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1.
Phytopathology ; 2021 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-33673752

RESUMO

Though V. dahliae is an asexually reproducing fungus, it is considered heterothallic owing to the presence of only one of the two mating-type idiomorphs (MAT1-1 or MAT1-2) in individual isolates. But sexual reproduction has never been observed either in nature or in the laboratory. All of the genomic information in the literature thus far has therefore come from studies on isolates carrying only the MAT1-2 idiomorph. Herein, we sequenced and compared high-quality reference genomes of MAT1-1 strain S011 and MAT1-2 strain S023 obtained from the same sunflower field. The two genomic sequences displayed high synteny, and encoded a similar number of genes, a similarity especially notable among pathogenicity-related genes. Homolog analysis between these two genomes revealed that 80% of encoded genes are highly conserved (95% identity and coverage), but only 20% of the single copy genes were identical. These novel genome resources will support the analysis of the structure and function of the two idiomorphs and provide valuable tools to elucidate the evolution and potential mechanisms of sexual reproduction in V. dahliae.

2.
Plant Cell Rep ; 40(4): 735-751, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33638657

RESUMO

KEY MESSAGE: GhMYB4 acts as a negative regulator in lignin biosynthesis, which results in alteration of cell wall integrity and activation of cotton defense response. Verticillium wilt of cotton (Gossypium hirsutum) caused by the soil-borne fungus Verticillium dahliae (V. dahliae) represents one of the most important constraints of cotton production worldwide. Mining of the genes involved in disease resistance and illuminating the molecular mechanisms that underlie this resistance is of great importance in cotton breeding programs. Defense-induced lignification in plants is necessary for innate immunity, and there are reports of a correlation between increased lignification and disease resistance. In this study, we present an example in cotton whereby plants with reduced lignin content also exhibit enhanced disease resistance. We identified a negative regulator of lignin synthesis, in cotton encoded in GhMYB4. Overexpression of GhMYB4 in cotton and Arabidopsis enhanced resistance to V. dahliae  with reduced lignin deposition. Moreover, GhMYB4 could bind the promoters of several genes involved in lignin synthesis, such as GhC4H-1, GhC4H-2, Gh4CL-4, and GhCAD-3, and impair their expression. The reduction of lignin content in GhMYB4-overexpressing cotton led to alterations of cell wall integrity (CWI) and released more oligogalacturonides (OGs) which may act as damage-associated molecular patterns (DAMPs) to stimulate plant defense responses. In support of this hypothesis, exogenous application with polygalacturonic acid (PGA) in cotton activated biosynthesis of jasmonic acid (JA) and JA-mediated defense against V. dahliae, similar to that described for cotton plants overexpressing GhMYB4. This study provides a new candidate gene for cotton disease-resistant breeding and an increased understanding of the relationship between lignin synthesis, OG release, and plant immunity.

3.
Front Plant Sci ; 11: 584997, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33250913

RESUMO

Soilborne plant pathogenic species in the fungal genus Verticillium cause destructive Verticillium wilt disease on economically important crops worldwide. Since R gene-mediated resistance is only effective against race 1 of V. dahliae, fortification of plant basal resistance along with cultural practices are essential to combat Verticillium wilts. Plant hormones involved in cell signaling impact defense responses and development, an understanding of which may provide useful solutions incorporating aspects of basal defense. In this review, we examine the current knowledge of the interplay between plant hormones, salicylic acid, jasmonic acid, ethylene, brassinosteroids, cytokinin, gibberellic acid, auxin, and nitric oxide, and the defense responses and signaling pathways that contribute to resistance and susceptibility in Verticillium-host interactions. Though we make connections where possible to non-model systems, the emphasis is placed on Arabidopsis-V. dahliae and V. longisporum interactions since much of the research on this interplay is focused on these systems. An understanding of hormone signaling in Verticillium-host interactions will help to determine the molecular basis of Verticillium wilt progression in the host and potentially provide insight on alternative approaches for disease management.

4.
Mol Plant Microbe Interact ; 33(11): 1265-1269, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32967552

RESUMO

Verticillium dahliae is a widespread fungal pathogen that causes Verticillium wilt on many economically important crops and ornamentals worldwide. Populations of V. dahliae have been divided into two distinct races based upon differential host responses in tomato and lettuce. Recently, the contemporary race 2 isolates were further divided into an additional race in tomato. Herein, we provide a high-quality reference genome for the race 1 strain VdLs.16 isolated from lettuce in California, U.S.A. This resource will contribute to ongoing research that aims to elucidate the genetic basis of V. dahliae pathogenicity and population genomic diversity.


Assuntos
Genoma Fúngico , Alface/microbiologia , Doenças das Plantas/microbiologia , Verticillium , Verticillium/genética , Virulência
5.
Mol Plant Pathol ; 21(11): 1451-1466, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32954659

RESUMO

Reactive oxygen/nitrogen species (ROS/RNS) play a fundamental role in plant-fungal interactions. How pathogenic fungi manipulate plant-derived ROS/RNS is of importance to the outcomes of these interactions. In this study, we explored the individual and combined contributions of three transcription factors, VdAtf1, VdYap1, and VdSkn7, in the response to ROS/RNS, microsclerotia formation, and virulence in the plant wilt pathogen Verticillium dahliae. We showed that VdYap1 is essential for ROS response. Additionally, mutants lacking any combination of the three genes shared significant hypersensitivity to nitro-oxidative stress like sodium nitroprusside dehydrate and double deletions lacking VdYap1 and VdAtf1 resulted in further increased sensitivity to ROS. Double deletion of VdAtf1 and VdSkn7 reduced melanin production and virulence while simultaneous lack of VdSkn7 and VdYap1 disrupted nitrogen metabolism and ROS resistance. Finally, comparison of transcriptional profiles of the respective single or double mutants in response to nitro-oxidative stress revealed that the three transcription factors are involved in denitrification of nitrated alkanes and lipids to protect against nitro-oxidative stress. Taken together, our results demonstrate convergent and distinctive functions of VdYap1, VdAtf1, and VdSkn7 in V. dahliae, and provide new data on their roles in response to ROS/RNS in fungi.

6.
Plant Dis ; 104(10): 2634-2641, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32787734

RESUMO

Downy mildew of spinach, caused by the obligate pathogen Peronospora effusa, remains the most important constraint in the major spinach production areas in the United States. This disease can potentially be initiated by asexual sporangiospores via "green bridges", sexually derived oospores from seed or soil, or dormant mycelium. However, the relative importance of the various types of primary inoculum is not well known. The ability of P. effusa sporangiospores to withstand abiotic stress, such as desiccation, and remain viable during short- and long-distance dispersal and the ability of oospores to germinate and infect seedlings remain unclear. Thus, the primary objectives of this research were to evaluate the impact of desiccation on sporangiospore survival and infection efficiency and examine occurrence, production, and germination of oospores. Results indicate that desiccation significantly reduces sporangiospore viability as well as infection potential. Leaf wetness duration of 4 h was needed for disease establishment by spinach downy mildew sporangiospores. Oospores were observed in leaves of numerous commercial spinach cultivars grown in California in 2018 and Arizona in 2019. Frequency of occurrence varied between the two states-years. The presence of opposite mating types in spinach production areas in the United States was demonstrated by pairing isolates in controlled crosses and producing oospores on detached leaves as well as intact plants. Information from the study of variables that affect sporangiospore viability and oospore production will help in improving our understanding of the epidemiology of this important pathogen, which has implications for management of spinach downy mildew.


Assuntos
Oomicetos , Peronospora , Arizona , Doenças das Plantas , Spinacia oleracea
7.
Sci Rep ; 10(1): 6719, 2020 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-32317662

RESUMO

Downy mildew of spinach is caused by the obligate oomycete pathogen, Peronospora effusa. The disease causes significant economic losses, especially in the organic sector of the industry where the use of synthetic fungicides is not permitted for disease control. New pathotypes of this pathogen are increasingly reported which are capable of breaking resistance. In this study, we took advantage of new spinach genome resources to conduct RNA-seq analyses of transcriptomic changes in leaf tissue of resistant and susceptible spinach cultivars Solomon and Viroflay, respectively, at an early stage of pathogen establishment (48 hours post inoculation, hpi) to a late stage of symptom expression and pathogen sporulation (168 hpi). Fold change differences in gene expression were recorded between the two cultivars to identify candidate genes for resistance. In Solomon, the hypersensitive inducible genes such as pathogenesis-related gene PR-1, glutathione-S-transferase, phospholipid hydroperoxide glutathione peroxidase and peroxidase were significantly up-regulated uniquely at 48 hpi and genes involved in zinc finger CCCH protein, glycosyltransferase, 1-aminocyclopropane-1-carboxylate oxidase homologs, receptor-like protein kinases were expressed at 48 hpi through 168 hpi. The types of genes significantly up-regulated in Solomon in response to the pathogen suggests that salicylic acid and ethylene signaling pathways mediate resistance. Furthermore, many genes involved in the flavonoid and phenylpropanoid pathways were highly expressed in Viroflay compared to Solomon at 168 hpi. As anticipated, an abundance of significantly down-regulated genes was apparent at 168 hpi, reflecting symptom development and sporulation in cultivar Viroflay, but not at 48 hpi. In the pathogen, genes encoding RxLR-type effectors were expressed during early colonization of cultivar Viroflay while crinkler-type effector genes were expressed at the late stage of the colonization. Our results provide insights on gene expression in resistant and susceptible spinach-P. effusa interactions, which can guide future studies to assess candidate genes necessary for downy mildew resistance in spinach.


Assuntos
Resistência à Doença/genética , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Peronospora/fisiologia , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Spinacia oleracea/genética , Spinacia oleracea/microbiologia , Suscetibilidade a Doenças , Ontologia Genética , Genoma de Planta , Polimorfismo de Nucleotídeo Único/genética , Propanóis/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transcriptoma/genética
8.
Mol Plant Pathol ; 21(5): 667-685, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32314529

RESUMO

Secreted small cysteine-rich proteins (SCPs) play a critical role in modulating host immunity in plant-pathogen interactions. Bioinformatic analyses showed that the fungal pathogen Verticillium dahliae encodes more than 100 VdSCPs, but their roles in host-pathogen interactions have not been fully characterized. Transient expression of 123 VdSCP-encoding genes in Nicotiana benthamiana identified three candidate genes involved in host-pathogen interactions. The expression of these three proteins, VdSCP27, VdSCP113, and VdSCP126, in N. benthamiana resulted in cell death accompanied by a reactive oxygen species burst, callose deposition, and induction of defence genes. The three VdSCPs mainly localized to the periphery of the cell. BAK1 and SOBIR1 (associated with receptor-like protein) were required for the immunity triggered by these three VdSCPs in N. benthamiana. Site-directed mutagenesis showed that cysteine residues that form disulphide bonds are essential for the functioning of VdSCP126, but not VdSCP27 and VdSCP113. VdSCP27, VdSCP113, and VdSCP126 individually are not essential for V. dahliae infection of N. benthamiana and Gossypium hirsutum, although there was a significant reduction of virulence on N. benthamiana and G. hirsutum when inoculated with the VdSCP27/VdSCP126 double deletion strain. These results illustrate that the SCPs play a critical role in the V. dahliae-plant interaction via an intrinsic virulence function and suppress immunity following infection.

9.
New Phytol ; 226(5): 1461-1479, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32040203

RESUMO

The fungus Verticillium dahliae causes vascular wilt disease on hundreds of plant species. Homologs of the bZIP transcription factor Atf1 are required for virulence in most pathogenic fungi, but the molecular basis for their involvement is largely unknown. We performed targeted gene deletion, expression analysis, biochemistry and pathogenicity assays to demonstrate that VdAtf1 governs pathogenesis via the regulation of nitrosative resistance and nitrogen metabolism in V. dahliae. VdAtf1 controls pathogenesis via the regulation of nitric oxide (NO) resistance and inorganic nitrogen metabolism rather than oxidative resistance and is important for penetration peg formation in V. dahliae. VdAtf1 affects ammonium and nitrate assimilation in response to various nitrogen sources. VdAtf1 may be involved in regulating the expression of VdNut1. VdAtf1 responds to NO stress by strengthening the fungal cell wall, and by causing over-accumulation of methylglyoxal and glycerol, which in turn impacts NO detoxification. We also verified that the VdAtf1 ortholog in Fusarium graminearum mediates nitrogen metabolism, suggesting conservation of this function in related plant pathogenic fungi. Our findings revealed new functions of VdAtf1 in pathogenesis, response to nitrosative stress and nitrogen metabolism in V. dahliae. The results provide novel insights into the regulatory mechanisms of the transcription factor VdAtf1 in virulence.

10.
Mol Plant Microbe Interact ; 33(5): 754-766, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32065029

RESUMO

SENESCENCE-ASSOCIATED GENE 13 (SAG13) of Arabidopsis is a widely conserved gene of unknown function that has been extensively used as a marker of plant senescence. SAG13 induction occurs during plant cell death processes, including senescence and hypersensitive response, a type of programmed cell death that occurs in response to pathogens. This implies that SAG13 expression is regulated through at least two different signaling pathways affecting these two different processes. Our work highlights a contrasting role for SAG13 in regulating resistance against disease-causing biotrophic bacterial and necrotrophic fungal pathogens with contrasting infection strategies. We provide further evidence that SAG13 is not only induced during oxidative stress but also plays a role in protecting the plant against other stresses. SAG13 is also required for normal seed germination, seedling growth, and anthocyanin accumulation. The work presented here provides evidence for the role of SAG13 in regulating multiple plant processes including senescence, defense, seed germination, and abiotic stress responses. SAG13 is a valuable molecular marker for these processes and is conserved in multiple plant species, and this knowledge has important implications for crop improvement.


Assuntos
Oxirredutases do Álcool/genética , Proteínas de Arabidopsis/genética , Arabidopsis/fisiologia , Estresse Oxidativo , Doenças das Plantas/genética , Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Doenças das Plantas/microbiologia
11.
Mol Plant Microbe Interact ; 33(4): 565-568, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31958033

RESUMO

Verticillium dahliae is a widely distributed soilborne pathogen that causes vascular wilt in more than 200 plant species. Defoliating and nondefoliating symptoms caused by the disease that result in either the loss or retention of leaves in infected plants, respectively, in hosts such as cotton, olive, and okra, divide the causal agent into defoliating and nondefoliating pathotypes. Our goal in this current work was to generate genome resources for the defoliating strain XJ592 and the nondefoliating strain XJ511 of V. dahliae isolated from cotton in China.


Assuntos
Genoma Fúngico , Plantas , Verticillium , China , Genoma Fúngico/genética , Doenças das Plantas/microbiologia , Folhas de Planta/microbiologia , Plantas/microbiologia , Verticillium/genética
12.
Plant Dis ; 104(1): 82-93, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31738689

RESUMO

The lettuce downy mildew pathogen, Bremia lactucae, is an obligate oomycete that causes extensive produce losses. Initial chlorotic symptoms that severely reduce the market value of the produce are followed by the appearance of white, downy sporulation on the abaxial side of the leaves. These spores become airborne and disseminate the pathogen. Controlling lettuce downy mildew has relied on repeated fungicide applications to prevent outbreaks. However, in addition to direct economic costs, heterogeneity and rapid adaptation of this pathogen to repeatedly applied fungicides has led to the development of fungicide-insensitivity in the pathogen. We deployed a quantitative PCR assay-based detection method using a species-specific DNA target for B. lactucae coupled with a spore trap system to measure airborne B. lactucae spore loads within three commercial fields that each contained experimental plots, designated EXP1 to EXP3. Based upon these measurements, when the spore load in the air reached a critical level (8.548 sporangia per m3 air), we advised whether or not to apply fungicides on a weekly basis within EXP1 to EXP3. This approach saved three sprays in EXP1, and one spray each in EXP2 and EXP3 without a significant increase in disease incidence. The reduction in fungicide applications to manage downy mildew can decrease lettuce production costs while slowing the development of fungicide resistance in B. lactucae by eliminating unnecessary fungicide applications.


Assuntos
Agricultura , Microbiologia do Ar , Alface , Oomicetos , Reação em Cadeia da Polimerase , Esporos Fúngicos , Agricultura/métodos , Ar , Alface/microbiologia , Oomicetos/genética , Doenças das Plantas/microbiologia , Esporos Fúngicos/genética
13.
Environ Microbiol ; 21(12): 4852-4874, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31667948

RESUMO

Verticillium dahliae is a soil-borne fungus that causes vascular wilt on numerous plants worldwide. The fungus survives in the soil for up to 14 years by producing melanized microsclerotia. The protective function of melanin in abiotic stresses is well documented. Here, we found that the V. dahliae tetraspan transmembrane protein VdSho1, a homolog of the Saccharomyces cerevisiae Sho1, acts as an osmosensor, and is required for plant penetration and melanin biosynthesis. The deletion mutant ΔSho1 was incubated on a cellophane membrane substrate that mimics the plant epidermis, revealing that the penetration of ΔSho1 strain was reduced compared to the wild-type strain. Furthermore, VdSho1 regulates melanin biosynthesis by a signalling mechanism requiring a kinase-kinase signalling module of Vst50-Vst11-Vst7. Strains, ΔVst50, ΔVst7 and ΔVst11 also displayed defective penetration and melanin production like the ΔSho1 strain. Defects in penetration and melanin production in ΔSho1 were restored by overexpression of Vst50, suggesting that Vst50 lies downstream of VdSho1 in the regulatory pathway governing penetration and melanin biosynthesis. Data analyses revealed that the transmembrane portion of VdSho1 was essential for both membrane penetration and melanin production. This study demonstrates that Vst50-Vst11-Vst7 module regulates VdSho1-mediated plant penetration and melanin production in V. dahliae, contributing to virulence.


Assuntos
Proteínas Fúngicas/metabolismo , Gossypium/microbiologia , Melaninas/biossíntese , Quinases de Proteína Quinase Ativadas por Mitógeno/metabolismo , Doenças das Plantas/microbiologia , Verticillium/metabolismo , Proteínas Fúngicas/genética , Regulação Fúngica da Expressão Gênica , Quinases de Proteína Quinase Ativadas por Mitógeno/genética , Metabolismo Secundário , Deleção de Sequência , Transdução de Sinais , Verticillium/genética , Verticillium/patogenicidade , Virulência
14.
mSphere ; 4(4)2019 07 10.
Artigo em Inglês | MEDLINE | ID: mdl-31292234

RESUMO

Verticillium dahliae causes destructive vascular wilt diseases on more than 200 plant species, including economically important crops and ornamental trees worldwide. The melanized microsclerotia enable the fungus to survive for years in soil and are crucial for its disease cycle. Previously, we found that the VdPbs2-VdHog1 (V. dahliae Pbs2-V. dahliae Hog1) module plays key roles in microsclerotial formation, stress responses, and virulence in V. dahliae In this study, two mitogen-activated protein kinase kinase kinases (MAPKKKs) homologous to Ssk2p and Ste11p, which activate the Pbs2p-Hog1p module by phosphorylation in budding yeast, were identified in the genome of V. dahliae Both ΔVdSsk2 (V. dahliae Ssk2) and ΔVdSte11 strains showed severe defects in microsclerotial formation and melanin biosynthesis, but the relative importance of these two genes in microsclerotial development was different. Deletion of VdSsk2, but not VdSte11, affected responses to osmotic stress, fungicidal response, and cell wall stressors. The ΔVdSsk2 strain exhibited a significant reduction in virulence, while the ΔVdSte11 strain was nonpathogenic due to failure to penetrate and form hyphopodia. Phosphorylation assays demonstrated that VdSsk2, but not VdSte11, can phosphorylate VdHog1 in V. dahliae Moreover, VdCrz1, encoding a calcineurin-responsive zinc finger transcription factor and a key regulator of calcium signaling in fungi, was misregulated in the ΔVdSsk2, ΔVdPbs2, and ΔVdHog1 mutants.IMPORTANCE These data provide insights into the distinctive functions of VdSsk2 and VdSte11 in pathogenicity, stress adaptation, and microsclerotial formation in V. dahliae.


Assuntos
Adaptação Fisiológica , Proteínas Fúngicas/genética , MAP Quinase Quinase Quinases/genética , Estresse Fisiológico , Verticillium/genética , Verticillium/patogenicidade , Regulação Fúngica da Expressão Gênica , Doenças das Plantas/microbiologia , Virulência , Fatores de Virulência/genética
15.
J Proteomics ; 207: 103449, 2019 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-31323424

RESUMO

Verticillium dahliae colonizes vascular tissue and causes vascular discoloration in susceptible hosts. Two well-defined races exist in V. dahliae populations from tomato and lettuce. In this study, proteins and metabolites obtained from stems of race 1-incompatible (Beefsteak) and -compatible (Early Pak) tomato cultivars were characterized. A total of 814 and 584 proteins in Beefsteak; and 456 and 637 proteins in Early Pak were identified in stem extracts of plants inoculated with races 1 and 2, respectively. A significant number of defense-related proteins were expressed in each tomato-V. dahliae interaction, as anticipated. However, phenylalanine ammonia-lyase (PAL), an important defense-associated enzyme of the phenylpropanoid pathway, in addition to remorin 1, NAD-dependent epimerase/dehydratase, and polyphenol oxidase were uniquely expressed in the incompatible interaction. Compared with the uninoculated control, significant overexpression of gene ontology terms associated with lignin biosynthesis, phenylpropanoid pathway and carbohydrate methylation were identified exclusively in the incompatible interaction. Phenolic compounds known to be involved in plant defense mechanisms were at higher levels in the incompatible relative to the compatible interactions. Based on our findings, PAL and enzymes involved defense-related secondary metabolism and the strengthening of cell walls is likely critical to confer resistance to race 1 of V. dahliae in tomato. SIGNIFICANCE: Verticillium dahliae, a soilborne fungal pathogen and a widely distributed fungal pathogen, colonizes vascular tissue and causes vascular discoloration in roots and stems, leaf wilting, and death of susceptible plant hosts. It causes billions of dollars in annual crop losses all over the world. The study focused on the proteomic and metabalomic of V. dahliae interactions (incompatible with Beefsteak and compatible with Early Pak tomato cultivars). Based on our findings, PAL and enzymes involved defense-related secondary metabolism and the strengthening of cell walls is likely critical to confer resistance to race 1 of V. dahliae in tomato.


Assuntos
Lycopersicon esculentum , Metaboloma , Doenças das Plantas/microbiologia , Proteínas de Plantas/metabolismo , Proteoma/metabolismo , Verticillium/metabolismo , Lycopersicon esculentum/metabolismo , Lycopersicon esculentum/microbiologia
16.
Plant Sci ; 285: 200-213, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31203885

RESUMO

NONRACE-SPECIFIC DISEASE RESISTANCE (NDR1) is a widely characterized gene that plays a key role in defense against multiple bacterial, fungal, oomycete and nematode plant pathogens. NDR1 is required for activation of resistance by multiple NB and LRR-containing (NLR) protein immune sensors and contributes to basal defense. The role of NDR1 in positively regulating salicylic acid (SA)-mediated plant defense responses is well documented. However, ndr1-1 plants flower earlier and show accelerated development in comparison to wild type (WT) Arabidopsis plants, indicating that NDR1 is a negative regulator of flowering and growth. Exogenous application of gibberellic acid (GA) further accelerates the early flowering phenotype in ndr1-1 plants, while the GA biosynthesis inhibitor paclobutrazol attenuated the early flowering phenotype of ndr1-1, but not to WT levels, suggesting partial resistance to paclobutrazol and enhanced GA response in ndr1-1 plants. Mass spectroscopy analyses confirmed that ndr1-1 plants have 30-40% higher levels of GA3 and GA4, while expression of various GA metabolic genes and major flowering regulatory genes is also altered in the ndr1-1 mutant. Taken together this study provides evidence of crosstalk between the ndr1-1-mediated defense and GA-regulated developmental programs in plants.


Assuntos
Arabidopsis/genética , Flores/crescimento & desenvolvimento , Giberelinas/fisiologia , Reguladores de Crescimento de Planta/fisiologia , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/fisiologia , Proteínas de Arabidopsis/fisiologia , Resistência à Doença/genética , Resistência à Doença/fisiologia , Giberelinas/metabolismo , Mutação/genética , Doenças das Plantas/imunologia , Doenças das Plantas/microbiologia , Reguladores de Crescimento de Planta/metabolismo , Ácido Salicílico/metabolismo , Fatores de Transcrição/fisiologia , Transcriptoma , Verticillium
17.
Environ Microbiol ; 21(8): 2977-2996, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31136051

RESUMO

The fungus Verticillium dahliae causes vascular wilt disease on more than 200 plant species worldwide. This fungus can survive for years in soil as melanized microsclerotia. We found that VdCmr1, a transcription factor, is required for the melanin production and increased survival following UV irradiation in V. dahliae but not for microsclerotia production or virulence. Here, we provided evidence how VdCmr1 protects against high temperature (HT) and UV irradiation in V. dahliae. The results indicate that VdCmr1 mediates entry to the diapause period in V. dahliae in response to HT and contributes to the expression of proteins to minimize protein misfolding and denaturation. VdCmr1 deletion results in the misregulation of DNA repair machinery, suggestive of reduced DNA repair capacity following UV irradiation and in correlation with the low survival rate of UV-treated VdCmr1 mutants. We discovered a putative VdCmr1-dependent gene cluster associated with secondary metabolism and stress responses. We also functionally characterized two VdCmr1-responsive genes participating in HT and UV response. These results shed further light on the roles of VdCmr1 in protection from HT or UV irradiation, and the additional insights into the mechanisms of this protection may be useful to exploit for more effective disease control.


Assuntos
Proteínas Fúngicas/metabolismo , Temperatura Alta , Raios Ultravioleta , Verticillium/efeitos da radiação , Proteínas Fúngicas/genética , Regulação Fúngica da Expressão Gênica/efeitos da radiação , Doenças das Plantas/microbiologia , Deleção de Sequência , Fatores de Transcrição/genética , Verticillium/genética , Virulência/genética
18.
Plant Dis ; 103(5): 791-803, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30939071

RESUMO

Downy mildew on spinach is caused by Peronospora effusa, an oomycete pathogen that poses a challenge to spinach production worldwide, especially in organic production. Following infection, P. effusa produces abundant amounts of asexual sporangia. Sporangia become windborne and initiate new infections locally or distantly, leading to widespread epidemics. Oospores produced from the union of opposite mating types have been observed within infected leaves and seeds and may remain viable for many years. Sexual reproduction increases the genetic diversity of P. effusa through sexual recombination, and thus, the movement of oospores on seed has likely fueled the rapid explosion of new pathotypes in different regions of the world over the past 20 years. This review summarizes recent advances in spinach downy mildew research, especially in light of the findings of oospores in contemporary commercial spinach seed lots as well as their germination. Knowledge of the role of the oospores and other aspects of the disease cycle can directly translate into new and effective disease management strategies.


Assuntos
Peronospora , Doenças das Plantas , Spinacia oleracea , Peronospora/fisiologia , Doenças das Plantas/prevenção & controle , Folhas de Planta/microbiologia , Spinacia oleracea/microbiologia
19.
Mol Plant Pathol ; 20(6): 857-876, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30957942

RESUMO

Improving genetic resistance is a preferred method to manage Verticillium wilt of cotton and other hosts. Identifying host resistance is difficult because of the dearth of resistance genes against this pathogen. Previously, a novel candidate gene involved in Verticillium wilt resistance was identified by a genome-wide association study using a panel of Gossypium hirsutum accessions. In this study, we cloned the candidate resistance gene from cotton that encodes a protein sharing homology with the TIR-NBS-LRR receptor-like defence protein DSC1 in Arabidopsis thaliana (hereafter named GhDSC1). GhDSC1 expressed at higher levels in response to Verticillium wilt and jasmonic acid (JA) treatment in resistant cotton cultivars as compared to susceptible cultivars and its product was localized to nucleus. The transfer of GhDSC1 to Arabidopsis conferred Verticillium resistance in an A. thaliana dsc1 mutant. This resistance response was associated with reactive oxygen species (ROS) accumulation and increased expression of JA-signalling-related genes. Furthermore, the expression of GhDSC1 in response to Verticillium wilt and JA signalling in A. thaliana displayed expression patterns similar to GhCAMTA3 in cotton under identical conditions, suggesting a coordinated DSC1 and CAMTA3 response in A. thaliana to Verticillium wilt. Analyses of GhDSC1 sequence polymorphism revealed a single nucleotide polymorphism (SNP) difference between resistant and susceptible cotton accessions, within the P-loop motif encoded by GhDSC1. This SNP difference causes ineffective activation of defence response in susceptible cultivars. These results demonstrated that GhDSC1 confers Verticillium resistance in the model plant system of A. thaliana, and therefore represents a suitable candidate for the genetic engineering of Verticillium wilt resistance in cotton.


Assuntos
Gossypium/metabolismo , Gossypium/microbiologia , Doenças das Plantas/microbiologia , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/microbiologia , Verticillium/patogenicidade , Arabidopsis/genética , Arabidopsis/metabolismo , Arabidopsis/microbiologia , Resistência à Doença/fisiologia , Regulação da Expressão Gênica de Plantas/fisiologia , Estudo de Associação Genômica Ampla , Gossypium/genética , Doenças das Plantas/genética , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas/genética
20.
New Phytol ; 222(2): 1012-1029, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30609067

RESUMO

Verticillium dahliae is a broad host-range pathogen that causes vascular wilts in plants. Interactions between three hosts and specific V. dahliae genotypes result in severe defoliation. The underlying mechanisms of defoliation are unresolved. Genome resequencing, gene deletion and complementation, gene expression analysis, sequence divergence, defoliating phenotype identification, virulence analysis, and quantification of V. dahliae secondary metabolites were performed. Population genomics previously revealed that G-LSR2 was horizontally transferred from the fungus Fusarium oxysporum f. sp. vasinfectum to V. dahliae and is exclusively found in the genomes of defoliating (D) strains. Deletion of seven genes within G-LSR2, designated as VdDf genes, produced the nondefoliation phenotype on cotton, olive, and okra but complementation of two genes restored the defoliation phenotype. Genes VdDf5 and VdDf6 associated with defoliation shared homology with polyketide synthases involved in secondary metabolism, whereas VdDf7 shared homology with proteins involved in the biosynthesis of N-lauroylethanolamine (N-acylethanolamine (NAE) 12:0), a compound that induces defoliation. NAE overbiosynthesis by D strains also appears to disrupt NAE metabolism in cotton by inducing overexpression of fatty acid amide hydrolase. The VdDfs modulate the synthesis and overproduction of secondary metabolites, such as NAE 12:0, that cause defoliation either by altering abscisic acid sensitivity, hormone disruption, or sensitivity to the pathogen.


Assuntos
Genômica , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Verticillium/genética , Verticillium/patogenicidade , Sequência de Bases , Etanolaminas/metabolismo , Genes Fúngicos , Variação Genética , Genoma Fúngico , Gossypium/genética , Ácidos Láuricos/metabolismo , Modelos Biológicos , Família Multigênica , Fenótipo , Metabolismo Secundário/genética
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