A proteomic approach to identifying proteins differentially expressed in conidia and mycelium of the entomopathogenic fungus Metarhizium acridum

Changes of Active Substances in Ganoderma lucidum during Different Growth Periods and Analysis of Their Molecular Mechanism

Ganoderma lucidum, renowned as an essential edible and medicinal mushroom in China, remains shrouded in limited understanding concerning the intrinsic mechanisms governing the accumulation of active components and potential protein expression across its diverse developmental stages. Accordingly, this study employed a meticulous integration of metabolomics and proteomics techniques to scrutinize the dynamic alterations in metabolite accumulation and protein expression in G. lucidum throughout its growth phases. The metabolomics analysis unveiled elevated levels of triterpenoids, steroids, and polyphenolic compounds during the budding stage (BS) of mushroom growth, with prominent compounds including Diplazium and Ganoderenic acids E, H, and I, alongside key steroids such as cholesterol and 4,4-dimethyl-5alpha-cholesta-8,14,24-trien-3beta-ol. Additionally, nutrients such as polysaccharides, flavonoids, and purines exhibited heightened presence during the maturation stage (FS) of ascospores. Proteomic scrutiny demonstrated the modulation of triterpenoid synthesis by the CYP450, HMGR, HMGS, and ERG protein families, all exhibiting a decline as G. lucidum progressed, except for the ARE family, which displayed an upward trajectory. Therefore, BS is recommended as the best harvesting period for G. lucidum. This investigation contributes novel insights into the holistic exploitation of G. lucidum.

Photoantimicrobials in agriculture

Classical approaches for controlling plant pathogens may be impaired by the development of pathogen resistance to chemical pesticides and by limited availability of effective antimicrobial agents. Recent increases in consumer awareness of and/or legislation regarding environmental and human health, and the urgent need to improve food security, are driving increased demand for safer antimicrobial strategies. Therefore, there is a need for a step change in the approaches used for controlling pre- and post-harvest diseases and foodborne human pathogens. The use of light-activated antimicrobial substances for the so-called antimicrobial photodynamic treatment is known to be effective not only in a clinical context, but also for use in agriculture to control plant-pathogenic fungi and bacteria, and to eliminate foodborne human pathogens from seeds, sprouted seeds, fruits, and vegetables. Here, we take a holistic approach to review and re-evaluate recent findings on: (i) the ecology of naturally-occurring photoantimicrobials, (ii) photodynamic processes including the light-activated antimicrobial activities of some plant metabolites, and (iii) fungus-induced photosensitization of plants. The inhibitory mechanisms of both natural and synthetic light-activated substances, known as photosensitizers, are discussed in the contexts of microbial stress biology and agricultural biotechnology. Their modes-of-antimicrobial action make them neither stressors nor toxins/toxicants (with specific modes of poisonous activity), but a hybrid/combination of both. We highlight the use of photoantimicrobials for the control of plant-pathogenic fungi and quantify their potential contribution to global food security.

Selection and characterization of thermotolerant Beauveria bassiana isolates and with insecticidal activity against the cotton-melon aphid Aphis gossypii (Glover) (Hemiptera: Aphididae)

BACKGROUND

Cotton-melon aphid Aphis gossypii (Glover) causes severe damage mainly to cucurbits. Twenty-two Beauveria sp. isolates were simultaneously assessed for their pathogenicity and heat tolerance. The selected isolates were identified molecularly and characterized in terms of conidial germination rate, mycelial growth, conidial yield and endophytic activity.

RESULTS

Screening bioassays showed that the B. bassiana isolates B3, B7, B9 and B12 were the most toxic, inducing mortality equal to or slightly higher than the commercialized strain B. bassiana BNat (70.7%). Median lethal concentration (LC₅₀ ) bioassays revealed that only isolate B12 had a significantly lower LC₅₀ value (5.4 × 10⁵ conidia ml^-1 ) than strain BNat (5 × 10⁶ conidia ml^-1 ). The heat tolerance screening test (1 h of exposure to 45°C) allowed us to select isolates B3, B7, B9 and B12 with germination rates of 57.5% to 80.1% after 24 h incubation at 25°C, all significantly higher than strain BNat (22.1%). The germination rates of all isolates decreased significantly after 2 h of exposure to 45°C, with the exception of isolate B12 which displayed the highest thermotolerance (72% germination). The four selected isolates were able to endophytically colonize cucumber leaves when applied to the foliage. Inoculation of cucumber plants with isolate B12 did not affect cucumber plant growth. However, several plant growth parameters were improved 5 weeks after root inoculation.

CONCLUSION

On the basis of its potent toxicity and thermotolerance, isolate B12 is a good candidate for further development as a biopesticide for use in integrated pest management strategies for aphid control. © 2022 Society of Chemical Industry.

Timing and duration of light exposure during conidia development determine tolerance to ultraviolet radiation

Metarhizium is an important genus of soil-inhabiting fungi that are used for the biological control of insects. The efficiency of biocontrol is dependent on the maintenance of inoculum viability under adverse field conditions such as solar ultraviolet (UV) radiation. Therefore, increasing the tolerance of Metarhizium to UV radiation is necessary. It was previously established that, in mycelium, exposure to visible light increases tolerance to UV radiation. Similarly, growth under visible light for 14 days induces the production of tolerant conidia. However, a study evaluating if and how visible light affects conidia and their relationship with UV radiation was never performed. Here, we report that a relatively short and timed exposure to light around the time of conidiation is sufficient to induce the production of conidia with increased photoreactivating capacity and UV tolerance in Metarhizium acridum. Conidia produced by this method retain their characteristic higher tolerance even after many days of being transferred to the dark. Furthermore, we show that mature conidia of M. acridum and Metarhizium brunneum can still answer to light and regulate UV tolerance, suggesting that gene expression is possible even in dormant spores. Being able to respond to light in the dormant stages of development is certainly an advantage conferring improved environmental persistence to Metarhizium.

Inactivation of Aspergillus species in real water matrices using medium pressure mercury lamps

The aim of this work is to understand the inactivation efficiency of medium pressure mercury lamps, measured in terms of growth inhibition as well as cell death, damage and response, using three strains from three different Aspergillus species (A. fumigatus, A. niger and, A. terreus) spiked in filtered surface water. A complete characterization of the effect of the treatment on each strain of the fungal species was assessed considering spores' morphology, cell wall integrity and enzymatic activity, the formation of pyrimidine dimers in the DNA and proteome analysis. Results showed that, when subjected to medium pressure mercury lamps, A. niger is the most resistant to inactivation, that both A. fumigatus and A. niger suffer more morphological changes and present a higher number of damaged spores and A. terreus presented more dead spores. DNA damages detected in A. niger were able to be repaired to some extent, under both light and dark conditions. Finally, proteome analysis showed that the UV radiation treatment triggered different types of stress response, including cell wall reorganization and DNA repair in A. fumigatus and A. terreus, and oxidative stress responses like the increase in production of citric acid and itaconic acid in A. niger and A. terreus, respectively.

Interaction between Metarhizium anisopliae and Its Host, the Subterranean Termite Coptotermes curvignathus during the Infection Process

Metarhizium anisopliae (Metchnikoff) Sorokin, a pathogenic fungus to insects, infects the subterranean termite, Coptotermes curvignathus Holmgren, a devastating pest of plantation trees in the tropics. Electron microscopy and proteomics were used to investigate the infection and developmental process of M. anisopliae in C. curvignathus. Fungal infection was initiated by germ tube penetration through the host's cuticle as observed at 6 h post-inoculation (PI), after which it elongated into the host's integumental tissue. The colonization process continued as seen from dissemination of blastospores in the hemocoel at 96 h PI. At this time point, the emergent mycelia had mummified the host and forty-eight hours later, new conidia were dispersed on the termites' body surface. Meanwhile, hyphal bodies were observed in abundance in the intercellular space in the host's body. The proteomes of the pathogen and host were isolated separately using inoculated termite samples withdrawn at each PI-time point and analyzed in two-dimensional electrophoresis (2-DE) gels. Proteins expressed in termites showed evidence of being related to cell regulation and the immune response, while those expressed in M. anisopliae, to transportation and fungal virulence. This study provides new information on the interaction between termites and its entomopathogen, with potential utilization for developing future biopesticide to control the termite population.

Fungal survival under temperature stress: a proteomic perspective

BACKGROUND

Increases in knowledge of climate change generally, and its impact on agricultural industries specifically, have led to a greater research effort aimed at improving understanding of the role of fungi in various fields. Fungi play a key role in soil ecosystems as the primary agent of decomposition, recycling of organic nutrients. Fungi also include important pathogens of plants, insects, bacteria, domestic animals and humans, thus highlighting their importance in many contexts. Temperature directly affects fungal growth and protein dynamics, which ultimately will cascade through to affect crop performance. To study changes in the global protein complement of fungi, proteomic approaches have been used to examine links between temperature stress and fungal proteomic profiles.

SURVEY METHODOLOGY AND OBJECTIVES

A traditional rather than a systematic review approach was taken to focus on fungal responses to temperature stress elucidated using proteomic approaches. The effects of temperature stress on fungal metabolic pathways and, in particular, heat shock proteins (HSPs) are discussed. The objective of this review is to provide an overview of the effects of temperature stress on fungal proteomes.

CONCLUDING REMARKS

Elucidating fungal proteomic response under temperature stress is useful in the context of increasing understanding of fungal sensitivity and resilience to the challenges posed by contemporary climate change processes. Although useful, a more thorough work is needed such as combining data from multiple -omics platforms in order to develop deeper understanding of the factor influencing and controlling cell physiology. This information can be beneficial to identify potential biomarkers for monitoring environmental changes in soil, including the agricultural ecosystems vital to human society and economy.

iTRAQ-based quantitative proteomic analysis of conidia and mycelium in the filamentous fungus Metarhizium robertsii

Metarhizium robertsii is widely applied in biological control via conidia application. To clarify the proteomic differences between conidia and mycelia and explore the underlying mechanisms of conidia as a unit responsible for dispersal and environmental stress, we carried out an iTRAQ (isobaric tags for relative and absolute quantitation)-based quantitative proteomic analysis for two developmental stages from M. robertsii. A total of 2052 proteins were detected, and 90 showed differential protein abundance between the conidia and mycelia. These 90 proteins were primarily associated with stress resistance, amino acid and protein metabolism, and energy metabolism. Further bioinformatics analysis showed that these proteins could be mapped to 52 pathways, five of which were significantly enriched after mapping to KEGG pathways. Interestingly, many proteins involved in the significantly enriched pathway of peroxisome, biosynthesis of secondary metabolites and glyoxylate and dicarboxylate metabolism, including catalase, peroxisomal membrane anchor protein, formate dehydrogenase and isocitrate lyase, were identified with higher abundance in conidia. The results deepened our understanding of the conidia proteome in M. robertsii and provide a basis for further exploration for improving the efficiency of the fungi as biocontrol agents.

The First Whole-Cell Proteome- and Lysine-Acetylome-Based Comparison between Trichophyton rubrum Conidial and Mycelial Stages

Trichophyton rubrum is the most common fungal pathogen in the world, which has been studied as an important dermatophyte model organism. Despite the prevalence of T. rubrum, the available antifungal therapies are not sufficiently efficient. In this study, we performed the first comparison between the two major growth stages of T. rubrum: conidial and mycelial stages, based on their whole-cell proteomes and lysine acetylomes. In total, 4343 proteins were identified in both stages, and 1879 proteins were identified as differentially expressed between the two stages. The results showed that secretory proteases were more abundant in conidia, while aerobic metabolism and protein synthesis were significantly activated in the mycelial stage. In addition, 386 acetylated sites on 285 proteins and 5414 acetylated sites on 2335 proteins were identified in conidia and mycelia, respectively. The acetylation modifications were highly involved in metabolism and protein synthesis in both stages but differentially involved in Kyoto Encyclopedia of Genes and Genomes pathways and in epigenetic regulation between the two stages. Furthermore, inhibition of acetyltransferases or deacetylases significantly inhibited fungal growth and induced apoptosis. These results will enhance our understanding of the biological and physiological characteristics of T. rubrum and facilitate the development of improved therapies targeting these medically important pathogenic fungi.

Potential molecular mechanisms for fruiting body formation of Cordyceps illustrated in the case of Cordyceps sinensis

The fruiting body formation mechanisms of Cordyceps sinensis are still unclear. To explore the mechanisms, proteins potentially related to the fruiting body formation, proteins from fruiting bodies, and mycelia of Cordyceps species were assessed by using two-dimensional fluorescence difference gel electrophoresis, and the differential expression proteins were identified by matrix-assisted laser desorption/ionisation tandem time of flight mass spectrometry. The results showed that 198 differential expression proteins (252 protein spots) were identified during the fruiting body formation of Cordyceps species, and 24 of them involved in fruiting body development in both C. sinensis and other microorganisms. Especially, enolase and malate dehydrogenase were first found to play an important role in fruiting body development in macro-fungus. The results implied that cAMP signal pathway involved in fruiting body development of C. sinensis, meanwhile glycometabolism, protein metabolism, energy metabolism, and cell reconstruction were more active during fruiting body development. It has become evident that fruiting body formation of C. sinensis is a highly complex differentiation process and requires precise integration of a number of fundamental biological processes. Although the fruiting body formation mechanisms for all these activities remain to be further elucidated, the possible mechanism provides insights into the culture of C. sinensis.

Protein profile and protein interaction network of Moniliophthora perniciosa basidiospores

BACKGROUND

Witches' broom, a disease caused by the basidiomycete Moniliophthora perniciosa, is considered to be the most important disease of the cocoa crop in Bahia, an area in the Brazilian Amazon, and also in the other countries where it is found. M. perniciosa germ tubes may penetrate into the host through intact or natural openings in the cuticle surface, in epidermis cell junctions, at the base of trichomes, or through the stomata. Despite its relevance to the fungal life cycle, basidiospore biology has not been extensively investigated. In this study, our goal was to optimize techniques for producing basidiospores for protein extraction, and to produce the first proteomics analysis map of ungerminated basidiospores. We then presented a protein interaction network by using Ustilago maydis as a model.

RESULTS

The average pileus area ranged from 17.35 to 211.24 mm(2). The minimum and maximum productivity were 23,200 and 6,666,667 basidiospores per basidiome, respectively. The protein yield in micrograms per million basidiospores were approximately 0.161; 2.307, and 3.582 for germination times of 0, 2, and 4 h after germination, respectively. A total of 178 proteins were identified through mass spectrometry. These proteins were classified according to their molecular function and their involvement in biological processes such as cellular energy production, oxidative metabolism, stress, protein synthesis, and protein folding. Furthermore, to better understand the expression pattern, signaling, and interaction events of spore proteins, we presented an interaction network using orthologous proteins from Ustilago maydis as a model. Most of the orthologous proteins that were identified in this study were not clustered in the network, but several of them play a very important role in hypha development and branching.

CONCLUSIONS

The quantities of basidiospores 7 × 10(9); 5.2 × 10(8), and 6.7 × 10(8) were sufficient to obtain enough protein mass for the three 2D-PAGE replicates, for the 0, 2, and 4 h-treatments, respectively. The protein extraction method that is based on sedimentation, followed by sonication with SDS-dense buffer, and phenolic extraction, which was utilized in this study, was effective, presenting a satisfactory resolution and reproducibility for M. perniciosa basidiospores. This report constitutes the first comprehensive study of protein expression during the ungerminated stage of the M. perniciosa basidiospore. Identification of the spots observed in the reference gel enabled us to know the main molecular interactions involved in the initial metabolic processes of fungal development.

Secretome Analysis of Metarhizium anisopliae Under Submerged Conditions Using Bombyx mori Chrysalis to Induce Expression of Virulence-Related Proteins

The entomopathogenic fungus Metarhizium anisopliae is used to control insect pests. This species is specialized for the secretion of an enzymatic complex consisting of proteases, lipases, and chitinases related to pathogenicity and virulence. In this context, the secretomes of strains IBCB 167 and IBCB 384 of M. anisopliae var. anisopliae, grown under submerged fermentation in the presence of chrysalis as an inducer, were analyzed. Analysis of two-dimensional gels showed qualitative and quantitative differences between secreted proteins in both isolates. Around 102 protein spots were analyzed, and 76 % of the corresponding proteins identified by mass spectrometry were grouped into different classes (hydrolases, oxidases, reductases, isomerases, kinases, WSC domains, and hypothetical proteins). Thirty-three per cent of all the proteins analyzed were found to be common in both strains. Several virulence-related proteins were identified as proteases and mannosidases. Endo-N-acetyl-β-D-glucosaminidase expression was observed to be 10.14-fold higher for strain IBCB 384 than for strain IBCB 167, which may be an important contributor to the high virulence of IBCB 384 in Diatraea ssaccharalis. These results are important for elucidation of the host-pathogen relationship and the differences in virulence observed between the two strains.

Comparative Proteomics Analyses of Two Races of Fusarium oxysporum f. sp. conglutinans that Differ in Pathogenicity

Fusarium oxysporum is a soil-inhabiting fungus that induces vascular wilt and root rot in a variety of plants. F. oxysporum f. sp. conglutinans (Foc), which comprises two races, can cause wilt disease in cabbage. Compared with race 1 (52557(-TM), R1), race 2 (58385(-TM), R2) exhibits much stronger pathogenicity. Here, we provide the first proteome reference maps for Foc mycelium and conidia and identify 145 proteins with different abundances among the two races. Of these proteins, most of the high-abundance proteins in the R2 mycelium and conidia are involved in carbohydrate, amino acid and ion metabolism, which indicates that these proteins may play important roles in isolate R2's stronger pathogenicity. The expression levels of 20 typical genes demonstrate similarly altered patterns compared to the proteomic analysis. The protein glucanosyltransferase, which is involved in carbohydrate metabolism, was selected for research. We knocked out the corresponding gene (gas1) and found that Foc-∆gas1 significantly reduced growth rate and virulence compared with wild type isolates. These results deepened our understanding of the proteins related to F. oxysporum pathogenicity in cabbage Fusarium wilt and provided new opportunities to control this disease.

Molecular and physiological effects of environmental UV radiation on fungal conidia

Conidia are specialized structures produced at the end of the asexual life cycle of most filamentous fungi. They are responsible for fungal dispersal and environmental persistence. In pathogenic species, they are also involved in host recognition and infection. Conidial production, survival, dispersal, germination, pathogenicity and virulence can be strongly influenced by exposure to solar radiation, although its effects are diverse and often species dependent. UV radiation is the most harmful and mutagenic waveband of the solar spectrum. Direct exposure to solar radiation for a few hours can kill conidia of most fungal species. Conidia are killed both by solar UV-A and UV-B radiation. In addition to killing conidia, which limits the size of the fungal population and its dispersion, exposures to sublethal doses of UV radiation can reduce conidial germination speed and virulence. The focus of this review is to provide an overview of the effects of solar radiation on conidia and on the major systems involved in protection from and repair of damage induced by solar UV radiation. The efforts that have been made to obtain strains of fungi of interest such as entomopathogens more tolerant to solar radiation will also be reviewed.

Proteome exploration to provide a resource for the investigation of Ganoderma lucidum

Ganoderma lucidum is a basidiomycete white rot fungus that has been used for medicinal purposes worldwide. Although information concerning its genome and transcriptome has recently been reported, relatively little information is available for G. lucidum at the proteomic level. In this study, protein fractions from G. lucidum at three developmental stages (16-day mycelia, and fruiting bodies at 60 and 90 days) were prepared and subjected to LC-MS/MS analysis. A search against the G. lucidum genome database identified 803 proteins. Among these proteins, 61 lignocellulose degrading proteins were detected, most of which (49 proteins) were found in the 90-day fruiting bodies. Fourteen TCA-cycle related proteins, 17 peptidases, two argonaute-like proteins, and two immunomodulatory proteins were also detected. A majority (470) of the 803 proteins had GO annotations and were classified into 36 GO terms, with "binding", "catalytic activity", and "hydrolase activity" having high percentages. Additionally, 357 out of the 803 proteins were assigned to at least one COG functional category and grouped into 22 COG classifications. Based on the results from the proteomic and sequence alignment analyses, a potentially new immunomodulatory protein (GL18769) was expressed and shown to have high immunomodulatory activity. In this study, proteomic and biochemical analyses of G. lucidum were performed for the first time, revealing that proteins from this fungus can play significant bioactive roles and providing a new foundation for the further functional investigations that this fungus merits.

Growth under visible light increases conidia and mucilage production and tolerance to UV-B radiation in the plant pathogenic fungus Colletotrichum acutatum

Light conditions can influence fungal development. Some spectral wavebands can induce conidial production, whereas others can kill the conidia, reducing the population size and limiting dispersal. The plant pathogenic fungus Colletotrichum acutatum causes anthracnose in several crops. During the asexual stage on the host plant, Colletototrichum produces acervuli with abundant mucilage-embedded conidia. These conidia are responsible for fungal dispersal and host infection. This study examined the effect of visible light during C. acutatum growth on the production of conidia and mucilage and also on the UV tolerance of these conidia. Conidial tolerance to an environmentally realistic UV irradiance was determined both in conidia surrounded by mucilage on sporulating colonies and in conidial suspension. Exposures to visible light during fungal growth increased production of conidia and mucilage as well as conidial tolerance to UV. Colonies exposed to light produced 1.7 times more conidia than colonies grown in continuous darkness. The UV tolerances of conidia produced under light were at least two times higher than conidia produced in the dark. Conidia embedded in the mucilage on sporulating colonies were more tolerant of UV than conidia in suspension that were washed free of mucilage. Conidial tolerance to UV radiation varied among five selected isolates.

Differential protein accumulations in isolates of the strawberry wilt pathogen Fusarium oxysporum f. sp. fragariae differing in virulence

This study was conducted to define differences in Fusarium oxysporum f. sp. fragariae (Fof) isolates with different virulence efficiency to strawberry at the proteome level, in combination with their differences in mycelial growth, conidial production and germination. Comparative proteome analyses revealed substantial differences in mycelial proteomes between Fof isolates, where the 54 differentially accumulated protein spots were consistently over-accumulated or exclusively in the highly virulent isolate. These protein spots were identified through MALDI-TOF/TOF mass spectrometry analyses, and the identified proteins were mainly related to primary and protein metabolism, antioxidation, electron transport, cell cycle and transcription based on their putative functions. Proteins of great potential as Fof virulence factors were those involved in ubiquitin/proteasome-mediated protein degradation and reactive oxygen species detoxification; the hydrolysis-related protein haloacid dehalogenase superfamily hydrolase; 3,4-dihydroxy-2-butanone 4-phosphate synthase associated with riboflavin biosynthesis; and those exclusive to the highly virulent isolate. In addition, post-translational modifications may also make an important contribution to Fof virulence.

BIOLOGICAL SIGNIFICANCE

F. oxysporum f. sp. fragariae (Fof), the causal agent of Fusarium wilt in strawberry, is a serious threat to commercial strawberry production worldwide. However, factors and mechanisms contributing to Fof virulence remained unknown. This study provides knowledge of the molecular basis for the differential expression of virulence in Fof, allowing new possibilities towards developing alternative and more effective strategies to manage Fusarium wilt.

Comparative transcriptomic analysis of the heat stress response in the filamentous fungus Metarhizium anisopliae using RNA-Seq

The entomopathogenic fungus Metarhizium anisopliae is widely used for biological control of a variety of insect pests. The effectiveness of the microbial pest control agent, however, is limited by poor thermotolerance. The molecular mechanism underlying the response to heat stress in the conidia of entomopathogenic fungi remains unclear. Here, we conducted high-throughput RNA-Seq to analyze the differential gene expression between control and heat treated conidia of M. anisopliae at the transcriptome level. RNA-Seq analysis generated 6,284,262 and 5,826,934 clean reads in the control and heat treated groups, respectively. A total of 2,722 up-regulated and 788 down-regulated genes, with a cutoff of twofold change, were identified by expression analysis. Among these differentially expressed genes, many were related to metabolic processes, biological regulation, cellular processes and response to stimuli. The majority of genes involved in endocytic pathways, proteosome pathways and regulation of autophagy were up-regulated, while most genes involved in the ribosome pathway were down-regulated. These results suggest that these differentially expressed genes may be involved in the heat stress response in conidia. As expected, significant changes in expression levels of genes encoding heat shock proteins and proteins involved in trehalose accumulation were observed in conditions of heat stress. These results expand our understanding of the molecular mechanisms of the heat stress response of conidia and provide a foundation for future investigations.

Secretome of the biocontrol agent metarhizium anisopliae induced by the cuticle of the cotton pest Dysdercus peruvianus reveals new insights into infection

Metarhizium anisopliae is an entomopathogenic fungus that has evolved specialized strategies to infect insect hosts. Here we analyzed secreted proteins related to Dysdercus peruvianus infection. Using shotgun proteomics, abundance changes in 71 proteins were identified after exposure to host cuticle. Among these proteins were classical fungal effectors secreted by pathogens to degrade physical barriers and alter host physiology. These include lipolytic enzymes, Pr1A, B, C, I, and J proteases, ROS-related proteins, oxidorreductases, and signaling proteins. Protein interaction networks were generated postulating interesting candidates for further studies, including Pr1C, based on possible functional interactions. On the basis of these results, we propose that M. anisopliae is degrading host components and actively secreting proteins to manage the physiology of the host. Interestingly, the secretion of these factors occurs in the absence of a host response. The findings presented here are an important step in understanding the host–pathogen interaction and developing more efficient biocontrol of D. peruvianus by M. anisopliae.

In vitro photodynamic inactivation of plant-pathogenic fungi Colletotrichum acutatum and Colletotrichum gloeosporioides with Novel Phenothiazinium photosensitizers

The increasing tolerance to currently used fungicides in both clinical and agricultural areas is of great concern. The nonconventional light-based approach of antimicrobial photodynamic treatment (APDT) is a promising alternative to conventional fungicides. We evaluated the effects of APDT with four phenothiazinium derivatives (methylene blue [MB], new methylene blue N [NMBN], toluidine blue O [TBO], and the novel pentacyclic phenothiazinium photosensitizer [PS] S137) on conidia of three fungal species (Colletotrichum acutatum, Colletotrichum gloeosporioides, and Aspergillus nidulans). The efficacy of APDT with each PS was determined, initially, based on photosensitizer MICs. Additionally, the effects of APDT with two selected PSs (NMBN and S137) on survival of conidia were evaluated. The subcellular localization of the PS in C. acutatum conidia was determined. The effects of photodynamic treatments on leaves of the plant host Citrus sinensis were also investigated. APDT with S137 showed the lowest MIC. MICs for S137 were 5 μM for the three fungal species when a fluence of 25 J cm(-2) was used. APDT with NMBN (50 μM) and S137 (10 μM) resulted in a reduction in the survival of the conidia of all species of approximately 5 logs with fluences of ≥15 J cm(-2). Washing of the conidia before light exposure did not prevent photodynamic inactivation. Both NMBN and S137 accumulated in cytoplasmic structures, such as lipid bodies, of C. acutatum conidia. No damage to orange tree leaves was observed after APDT.

Furocoumarins and coumarins photoinactivate Colletotrichum acutatum and Aspergillus nidulans fungi under solar radiation

The increasing tolerance to currently-used fungicides is a major problem both in clinical and agricultural areas leading to an urgent need for the development of novel antifungal strategies. This study investigated the in vitro antimicrobial photo treatment (APT) of conidia of the plant-pathogenic fungus Colletotrichum acutatum and the ascomycete Aspergillus nidulans with the furocoumarins 8-methoxypsoralen (8-MOP) and isopimpinellin, and a mixture of two coumarins (7-methoxy coumarin and citropten). Subcellular localization of the photosensitizer 8-MOP was also determined in C. acutatum conidia. Additionally, the effects of APT on the leaves of the plant host Citrus sinensis were determined. APT with 8-MOP (50μM) led to a reduction of approximately 4 logs in the survival of the conidia of both species, and the mixture of the two coumarins (12.5mgL(-1)) resulted in a reduction of approximately 4 logs for A. nidulans and 3 logs for C. acutatum. Isopimpinellin (50μM) displayed a reduction of 4 logs for A. nidulans but less than 2 logs for C. acutatum. Washing the conidia to remove unbound photosensitizers before light exposure reduced the photodynamic inactivation of C. acutatum both with 8-MOP and the mixture of the two coumarins. The reduction was smaller for A. nidulans. 8-MOP spread throughout the cytoplasm and accumulated in structures such as lipid bodies of C. acutatum conidia. No damage to orange tree leaves was observed after APT with any of the photosensitizers.

Microbial culture collections as pillars for promoting fungal diversity, conservation and exploitation

Fungi are a diverse group of organisms with an overall global number of 1.5M up to 3.3M species on Earth. Besides their ecological roles as decomposers, fungi are important in several aspects of applied research. Here, we review how culture collections may promote the knowledge on diversity, conservation and biotechnological exploitation of fungi. The impact of fungi diversity on biotechnological studies is discussed. We point out the major roles of microbial repositories, including fungal preservation, prospecting, identification, authentication and supply. A survey on the World Data Center for Microorganisms (WDCM) powered by the World Federation for Culture Collections and on the Genetic Heritage Management Council (CGEN) database revealed that 46 Brazilian culture collections registered in these databases are dedicate to preserving fungi. Most of these culture collections are located in the Southeast of Brazil. This scenario also demonstrates that Brazil has many collections focused on fungal strains, but the lack of up-to-date information in WDCM as well as of a solid national platform for culture collections registration do not allow accurate assessment of fungal preservation.

Proteins differentially expressed in conidia and mycelia of the entomopathogenic fungus Metarhizium anisopliae sensu stricto

Metarhizium anisopliae is a well-characterized entomopathogenic fungus that attacks a variety of insects. Its conidia are involved in its propagation and also in its infection of host insects. To investigate the protein expression profiles and to identify the proteins related to development and pathogenesis, we performed a comparative proteomic analysis of the conidia and mycelia of an M. anisopliae strain (Ma1291). The analysis used 2-dimensional gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. We detected 898 ± 37 protein spots in conidia and 1072 ± 24 in mycelia of strain Ma1291. A comparison of the 2 protein-expression profiles indicated that only 28% of protein spots were common to both developmental stages. Finally, we identified 30 proteins (19 from conidia and 11 from mycelia). The identified proteins exclusive to conidia were those involved in protective processes, appressorium formation, and degradation of the host cuticle (protease PR1H). The identified proteins exclusive to mycelia included major proteins participating in biosynthetic and energy metabolism, such as UTP-glucose-1-phosphate uridylyltransferase and heat shock protein 70. This research provides the first proteomic analysis of different developmental stages of M. anisopliae, and the results should facilitate clarification of the molecular basis of these epigenetic variations.

Inhibition of ecto-phosphatase activity in conidia reduces adhesion and virulence of Metarhizium anisopliae on the host insect Dysdercus peruvianus

Metarhizium anisopliae is an entomopathogenic fungus with the ability to infect a broad range of arthropods, and have evolved distinct strategies for their attachment to hosts. Here, we describe the characterisation of ecto-phosphatase activity on the conidia surface of M. anisopliae and its relevance in the host interaction process. Ecto-phosphatase activity was linear for 60 min and during this time, was linear with the increase of cell density. The optimum pH was in the acidic range and some divalent metals, such as Cu(2+), Cd(2+) and Zn(2+), inhibited ecto-phosphatase activity. The activity was also reduced by phosphatase inhibitors. Importantly, the inhibition of phosphatase activity in conidia reduced the adhesion to Dysdercus peruvianus (Hemiptera: Pyrrhocoridae) integument and, consequently and indirectly, M. anisopliae infection. The results herein presented show, for the first time, the importance of ecto-phosphatase activity in M. anisopliae conidia and provide the first evidence of its direct involvement in adhesion and host infection.

Proteomic analysis of proteins differentially expressed in conidia and mycelium of the entomopathogenic fungus Aschersonia placenta

The infection of insects by the entomopathogenic fungus Aschersonia placenta depends on conidia. To identify proteins differentially expressed in A. placenta conidia vs mycelia, we performed a comparative proteomic analysis of A. placenta using 2-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF-MS). We detected 1022 2-DE protein spots in conidia and 1049 in mycelia and analyzed 48 (13 from conidia and 35 from mycelia) using MALDI-TOF-MS. Finally, we identified 28 proteins (7 from conidia and 21 from mycelia). The identified proteins exclusive to conidia included major proteins participating in oxidation–reduction processes and vegetative insecticidal protein 1 (Vip1), a protein that is likely involved in pathogenicity. The identified proteins exclusive to mycelia were those involved in biosynthesis and metabolism, including uridine diphosphate galactopyranose mutase, which might play key roles in hyphal morphogenesis. This report provides the first proteomic analysis of different developmental stages of an Aschersonia species. Although only a small number of proteins were identified, the data represent a useful foundation for future studies concerning the molecular basis of entomopathogenicity in the species A. placenta and in the genus Aschersonia.

Fungal proteomics: from identification to function

Some fungi cause disease in humans and plants, while others have demonstrable potential for the control of insect pests. In addition, fungi are also a rich reservoir of therapeutic metabolites and industrially useful enzymes. Detailed analysis of fungal biochemistry is now enabled by multiple technologies including protein mass spectrometry, genome and transcriptome sequencing and advances in bioinformatics. Yet, the assignment of function to fungal proteins, encoded either by in silico annotated, or unannotated genes, remains problematic. The purpose of this review is to describe the strategies used by many researchers to reveal protein function in fungi, and more importantly, to consolidate the nomenclature of 'unknown function protein' as opposed to 'hypothetical protein' - once any protein has been identified by protein mass spectrometry. A combination of approaches including comparative proteomics, pathogen-induced protein expression and immunoproteomics are outlined, which, when used in combination with a variety of other techniques (e.g. functional genomics, microarray analysis, immunochemical and infection model systems), appear to yield comprehensive and definitive information on protein function in fungi. The relative advantages of proteomic, as opposed to transcriptomic-only, analyses are also described. In the future, combined high-throughput, quantitative proteomics, allied to transcriptomic sequencing, are set to reveal much about protein function in fungi.

Quantification of cyclobutane pyrimidine dimers induced by UVB radiation in conidia of the fungi Aspergillus fumigatus, Aspergillus nidulans, Metarhizium acridum and Metarhizium robertsii

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.