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1.
Int J Mol Sci ; 22(16)2021 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-34445145

RESUMO

The main goal of growing plants under various photoperiods is to optimize photosynthesis for using the effect of day length that often acts on plants in combination with biotic and/or abiotic stresses. In this study, Brassica juncea plants were grown under four different day-length regimes, namely., 8 h day/16 h night, 12 h day/12 h night, 16 h day/8 h night, and continuous light, and were infected with a necrotrophic fungus Alternaria brassicicola. The development of necroses on B. juncea leaves was strongly influenced by leaf position and day length. The largest necroses were formed on plants grown under a 16 h day/8 h night photoperiod at 72 h post-inoculation (hpi). The implemented day-length regimes had a great impact on leaf morphology in response to A. brassicicola infection. They also influenced the chlorophyll and carotenoid contents and photosynthesis efficiency. Both the 1st (the oldest) and 3rd infected leaves showed significantly higher minimal fluorescence (F0) compared to the control leaves. Significantly lower values of other investigated chlorophyll a fluorescence parameters, e.g., maximum quantum yield of photosystem II (Fv/Fm) and non-photochemical quenching (NPQ), were observed in both infected leaves compared to the control, especially at 72 hpi. The oldest infected leaf, of approximately 30% of the B. juncea plants, grown under long-day and continuous light conditions showed a 'green island' phenotype in the form of a green ring surrounding an area of necrosis at 48 hpi. This phenomenon was also reflected in changes in the chloroplast's ultrastructure and accelerated senescence (yellowing) in the form of expanding chlorosis. Further research should investigate the mechanism and physiological aspects of 'green islands' formation in this pathosystem.


Assuntos
Alternaria/patogenicidade , Mostardeira/microbiologia , Mostardeira/fisiologia , Necrose/microbiologia , Necrose/patologia , Fotossíntese/fisiologia , Doenças das Plantas/microbiologia , Carotenoides/metabolismo , Clorofila/metabolismo , Clorofila A/metabolismo , Fluorescência , Mostardeira/metabolismo , Necrose/metabolismo , Fotoperíodo , Complexo de Proteína do Fotossistema II/metabolismo , Folhas de Planta/metabolismo , Folhas de Planta/microbiologia
2.
J Genet ; 1002021.
Artigo em Inglês | MEDLINE | ID: mdl-34238774

RESUMO

Faba bean (Vicia faba L.) is one of the earliest domesticated food legumes after chickpea and pea in the world. It is been produced in many countries including China, Ethiopia, Egypt, northern Europe, the Mediterranean region, central Asia, East Asia, Latin America and as a minor crop in India. The crop is affected by many diseases and alternaria leaf blight (Alternaria spp.) is one of the serious threat to faba bean production. Twenty-five lines of faba bean were selected from three international nurseries and were evaluated at ICARDA-FLRP-Amlaha during 2016-2017 and 2017-2018, to identify resistant lines against alternaria blight disease. A wide range of variation to disease reaction was observed among faba bean genotypes. One faba bean line (S2011-134) found tolerant, six genotypes (S2011-116, FLIP15-139, FLIP15-156, FLIP15-159, FLIP15-164-S2 and FLIP15-169) were found moderately tolerant and 16 genotypes were found susceptible to alternaria blight. The faba bean genotypes showed resistance to the disease scoring (0-9) with high yield as compared to the checks, Giza and Gwalior local. The identified sources of resistance can be utilized in faba bean breeding programmes for the development of disease tolerant cultivars with high yield.


Assuntos
Resistência à Doença/genética , Melhoramento Vegetal , Doenças das Plantas/genética , Vicia faba/genética , Alternaria/patogenicidade , China , Europa (Continente) , Genótipo , Índia , Doenças das Plantas/microbiologia , Vicia faba/crescimento & desenvolvimento , Vicia faba/microbiologia
3.
Chem Biodivers ; 18(5): e2100079, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33821531

RESUMO

Eight natural biphenyl-type phytoalexins exhibiting antifungal effect were isolated from the leaves of Sorbus pohuashanensis, which invaded by Alternaria tenuissi, and their growth inhibition rate towards A. tenuissi were 50.3 %, 54.0 %, 66.4 %, 58.8 %, 48.5 %, 51.0 %, 33.3 %, and 37.0 %, respectively. In vivo activity assay verified the protective effect of these natural biphenyls on tobacco leaves. The observation of mycelial morphology revealed that these compounds possessed adverse effects on mycelial growth of A. tenuissi. Subsequently, the most potent active compounds, 3',4',5'-trimethoxy[1,1'-biphenyl]-4-ol (3) and 3,4,4',5-tetramethoxy-1,1'-biphenyl (4), were conducted to the further antifungal evaluation and showed significant activity against the other four crop pathogens, Fusarium graminearum, Helminthosporium maydis, Sclerotinia sclerotiorum, and Exserohilum turcicum. Further, the structure-activity relationships and biosynthesis of these compounds were speculated in this work.


Assuntos
Alternaria/efeitos dos fármacos , Antifúngicos/farmacologia , Compostos de Bifenilo/farmacologia , Sorbus/química , Alternaria/crescimento & desenvolvimento , Alternaria/patogenicidade , Antifúngicos/química , Antifúngicos/isolamento & purificação , Ascomicetos/efeitos dos fármacos , Ascomicetos/patogenicidade , Compostos de Bifenilo/química , Compostos de Bifenilo/isolamento & purificação , Bipolaris/efeitos dos fármacos , Bipolaris/patogenicidade , Fusarium/efeitos dos fármacos , Fusarium/patogenicidade , Testes de Sensibilidade Microbiana , Estrutura Molecular , Extratos Vegetais , Folhas de Planta/química
4.
Molecules ; 26(8)2021 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-33919567

RESUMO

Essential oils are gaining interest as environmentally friendly alternatives to synthetic fungicides for management of seedborne pathogens. Here, seven essential oils were initially tested in vivo for disinfection of squash seeds (Cucurbita maxima) naturally contaminated by Stagonosporopsis cucurbitacearum, Alternaria alternata, Fusarium fujikuro, Fusarium solani, Paramyrothecium roridum, Albifimbria verrucaria, Curvularia spicifera, and Rhizopus stolonifer. The seeds were treated with essential oils from Cymbopogon citratus, Lavandula dentata, Lavandula hybrida, Melaleuca alternifolia, Laurus nobilis, and Origanum majorana (#1 and #2). Incidence of S. cucurbitacearum was reduced, representing a range between 67.0% in L. nobilis to 84.4% in O. majorana #2. Treatments at 0.5 mg/mL essential oils did not affect seed germination, although radicles were shorter than controls, except with C. citratus and O. majorana #1 essential oils. Four days after seeding, seedling emergence was 20%, 30%, and 10% for control seeds and seeds treated with C. citratus essential oil (0.5 mg/mL) and fungicides (25 g/L difenoconazole plus 25 g/L fludioxonil). S. cucurbitacearum incidence was reduced by ~40% for plantlets from seeds treated with C. citratus essential oil. These data show the effectiveness of this essential oil to control the transmission of S. cucurbitacearum from seeds to plantlets, and thus define their potential use for seed decontamination in integrated pest management and organic agriculture.


Assuntos
Cucurbita/microbiologia , Óleos Voláteis/farmacologia , Óleos Vegetais/farmacologia , Sementes/efeitos dos fármacos , Alternaria/efeitos dos fármacos , Alternaria/patogenicidade , Ascomicetos/patogenicidade , Cucurbita/efeitos dos fármacos , Curvularia/efeitos dos fármacos , Curvularia/patogenicidade , Fungicidas Industriais/química , Fungicidas Industriais/farmacologia , Fusarium/efeitos dos fármacos , Fusarium/patogenicidade , Hypocreales/efeitos dos fármacos , Hypocreales/patogenicidade , Óleos Voláteis/química , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Óleos Vegetais/química , Rhizopus/efeitos dos fármacos , Rhizopus/patogenicidade , Sementes/microbiologia
5.
Microbiol Res ; 248: 126747, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33740671

RESUMO

The host-selective ACT toxin is essential for the pathogenesis of the citrus fungal pathogen Alternaria alternata. However, the mechanism of ACT-toxin gene clusters ACT-toxin biosynthesis regulated by is still poorly understood. The biosynthesis of ACT toxin is mainly regulated by multiple ACT toxin genes located in the secondary metabolite gene cluster. In this study, we reported a transcription regulator ACTR contributes ACT toxin biosynthesis through mediating ACT toxin synthesis gene ACTS4 in Alternaria alternata. We generated ACTR-disrupted and -silenced mutants in the tangerine pathotype of A. alternata. Phenotype analysis showed that the ACTR mutants displayed a significant loss of ACT toxin production and a decreased virulence on citrus leaves whereas the vegetative growth and sporulation were not affected, indicating an essential role of ACTR in both ACT toxin biosynthesis and pathogenicity. To elucidate the transcription network of ACTR, we performed RNA-Seq experiments on wild-type and ACTR null mutant and identified genes that were differentially expressed between two genotypes. Transcriptome profiling and RT-qPCR analysis demonstrated that the ACT toxin biosynthetic gene ACTS4 is down-regulated in ACTR mutant. We generated ACTS4 knock-down mutant and found that the pathogenicity of ACTS4 mutant was severely impaired. Interestingly, both ACTR and ACTS4 are not involved in the response to different abiotic stresses including oxidative stress, salt stress, cell-wall disrupting regents, and metal ion stress, indicating the function of these two genes is highly specific. In conclusion, our results highlight the important regulatory role of ACTR in ACT toxin biosynthesis through mediating ACT toxin synthesis gene ACTS4 and underline the essential role of in the tangerine pathotype of A. alternata.


Assuntos
Alternaria/metabolismo , Micotoxinas/biossíntese , Fatores de Transcrição/metabolismo , Alternaria/genética , Alternaria/patogenicidade , Vias Biossintéticas , Citrus/microbiologia , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Regulação Fúngica da Expressão Gênica , Família Multigênica , Doenças das Plantas/microbiologia , Metabolismo Secundário , Fatores de Transcrição/genética , Virulência
6.
Mol Biol Rep ; 48(3): 3001-3006, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33687701

RESUMO

Tomato plants displaying early blight symptoms were collected from different localities in the provinces of Assiut and Sohag, Egypt. The causal pathogens were isolated on potato dextrose agar plates. Pathogenicity tests with 48 isolates were carried out under greenhouse conditions on tomato cultivar (CV 844). All tested isolates caused symptoms of early blight disease with different degrees. The highest disease severity on tomato plants was found after inoculation with isolate No. 6 followed by isolates No. 20 and No. 31. The most pathogenic isolates were identified by sequence analysis using ITS1 and ITS4 primers. The analysis of the amplified sequences from fungal isolates No. 6, 20 and 31 displayed 99-100% nucleotide identity with Alternaria solani, Curvularia lunata and A. alternata, respectively. To our knowledge, this is the first report of Curvularia lunata as one of the causal pathogens of early blight disease of tomato plants in Egypt.


Assuntos
Curvularia/patogenicidade , Lycopersicon esculentum/microbiologia , Doenças das Plantas/microbiologia , Alternaria/patogenicidade , Curvularia/isolamento & purificação , DNA Intergênico/genética , Egito , Funções Verossimilhança , Filogenia
7.
J Appl Microbiol ; 131(3): 1431-1439, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33524179

RESUMO

AIMS: In this study, volatile compounds released from mycelia of some aromatic mushrooms were investigated for their inhibitory activity against plant-pathogenic bacteria and fungi. METHODS AND RESULTS: A screening revealed that volatile compounds from mycelia of Porostereum spadiceum remarkably inhibited the colony formation of plant-pathogenic bacteria, including Clavibacter michiganensis subsp. michiganensis and Ralstonia solanacearum while also inhibiting the conidial germination of plant-pathogenic fungi including Alternaria brassicicola and Colletotrichum orbiculare. The volatile compounds were isolated from the culture filtrate of P. spadiceum, and 3,4-dichloro-4-methoxybenzaldehyde (DCMB) was identified as a major compound. DCMB significantly inhibited bacterial colonization at 10 µg ml-1 and fungal conidial germination at 0·1-1 µg ml-1 as a vapour. CONCLUSIONS: This is the first report on the production of the volatile compound DCMB by P. spadiceum and on the antimicrobial activity of DCMB against plant-pathogenic bacteria and fungi at low concentrations. It may be possible to use the compound as an agent for protecting crops from bacterial and fungal diseases during cultivation and storage. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides an understanding of antimicrobial activity of the mushroom volatile compound that may be useful as a novel biological control agent for protecting various plant diseases.


Assuntos
Anti-Infecciosos , Benzaldeídos/farmacologia , Polyporales/química , Compostos Orgânicos Voláteis/farmacologia , Alternaria/patogenicidade , Anti-Infecciosos/farmacologia , Bactérias/patogenicidade , Agentes de Controle Biológico/química , Colletotrichum/patogenicidade , Doenças das Plantas/microbiologia
8.
Sci Rep ; 11(1): 1488, 2021 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-33452278

RESUMO

Nonhost resistance of Arabidopsis thaliana against the hemibiotrophic fungus Colletotrichum tropicale requires PEN2-dependent preinvasive resistance and CYP71A12 and CYP71A13-dependent postinvasive resistance, which both rely on tryptophan (Trp) metabolism. We here revealed that CYP71A12, CYP71A13 and PAD3 are critical for Arabidopsis' postinvasive basal resistance toward the necrotrophic Alternaria brassicicola. Consistent with this, gene expression and metabolite analyses suggested that the invasion by A. brassicicola triggered the CYP71A12-dependent production of indole-3-carboxylic acid derivatives and the PAD3 and CYP71A13-dependent production of camalexin. We next addressed the activation of the CYP71A12 and PAD3-dependent postinvasive resistance. We found that bak1-5 mutation significantly reduced postinvasive resistance against A. brassicicola, indicating that pattern recognition contributes to activation of this second defense-layer. However, the bak1-5 mutation had no detectable effects on the Trp-metabolism triggered by the fungal penetration. Together with this, further comparative gene expression analyses suggested that pathogen invasion in Arabidopsis activates (1) CYP71A12 and PAD3-related antifungal metabolism that is not hampered by bak1-5, and (2) a bak1-5 sensitive immune pathway that activates the expression of antimicrobial proteins.


Assuntos
Alternaria/metabolismo , Proteínas de Arabidopsis/genética , Proteínas Serina-Treonina Quinases/genética , Triptofano/metabolismo , Alternaria/imunologia , Alternaria/patogenicidade , Arabidopsis/genética , Arabidopsis/imunologia , Sistema Enzimático do Citocromo P-450/genética , Resistência à Doença/genética , Regulação da Expressão Gênica de Plantas/genética , Indóis/metabolismo , Doenças das Plantas/microbiologia , Tiazóis/metabolismo
9.
J Appl Microbiol ; 131(2): 833-843, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33420735

RESUMO

AIMS: Alternaria alternata is a major contaminant of wine grapes, meaning a health risk for wine consumers due to the accumulation of toxic metabolites. To develop a successful biofungicide, the effectiveness of epiphytic wine grape yeasts against A. alternata growth and toxin production was assessed in vitro under temperature and aW conditions that simulate those present in the field. METHODS AND RESULTS: The effect of 14 antagonistic yeasts was evaluated on growth and alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TA) production by three A. alternata strains in a synthetic medium with composition similar to grape (SN) at three temperatures (15, 25 and 30°C). All Metschnikowia sp. yeast strains evaluated completely prevented A. alternata growth and mycotoxin production at all temperatures in SN medium. Meanwhile, the growth inhibition exerted by Starmerella bacillaris yeast strains was higher at 30°C, followed by 25 and 15°C, being able to show a stimulating or inhibiting effect. Hanseniaspora uvarum yeast strains showed a growth promoting activity higher at 15°C, followed by 25 and 30°C. Even at conditions where A. alternata growth was stimulated by the S. bacillaris and H. uvarum yeasts, high inhibitions of mycotoxin production (AOH, AME and TA) were observed, indicating a complex interaction between growth and mycotoxin production. CONCLUSION: There is a significant influence of temperature on the effectiveness of biocontrol against A. alternata growth and mycotoxin production. Metschnikowia sp. strains are good candidates to compose a biofungicide against A. alternata. SIGNIFICANCE AND IMPACT OF THE STUDY: Among the different antagonistic yeasts evaluated, only Metschnikowia sp. strains were equally effective reducing A. alternata growth and mycotoxin at different temperatures underlining the importance of considering environmental factors in the selection of the antagonists.


Assuntos
Antibiose , Micotoxinas , Vitis , Leveduras/fisiologia , Alternaria/patogenicidade , Frutas/microbiologia , Hanseniaspora , Lactonas/análise , Micotoxinas/análise , Saccharomycetales , Vitis/microbiologia , Vinho
10.
Methods Mol Biol ; 2232: 193-208, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33161549

RESUMO

Studying the plant phyllosphere to understand inhibition patterns to the growth of fungal foliar pathogens by using the Arabidopsis thaliana pathosystem offers unique opportunities for evaluating strategies for plant protection against foliar diseases. The wide array of bacteria inhabiting the phylloplane of plants has been researched to a much lesser extent compared to the bacteria in the rhizosphere. This difference is especially evident as bacteria derived from the aerial section of plants are rarely used in formulations of foliage sprays against pathogens and pests. In this chapter we outline easy and reliable methods for sample preparation to profile phyllosphere bacteria using high throughput amplicon sequencing and isolate/characterize potentially beneficial phyllosphere bacteria from Arabidopsis thaliana that inhibit in vitro the growth of foliar pathogens such as Alternaria brassicicola. The use of the described methods for profiling and screening phyllosphere bacteria may provide tangible progress on the discovery of new potential biological control agents against agriculturally important pathogens.


Assuntos
Alternaria/patogenicidade , Arabidopsis/microbiologia , Doenças das Plantas/microbiologia , Manejo de Espécimes/métodos , Arabidopsis/genética , Bactérias/patogenicidade , Resistência à Doença/genética , Fungos/patogenicidade , Doenças das Plantas/genética , Folhas de Planta/genética , Folhas de Planta/microbiologia , Rizosfera
11.
PLoS One ; 15(12): e0242545, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33259527

RESUMO

Heavy losses by dark leaf spot disease in oilseed Brassica have incited research towards identifying sources of genetic tolerance against causal pathogen, Alternaria brassicicola. Several morpho-molecular parameters were evaluated to test the performance of field mustard and rapeseed genotypes under artificial inoculation with this pathogen. During Brassica-Alternaria interaction, physio-biochemical defense response was witnessed in tolerant genotypes. Two tolerant genotypes (one for field mustard and one for rapeseed), i.e., EC250407 and EC1494 were identified. However, necrotic lesions were more prominent in susceptible genotypes with minimum chlorophyll (chlorophyll a, chlorophyll b and total chlorophyll) and carotenoids contents. Contrary to photosynthetic pigments, increase in total soluble protein (TSP) contents was observed with disease progression in susceptible genotypes. Tolerant genotypes of field mustard and rapeseed displayed remarkable increase in the activities of redox enzyme in infected leaves with least yield loss (6.47% and 5.74%) and disease severity index (DSI) of 2.9 and 2.1, respectively. However, yield/plant showed close association with other morpho-yield parameters, photosynthetic pigments and redox enzymes (superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD)) activities except silique length and TSP. Based on the results of morpho-biochemical analyses, redox enzymes and morphological parameters; their interplay is proposed to determine the tolerance outcome of the Brassica-A. brassicicola interaction.


Assuntos
Alternaria/patogenicidade , Brassica napus/genética , Brassica rapa/genética , Brassicaceae/genética , Antioxidantes/metabolismo , Brassica napus/crescimento & desenvolvimento , Brassicaceae/crescimento & desenvolvimento , Brassicaceae/parasitologia , Carotenoides , Catalase/genética , Clorofila/genética , Clorofila A/genética , Resistência à Doença/genética , Genótipo , Oxirredução , Fotossíntese , Doenças das Plantas/genética , Doenças das Plantas/parasitologia , Superóxido Dismutase/genética
12.
Mol Plant Microbe Interact ; 33(12): 1405-1410, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33104446

RESUMO

The black mold Alternaria alternata causes dramatic losses in agriculture due to postharvest colonization and mycotoxin formation and is a weak pathogen on living plants. Fungal signaling processes are crucial for successful colonization of a host plant. Because the mitogen-activated protein kinase HogA is important for the expression of stress-associated genes, we tested a ∆hogA-deletion strain for pathogenicity. When conidia were used as inoculum, the ∆hogA-deletion strain was largely impaired in colonizing tomato and apple. In comparison, hyphae as inoculum colonized the fruit very well. Hence, HogA appears to be important only in the initial stages of plant colonization. A similar difference between conidial inoculum and hyphal inoculum was observed on artificial medium in the presence of different stress agents. Whereas wild-type conidia adapted well to different stresses, the ∆hogA-deletion strain failed to grow under the same conditions. With hyphae as inoculum, the wild type and the ∆hogA-deletion strain grew in a very similar way. At the molecular level, we observed upregulation of several catalase (catA, -B, and -D) and superoxide dismutase (sodA, -B, and -E) genes in germlings but not in hyphae after exposure to 4 mM hydrogen peroxide. The upregulation required the high osmolarity glycerol (HOG) pathway. In contrast, in mycelia, catD, sodA, sodB, and sodE were upregulated upon stress in the absence of HogA. Several other stress-related genes behaved in a similar way.


Assuntos
Alternaria , Proteínas Fúngicas , Hifas , Transdução de Sinais , Esporos Fúngicos , Virulência , Alternaria/genética , Alternaria/patogenicidade , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Hifas/genética , Hifas/patogenicidade , Lycopersicon esculentum/microbiologia , Malus/microbiologia , Transdução de Sinais/fisiologia , Esporos Fúngicos/genética , Esporos Fúngicos/patogenicidade , Virulência/genética
13.
Microbiol Res ; 241: 126566, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33032167

RESUMO

The tangerine pathotype of Alternaria alternata affects many citrus cultivars, resulting in yield losses. The capability to produce the host-selective toxin and cell-wall-degrading enzymes and to mitigate toxic reactive oxygen species is crucial for A. alternata pathogenesis to citrus. Little is known about nutrient availability within citrus tissues to the fungal pathogen. In the present study, we assess the infectivity of a biotin deficiency mutant (ΔbioB) and a complementation strain (CP36) on citrus leaves to determine how biotin impacts A. alternata pathogenesis. Growth and sporulation of ΔbioB are highly dependent on biotin. ΔbioB retains its ability to acquire and transport biotin from the surrounding environment. Growth deficiency of ΔbioB can also be partially restored by the presence of oleic acid or Tween 20, suggesting the requirement of biotin in lipid metabolism. Experimental evidence indicates that de novo biotin biosynthesis is regulated by the NADPH oxidase, implicating in the production of H2O2, and is affected by the function of peroxisomes. Three genes involved in the biosynthesis of biotin are clustered and co-regulated by biotin indicating a transcriptional feedback loop activation. Infectivity assays using fungal mycelium reveal that ΔbioB cultured on medium without biotin fails to infect citrus leaves; co-inoculation with biotin fully restores infectivity. The CP36 strain re-expressing a functional copy of bioB displays wild-type growth, sporulation and virulence. Taken together, we conclude that the attainability or accessibility of biotin is extremely restricted in citrus cells. A. alternata must be able to synthesize biotin in order to utilize nutrients for growth, colonization and development within the host.


Assuntos
Alternaria/metabolismo , Alternaria/patogenicidade , Biotina/biossíntese , Citrus/microbiologia , Esporos Fúngicos/crescimento & desenvolvimento , Alternaria/genética , Biotina/deficiência , Biotina/genética , Metabolismo dos Lipídeos/fisiologia , NADPH Oxidases/metabolismo , Ácido Oleico/metabolismo , Peroxissomos/metabolismo , Doenças das Plantas/microbiologia , Polissorbatos/metabolismo , Espécies Reativas de Oxigênio/metabolismo
14.
Biol Aujourdhui ; 214(1-2): 55-61, 2020.
Artigo em Francês | MEDLINE | ID: mdl-32773030

RESUMO

Cherry tomato is very susceptible to fungal infections that can cause considerable damage in crops and during storage. Alternaria infection is one of the most common and dangerous alterations for this fruit. They are caused by Alternaria alternata or some other species belonging to the same genus. In this work, we tested the antifungal activity of methanol extracts from five plants harvested in the region of Jijel (Algeria) on A. alternata. The activity was first tested in vitro and then on greenhouse cherry tomato plants: extracts were applied to healthy plants before infection in order to test their preventive action, and after infection to determine whether they are able to knock out Alternaria. Results showed that Rosmarinus officinalis and Lavandula angustifolia extracts were the most active in vitro on A. alternata. Microscopic observations of the mold indicated that these extracts inhibited the dictyospores production. The antifungal activity tested on the plants grown in greenhouse revealed that R. officinalis extract still was the most active. Extracts of L. angustifolia and Punica granatum did not protect the plants from Alternaria infection, but provided a total cure at the end of the treatment. Extracts from Quercus suber and Eucalyptus globulus were the least active. They did not bestow any protection nor complete healing of the plants. Dictyospores counting on fruits at the end of the treatment confirmed the results obtained for the greenhouse crops.


Assuntos
Alternaria/efeitos dos fármacos , Alternariose/prevenção & controle , Lycopersicon esculentum/química , Extratos Vegetais/farmacologia , Agricultura/métodos , Alternaria/patogenicidade , Alternariose/microbiologia , Antifúngicos/química , Antifúngicos/farmacologia , Agentes de Controle Biológico/química , Agentes de Controle Biológico/farmacologia , Produtos Biológicos/farmacologia , Eucalyptus/efeitos dos fármacos , Eucalyptus/microbiologia , Frutas/química , Lavandula/efeitos dos fármacos , Lavandula/microbiologia , Lycopersicon esculentum/microbiologia , Metanol/química , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Extratos Vegetais/química , Romã (Fruta)/efeitos dos fármacos , Romã (Fruta)/microbiologia , Quercus/efeitos dos fármacos , Quercus/microbiologia , Rosmarinus/efeitos dos fármacos , Rosmarinus/microbiologia
15.
Microbiol Res ; 240: 126537, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32739584

RESUMO

Subtilisin-like serine protease secreted by pathogenic fungi can facilitate the infection and acquisition of nutrients. Functions of subtilisin-like serine proteases in the phytopathogenic fungus Alternaria alternata remains unknown. In the current study, 15 subtilisin-like serine proteases were individually deleted in the citrus fungal pathogen A. alternata. Only one, designated AaPrb1, was found to be required for A. alternata pathogenesis. The AaPrb1 deficiency strain (ΔAaprb1) reduced growth, conidiation, the formation of aerial hyphae, protease production, and virulence on citrus leaves. However, biochemical analyses and bioassays revealed that ΔAaprb1 plays no role in the production of ACT toxin. Through Y2H assays, Aaprb1 was found to interact with Aapep4, a vacuole-localized proteinase A in A. alternata. Furthermore, silencing AaPep4 in A. alternata resulted in phenotypes similar with those of ΔAaprb1. Expression of AaPrb1 was found to be regulated by AaPep4. TEM showed that AaPrb1and AaPep4 were involved in the suppression of the degradation of autophagosomes. Deletion of the autophagy gene AaAtg8 in A. alternata decreased conidiation, the formation of aerial hyphae and pathogenicity similar to ΔAaprb1, implying that some phenotypes of ΔAaprb1 were due to the impairment of autophagy. Overall, this study expands our understanding of how A. alternata utilizes the subtilisin-like serine protease to achieve successful infection in the plant host.


Assuntos
Alternaria/enzimologia , Alternaria/patogenicidade , Autofagia/fisiologia , Citrus/microbiologia , Peptídeo Hidrolases/metabolismo , Doenças das Plantas/microbiologia , Alternaria/classificação , Alternaria/genética , Autofagia/genética , Proteínas Fúngicas/genética , Regulação Fúngica da Expressão Gênica , Genes Fúngicos/genética , Hifas , Mutagênese Sítio-Dirigida , Fenótipo , Doenças das Plantas/prevenção & controle , Folhas de Planta/microbiologia , Virulência
16.
Plant Physiol Biochem ; 155: 626-636, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32858425

RESUMO

Brassica genus comprises many prominent species valuable for human nutrition including vegetable crops and oilseed. Production of B. juncea is challenged by many abiotic and biotic stresses, Alternaria blight caused by a necrotrophic fungal pathogen Alternaria brassicae is one of the most prominent diseases of cruciferous crops including B. juncea. However, some closely related wild species like Sinapis alba and Camelina sativa exhibit a variable level of resistance towards the pathogen. Apart from the host resistance, intra-specific pathogen variability also influences disease severity to a larger extent. In this study, we identified and isolated two strains of A. brassicae viz ABS1 and ABS2 exhibiting morphological and pathological variability. These isolates were further used to artificially inoculate B. juncea and two of its wild relatives under in-vitro as well as in-vivo conditions to inspect their pathogenicity in a susceptible, a moderately resistant and a highly resistant host. virulent isolate (ABS2) was able to readily establish infection in all the three species whereas the less virulent isolate (ABS1) readily infected susceptible species B. juncea but delayed and mild infection was noticed in tolerant hosts. Variable physiological and molecular host response towards the differential level of virulence of pathogen were established with many confirmatory experiments like DAB staining study, Disease severity index and microscopic analysis. Real-time PCR results confirm that these two isolates induce a variable level of induction in genes PR1 and PDF1.2 within 48 h of the artificial inoculation in B. juncea and its wild relatives.


Assuntos
Alternaria/patogenicidade , Brassicaceae/microbiologia , Doenças das Plantas/microbiologia , Virulência , Brassicaceae/fisiologia , Resistência à Doença , Mostardeira/microbiologia , Mostardeira/fisiologia , Sinapis/microbiologia , Sinapis/fisiologia
17.
Mol Plant Pathol ; 21(10): 1337-1352, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32776683

RESUMO

The basal transcription factor II H (TFIIH) is a multicomponent complex. In the present study, we characterized a TFIIH subunit Tfb5 by analysing loss- and gain-of-function mutants to gain a better understanding of the molecular mechanisms underlying stress resistance and pathogenicity in the citrus fungal pathogen Alternaria alternata. Tfb5 deficiency mutants (ΔAatfb5) decreased sporulation and pigmentation, and were impaired in the maintenance of colony surface hydrophobicity and cell wall integrity. ΔAatfb5 increased sensitivity to ultraviolet light, DNA-damaging agents, and oxidants. The expression of Aatfb5 was up-regulated in the wild type upon infection in citrus leaves, implicating the requirement of Aatfb5 in fungal pathogenesis. Biochemical and virulence assays revealed that ΔAatfb5 was defective in toxin production and cellwall-degrading enzymes, and failed to induce necrotic lesions on detached citrus leaves. Aatfb5 fused with green fluorescent protein (GFP) was localized in the cytoplasm and nucleus and physically interacted with another subunit, Tfb2, based on yeast two-hybrid and co-immunoprecipitation analyses. Transcriptome and Antibiotics & Secondary Metabolite Analysis Shell (antiSMASH) analyses revealed the positive and negative roles of Aatfb5 in the production of various secondary metabolites and in the regulation of many metabolic and biosynthetic processes in A. alternata. Aatfb5 may play a negative role in oxidative phosphorylation and a positive role in peroxisome biosynthesis. Two cutinase-coding genes (AaCut2 and AaCut15) required for full virulence were down-regulated in ΔAatfb5. Overall, this study expands our understanding of how A. alternata uses the basal transcription factor to deal with stress and achieve successful infection in the plant host.


Assuntos
Alternaria/patogenicidade , Fatores de Elongação da Transcrição/genética , Alternaria/genética , Alternaria/metabolismo , Hidrolases de Éster Carboxílico/genética , Hidrolases de Éster Carboxílico/metabolismo , Citrus/microbiologia , Dano ao DNA , Proteínas Fúngicas/metabolismo , Perfilação da Expressão Gênica/métodos , Regulação Fúngica da Expressão Gênica , Mutação , Micotoxinas/metabolismo , Estresse Oxidativo/genética , Doenças das Plantas/microbiologia , Folhas de Planta/microbiologia , Metabolismo Secundário/genética , Estresse Fisiológico/genética , Fatores de Elongação da Transcrição/química , Fatores de Elongação da Transcrição/metabolismo , Transcriptoma , Virulência/genética
18.
Rev. cir. (Impr.) ; 72(4): 347-349, ago. 2020. ilus
Artigo em Espanhol | LILACS | ID: biblio-1138721

RESUMO

Resumen Introducción: Los hongos dematiáceos se caracterizan por la presencia de abundante melanina en su pared celular. Presentan una distribución mundial, siendo más comunes en climas tropicales y subtropicales. Producen infecciones cutáneas y subcutáneas, además de enfermedades alérgicas, neumonías, abscesos cerebrales o infecciones diseminadas. Caso Clínico: Presentamos el caso de un paciente con adenocarcinoma de recto intervenido quirúrgicamente con hallazgo incidental de divertículo de Meckel y en el cual en el estudio anatomopatológico reveló la presencia de un hongo dematiáceo


Introduction: Dematiaceous fungi are characterized by the presence of brown melanine or melanine like pigments in their cell wall. They are generally distributed worldwide, being more common in tropical and subtropical climates. The clinical syndromes are often cutaneous and subcutaneous infections, but can be also responsible of allergic diseases, pneumonias, cerebral abscesses or disseminated infections. Clinical Case: We present the case of a patient with a diagnosis of rectal adenocarcinoma intervening surgically and with an incidental finding of Meckel's Diverticulum. The anatomopathological study revealed the presence of a dematiaceous fungi.


Assuntos
Humanos , Masculino , Idoso , Diverticulite/cirurgia , Alternaria/patogenicidade , Divertículo Ileal/cirurgia , Colostomia/métodos
19.
Sci Rep ; 10(1): 10750, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32612111

RESUMO

Within several plant species, a high variation in the composition of particular defence metabolites can be found, forming distinct chemotypes. Such chemotypes show different effects on specialist and generalist plant enemies, whereby studies examining interactions with pathogens are underrepresented. We aimed to determine factors mediating the interaction of two chemotypes of Bunias orientalis (Brassicaceae) with two plant pathogenic fungal species of different host range, Alternaria brassicae (narrow host range = specialist) and Botrytis cinerea (broad host-range = generalist) using a combination of controlled bioassays. We found that the specialist, but not the generalist, was sensitive to differences between plant chemotypes in vivo and in vitro. The specialist fungus was more virulent (measured as leaf water loss) on one chemotype in vivo without differing in biomass produced during infection, while extracts from the same chemotype caused strong growth inhibition in that species in vitro. Furthermore, fractions of extracts from B. orientalis had divergent in vitro effects on the specialist versus the generalist, supporting presumed adaptations to certain compound classes. This study underlines the necessity to combine various experimental approaches to elucidate the complex interplay between plants and different pathogens.


Assuntos
Alternaria/patogenicidade , Botrytis/patogenicidade , Brassicaceae/microbiologia , Especificidade de Hospedeiro , Biomassa , Brassicaceae/química , Glucosinolatos/metabolismo , Doenças das Plantas/microbiologia , Folhas de Planta/química , Folhas de Planta/microbiologia , Especificidade da Espécie , Água
20.
Sci Rep ; 10(1): 10319, 2020 06 25.
Artigo em Inglês | MEDLINE | ID: mdl-32587286

RESUMO

The plant hormones salicylic acid (SA) and jasmonic acid (JA) regulate defense mechanisms capable of overcoming different plant stress conditions and constitute distinct but interconnected signaling pathways. Interestingly, several other molecules are reported to trigger stress-specific defense responses to biotic and abiotic stresses. In this study, we investigated the effect of 14 elicitors against diverse but pivotal types of abiotic (drought) and biotic (the chewing insect Ascia monuste, the hemibiotrophic bacterium Pseudomonas syringae DC 3000 and the necrotrophic fungus Alternaria alternata) stresses on broccoli and Arabidopsis. Among the main findings, broccoli pre-treated with SA and chitosan showed the highest drought stress recovery in a dose-dependent manner. Several molecules led to increased drought tolerance over a period of three weeks. The enhanced drought tolerance after triggering the SA pathway was associated with stomata control. Moreover, methyl jasmonate (MeJA) reduced A. monuste insect development and plant damage, but unexpectedly, other elicitors increased both parameters. GUS reporter assays indicated expression of the SA-dependent PR1 gene in plants treated with nine elicitors, whereas the JA-dependent LOX2 gene was only expressed upon MeJA treatment. Overall, elicitors capable of tackling drought and biotrophic pathogens mainly triggered the SA pathway, but adversely also induced systemic susceptibility to chewing insects. These findings provide directions for potential future in-depth characterization and utilization of elicitors and induced resistance in plant protection.


Assuntos
Arabidopsis/imunologia , Brassica/imunologia , Resistência à Doença , Doenças das Plantas/imunologia , Acetatos/metabolismo , Alternaria/patogenicidade , Animais , Arabidopsis/microbiologia , Arabidopsis/parasitologia , Brassica/microbiologia , Brassica/parasitologia , Borboletas/patogenicidade , Ciclopentanos/metabolismo , Secas , Regulação da Expressão Gênica de Plantas/imunologia , Oxilipinas/metabolismo , Doenças das Plantas/microbiologia , Doenças das Plantas/parasitologia , Proteínas de Plantas/metabolismo , Pseudomonas syringae/patogenicidade , Ácido Salicílico/metabolismo
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