Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 21
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Fungal Biol ; 125(7): 541-550, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34140150

RESUMO

Continuous passaging in vitro can lead to the accumulation of changes in DNA sequence that potentially affect the properties of microbes, making them different from the original isolates. The identification of such genetic alterations is rare in fungi. A set of insertional mutants in the plant pathogenic fungus Leptosphaeria maculans, all derived from the same transformation experiment, had independent Agrobacterium T-DNA insertions and reduced pathogenicity on canola (Brassica napus). None of the insertions co-segregated in progeny from crosses with the reduction in pathogenicity. Genome sequences of three strains were analysed, and a mutation identified in a gene (ptf1, for pathogenicity-associated transcription factor 1) encoding a putative Zn2(II)Cys6 transcription factor. Homologs are found in other ascomycetes, and are required for pathogenicity by Fusarium graminearum, Fusarium oxysporum and Magnaporthe oryzae. The mutation in the L. maculans ptf1 gene co-segregates in progeny from crosses with the reduction in pathogenicity, a strain with an independent mutant allele isolated using CRISPR-Cas9 editing has reduced pathogenicity, and addition of wild type copies of the gene restores pathogenicity. Thus, this work defines a base pair substitution that occurred during in vitro passaging of a fungus that contributed to an attenuation of pathogenicity.


Assuntos
Leptosphaeria , Fatores de Transcrição , Ascomicetos/genética , Fusarium/genética , Leptosphaeria/genética , Leptosphaeria/patogenicidade , Doenças das Plantas/microbiologia , Fatores de Transcrição/genética , Virulência/genética
2.
PLoS One ; 16(6): e0252333, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34111151

RESUMO

Sirodesmin, the major secondary metabolite produced by the plant pathogenic fungus Leptosphaeria maculans in vitro, has been linked to disease on Brassica species since the 1970s, and yet its role has remained ambiguous. Re-examination of gene expression data revealed that all previously described genes and two newly identified genes within the sir gene cluster in the genome are down-regulated during the crucial early establishment stages of blackleg disease on Brassica napus. To test if this is a strategy employed by the fungus to avoid damage to and then detection by the host plant during the L. maculans asymptomatic biotrophic phase, sirodesmin was produced constitutively by overexpressing the sirZ gene encoding the transcription factor that coordinates the regulation of the other genes in the sir cluster. The sirZ over-expression strains had a major reduction in pathogenicity. Mutation of the over-expression construct restored pathogenicity. However, mutation of two genes, sirP and sirG, required for specific steps in the sirodesmin biosynthesis pathway, in the sirZ over-expression background resulted in strains that were unable to synthesize sirodesmin, yet were still non-pathogenic. Elucidating the basis for this pathogenicity defect or finding ways to overexpress sirZ during disease may provide new strategies for the control of blackleg disease.


Assuntos
Proteínas Fúngicas/metabolismo , Regulação Fúngica da Expressão Gênica , Leptosphaeria/metabolismo , Leptosphaeria/patogenicidade , Fatores de Transcrição/metabolismo , Leptosphaeria/genética , Piperazinas/metabolismo , Virulência
3.
Theor Appl Genet ; 134(10): 3123-3145, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34104999

RESUMO

KEY MESSAGE: Quantitative resistance (QR) loci discovered through genetic and genomic analyses are abundant in the Brassica napus genome, providing an opportunity for their utilization in enhancing blackleg resistance. Quantitative resistance (QR) has long been utilized to manage blackleg in Brassica napus (canola, oilseed rape), even before major resistance genes (R-genes) were extensively explored in breeding programmes. In contrast to R-gene-mediated qualitative resistance, QR reduces blackleg symptoms rather than completely eliminating the disease. As a polygenic trait, QR is controlled by numerous genes with modest effects, which exerts less pressure on the pathogen to evolve; hence, its effectiveness is more durable compared to R-gene-mediated resistance. Furthermore, combining QR with major R-genes has been shown to enhance resistance against diseases in important crops, including oilseed rape. For these reasons, there has been a renewed interest among breeders in utilizing QR in crop improvement. However, the mechanisms governing QR are largely unknown, limiting its deployment. Advances in genomics are facilitating the dissection of the genetic and molecular underpinnings of QR, resulting in the discovery of several loci and genes that can be potentially deployed to enhance blackleg resistance. Here, we summarize the efforts undertaken to identify blackleg QR loci in oilseed rape using linkage and association analysis. We update the knowledge on the possible mechanisms governing QR and the advances in searching for the underlying genes. Lastly, we lay out strategies to accelerate the genetic improvement of blackleg QR in oilseed rape using improved phenotyping approaches and genomic prediction tools.


Assuntos
Brassica napus/genética , Mapeamento Cromossômico/métodos , Cromossomos de Plantas/genética , Resistência à Doença/imunologia , Leptosphaeria/fisiologia , Doenças das Plantas/imunologia , Locos de Características Quantitativas , Brassica napus/crescimento & desenvolvimento , Brassica napus/microbiologia , Resistência à Doença/genética , Genes de Plantas , Fenótipo , Melhoramento Vegetal , Doenças das Plantas/genética , Doenças das Plantas/microbiologia
4.
Int J Mol Sci ; 22(9)2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-34062819

RESUMO

An oxidative burst is an early response of plants to various biotic/abiotic stresses. In plant-microbe interactions, the plant body can induce oxidative burst to activate various defense mechanisms to combat phytopathogens. A localized oxidative burst is also one of the typical behaviors during hypersensitive response (HR) caused by gene-for-gene interaction. In this study, the occurrence of oxidative burst and its signaling pathways was studied from different levels of disease severity (i.e., susceptible, intermediate, and resistant) in the B. napus-L. maculans pathosystem. Canola cotyledons with distinct levels of resistance exhibited differential regulation of the genes involved in reactive oxygen species (ROS) accumulation and responses. Histochemical assays were carried out to understand the patterns of H2O2 accumulation and cell death. Intermediate and resistant genotypes exhibited earlier accumulation of H2O2 and emergence of cell death around the inoculation origins. The observations also suggested that the cotyledons with stronger resistance were able to form a protective region of intensive oxidative bursts between the areas with and without hyphal intrusions to block further fungal advancement to the uninfected regions. The qPCR analysis suggested that different onset patterns of some marker genes in ROS accumulation/programmed cell death (PCD) such as RBOHD, MPK3 were associated with distinct levels of resistance from B. napus cultivars against L. maculans. The observations and datasets from this article indicated the distinct differences in ROS-related cellular behaviors and signaling between compatible and incompatible interactions.


Assuntos
Cotilédone/genética , Resistência à Doença/genética , Doenças das Plantas/genética , Explosão Respiratória/genética , Brassica napus/genética , Brassica napus/parasitologia , Morte Celular/genética , Cotilédone/parasitologia , Epistasia Genética , Genótipo , Peróxido de Hidrogênio/metabolismo , Leptosphaeria/genética , Leptosphaeria/patogenicidade , Doenças das Plantas/parasitologia , Proteínas de Plantas/genética , Transdução de Sinais/genética , Estresse Fisiológico/genética
5.
Int J Mol Sci ; 22(9)2021 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-33946839

RESUMO

Hormone signaling plays a pivotal role in plant-microbe interactions. There are three major phytohormones in plant defense: salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). The activation and trade-off of signaling between these three hormones likely determines the strength of plant defense in response to pathogens. Here, we describe the allocation of hormonal signaling in Brassica napus against the fungal pathogen Leptosphaeria maculans. Three B. napus genotypes (Westar, Surpass400, and 01-23-2-1) were inoculated with two L. maculans isolates (H75 8-1 and H77 7-2), subsequently exhibiting three levels of resistance: susceptible, intermediate, and resistant. Quantitative analyses suggest that the early activation of some SA-responsive genes, including WRKY70 and NPR1, contribute to an effective defense against L. maculans. The co-expression among factors responding to SA/ET/JA was also observed in the late stage of infection. The results of conjugated SA measurement also support that early SA activation plays a crucial role in durable resistance. Our results demonstrate the relationship between the onset patterns of certain hormone regulators and the effectiveness of the defense of B. napus against L. maculans.


Assuntos
Brassica napus/fisiologia , Ciclopentanos/metabolismo , Etilenos/metabolismo , Regulação da Expressão Gênica de Plantas , Interações Hospedeiro-Patógeno/fisiologia , Leptosphaeria/crescimento & desenvolvimento , Oxilipinas/metabolismo , Doenças das Plantas/microbiologia , Ácido Salicílico/metabolismo , Brassica napus/genética , Brassica napus/microbiologia , Cotilédone/metabolismo , Cotilédone/microbiologia , Resistência à Doença , Genes de Plantas , Genótipo , Interações Hospedeiro-Patógeno/genética , Hifas/ultraestrutura , Proteínas de Plantas/biossíntese , Proteínas de Plantas/genética , Transdução de Sinais , Fatores de Transcrição/fisiologia
6.
Chromosome Res ; 29(2): 219-236, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-34018080

RESUMO

Leptosphaeria maculans 'brassicae' (Lmb) and Leptosphaeria maculans 'lepidii' (Lml) are closely related phytopathogenic species that exhibit a large macrosynteny but contrasting genome structure. Lmb has more than 30% of repeats clustered in large repeat-rich regions, while the Lml genome has only a small amount of evenly distributed repeats. Repeat-rich regions of Lmb are enriched in effector genes, expressed during plant infection. The distinct genome structures of Lmb and Lml provide an excellent model for comparing the organization of pathogenicity genes in relation to the chromatin landscape in two closely related phytopathogenic fungi. Here, we performed chromatin immunoprecipitation (ChIP) during axenic culture, targeting histone modifications typical for heterochromatin or euchromatin, combined with transcriptomic analysis to analyze the influence of chromatin organization on gene expression. In both species, we found that facultative heterochromatin is enriched with genes lacking functional annotation, including numerous effector and species-specific genes. Notably, orthologous genes located in H3K27me3 domains are enriched with effector genes. Compared to other fungal species, including Lml, Lmb is distinct in having large H3K9me3 domains associated with repeat-rich regions that contain numerous species-specific effector genes. Discovery of these two distinctive heterochromatin landscapes now raises questions about their involvement in the regulation of pathogenicity, the dynamics of these domains during plant infection and the selective advantage to the fungus to host effector genes in H3K9me3 or H3K27me3 domains.


Assuntos
Ascomicetos , Brassica napus , Ascomicetos/genética , Brassica napus/genética , Genômica , Código das Histonas , Leptosphaeria
7.
BMC Biol ; 19(1): 55, 2021 03 23.
Artigo em Inglês | MEDLINE | ID: mdl-33757516

RESUMO

BACKGROUND: The fungus Leptosphaeria maculans has an exceptionally long and complex relationship with its host plant, Brassica napus, during which it switches between different lifestyles, including asymptomatic, biotrophic, necrotrophic, and saprotrophic stages. The fungus is also exemplary of "two-speed" genome organisms in the genome of which gene-rich and repeat-rich regions alternate. Except for a few stages of plant infection under controlled conditions, nothing is known about the genes mobilized by the fungus throughout its life cycle, which may last several years in the field. RESULTS: We performed RNA-seq on samples corresponding to all stages of the interaction of L. maculans with its host plant, either alive or dead (stem residues after harvest) in controlled conditions or in field experiments under natural inoculum pressure, over periods of time ranging from a few days to months or years. A total of 102 biological samples corresponding to 37 sets of conditions were analyzed. We show here that about 9% of the genes of this fungus are highly expressed during its interactions with its host plant. These genes are distributed into eight well-defined expression clusters, corresponding to specific infection lifestyles or to tissue-specific genes. All expression clusters are enriched in effector genes, and one cluster is specific to the saprophytic lifestyle on plant residues. One cluster, including genes known to be involved in the first phase of asymptomatic fungal growth in leaves, is re-used at each asymptomatic growth stage, regardless of the type of organ infected. The expression of the genes of this cluster is repeatedly turned on and off during infection. Whatever their expression profile, the genes of these clusters are enriched in heterochromatin regions associated with H3K9me3 or H3K27me3 repressive marks. These findings provide support for the hypothesis that part of the fungal genes involved in niche adaptation is located in heterochromatic regions of the genome, conferring an extreme plasticity of expression. CONCLUSION: This work opens up new avenues for plant disease control, by identifying stage-specific effectors that could be used as targets for the identification of novel durable disease resistance genes, or for the in-depth analysis of chromatin remodeling during plant infection, which could be manipulated to interfere with the global expression of effector genes at crucial stages of plant infection.


Assuntos
Brassica napus/microbiologia , Proteínas Fúngicas/genética , Interações Hospedeiro-Patógeno , Leptosphaeria/genética , Transcriptoma/fisiologia , Proteínas Fúngicas/metabolismo , Genes Fúngicos , Leptosphaeria/fisiologia , Doenças das Plantas/microbiologia
8.
Theor Appl Genet ; 134(7): 2035-2050, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33768283

RESUMO

KEY MESSAGE: One hundred and sixty-seven B. juncea varieties were genotyped on the 90K Brassica assay (42,914 SNPs), which led to the identification of sixteen candidate genes for Rlm6. Brassica species are at high risk of severe crop loss due to pathogens, especially Leptosphaeria maculans (the causal agent of blackleg). Brassica juncea (L.) Czern is an important germplasm resource for canola improvement, due to its good agronomic traits, such as heat and drought tolerance and high blackleg resistance. The present study is the first using genome-wide association studies to identify candidate genes for blackleg resistance in B. juncea based on genome-wide SNPs obtained from the Illumina Infinium 90 K Brassica SNP array. The verification of Rlm6 in B. juncea was performed through a cotyledon infection test. Genotyping 42,914 single nucleotide polymorphisms (SNPs) in a panel of 167 B. juncea lines revealed a total of seven SNPs significantly associated with Rlm6 on chromosomes A07 and B04 in B. juncea. Furthermore, 16 candidate Rlm6 genes were found in these regions, defined as nucleotide binding site leucine-rich-repeat (NLR), leucine-rich repeat RLK (LRR-RLK) and LRR-RLP genes. This study will give insights into the blackleg resistance in B. juncea and facilitate identification of functional blackleg resistance genes which can be used in Brassica breeding.


Assuntos
Resistência à Doença/genética , Leptosphaeria/patogenicidade , Mostardeira/genética , Doenças das Plantas/genética , Genes de Plantas , Estudos de Associação Genética , Genótipo , Mostardeira/microbiologia , Doenças das Plantas/microbiologia , Polimorfismo de Nucleotídeo Único
9.
Sci Rep ; 11(1): 4407, 2021 02 23.
Artigo em Inglês | MEDLINE | ID: mdl-33623070

RESUMO

Genetic resistance to blackleg (Leptosphaeria maculans, Lm) of canola (Brassica napus, Bn) has been extensively studied, but the mechanisms underlying the host-pathogen interaction are still not well understood. Here, a comparative transcriptome analysis was performed on a resistant doubled haploid Bn line carrying the resistance gene Rlm1 following inoculation with a virulent (avrLm1) or avirulent (AvrLm1) Lm isolate on cotyledons. A total of 6999 and 3015 differentially expressed genes (DEGs) were identified, respectively, in inoculated local tissues with compatible (susceptible) and incompatible (resistant) interactions. Functional enrichment analysis found several biological processes, including protein targeting to membrane, ribosome and negative regulation of programmed cell death, were over-represented exclusively among up-regulated DEGs in the resistant reaction, whereas significant enrichment of salicylic acid (SA) and jasmonic acid (JA) pathways observed for down-regulated DEGs occurred only in the susceptible reaction. A heat-map analysis showed that both biosynthesis and signaling of SA and JA were induced more significantly in the resistant reaction, implying that a threshold level of SA and JA signaling is required for the activation of Rlm1-mediated resistance. Co-expression network analysis revealed close correlation of a gene module with the resistance, involving DEGs regulating pathogen-associated molecular pattern recognition, JA signaling and transcriptional reprogramming. Substantially fewer DEGs were identified in mock-inoculated (control) cotyledons, relative to those in inoculated local tissues, including those involved in SA pathways potentially contributing to systemic acquired resistance (SAR). Pre-inoculation of cotyledon with either an avirulent or virulent Lm isolate, however, failed to induce SAR on remote tissues of same plant despite elevated SA and PR1 protein. This study provides insights into the molecular mechanism of Rlm1-mediated resistance to blackleg.


Assuntos
Brassica napus/genética , Resistência à Doença , Leptosphaeria/patogenicidade , Transcriptoma , Brassica napus/parasitologia , Genes de Plantas
10.
Phytopathology ; 111(2): 281-292, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32804045

RESUMO

Proteins containing valine-glutamine (VQ) motifs play important roles in plant growth and development as well as in defense responses to both abiotic and biotic stresses. Blackleg disease, which is caused by Leptosphaeria maculans, is the most important disease in canola (Brassica napus) worldwide; however, the identification of Brassica napus VQs and their functions in response to blackleg disease have not yet been reported. In this study, we conducted a genome-wide identification and characterization of the VQ gene family in Brassica napus, including chromosome location, phylogenetic relations, gene structure, motif domain, synteny analysis, and cis-elements categorization of their promoter regions. To understand Brassica napus VQ gene function in response to blackleg disease, we overexpressed BnVQ7 (BnaA01g36880D, also known as the mitogen-activated protein kinase 4 substrate 1 [MKS1] gene) in a blackleg-susceptible canola variety, Westar. Overexpression of BnMKS1 in canola did not improve its resistance to blackleg disease at the seedling stage; however, transgenic canola plants overexpressing BnMKS1 displayed an enhanced resistance to L. maculans infection at the adult plant stage. Expression levels of downstream and defense marker genes in cotyledons increased significantly at the necrotrophic stage of L. maculans infection in the overexpression line of BnMKS1, suggesting that the salicylic acid- and jasmonic acid-mediated signaling pathways were both involved in the defense responses. Together, these results suggest that BnMKS1 might play an important role in defense against L. maculans.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.


Assuntos
Ascomicetos , Brassica napus , Brassica napus/genética , Glutamina , Leptosphaeria , Filogenia , Doenças das Plantas , Valina
11.
Plant Dis ; 105(5): 1440-1447, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33100150

RESUMO

Blackleg, caused by Leptosphaeria maculans, is a major disease of canola in Canada, Australia, and Europe. For effective deployment of resistant varieties and disease management, it is crucial to understand the population structure of L. maculans. In this study, we analyzed L. maculans isolates from commercial fields in western Canada from 2014 to 2016 for the presence and frequency of avirulence (Avr) genes. A total of 1,584 isolates were examined for the presence of Avr genes AvrLm1, AvrLm2, AvrLm3, AvrLm4, AvrLm6, AvrLm7, AvrLm9, AvrLepR1, AvrLepR2, and AvrLmS via a set of differential host genotypes carrying known resistance genes and a PCR assay. Several Avr genes showed a higher frequency in the pathogen population, such as AvrLm6 and AvrLm7, which were present in >90% of isolates, whereas AvrLm3, AvrLm9, and AvrLepR2 showed frequencies of <10%. A total of 189 races (different combinations of Avr genes) were detected, with Avr-2-4-6-7-S, Avr-1-4-6-7, and Avr-2-4-6-7 as the three predominant races. When the effect of crop rotation was assessed, only a 3-year rotation showed a significantly higher frequency of AvrLm2 relative to shorter rotations. This study provides the information for producers to select effective canola varieties for blackleg management and for breeders to deploy new R genes in disease resistance breeding in western Canada.


Assuntos
Ascomicetos , Ascomicetos/genética , Canadá , Frequência do Gene , Leptosphaeria , Melhoramento Vegetal , Doenças das Plantas
12.
Sci Rep ; 10(1): 14300, 2020 08 31.
Artigo em Inglês | MEDLINE | ID: mdl-32868838

RESUMO

Blackleg disease causes yield losses in canola (Brassica napus L.). To identify resistance genes and genomic regions, genome-wide association studies (GWAS) of 585 diverse winter and spring canola accessions were performed using imputed whole-genome sequence (WGS) and transcriptome genotype-by-sequencing (GBSt). Blackleg disease phenotypes were collected across three years in six trials. GWAS were performed in several ways and their respective power was judged by the number of significant single nucleotide polymorphisms (SNP), the false discovery rate (FDR), and the percentage of SNP that validated in additional field trials in two subsequent years. WGS GWAS with 1,234,708 million SNP detected a larger number of significant SNP, achieved a lower FDR and a higher validation rate than GBSt with 64,072 SNP. A meta-analysis combining survival and average internal infection resulted in lower FDR but also lower validation rates. The meta-analysis GWAS identified 79 genomic regions (674 SNP) conferring potential resistance to L. maculans. While several GWAS signals localised in regions of known Rlm genes, fifty-three new potential resistance regions were detected. Seventeen regions had underlying genes with putative functions related to disease defence or stress response in Arabidopsis thaliana. This study provides insight into the genetic architecture and potential molecular mechanisms underlying canola L. maculans resistance.


Assuntos
Brassica napus/genética , Resistência à Doença/genética , Leptosphaeria , Doenças das Plantas/microbiologia , Sequenciamento Completo do Genoma , Brassica napus/microbiologia , Genes de Plantas/genética , Genoma de Planta/genética , Estudo de Associação Genômica Ampla , Característica Quantitativa Herdável
13.
Mol Biol Rep ; 47(9): 7115-7123, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32897523

RESUMO

Blackleg, which is caused by the fungus Leptosphaeria maculans (L. maculans), is a major disease of canola in western Canada and worldwide. Long-term use of one source of resistance could cause the breakdown of its effectiveness. Therefore, appropriate use of R genes is very important, and knowledge about the distribution of avirulence genes is a prerequisite for effectively deploying resistance. Of the 14 avirulence genes identified in L. maculans, AvrLm5 and AvrLm9 were recognized as the two alleles of the same gene based on two single nucleotide polymorphisms, C85T and G164A/C. In this study, a specific marker was developed to identify AvrLm5 and AvrLm9 based on two single nucleotide polymorphisms, C85T and G164A/C, which are responsible for the function of AvrLm9. The specific marker can be used to discriminate the AvrLm9 from avrLm9 accurately in L. maculans isolates, which is consistent with inoculation tests in isolates without AvrLm4-7. This specific marker was used to screen 1229 isolates collected from fields in the years 2014 through 2016 in Manitoba. From 68 to 84% of the isolates were found to contain the AvrLm9 allele; while 4-7% of them were avirulent on the variety Goéland with Rlm9 loci. Furthermore, no isolates having both AvrLm9 and AvrLm7 were detected using a cotyledon test, while 67% to 84% of isolates contained both avirulence genes via PCR detection, implying suppression of AvrLm9 by AvrLm7. In addition, avirulence gene profiles of the other 10 avirulence alleles were examined with the 1229 isolates using cotyledon tests or PCR amplifications. Taken together, this research enables the fast identification of AvrLm5/9, provides the Avr genes' landscape of western Canada and elaborates the relationship between AvrLm9 and AvrLm7 using isolates from grower fields.


Assuntos
Alelos , Proteínas Fúngicas/genética , Leptosphaeria , Fatores de Virulência/genética , Brassica napus/microbiologia , Leptosphaeria/genética , Leptosphaeria/patogenicidade , Doenças das Plantas/genética , Doenças das Plantas/microbiologia
14.
Fungal Biol ; 124(10): 864-876, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32948274

RESUMO

To examine how host plant genotype, endophytic fungal species, and their interaction may affect growth and key chemical content and composition in an important orchid species, we assessed four Dendrobium catenatum cultivars co-cultured with three fungi previously isolated from D. catenatum. Fungal endophytes (Tulasnella sp., Leptosphaeria microscopica, and Guignardia sp.) specifically affected the growth and chemical composition of the four cultivars. Fungal infection significantly increased certain growth traits, especially mid-stem thickness, stem biomass, stem polysaccharide and ethanol-soluble extractive content, and leaf flavonoid and phenol content. Presence or abundance of some key chemical components was also altered by fungal treatment. These increases and alterations were highly dependent on the host genotype. The findings of this study contribute to our understanding of Dendrobium and endophytic fungi interactions, and provide vital information for improving the development and use of endophytic fungi in D. catenatum breeding.


Assuntos
Ascomicetos , Basidiomycota , Dendrobium/química , Leptosphaeria , Dendrobium/genética , Dendrobium/microbiologia , Endófitos , Genótipo
15.
Mol Plant Pathol ; 21(12): 1545-1558, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32975002

RESUMO

Oilseed rape residues are a crucial determinant of stem canker epidemiology as they support the sexual reproduction of the fungal pathogen Leptosphaeria maculans. The aim of this study was to characterize the impact of a resistance gene against L. maculans infection on residue microbial communities and to identify microorganisms interacting with this pathogen during residue degradation. We used near-isogenic lines to obtain healthy and infected host plants. The microbiome associated with the two types of plant residues was characterized by metabarcoding. A combination of linear discriminant analysis and ecological network analysis was used to compare the microbial communities and to identify microorganisms interacting with L. maculans. Fungal community structure differed between the two lines at harvest, but not subsequently, suggesting that the presence/absence of the resistance gene influences the microbiome at the base of the stem whilst the plant is alive, but that this does not necessarily lead to differential colonization of the residues by fungi. Direct interactions with other members of the community involved many fungal and bacterial amplicon sequence variants (ASVs). L. maculans appeared to play a minor role in networks, whereas one ASV affiliated to Plenodomus biglobosus (synonym Leptosphaeria biglobosa) from the Leptosphaeria species complex may be considered a keystone taxon in the networks at harvest. This approach could be used to identify and promote microorganisms with beneficial effects against residue-borne pathogens and, more broadly, to decipher the complex interactions between multispecies pathosystems and other microbial components in crop residues.


Assuntos
Brassica napus/genética , Resistência à Doença/genética , Interações Hospedeiro-Patógeno , Leptosphaeria/fisiologia , Microbiota , Doenças das Plantas/imunologia , Brassica napus/imunologia , Brassica napus/microbiologia , Doenças das Plantas/microbiologia
16.
Plant J ; 104(4): 892-900, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32794614

RESUMO

In plants, race-specific defence against microbial pathogens is facilitated by resistance (R) genes which correspond to specific pathogen avirulence genes. This study reports the cloning of a blackleg R gene from Brassica napus (canola), Rlm9, which encodes a wall-associated kinase-like (WAKL) protein, a newly discovered class of race-specific plant RLK resistance genes. Rlm9 provides race-specific resistance against isolates of Leptosphaeria maculans carrying the corresponding avirulence gene AvrLm5-9, representing only the second WAKL-type R gene described to date. The Rlm9 protein is predicted to be cell membrane-bound and while not conclusive, our work did not indicate direct interaction with AvrLm5-9. Rlm9 forms part of a distinct evolutionary family of RLK proteins in B. napus, and while little is yet known about WAKL function, the Brassica-Leptosphaeria pathosystem may prove to be a model system by which the mechanism of fungal avirulence protein recognition by WAKL-type R genes can be determined.


Assuntos
Brassica napus/genética , Resistência à Doença/genética , Leptosphaeria/patogenicidade , Doenças das Plantas/imunologia , Proteínas Quinases/metabolismo , Brassica napus/imunologia , Brassica napus/microbiologia , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Proteínas Quinases/genética , Especificidade da Espécie , Virulência
17.
Acta Biochim Pol ; 67(3): 295-301, 2020 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-32853518

RESUMO

Melanin occurrence in Plenodomus biglobosus was investigated using electron paramagnetic (spin) resonance (EPR, ESR) spectroscopy. The fungus was isolated from living and dead leaves of European ash (Fraxinus excelsior L.). Dark pigmentation of P. biglobosus mycelium in vitro, especially on the reverse, was observed. The black coloration intensified with the age of the culture and inspired us to check if the analyzed fungus species synthesizes melanin. Melanin contains unpaired electrons, thus, EPR spectroscopy was applied, as a specific technique, to verify its presence in P. biglobosus. The EPR spectrum of the mycelium showed a very strong melanin signal, revealing pheomelanin-like features. Thus, the black pigment of P. biglobosus was clearly identified as melanin. However, no melanin was detected in the apparently dark culture medium even when zinc (II) acetate was added to increase the sensitivity of detection. Pheomelanin has many unusual biological functions but it is not commonly found in fungi. Detection of this type of melanin in P. biglobosus, which can be both endophytic or pathogenic, suggests a closer examination of the potential role of this melanin in host-parasite interaction.


Assuntos
Leptosphaeria/metabolismo , Melaninas/análise , Melaninas/química , Micélio/metabolismo , Pigmentação/fisiologia , Cor , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Fraxinus/metabolismo , Interações Hospedeiro-Parasita/fisiologia , Leptosphaeria/isolamento & purificação , Micélio/isolamento & purificação , Polônia , Acetato de Zinco/química
18.
BMC Genomics ; 21(1): 501, 2020 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-32693834

RESUMO

BACKGROUND: The fungal pathogen Leptosphaeria maculans (Lm). causes blackleg disease on canola/rapeseed in many parts of the world. It is important to use resistant cultivars to manage the disease and minimize yield losses. In this study, twenty-two Lm isolates were used to identify resistance genes in a collection of 243 canola/rapeseed (Brassica napus L.) accessions from Canada and China. These Lm isolates carry different compliments of avirulence genes, and the investigation was based on a genome-wide association study (GWAS) and genotype-by-sequencing (GBS). RESULTS: Using the CROP-SNP pipeline, a total of 81,471 variants, including 78,632 SNPs and 2839 InDels, were identified. The GWAS was performed using TASSEL 5.0 with GLM + Q model. Thirty-two and 13 SNPs were identified from the Canadian and Chinese accessions, respectively, tightly associated with blackleg resistance with P values < 1 × 10- 4. These SNP loci were distributed on chromosomes A03, A05, A08, A09, C01, C04, C05, and C07, with the majority of them on A08 followed by A09 and A03. The significant SNPs identified on A08 were all located in a 2010-kb region and associated with resistance to 12 of the 22 Lm isolates. Furthermore, 25 resistance gene analogues (RGAs) were identified in these regions, including two nucleotide binding site (NBS) domain proteins, fourteen RLKs, three RLPs and six TM-CCs. These RGAs can be the potential candidate genes for blackleg resistance. CONCLUSION: This study provides insights into potentially new genomic regions for discovery of additional blackleg resistance genes. The identified regions associated with blackleg resistance in the germplasm collection may also contribute directly to the development of canola varieties with novel resistance genes against blackleg of canola.


Assuntos
Ascomicetos , Brassica napus , Ascomicetos/genética , Brassica napus/genética , Canadá , China , Estudo de Associação Genômica Ampla , Leptosphaeria , Doenças das Plantas/genética
19.
Res Microbiol ; 171(5-6): 174-184, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32540203

RESUMO

Auxins are hormones that regulate growth and development in plants. Besides plants, various microorganisms also produce auxins. Here we investigate whether and how the phytopathogenic fungus Leptosphaeria maculans biosynthesizes auxins. We characterized the auxin profile of in vitro grown L. maculans. The culture was further supplied with the auxin biosynthetic-precursors tryptophan and tryptamine and gene expression and phytohormone content was analyzed. L. maculans in vitro produced IAA (indole-3-acetic acid) as the predominant auxin metabolite. IAA production could be further stimulated by supplying precursors. Expression of indole-3-pyruvate decarboxylase LmIPDC2, tryptophan aminotransferase LmTAM1 and nitrilase LmNIT1 genes was mainly upregulated after adding tryptophan and correlated with IAA production, suggesting that these genes are the key components of auxin biosynthesis in L. maculans. Tryptamine acted as a potent inducer of IAA production, though a pathway independent of LmIPDC2/LmTAM1 may be involved. Despite L. maculans being a rich source of bioactive IAA, the auxin metabolic profile of host plant Brassica napus was not altered upon infection. Exogenous IAA inhibited the growth of L. maculans in vitro when supplied in high concentration. Altogether, we showed that L. maculans is capable of IAA production and we have identified biosynthetic genes that were responsive to tryptophan treatment.


Assuntos
Carboxiliases/genética , Ácidos Indolacéticos/metabolismo , Leptosphaeria/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Triptofano Transaminase/genética , Aminoidrolases/genética , Vias Biossintéticas , Brassica napus/microbiologia , Carboxiliases/metabolismo , Fungos/classificação , Fungos/genética , Fungos/metabolismo , Regulação Fúngica da Expressão Gênica , Ácidos Indolacéticos/farmacologia , Leptosphaeria/enzimologia , Leptosphaeria/genética , Leptosphaeria/crescimento & desenvolvimento , Filogenia , Transcrição Genética , Triptaminas/metabolismo , Triptaminas/farmacologia , Triptofano/metabolismo , Triptofano/farmacologia , Triptofano Transaminase/metabolismo , Regulação para Cima
20.
Fungal Genet Biol ; 136: 103320, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31863838

RESUMO

Leptosphaeria maculans is the causal agent of blackleg disease on Brassica napus. Determining the underlying functions of genes required for pathogenesis is essential for understanding the infection process. A chitin-binding protein (LmCBP1) was discovered as a pathogenicity factor for the infection of B. napus by L. maculans through gene knockout using the CRISPR-Cas9 system. Chitin-binding activity was demonstrated through a chitin-protein binding assay. A secreted signal peptide was detected using a yeast secreted-signal peptide trap assay. An increased expression level during the infection stage was also observed, suggesting that LmCBP1 is a secreted protein. The knockout mutants showed decreased infection on B. napus, with reduced pathogenicity on ten cultivars with/without diverse R genes. The mutants were more sensitive to H2O2 compared to wild type L. maculans isolate JN3. This study provides evidence of the virulence of a novel chitin-binding protein LmCBP1 on B. napus through mutants created via the CRISPR-Cas9 system.


Assuntos
Brassica napus/microbiologia , Proteínas de Transporte/genética , Proteínas Fúngicas/genética , Leptosphaeria/genética , Leptosphaeria/patogenicidade , Doenças das Plantas/microbiologia , Sistemas CRISPR-Cas , Proteínas de Transporte/metabolismo , Quitina/metabolismo , DNA Fúngico , Proteínas Fúngicas/metabolismo , Técnicas de Inativação de Genes , Interações Hospedeiro-Patógeno , Peróxido de Hidrogênio/farmacologia , Leptosphaeria/metabolismo , Filogenia , Espécies Reativas de Oxigênio/metabolismo , Virulência/genética
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...