from urbanization, industrialization, as well as outrageous use of chemical fertilizers and pesticides have posed a severe threat to the sustainability of the agroecosystems. For many decades, the use of chemical pesticides against insect and microbial pests has become an integrative part of agriculture and contributed significantly to the crop improvement. But, their long-term persistence, cytotoxicity, and microbial resistance have resulted negative impact on the biosphere, thus creating pollution of diverse ecosystems, land degradation, and biodiversity losses. For the last two decades, alternate pest management strategies have become the new avenues for controlling pest and diseases in a greener, safer, and eco-friendly manner. The use of biological control agents (termed as biocides) such as both microbe- and plant-based formulations has been known to be the major emerging tool in crop disease/pest management and appealing alternative to the chemical pesticide in sustainable agriculture. Biopesticides employ the use of naturally occurring substances, i.e., living organisms (natural enemies) or their products (phytochemicals, microbial products) or by-products (semiochemicals) that control pests by nontoxic mechanisms, with high targeted activity against causal agents (insects, fungi, weeds, viruses, nematodes, etc.), and nonpersistence in the environment. The use of biopesticide alone or in combination with agrochemicals has become the new tool in crop protection as a part of biointensive integrated pest management (IPM) strategies. Although biopesticides are slowly substituting the chemical pesticides with great promise, its use to the desired extent is lacking; hence insight on such biological agents is a prerequisite. In this chapter, we have summarized the sources of biopesticides, their plant protective mechanisms (mode of action), availability, and status in India, as well as some critical pros and cons of its use.
... There is however little information about this phenomenon and how EPF stability changes when cultured on artificial media, but Brownbridge et al. (2001) believed the attenuation of virulence may be due to random mutation or caused by subculture conditions. Wang et al. (2005b) and Wang and St Leger (2005) studies on M. anisopliae returned this to the pathogenicity-related genes, which are upregulated differently when the fungus grows on different artificial media or media containing insect hemolymph. ...
Background
Metarhizium species are considered one of the most outstanding powerful biological control agents that have been commercialized as biopesticides against various agricultural pests. Fungal stability with successive in vitro cultivation is a desirable trait for a large-scale production of fungal biopesticide.
Main body
The new Egyptian strain Metarhizium anisopliae AUMC 3262 exhibited auspicious results when compared to Metarhizium brunneum ARSEF 4556 and M. brunneum V275 based on the variations of fungal characteristics, and essential quality control parameters (radial growth rate, conidial yield, viability, and virulence) after repeated in vitro subculturing. Changes in morphological characteristics were noted at both AUMC 3262 and ARSEF 4556. Following the 5th subculture, decreased conidial yield was noted, though radial growth remained stable, confirming that there is a non-positive correlation between conidial yield and radial growth rate for these species. In contrast, V275 showed a high morphological stability, conidial yield, and radial growth rate after repeated subculture. The three tested strains manifested high viability up to 100% and displayed the same pattern of Pr1 production. A slight variation was recorded in the median lethal time (LT 50 ) values against the great wax moth, Galleria mellonella (L.), larvae between different subcultures of the tested Metarhizium strains.
Conclusion
The new Egyptian strain AUMC 3262 showed a high stability with a slight difference in some parameters after the successive subculture compared to both ARSEF4556 and V275.
... CDEs play pivotal roles in the infection mechanism and are considered as essential virulence governing factors of B. bassiana. CDEs enable B. bassiana to coexist with the changing metabolic processes associated with the host's disease (Wang et al. 2005;Cho et al. 2006). In addition to CDEs, B. bassiana has evolved several stressrelated enzymes such as superoxide dismutases (SODs), catalases, and thioredoxins (TRXs). ...
Intensive crop production and extensive use of harmful synthetic chemical pesticides create numerous socioeconomic problems worldwide. Therefore, sustainable solutions are needed for insect pest control, such as biological control agents. The fungal insect pathogen Beauveria bassiana has shown considerable potential as a biological control agent against a broad range of insects. The insight into the virulence mechanism of B. bassiana is essential to show the robustness of its use. B. bassiana has several determinants of virulence, including the production of cuticle-degrading enzymes (CDEs), such as proteases, chitinases, and lipases. CDEs are essential in the infection process as they hydrolyze the significant components of the insect's cuticle. Moreover, B. bassiana has evolved effective antioxidant mechanisms that include enzyme families that act as reactive oxygen species (ROS) scavengers, e.g., superoxide dismutases, catalases, peroxidases, and thioredoxins. In B. bassiana, the number of CDEs and antioxidant enzymes are characterized in recent years. These enzymes are believed to be crucial player of evolutionary process in this organism and their role in various mechanism of biological control. Recent discoveries have significantly increased our potential understanding on several potentially wanted unknown mechanisms of B. bassiana infection. This review focuses on the progress detailed in the studies of these enzymes and provides an overview of enzymatic activities and their contributions to virulence.
... The large secretomes of insect pathogens probably reflect the many microhabitats they must adapt to in insecta, including the cuticle and the haemolymph, as well as additional environmental habitats in the soil and with plants. These complex lifestyles are reflected in transcriptional reprogramming involving hundreds of differentially expressed genes as Metarhizium strains rapidly adapt to host cuticles, haemolymph or root exudate [61,62]. The ability to recognize appropriate hosts, and penetrate their cuticle, are among the necessary steps for the transition from either saprophyte or root colonizer to pathogen. ...
The genus Metarhizium and Pochonia chlamydosporia comprise a monophyletic clade of highly abundant globally distributed fungi that can transition between long-term beneficial associations with plants to transitory pathogenic associations with frequently encountered protozoans, nematodes or insects. Some very common ‘specialist generalist’ species are adapted to particular soil and plant ecologies, but can overpower a wide spectrum of insects with numerous enzymes and toxins that result from extensive gene duplications made possible by loss of meiosis and associated genome defence mechanisms. These species use parasexuality instead of sex to combine beneficial mutations from separate clonal individuals into one genome (Vicar of Bray dynamics). More weakly endophytic species which kill a narrow range of insects retain sexuality to facilitate host–pathogen coevolution (Red Queen dynamics). Metarhizium species can fit into numerous environments because they are very flexible at the genetic, physiological and ecological levels, providing tractable models to address how new mechanisms for econutritional heterogeneity, host switching and virulence are acquired and relate to diverse sexual life histories and speciation. Many new molecules and functions have been discovered that underpin Metarhizium associations, and have furthered our understanding of the crucial ecology of these fungi in multiple habitats.
... Rather, this genus exhibits extraordinary transcriptional plasticity, modulating the transcriptome to allow for physiological adaptation to environments with diverse and dynamic exploitable nutrient sources, including decaying organic matter, plants, and soil insects. Expressed sequence tag and cDNA microarray experiments have demonstrated this phenomenon of adaptive transcriptional control, with Metarhizium exhibiting largescale changes in gene expression patterns when grown in insect cuticle, hemolymph, and plant root exudate (a model for growth in the rhizosphere) (Wang et al. 2005). ...
The genus Metarhizium is comprised of a diverse group of common soil fungi that exhibit multifunctional lifestyles with varying degrees of saprotrophic, endophytic, and insect pathogenic modes of nutrient acquisition. The transcriptome of these species is modulated to reflect immediate needs of the fungus and availability of resources—a form of transcriptional plasticity that allows for physiological adaptation to environments with diverse and dynamic exploitable nutrient sources. In this review, we discuss the endophytic, insect pathogenic lifestyles of Metarhizium spp., including their symbiotic interface, origins, and evolution, and agricultural applications. Isotope labeling experiments have demonstrated that a mutually beneficial exchange of limiting nutrients occurs between the fungus and its host plant, with nitrogen derived via insect pathogenesis being translocated from Metarhizium to host plants in exchange for fixed carbon in the form of photosynthate. Thus, the endophytic and entomopathogenic abilities of Metarhizium spp. are not exclusive of one another, but rather are interdependent and reciprocal in nature. Although endophytic, insect pathogenic fungi (EIPF) could certainly have evolved from insect pathogenic fungi, phylogenomic evidence indicates that this genus is more closely related to plant-associated fungi than animal pathogens, suggesting that Metarhizium evolved from a lineage of plant symbionts, which subsequently acquired genes for insect pathogenesis. Entomopathogenicity may have been an adaptive trait, allowing for procurement of insect-derived nitrogen that could be translocated to host plants and bartered for fixed carbon, thereby improving the stability of fungal-plant symbioses. Given their ability to simultaneously parasitize soil insects, including a number of pests of agriculturally important crops, as well as promote plant health, growth, and productivity, Metarhizium spp. are considered promising alternatives to the chemical pesticides and fertilizers that have wreaked havoc on the health and integrity of ecosystems.
Key points
• Metarhizium is a fungus that is an insect pathogen as well as a plant symbiont.
• The genus Metarhizium has specialist and generalist insect pathogens.
• Metarhizium is phylogenetically most closely related to plant endophytes.
... CDEs play pivotal roles in the infection mechanism and are considered as essential virulence governing factors of B. bassiana. CDEs enable B. bassiana to coexist with the changing metabolic processes associated with the host's disease (Wang et al. 2005;Cho et al. 2006). In addition to CDEs, B. bassiana has evolved several stressrelated enzymes such as superoxide dismutases (SODs), catalases, and thioredoxins (TRXs). ...
Intensive crop production and extensive use of harmful synthetic chemical pesticides create numerous socio-economic problems worldwide. Therefore, sustainable solutions are needed for insect pest control, such as biological control agents. The fungal insect pathogen Beauveria bassiana has shown considerable potential as a biological control agent against a broad range of insects. The insight into the virulence mechanism of B. bassiana is essential to show the robustness of its use. B. bassiana has several determinants of virulence, including the production of cuticle-degrading enzymes (CDEs), such as proteases, chitinases, and lipases. CDEs are essential in the infection process as they hydrolyze the significant components of the insect's cuticle. Moreover, B. bassiana has evolved effective antioxidant mechanisms that include enzyme families that act as reactive oxygen species (ROS) scavengers, e.g., superoxide dismutases, catalases, peroxidases, and thioredoxins. In B. bassiana, the number of CDEs and antioxidant enzymes are characterized in recent years. These enzymes are believed to be crucial player of evolutionary process in this organism and their role in various mechanism of biological control. Recent discoveries have significantly increased our potential understanding on several potentially wanted unknown mechanisms of B. bassiana infection. This review focuses on the progress detailed in the studies of these enzymes and provides an overview of enzymatic activities and their contributions.
... The integument is made up of polysaccharide glucosamine polyose fibrils inset with pigments, proteins, lipids, and N-acyl catecholamines (Richard et al. 2010). Extracellular fluid containing enzymes, lipases, proteases, and chitinases is released and degrades the main components of the cuticle (i.e., lipids, proteins, and chitin), allowing penetration of the fungus (Wang et al. 2005;Cho et al. 2006a). Lipase enzymes have complicated pathogen acrimony and play various roles in the process of microbial infection (Stehr et al. 2003). ...
... However, the main problem limiting the marketability of mycobiopesticides is that they take more time to kill their target hosts than chemical pesticides do ( view enhance as well as ameliorate acerbity of such mold to a bigger expanse than its personal action that accelerates application of formulated products present in market. Excellent quantity of transcribe and gene modification work of entomopathogenic molds contamination procedure let out availability few different genes participate in the pathogenic action in the same way as chitinase enzymes (Cho et al. 2006b(Cho et al. , 2007Wang et al. 2005;Fang et al. 2005;Bagga et al. 2004). Guanine nucleotide-binding protein and its regulator (Fang et al. , 2008, adhesin, aid the attachment of spores. ...
