Journal of Fungi

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3 pages, 208 KiB

Open AccessEditorial

Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions

by Ivan M. Dubovskiy and Tariq Butt

J. Fungi 2023, 9(8), 825; https://doi.org/10.3390/jof9080825 - 04 Aug 2023

Viewed by 982

Abstract

Plant protection faces a growing number of challenges, partly stemming from intensification of plant cultivation to ensure food security for a rapidly growing global population [...] Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

Research

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17 pages, 3403 KiB

Open AccessArticle

Entomopathogenic Fungi-Mediated Solubilization and Induction of Fe Related Genes in Melon and Cucumber Plants

by Fabián García-Espinoza, Enrique Quesada-Moraga, María José García del Rosal and Meelad Yousef-Yousef

J. Fungi 2023, 9(2), 258; https://doi.org/10.3390/jof9020258 - 15 Feb 2023

Cited by 8 | Viewed by 2277

Abstract

Endophytic insect pathogenic fungi have a multifunctional lifestyle; in addition to its well-known function as biocontrol agents, it may also help plants respond to other biotic and abiotic stresses, such as iron (Fe) deficiency. This study explores M. brunneum EAMa 01/58-Su strain attributes [...] Read more.

Endophytic insect pathogenic fungi have a multifunctional lifestyle; in addition to its well-known function as biocontrol agents, it may also help plants respond to other biotic and abiotic stresses, such as iron (Fe) deficiency. This study explores M. brunneum EAMa 01/58-Su strain attributes for Fe acquisition. Firstly, direct attributes include siderophore exudation (in vitro assay) and Fe content in shoots and in the substrate (in vivo assay) were evaluated for three strains of Beauveria bassiana and Metarhizium bruneum. The M. brunneum EAMa 01/58-Su strain showed a great ability to exudate iron siderophores (58.4% surface siderophores exudation) and provided higher Fe content in both dry matter and substrate compared to the control and was therefore selected for further research to unravel the possible induction of Fe deficiency responses, Ferric Reductase Activity (FRA), and relative expression of Fe acquisition genes by qRT-PCR in melon and cucumber plants.. In addition, root priming by M. brunneum EAMa 01/58-Su strain elicited Fe deficiency responses at transcriptional level. Our results show an early up-regulation (24, 48 or 72 h post inoculation) of the Fe acquisition genes FRO1, FRO2, IRT1, HA1, and FIT as well as the FRA. These results highlight the mechanisms involved in the Fe acquisition as mediated by IPF M. brunneum EAMa 01/58-Su strain. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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13 pages, 2081 KiB

Open AccessArticle

Lethal Concentration and Sporulation by Contact and Direct Spray of the Entomopathogenic Fungus Beauveria bassiana on Different Stages of Nezara viridula (Heteroptera: Pentatomidae)

by Maribel Portilla, Minling Zhang, James Paul Glover, Gadi V. P. Reddy and Chris Johnson

J. Fungi 2022, 8(11), 1164; https://doi.org/10.3390/jof8111164 - 04 Nov 2022

Cited by 3 | Viewed by 1426

Abstract

The southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae) is the most significant pest of soybean worldwide. The present study was conducted to compare the effectiveness of a Delta native strain NI8 of Beauveria bassiana by contact and direct spray on nymphs [...] Read more.

The southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae) is the most significant pest of soybean worldwide. The present study was conducted to compare the effectiveness of a Delta native strain NI8 of Beauveria bassiana by contact and direct spray on nymphs (2nd to 5th instar) and adults of N. viridula. Water control and four concentrations of B. bassiana were used to evaluate the survival, mortality, and molting percentage and to estimate median lethal concentration (LC₅₀), median lethal sporulation (LS₅₀), and resistance ratio (RR₅₀). Direct spray at all concentrations observed the greatest reduction in survival on all life stages. Mortality and sporulation were positively correlated by concentration, while molting was highly variable with a significantly lower negative correlation on insects that were directly sprayed. Pathogenicity exhibited reduction as young stages developed and emerged to adult. The LC₅₀ (Contact: 612 spores/mm²; Direct spray: 179 spores/mm²) and LS₅₀ (Contact: 1960 spores/mm² Spray: 3.3 × 10⁶) values showed that adults of N. viridula were highly resistant than any other life stage when exposed to either contact or direct spray. Fourth instar was the most susceptible (LC₅₀: Contact: 18 spores/mm²; Direct spray: 23 spores/mm²) (LS₅₀: Contact: 53 spores/mm²; Direct spray: 26 spores/mm²) followed by second, third, and fifth instars. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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16 pages, 2671 KiB

Open AccessArticle

Resporulation of Calcium Alginate Encapsulated Metarhizium anisopliae on Metham^®-Fumigated Soil and Infectivity on Larvae of Tenebrio molitor

by Sudhan Shah, Gavin J. Ash and Bree A. L. Wilson

J. Fungi 2022, 8(10), 1114; https://doi.org/10.3390/jof8101114 - 21 Oct 2022

Cited by 3 | Viewed by 2091

Abstract

Metarhizium anisopliae infects and kills a large range of insects and is a promising biocontrol agent to manage soil insects, such as wireworm in sweetpotato. The presence of other soil microbes, which exhibit competitive fungistasis, may inhibit the establishment of M. anisopliae in [...] Read more.

Metarhizium anisopliae infects and kills a large range of insects and is a promising biocontrol agent to manage soil insects, such as wireworm in sweetpotato. The presence of other soil microbes, which exhibit competitive fungistasis, may inhibit the establishment of M. anisopliae in soil. Microbially depleted soil, for example, sterilized soil, has been shown to improve the resporulation of the fungus from nutrient-fortified M. anisopliae. Prior to planting, sweetpotato plant beds can be disinfected with fumigants, such as Metham^®, to control soil-borne pests and weeds. Metham^® is a broad-spectrum soil microbial suppressant; however, its effect on Metarhizium spp. is unclear. In the research presented here, fungal resporulation was examined in Metham^®-fumigated soil and the infectivity of the resulting granule sporulation was evaluated on mealworm, as a proxy for wireworm. The fungal granules grown on different soil treatments (fumigated, field and pasteurized soil) resporulated profusely (for example, 4.14 × 10⁷ (±2.17 × 10⁶) conidia per granule on fumigated soil), but the resporulation was not significantly different among the three soil treatments. However, the conidial germination of the resporulated granules on fumigated soil was >80%, which was significantly higher than those on pasteurized soil or field soil. The resporulated fungal granules were highly infective, causing 100% insect mortality 9 days after the inoculation, regardless of soil treatments. The results from this research show that the fungal granules applied to soils could be an infective inoculant in sweetpotato fields in conjunction with soil fumigation. Additional field studies are required to validate these results and to demonstrate integration with current farming practices. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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16 pages, 5608 KiB

Open AccessArticle

Identification of Exoenzymes Secreted by Entomopathogenic Fungus Beauveria pseudobassiana RGM 2184 and Their Effect on the Degradation of Cocoons and Pupae of Quarantine Pest Lobesia botrana

by Matias Arias-Aravena, Fabiola Altimira, Daniela Gutiérrez, Jian Ling and Eduardo Tapia

J. Fungi 2022, 8(10), 1083; https://doi.org/10.3390/jof8101083 - 14 Oct 2022

Cited by 1 | Viewed by 1977

Abstract

Beauveria pseudobassiana RGM 2184 has shown 80% maximum efficacy against the pest Lobesia botrana in the autumn and winter seasons. This suggests that the strain possesses an interesting battery of enzymes that are cold-adapted to penetrate the thick and hydrophobic cocoon of L. [...] Read more.

Beauveria pseudobassiana RGM 2184 has shown 80% maximum efficacy against the pest Lobesia botrana in the autumn and winter seasons. This suggests that the strain possesses an interesting battery of enzymes that are cold-adapted to penetrate the thick and hydrophobic cocoon of L. botrana. In this study, screening of the proteolytic, lipolytic, and chitinolytic activity of enzyme extracts secreted by the RGM 2184 strain was carried out in various culture media. The enzyme extracts with the highest activity were subjected to zymography and mass spectrometry. These analyses allowed the identification of two proteases, two lipases, and three chitinases. Comparative analysis indicated that the degree of similarity between these enzymes was substantially reduced when the highest degree of taxonomic relatedness between RGM 2184 and the entomopathogenic fungus strain was at the family level. These results suggest that there is a wide variety of exoenzymes in entomopathogenic fungi species belonging to the order Hypocreales. On the other hand, exoenzyme extract exposure of cocoons and pupae of L. botrana provoked damage at 10 °C. Additionally, an analysis of the amino acid composition of the RGM 2184 exoenzyme grouped them close to the cold-adapted protein cluster. These results support the use of this strain to control pests in autumn and winter. Additionally, these antecedents can form a scaffold for the future characterization of these exoenzymes along with the optimization of the strain’s biocontrol ability by overexpressing them. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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17 pages, 4681 KiB

Open AccessArticle

Metarhizium brunneum (Hypocreales: Clavicipitaceae) and Its Derived Volatile Organic Compounds as Biostimulants of Commercially Valuable Angiosperms and Gymnosperms

by Martyn J. Wood, Alexandra M. Kortsinoglou, Salim Khoja, Vassili N. Kouvelis, Arben Myrta, Audun Midthassel, E. Joel Loveridge and Tariq M. Butt

J. Fungi 2022, 8(10), 1052; https://doi.org/10.3390/jof8101052 - 08 Oct 2022

Cited by 6 | Viewed by 1941

Abstract

Metarhizium brunneum is a highly effective entomopathogenic fungus that also functions as a plant biostimulant. It can act as both an endophyte and rhizosphere colonizer; however, the mechanisms driving biostimulation are multifactorial. In this work, oilseed rape (Brassica napus) seeds were [...] Read more.

Metarhizium brunneum is a highly effective entomopathogenic fungus that also functions as a plant biostimulant. It can act as both an endophyte and rhizosphere colonizer; however, the mechanisms driving biostimulation are multifactorial. In this work, oilseed rape (Brassica napus) seeds were grown in composts treated with different concentrations of M. brunneum strains ARSEF 4556 or V275, or the M. brunneum-derived volatile organic compounds 1-octen-3-ol and 3-octanone. Biostimulation efficacy was found to be strongly dose dependent. Concentrations of 1 × 10⁶ conidia g⁻¹ compost were found to be most effective for the M. brunneum, whereas dosages of 1 µL 100 g⁻¹ compost were found to be efficacious for the volatiles. These optimized doses were assessed individually and in combined formulations with a hydrogel against oilseed rape (Brassica napus), sitka spruce (Picea sitchensis), maize (Zea mays) and strawberry (Fragaria annanassa). Both volatile compounds were highly effective biostimulants and were found to increase in biostimulatory efficiency when combined with M. brunneum conidia. Hydrogels were not found to interact with the growth process and may offer avenues for novel formulation technologies. This study demonstrates that Metarhizium-derived volatile organic compounds are actively involved in plant growth promotion and have potential for use in novel formulations to increase the growth of a wide range of commercially relevant crops. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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18 pages, 2517 KiB

Open AccessEditor’s ChoiceArticle

Root Colonization by Fungal Entomopathogen Systemically Primes Belowground Plant Defense against Cabbage Root Fly

by Catalina Posada-Vergara, Katharina Lohaus, Mohammad Alhussein, Stefan Vidal and Michael Rostás

J. Fungi 2022, 8(9), 969; https://doi.org/10.3390/jof8090969 - 16 Sep 2022

Cited by 4 | Viewed by 2354

Abstract

Entomopathogenic fungi infect insects via spores but also live inside plant tissues as endophytes. Frequently, colonization by entomopathogens provides plants with increased resistance against insects, but the mechanisms are little understood. This study investigated direct, local, and systemic root-mediated interactions between isolates of [...] Read more.

Entomopathogenic fungi infect insects via spores but also live inside plant tissues as endophytes. Frequently, colonization by entomopathogens provides plants with increased resistance against insects, but the mechanisms are little understood. This study investigated direct, local, and systemic root-mediated interactions between isolates of the fungus Metarhizium brunneum and larvae of the cabbage root fly (CRF) Delia radicum attacking Brassica napus plants. All fungal isolates infected CRF when conidia were present in the soil, leading to 43–93% mortality. Locally, root-associated M. brunneum isolates reduced herbivore damage by 10–20% and in three out of five isolates caused significant insect mortality due to plant-mediated and/or direct effects. A split-root experiment with isolate Gd12 also demonstrated systemic plant resistance with significantly reduced root collar damage by CRF. LC-MS analyses showed that fungal root colonization did not induce changes in phytohormones, while herbivory increased jasmonic acid (JA) and glucosinolate concentrations. Proteinase inhibitor gene expression was also increased. Fungal colonization, however, primed herbivore-induced JA and the expression of the JA-responsive plant defensin 1.2 (PDF1.2) gene. We conclude that root-associated M. brunneum benefits plant health through multiple mechanisms, such as the direct infection of insects, as well as the local and systemic priming of the JA pathway. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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13 pages, 2164 KiB

Open AccessArticle

Toxicological and Biochemical Description of Synergism of Beauveria bassiana and Emamectin Benzoate against Megalurothrips usitatus (Bagrall)

by Youdan Zhang, Xiaochen Zhang, Qingheng Tian, Shaukat Ali, Liangde Tang and Jianhui Wu

J. Fungi 2022, 8(9), 916; https://doi.org/10.3390/jof8090916 - 29 Aug 2022

Cited by 6 | Viewed by 1525

Abstract

The prophylactic application of synthetic insecticides to manage Megalurothrips usitatus (Bagrall) has resulted in insecticide resistance and negative impacts upon natural ecosystems. This has driven the need for developing alternative pest control strategies. In the present study, we investigated the synergistic interaction between [...] Read more.

The prophylactic application of synthetic insecticides to manage Megalurothrips usitatus (Bagrall) has resulted in insecticide resistance and negative impacts upon natural ecosystems. This has driven the need for developing alternative pest control strategies. In the present study, we investigated the synergistic interaction between the entomopathogenic fungus Beauveria bassiana and the insecticide emamectin benzoate on M. usitatus. The results of our research exhibited that higher doses of emamectin benzoate inhibited the germination rate and colony growth of B. bassiana. The percentage of M. usitatus mortality following B. bassiana and emamectin benzoate treatment indicated a dose–mortality effect. All concentrations of emamectin benzoate combined with different concentrations of B. bassiana demonstrated a synergistic effect five days post-treatment. When B. bassiana and emamectin benzoate were applied alone or in combination, antioxidant enzyme activities, including acetylcholinesterase, catalase, superoxide dismutase, and peroxidase, were significantly lower in M. usiatus than in the controls at the end of the experimental period. The findings of our study confirm the synergistic effect of B. bassiana and emamectin benzoate on M. usitatus, as well as the biochemical process that might be involved in the regulation of the synergistic effect. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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16 pages, 3720 KiB

Open AccessArticle

Genome-Wide Identification and Characterization of Toll-like Receptors (TLRs) in Diaphorina citri and Their Expression Patterns Induced by the Endophyte Beauveria bassiana

by Luis Carlos Ramos Aguila, Hafiza Javaira Ashraf, Jessica Paola Sánchez Moreano, Komivi Senyo Akutse, Bamisope Steve Bamisile, Liuyang Lu, Xiaofang Li, Jingyi Lin, Qing Wu and Liande Wang

J. Fungi 2022, 8(8), 888; https://doi.org/10.3390/jof8080888 - 22 Aug 2022

Cited by 3 | Viewed by 1744

Abstract

Toll-like receptors (TLRs) are pathogen recognition receptors (PRRs), which play key roles in helping the host immune system fight pathogen invasions. Systematic information on TLRs at the genome-wide level and expression profiling in response to endophytic colonization is very important to understand their [...] Read more.

Toll-like receptors (TLRs) are pathogen recognition receptors (PRRs), which play key roles in helping the host immune system fight pathogen invasions. Systematic information on TLRs at the genome-wide level and expression profiling in response to endophytic colonization is very important to understand their functions but is currently lacking in this field. Here, a total of two TLR genes were identified and characterized in Diaphorina citri. The TLR genes of D. citri were clustered into five families according to the phylogenetic analysis of different species’ TLRs. The domain organization analyses suggested that the TLRs were constituted of three important parts: a leucine-rich repeat (LRR) domain, a transmembrane region (TR) and a Toll/interleukin-1 receptor (TIR) domain. The mRNA expression levels of the two TLR genes (DcTOLL and DcTLR7) were highly regulated in both nymphs and adults of D. citri. These results elucidated the potentiated TLR gene expression in response to endophytically colonized plants. Furthermore, the 3D structures of the TIR domain were highly conserved during evolution. Collectively, these findings elucidate the crucial roles of TLRs in the immune response of D. citri to entomopathogens systematically established as endophytes, and provide fundamental knowledge for further understanding of the innate immunity of D. citri. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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13 pages, 309 KiB

Open AccessArticle

Interactive Effects of Water Deficiency and Endophytic Beauveria bassiana on Plant Growth, Nutrient Uptake, Secondary Metabolite Contents, and Antioxidant Activity of Allium cepa L.

by Lizeka Pretty Gana, Ninon G. E. R. Etsassala and Felix Nchu

J. Fungi 2022, 8(8), 874; https://doi.org/10.3390/jof8080874 - 19 Aug 2022

Cited by 5 | Viewed by 1586

Abstract

The main aim of this research study was to assess the interactive effects of water deficiency and the inoculation of a growth medium with Beauveria bassiana on plant growth, nutrient uptake, secondary metabolite contents, and antioxidant capacity of Allium cepa. A. cepa [...] Read more.

The main aim of this research study was to assess the interactive effects of water deficiency and the inoculation of a growth medium with Beauveria bassiana on plant growth, nutrient uptake, secondary metabolite contents, and antioxidant capacity of Allium cepa. A. cepa seedlings were simultaneously exposed to one of three watering regime treatments (3-day, 5-day, and 7-day watering intervals) and B. bassiana or no-fungus treatment. While the longest watering interval induced reduced plant growth, plants inoculated with B. bassiana had better results than those in the no-fungus treatment. Significant interactive effects (DF = 2.0; p < 0.05) between fungus and the watering regime on P, K, and Fe contents were observed. Remarkably, at the 7-day watering interval, the polyphenol content (64.0 mg GAE/L) was significantly higher in the plants treated with B. bassiana than in the no-fungus-treated plants. The watering interval significantly affected (DF = 2, 6; F = 7.4; p < 0.05) total flavonol contents among the fungus-treated plants. The interaction of the watering interval and B. bassiana inoculation (DF = 2.0; F = 3.8; p < 0.05) significantly influenced the flavonol content in the onion bulbs and the antioxidant activities of onion bulbs in the FRAP assay (DF = 2.0; F = 4.1; p < 0.05). Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

19 pages, 3076 KiB

Open AccessArticle

The Elongator Subunit Elp3 Regulates Development, Stress Tolerance, Cell Cycle, and Virulence in the Entomopathogenic Fungus Beauveria bassiana

by Qing Cai, Juanjuan Wang, Jiatao Xie, Daohong Jiang and Nemat O. Keyhani

J. Fungi 2022, 8(8), 834; https://doi.org/10.3390/jof8080834 - 10 Aug 2022

Cited by 2 | Viewed by 2089

Abstract

Transcriptional activity is mediated by chromatin remodeling, which in turn is affected by post-translational modifications, including histone acetylation. Histone acetyltransferases (HATs) are capable of promoting euchromatin formation and then activating gene transcription. Here, we characterize the Elp3 GNAT family HAT, which is also [...] Read more.

Transcriptional activity is mediated by chromatin remodeling, which in turn is affected by post-translational modifications, including histone acetylation. Histone acetyltransferases (HATs) are capable of promoting euchromatin formation and then activating gene transcription. Here, we characterize the Elp3 GNAT family HAT, which is also a subunit of Elongator complex, in the environmentally and economically important fungal insect pathogen, Beauveria bassiana. BbElp3 showed high localization levels to mitochondria, with some nuclear and cytoplasmic localization also apparent. Targeted gene knockout of BbElp3 resulted in impaired asexual development and morphogenesis, reduced tolerances to multiple stress conditions, reduced the ability of the fungus to utilize various carbon/nitrogen sources, increased susceptibility to rapamycin, and attenuated virulence in bioassays using the greater wax moth, Galleria mellonella. The ΔBbElp3 mutant also showed disrupted cell cycle, abnormal hyphal septation patterns, and enlarged autophagosomes in vegetative hyphae. Transcriptome analyses revealed differential expression of 775 genes (DEGs), including 336 downregulated and 438 upregulated genes in the ΔBbElp3 strain as compared to the wild type. Downregulated genes were mainly enriched in pathways involved in DNA processing and transcription, cell cycle control, cellular transportation, cell defense, and virulence, including hydrophobins, cellular transporters (ABC and MFS multidrug transporters), and insect cuticular degrading enzymes, while upregulated genes were mainly enriched in carbohydrate metabolism and amino acid metabolism. These data indicate pleiotropic effects of BbElp3 in impacting specific cellular processes related to asexual development, cell cycle, autophagy, and virulence. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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15 pages, 4935 KiB

Open AccessArticle

Bioinformatics Analysis and Functional Characterization of the CFEM Proteins of Metarhizium anisopliae

by Ni Cai, Rong Liu, Duozi Yan, Neng Zhang, Kaihui Zhu, Daogang Zhang, Xiangqun Nong, Xiongbing Tu, Zehua Zhang and Guangjun Wang

J. Fungi 2022, 8(7), 661; https://doi.org/10.3390/jof8070661 - 24 Jun 2022

Cited by 4 | Viewed by 2195

Abstract

The entomopathogen Metarhizium anisopliae is a facultative rhizosphere or endophytic fungus available for managing pests and improving plant growth. The CFEM (common in fungal extracellular membrane) proteins form a unique group in fungi but are rarely reported in entomopathogens. In this study, we [...] Read more.

The entomopathogen Metarhizium anisopliae is a facultative rhizosphere or endophytic fungus available for managing pests and improving plant growth. The CFEM (common in fungal extracellular membrane) proteins form a unique group in fungi but are rarely reported in entomopathogens. In this study, we cloned and identified 13 CFEM genes from M. anisopliae (MaCFEMs). Sequence alignment and WebLogo analysis showed that eight cysteines were the most conserved amino acids in their CFEM domain. Phylogenic analysis suggested that these 13 proteins could be divided into 4 clades based on the presence of the transmembrane region and the position of CFEM domain in the whole sequence. Six MaCFEM proteins with a signal peptide and without a transmembrane domain were considered candidate effector proteins. According to Phyre2 analysis, the MaCFEM88 and MaCFEM85 have the most homologous to Csa2 in Candida albicans. Subcellular localization analysis revealed that five effectors were located in the plasma membrane, while MaCFEM88 may locate in both plasma membrane and nucleus in the treated Nicotiana benthamiana. Expression pattern analysis showed that MaCFEM81, 85, 88, and 89 expression level was significantly higher in the sporulation stage compared to other growth stages. Furthermore, the yeast secretion assay showed that six candidate effectors were able to secrete out of the cell. All of the MaCFEMs couldn’t affect INF1-induced programmed cell death (PCD), but MaCFEM85 and 88 could trigger a slight hypersensitive response both when applied separately or in combination with INF1 in N. benthamiana leaves. These findings showed that six MaCFEM potential effectors with various structures and subcellular localizations in host cells might be used to illustrate the roles of MaCFEM proteins during M. anisopliae-plant interactions. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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14 pages, 1821 KiB

Open AccessArticle

Production of Microsclerotia by Metarhizium sp., and Factors Affecting Their Survival, Germination, and Conidial Yield

by Meelad Yousef-Yousef, Antonia Romero-Conde, Enrique Quesada-Moraga and Inmaculada Garrido-Jurado

J. Fungi 2022, 8(4), 402; https://doi.org/10.3390/jof8040402 - 14 Apr 2022

Cited by 5 | Viewed by 2687

Abstract

Microsclerotia (MS) produced by some species of Metarhizium can be used as active ingredients in mycoinsecticides for the control of soil-dwelling stages of geophilic pests. In this study, the MS production potential of two Metarhizium brunneum strains and one M. robertsii strain was [...] Read more.

Microsclerotia (MS) produced by some species of Metarhizium can be used as active ingredients in mycoinsecticides for the control of soil-dwelling stages of geophilic pests. In this study, the MS production potential of two Metarhizium brunneum strains and one M. robertsii strain was evaluated. The three strains were able to produce MS in liquid fermentation, yielding between 4.0 × 10⁶ (M. robertsii EAMa 01/158-Su strain) and 1.0 × 10⁷ (M. brunneum EAMa 01/58-Su strain) infective propagules (CFU) per gram of MS. The EAMa 01/58-Su strain was selected for further investigation into the effects of key abiotic factors on their survival and conidial yield. The MS were demonstrated to be stable at different storage temperatures (−80, −18, and 4 °C), with a shelf-life up to one year. The best temperature for MS storage was −80 °C, ensuring good viability of MS for up to one year (4.9 × 10¹⁰ CFU/g MS). Moreover, soil texture significantly affected CFU production by MS; sandy soils were the best driver of infective propagule production. Finally, the best combination of soil temperature and humidity for MS germination was 22.7 °C and 7.3% (wt./wt.), with no significant effect of UV-B exposure time on MS viability. These results provide key insights into the handling and storage of MS, and for decision making on MS dosage and timing of application. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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15 pages, 6163 KiB

Open AccessArticle

Antimicrobial Volatiles of the Insect Pathogen Metarhizium brunneum

by Esam Hamid Hummadi, Yarkin Cetin, Merve Demirbek, Nadeems M. Kardar, Shazia Khan, Christopher J. Coates, Daniel C. Eastwood, Ed Dudley, Thierry Maffeis, Joel Loveridge and Tariq M. Butt

J. Fungi 2022, 8(4), 326; https://doi.org/10.3390/jof8040326 - 22 Mar 2022

Cited by 13 | Viewed by 3538

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 entomopathogenic fungus Metarhizium brunneum were identified via GC-MS and screened for antimicrobial activity. The VOC profiles varied with [...] Read more.

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 entomopathogenic 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 antimicrobial 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. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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14 pages, 3133 KiB

Open AccessArticle

Slt2-MAPK/RNS1 Controls Conidiation via Direct Regulation of the Central Regulatory Pathway in the Fungus Metarhizium robertsii

by Yamin Meng, Xingyuan Tang, Yuting Bao, Mingxiang Zhang, Dan Tang, Xing Zhang, Xiaoxuan Chen and Weiguo Fang

J. Fungi 2022, 8(1), 26; https://doi.org/10.3390/jof8010026 - 28 Dec 2021

Cited by 3 | Viewed by 1560

Abstract

Ascomycete fungi usually produce small hydrophobic asexual conidia that are easily dispersed and essential for long-term survival under a variety of environmental conditions. Several upstream signaling regulators have been documented to control conidiation via regulation of the central regulatory pathway that contains the [...] Read more.

Ascomycete fungi usually produce small hydrophobic asexual conidia that are easily dispersed and essential for long-term survival under a variety of environmental conditions. Several upstream signaling regulators have been documented to control conidiation via regulation of the central regulatory pathway that contains the transcription factors BrlA, AbaA and WetA. Here, we showed that the Slt2-MAPK signaling pathway and the transcription factor RNS1 constitute a novel upstream signaling cascade that activates the central regulatory pathway for conidiation in the Ascomycetes fungus M. robertsii. The BrlA gene has two overlapping transcripts BrlAα and BrlAβ; they have the same major ORF, but the 5’ UTR of BrlAβ is 835 bp longer than the one of BrlAα. During conidiation, Slt2 phosphorylates the serine residue at the position 306 in RNS1, which self-induces. RNS1 binds to the BM2 motif in the promoter of the BrlA gene and induces the expression of the transcript BlrAα, which in turn activates the expression of the genes AbaA and WetA. In conclusion, the Slt2/RNS1 cascade represents a novel upstream signaling pathway that initiates conidiation via direct activation of the central regulatory pathway. This work provides significant mechanistic insights into the production of asexual conidia in an Ascomycete fungus. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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16 pages, 3473 KiB

Open AccessArticle

Spatio-Temporal Profiling of Metarhizium anisopliae—Responsive microRNAs Involved in Modulation of Plutella xylostella Immunity and Development

by Junaid Zafar, Yuxin Zhang, Junlin Huang, Shoaib Freed, Rana Fartab Shoukat, Xiaoxia Xu and Fengliang Jin

J. Fungi 2021, 7(11), 942; https://doi.org/10.3390/jof7110942 - 08 Nov 2021

Cited by 10 | Viewed by 2283

Abstract

Metarhizium anisopliae, a ubiquitous pathogenic fungus, regulates a wide array of the insect pest population. The fungus has been employed to control Plutella xylostella, an insecticide-resistant destructive lepidopteran pest, which causes substantial economic losses in crops worldwide. Integration of modern gene-silencing [...] Read more.

Metarhizium anisopliae, a ubiquitous pathogenic fungus, regulates a wide array of the insect pest population. The fungus has been employed to control Plutella xylostella, an insecticide-resistant destructive lepidopteran pest, which causes substantial economic losses in crops worldwide. Integration of modern gene-silencing technologies in pest control strategies has become more crucial to counter pesticide-resistant insects. MicroRNAs (miRNA) play essential roles in the various biological process via post-transcriptional gene regulation. In the present study, RNA-seq analysis of control (CK36h, CK72h) and fungal-infected (T36h, T72h) midguts was performed to reveal underlying molecular mechanisms occurring in larval midgut at different time courses. We aimed at exploring M. anisopliae-responsive miRNAs and their target genes involved in development and immunity. After data filtration, a combined set of 170 miRNAs were identified from all libraries. Interestingly, miR-281, miR-263, miR-1, miR-6094 and miR-8 were listed among the most abundantly expressed conserved miRNAs. Furthermore, we experimentally studied the role of differentially expressed miR-11912-5p in regulating corresponding target trypsin-like serine proteinase (Px_TLSP). The luciferase assay (in vitro) revealed that miRNA-11912-5p significantly downregulated its target gene, suggesting it might play a crucial role in defense mechanism of P. xylostella against M.+ anisopliae infection. We used synthetic miRNA mimic/inhibitor (in vivo), to overexpress/silence miRNA, which showed harmful effects on larval duration, survival and adult fecundity. Additionally, fungal application in the presence of mimics revealed enhanced sensitivity of P. xylostella to infection. Our finding provides an insight into the relatively obscure molecular mechanisms involved in insect midgut during the fungal infection. Full article

(This article belongs to the Special Issue Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions)

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