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Mariehelene Balesdent - One of the best experts on this subject based on the ideXlab platform.
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one gene one name the avrlmj1 avirulence gene of Leptosphaeria maculans is avrlm5
Molecular Plant Pathology, 2018Co-Authors: Clémence Plissonneau, Thierry Rouxel, Angela P. Van De Wouw, Annemarie Chevre, Mariehelene BalesdentAbstract:Summary Leptosphaeria maculans, the causal agent of blackleg disease, interacts with Brassica napus (oilseed rape, canola) and other Brassica hosts, in a gene-for-gene manner. The avirulence gene AvrLmJ1 was previously cloned and shown to interact with an unidentified B. juncea resistance gene. In this study, we show that the AvrLmJ1 gene maps to the same position as the AvrLm5 locus. Furthermore, isolates complemented with the AvrLmJ1 locus confer avirulence towards B. juncea genotypes harbouring Rlm5. These findings demonstrate AvrLmJ1 is AvrLm5 and highlight the need for shared resources to characterise accurately avirulence and/or resistance genes. This article is protected by copyright. All rights reserved.
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One gene-one name: the AvrLmJ1 avirulence gene of Leptosphaeria maculans is AvrLm5
Molecular Plant Pathology, 2018Co-Authors: Clémence Plissonneau, Thierry Rouxel, Annemarie Chevre, Angela P. Van De Wouw, Mariehelene BalesdentAbstract:Leptosphaeria maculans, the causal agent of blackleg disease, interacts with Brassica napus (oilseed rape, canola) and other Brassica hosts in a gene-for-gene manner. The avirulence gene AvrLmJ1 has been cloned previously and shown to interact with an unidentified Brassica juncea resistance gene. In this study, we show that the AvrLmJ1 gene maps to the same position as the AvrLm5 locus. Furthermore, isolates complemented with the AvrLmJ1 locus confer avirulence towards B. juncea genotypes harbouring Rlm5. These findings demonstrate that AvrLmJ1 is AvrLm5 and highlight the need for shared resources to characterize accurately avirulence and/or resistance genes.
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life death and rebirth of avirulence effectors in a fungal pathogen of brassica crops Leptosphaeria maculans
New Phytologist, 2017Co-Authors: Thierry Rouxel, Mariehelene BalesdentAbstract:Contents 'Summary' 526 I. 'Introduction' 526 II. 'A new crop, novel resistance genes and ‘boom and bust’ cycles' 527 III. 'The ‘two-speed’ genome and specific genome environment of avirulence genes in Leptosphaeria maculans' 527 IV. 'Deletion and other types of inactivations: the easy way to go?' 529 V. 'Is extinction the common scheme?' 529 VI. '‘Rebirth’ of AvrLm3' 530 VII. 'Conclusions' 530 'Acknowledgements' 531 References 531 Summary In agricultural systems, major (R) genes for resistance in plants exert strong selection pressure on cognate/corresponding avirulence effector genes of phytopathogens. However, a complex interplay often exists between trade-offs linked to effector function and the need to escape R gene recognition. Here, using the Leptosphaeria maculans–oilseed rape pathosystem we review evolution of effectors submitted to multiple resistance gene selection. Characteristics of this pathosystem include a crop in which resistance genes have been deployed intensively resulting in ‘boom and bust’ cycles; a fungal pathogen with a high adaptive potential in which seven avirulence genes are cloned and for which population surveys have been coupled with molecular analysis of events responsible for virulence. The mode of evolution of avirulence genes, all located in dispensable parts of the ‘two-speed’ genome, is a highly dynamic gene-specific process. In some instances, avirulence genes are readily deleted under selection. However, others, even when located in the most plastic genome regions, undergo only limited point mutations or their avirulence phenotype is ‘camouflaged’ by another avirulence gene. Thus, while hundreds of effector genes are present, some effectors are likely to have an important and nonredundant function, suggesting functional redundancy and dispensability of effectors might not be the rule.
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migration patterns and changes in population biology associated with the worldwide spread of the oilseed rape pathogen Leptosphaeria maculans
Molecular Ecology, 2012Co-Authors: Azita Dilmaghani, Lilian Gout, Patrick C Brunner, Pierre Gladieux, Tatiana Giraud, Agnieszka Stachowiak, Mariehelene BalesdentAbstract:Pathogen introductions into novel areas can lead to the emergence of new fungal diseases of plants. Understanding the origin, introduction pathways, possible changes in reproductive system and population size of fungal pathogens is essential in devising an integrated strategy for the control of these diseases. We used minisatellite markers to infer the worldwide invasion history of the fungal plant pathogen Leptosphaeria maculans, which causes stem canker (blackleg) of oilseed and vegetable brassicas. Clustering analyses partitioned genotypes into distinct populations corresponding to major geographic regions, along with two differentiated populations in Western Canada. Comparison of invasion scenarios using Approximate Bayesian Computation suggested an origin of the pathogen in the USA, the region where epidemics were first recorded, and independent introductions from there over the last few decades into Eastern Canada (Ontario), Europe and Australia. The population in Western Canada appeared to be founded from a source in Ontario and the population in Chile resulted from an admixture between multiple sources. A bottleneck was inferred for the introduction into Western Canada but not into Europe, Ontario or Australia. Clonality appeared high in Western Canada, possibly because environmental conditions there were less conducive to sexual reproduction. Leptosphaeria maculans is a model invasive pathogen with contrasting features in different regions: shallow population structure, high genetic variability and regular sexual recombination in some regions, by comparison with reduced genetic variability, high rates of asexual multiplication, strong population structure or admixture in others.
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the Leptosphaeria maculans Leptosphaeria biglobosa species complex in the american continent
Plant Pathology, 2009Co-Authors: Azita Dilmaghani, Mariehelene Balesdent, Martin J. Barbetti, J. Davey, D. Phillips, J P Didier, C Wu, Hua Li, Onesimo Morenorico, J. DespeghelAbstract:Stem canker of oilseed rape (canola, Brassica napus) is associated with a species complex of two closely related fungal species, Leptosphaeria maculans and L. biglobosa. Of these, L. maculans is the most damaging and develops gene-for-gene relationships with the host. Here, a wide scale analysis of the L. maculans - L. biglobosa species complex was performed throughout the American continent (23 locations from Chile to Canada) plus several locations in Western Australia for comparison purposes, based on a collection of 1132 isolates from infected tissues of a susceptible cultivar. Fungal species were discriminated on the basis of morphological, phytopathological and molecular criteria and showed that L. biglobosa was closely associated with L. maculans in most of the locations. Multiple gene phylogeny using sequences of ITS, actin and β-tubulin confirmed the prevalence of the L. biglobosa‘canadensis’ sub-clade in Canada, whereas up to three different sub-clades of L. biglobosa were found in Georgia (USA). Race structure of L. maculans was investigated using a combination of pathogenicity tests and PCR amplification of avirulence alleles AvrLm1, AvrLm4 and AvrLm6. Three contrasting situations were observed: (i) race structure in Ontario, Chile and Georgia was related to that of European and Western Australian populations, with a low race diversity; (ii) only one race was found in Mexico, and not found outside of this country; (iii) a large diversity of races was observed in central Canada (Manitoba, Alberta and Saskatchewan) with very specific features including maintenance of avirulence alleles absent from Europe, absence of the AvrLm7 allele common in Europe (or eastern Canada) and wide location-to-location variability.
Bruce D L Fitt - One of the best experts on this subject based on the ideXlab platform.
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mycovirus induced hypervirulence of Leptosphaeria biglobosa enhances systemic acquired resistance to Leptosphaeria maculans in brassica napus
Molecular Plant-microbe Interactions, 2020Co-Authors: Unnati A. Shah, Bruce D L Fitt, Ioly Kottaloizou, Robert H. A. CouttsAbstract:© 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
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mycovirus induced hypervirulence of Leptosphaeria biglobosa enhances systemic acquired resistance to Leptosphaeria maculans in brassica napus
Molecular Plant-microbe Interactions, 2020Co-Authors: Unnati A. Shah, Bruce D L Fitt, Ioly Kottaloizou, Robert H. A. CouttsAbstract:: Phoma stem canker (blackleg) is one of the most important diseases of winter oilseed rape (Brassica napus) worldwide and is caused by a complex that comprises at least two species: Leptosphaeria maculans and L. biglobosa. Screening a panel of field Leptosphaeria isolates from B. napus for the presence of mycoviruses revealed the presence of a novel double-stranded RNA quadrivirus in L. biglobosa and no viruses in L. maculans. Following elimination of the mycovirus, virus-infected and virus-free isogenic lines of L. biglobosa were created. A direct comparison of the growth and virulence of these isogenic lines illustrated that virus infection caused hypervirulence and resulted in induced systemic resistance toward L. maculans in B. napus following lower leaf preinoculation with the virus-infected isolate. Analysis of the plant transcriptome suggests that the presence of the virus leads to subtle alterations in metabolism and plant defenses. For instance, transcripts involved in carbohydrate and amino acid metabolism are enriched in plants treated with the virus-infected isolate, while pathogenesis-related proteins, chitinases and WRKY transcription factors are differentially expressed. These results illustrate the potential for deliberate inoculation of plants with hypervirulent L. biglobosa to decrease the severity of Phoma stem canker later in the growing season.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
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mycovirus induced hypervirulence of Leptosphaeria biglobosa enhances systemic acquired resistance to Leptosphaeria maculans in brassica napus
Access Microbiology, 2019Co-Authors: Unnati A. Shah, Bruce D L Fitt, Ioly Kottaloizou, Robert H. A. CouttsAbstract:Phoma stem canker is one of the most important diseases of winter oil seed rape (Brassica napus) world-wide and is caused by a complex that comprises at least two species: Leptosphaeria maculans and Leptosphaeria biglobosa. Screening a panel of field Leptosphaeria isolates from B. napus for the presence of mycoviruses revealed the presence of a novel double stranded (ds) RNA virus in L. biglobosa and no viruses in L. maculans. The virus forms isometric particles ca. 40–45 nm in diameter and has four genomic segments, each possessing a single open reading frame flanked by untranslated regions. Phylogenetic analysis revealed modest similarities to known and suspected members of the family Quadriviridaeand therefore the virus was nominated Leptosphaeria biglobosa quadrivirus-1. Following eradication of the mycovirus, virus-infected and virus-free isogenic lines of L. biglobosa were created. A direct comparison of the growth and virulence of these isogenic lines illustrated that virus infection caused hypervirulence and resulted in induced systemic resistance towards L. maculans in B. napus following lower leaf pre-inoculation with the virus-infected isolate. Analysis of the plant transcriptome suggests that the presence of the virus leads to subtle alterations in metabolism and plant defences. For instance, transcripts involved in carbohydrate and amino acid metabolism are enriched in plants treated with the virus-infected isolate, while pathogenesis-related proteins, chitinases and WRKY transcription factors are differentially expressed. These results illustrate the potential for deliberate inoculation of plants with hypervirulent L. biglobosa to decrease the severity of phoma stem canker later in the growing season.
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Phoma stem canker severity in controlled environment experiment.
2018Co-Authors: Yongju Huang, Georgia K. Mitrousia, Siti Nordahliawate M. Sidique, Bruce D L FittAbstract:Cultivar difference in the severity of phoma stem canker scored on a 0–6 scale (A) and the internal length of phoma stem canker symptoms (B) that had developed at 20°C by 49 days after inoculation of leaf petioles of different cultivars/lines with conidial suspensions of Leptosphaeria maculans isolates. For details of isolates, see Table 2. Error bars are standard errors of the difference. Multiple comparisons were done using the least significance difference at significance level P≤0.05. The values for phoma stem canker severity or the internal length of phoma stem canker symptoms that had different letters differed significantly at P≤0.05.
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Phoma stem canker symptoms that developed in a controlled environment experiment.
2018Co-Authors: Yongju Huang, Georgia K. Mitrousia, Siti Nordahliawate M. Sidique, Bruce D L FittAbstract:External (A, B, C) and internal (D, E, F) phoma stem canker symptoms on DH line A30 (A, D), cultivars Bilbao (B, E) and Adriana (C, F). A30 with no known Rlm resistance genes and no quantitative resistance (QR), Bilbao (Rlm4) with resistance gene Rlm4, Adriana (Rlm4 + QR) with Rlm4 and QR. Leaf petioles were inoculated with conidia of Leptosphaeria maculans isolate v23.11.9, which is virulent against Rlm4. Inoculated plants were kept at 20°C with 12h light/12h darkness and sampled at 49 days after inoculation.
Thierry Rouxel - One of the best experts on this subject based on the ideXlab platform.
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Genome-wide mapping of histone modifications during axenic growth in two species of Leptosphaeria maculans showing contrasting genomic organization
Chromosome Research, 2021Co-Authors: Jessica L Soyer, Thierry Rouxel, Nicolas Lapalu, Colin Clairet, Elise J. Gay, Eva H. Stukenbrock, Isabelle FudalAbstract: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.
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one gene one name the avrlmj1 avirulence gene of Leptosphaeria maculans is avrlm5
Molecular Plant Pathology, 2018Co-Authors: Clémence Plissonneau, Thierry Rouxel, Angela P. Van De Wouw, Annemarie Chevre, Mariehelene BalesdentAbstract:Summary Leptosphaeria maculans, the causal agent of blackleg disease, interacts with Brassica napus (oilseed rape, canola) and other Brassica hosts, in a gene-for-gene manner. The avirulence gene AvrLmJ1 was previously cloned and shown to interact with an unidentified B. juncea resistance gene. In this study, we show that the AvrLmJ1 gene maps to the same position as the AvrLm5 locus. Furthermore, isolates complemented with the AvrLmJ1 locus confer avirulence towards B. juncea genotypes harbouring Rlm5. These findings demonstrate AvrLmJ1 is AvrLm5 and highlight the need for shared resources to characterise accurately avirulence and/or resistance genes. This article is protected by copyright. All rights reserved.
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One gene-one name: the AvrLmJ1 avirulence gene of Leptosphaeria maculans is AvrLm5
Molecular Plant Pathology, 2018Co-Authors: Clémence Plissonneau, Thierry Rouxel, Annemarie Chevre, Angela P. Van De Wouw, Mariehelene BalesdentAbstract:Leptosphaeria maculans, the causal agent of blackleg disease, interacts with Brassica napus (oilseed rape, canola) and other Brassica hosts in a gene-for-gene manner. The avirulence gene AvrLmJ1 has been cloned previously and shown to interact with an unidentified Brassica juncea resistance gene. In this study, we show that the AvrLmJ1 gene maps to the same position as the AvrLm5 locus. Furthermore, isolates complemented with the AvrLmJ1 locus confer avirulence towards B. juncea genotypes harbouring Rlm5. These findings demonstrate that AvrLmJ1 is AvrLm5 and highlight the need for shared resources to characterize accurately avirulence and/or resistance genes.
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life death and rebirth of avirulence effectors in a fungal pathogen of brassica crops Leptosphaeria maculans
New Phytologist, 2017Co-Authors: Thierry Rouxel, Mariehelene BalesdentAbstract:Contents 'Summary' 526 I. 'Introduction' 526 II. 'A new crop, novel resistance genes and ‘boom and bust’ cycles' 527 III. 'The ‘two-speed’ genome and specific genome environment of avirulence genes in Leptosphaeria maculans' 527 IV. 'Deletion and other types of inactivations: the easy way to go?' 529 V. 'Is extinction the common scheme?' 529 VI. '‘Rebirth’ of AvrLm3' 530 VII. 'Conclusions' 530 'Acknowledgements' 531 References 531 Summary In agricultural systems, major (R) genes for resistance in plants exert strong selection pressure on cognate/corresponding avirulence effector genes of phytopathogens. However, a complex interplay often exists between trade-offs linked to effector function and the need to escape R gene recognition. Here, using the Leptosphaeria maculans–oilseed rape pathosystem we review evolution of effectors submitted to multiple resistance gene selection. Characteristics of this pathosystem include a crop in which resistance genes have been deployed intensively resulting in ‘boom and bust’ cycles; a fungal pathogen with a high adaptive potential in which seven avirulence genes are cloned and for which population surveys have been coupled with molecular analysis of events responsible for virulence. The mode of evolution of avirulence genes, all located in dispensable parts of the ‘two-speed’ genome, is a highly dynamic gene-specific process. In some instances, avirulence genes are readily deleted under selection. However, others, even when located in the most plastic genome regions, undergo only limited point mutations or their avirulence phenotype is ‘camouflaged’ by another avirulence gene. Thus, while hundreds of effector genes are present, some effectors are likely to have an important and nonredundant function, suggesting functional redundancy and dispensability of effectors might not be the rule.
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Genomes and Transcriptomes of Partners in Plant-Fungal- Interactions between Canola (Brassica napus) and Two Leptosphaeria Species
PLoS ONE, 2014Co-Authors: Rohan Gt Lowe, Thierry Rouxel, Jonathan Grandaubert, Angela P. Van De Wouw, Andrew Cassin, Bethany L Clark, Barbara J HowlettAbstract:Leptosphaeria maculans ‘brassicae’ is a damaging fungal pathogen of canola (Brassica napus), causing lesions on cotyledons and leaves, and cankers on the lower stem. A related species, L. biglobosa ‘canadensis’, colonises cotyledons but causes few stem cankers. We describe the complement of genes encoding carbohydrate-active enzymes (CAZys) and peptidases of these fungi, as well as of four related plant pathogens. We also report dual-organism RNA-seq transcriptomes of these two Leptosphaeria species and B. napus during disease. During the first seven days of infection L. biglobosa ‘canadensis’, a necrotroph, expressed more cell wall degrading genes than L. maculans ‘brassicae’, a hemi-biotroph. L. maculans ‘brassicae’ expressed many genes in the Carbohydrate Binding Module class of CAZy, particularly CBM50 genes, with potential roles in the evasion of basal innate immunity in the host plant. At this time, three avirulence genes were amongst the top 20 most highly upregulated L. maculans ‘brassicae’ genes in planta. The two fungi had a similar number of peptidase genes, and trypsin was transcribed at high levels by both fungi early in infection. L. biglobosa ‘canadensis’ infection activated the jasmonic acid and salicylic acid defence pathways in B. napus, consistent with defence against necrotrophs. L. maculans‘brassicae’ triggered a high level of expression of isochorismate synthase 1, a reporter for salicylic acid signalling. L. biglobosa ‘canadensis’ infection triggered coordinated shutdown of photosynthesis genes, and a concomitant increase in transcription of cell wall remodelling genes of the host plant. Expression of particular classes of CAZy genes and the triggering of host defence and particular metabolic pathways are consistent with the necrotrophic lifestyle of L. biglobosa ‘canadensis’, and the hemibiotrophic life style of L. maculans ‘brassicae’.
Matthew G Links - One of the best experts on this subject based on the ideXlab platform.
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transposable element assisted evolution and adaptation to host plant within the Leptosphaeria maculans Leptosphaeria biglobosa species complex of fungal pathogens
BMC Genomics, 2014Co-Authors: Jonathan Grandaubert, Angela P. Van De Wouw, Rohan Gt Lowe, Conrad L. Schoch, Jessica L Soyer, Isabelle Fudal, Barbara Robbertse, Nicolas Lapalu, Matthew G LinksAbstract:Many plant-pathogenic fungi have a tendency towards genome size expansion, mostly driven by increasing content of transposable elements (TEs). Through comparative and evolutionary genomics, five members of the Leptosphaeria maculans-Leptosphaeria biglobosa species complex (class Dothideomycetes, order Pleosporales), having different host ranges and pathogenic abilities towards cruciferous plants, were studied to infer the role of TEs on genome shaping, speciation, and on the rise of better adapted pathogens. L. maculans ‘brassicae’, the most damaging species on oilseed rape, is the only member of the species complex to have a TE-invaded genome (32.5%) compared to the other members genomes (<4%). These TEs had an impact at the structural level by creating large TE-rich regions and are suspected to have been instrumental in chromosomal rearrangements possibly leading to speciation. TEs, associated with species-specific genes involved in disease process, also possibly had an incidence on evolution of pathogenicity by promoting translocations of effector genes to highly dynamic regions and thus tuning the regulation of effector gene expression in planta. Invasion of L. maculans ‘brassicae’ genome by TEs followed by bursts of TE activity allowed this species to evolve and to better adapt to its host, making this genome species a peculiarity within its own species complex as well as in the Pleosporales lineage.
Robert H. A. Coutts - One of the best experts on this subject based on the ideXlab platform.
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mycovirus induced hypervirulence of Leptosphaeria biglobosa enhances systemic acquired resistance to Leptosphaeria maculans in brassica napus
Molecular Plant-microbe Interactions, 2020Co-Authors: Unnati A. Shah, Bruce D L Fitt, Ioly Kottaloizou, Robert H. A. CouttsAbstract:© 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
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mycovirus induced hypervirulence of Leptosphaeria biglobosa enhances systemic acquired resistance to Leptosphaeria maculans in brassica napus
Molecular Plant-microbe Interactions, 2020Co-Authors: Unnati A. Shah, Bruce D L Fitt, Ioly Kottaloizou, Robert H. A. CouttsAbstract:: Phoma stem canker (blackleg) is one of the most important diseases of winter oilseed rape (Brassica napus) worldwide and is caused by a complex that comprises at least two species: Leptosphaeria maculans and L. biglobosa. Screening a panel of field Leptosphaeria isolates from B. napus for the presence of mycoviruses revealed the presence of a novel double-stranded RNA quadrivirus in L. biglobosa and no viruses in L. maculans. Following elimination of the mycovirus, virus-infected and virus-free isogenic lines of L. biglobosa were created. A direct comparison of the growth and virulence of these isogenic lines illustrated that virus infection caused hypervirulence and resulted in induced systemic resistance toward L. maculans in B. napus following lower leaf preinoculation with the virus-infected isolate. Analysis of the plant transcriptome suggests that the presence of the virus leads to subtle alterations in metabolism and plant defenses. For instance, transcripts involved in carbohydrate and amino acid metabolism are enriched in plants treated with the virus-infected isolate, while pathogenesis-related proteins, chitinases and WRKY transcription factors are differentially expressed. These results illustrate the potential for deliberate inoculation of plants with hypervirulent L. biglobosa to decrease the severity of Phoma stem canker later in the growing season.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
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mycovirus induced hypervirulence of Leptosphaeria biglobosa enhances systemic acquired resistance to Leptosphaeria maculans in brassica napus
Access Microbiology, 2019Co-Authors: Unnati A. Shah, Bruce D L Fitt, Ioly Kottaloizou, Robert H. A. CouttsAbstract:Phoma stem canker is one of the most important diseases of winter oil seed rape (Brassica napus) world-wide and is caused by a complex that comprises at least two species: Leptosphaeria maculans and Leptosphaeria biglobosa. Screening a panel of field Leptosphaeria isolates from B. napus for the presence of mycoviruses revealed the presence of a novel double stranded (ds) RNA virus in L. biglobosa and no viruses in L. maculans. The virus forms isometric particles ca. 40–45 nm in diameter and has four genomic segments, each possessing a single open reading frame flanked by untranslated regions. Phylogenetic analysis revealed modest similarities to known and suspected members of the family Quadriviridaeand therefore the virus was nominated Leptosphaeria biglobosa quadrivirus-1. Following eradication of the mycovirus, virus-infected and virus-free isogenic lines of L. biglobosa were created. A direct comparison of the growth and virulence of these isogenic lines illustrated that virus infection caused hypervirulence and resulted in induced systemic resistance towards L. maculans in B. napus following lower leaf pre-inoculation with the virus-infected isolate. Analysis of the plant transcriptome suggests that the presence of the virus leads to subtle alterations in metabolism and plant defences. For instance, transcripts involved in carbohydrate and amino acid metabolism are enriched in plants treated with the virus-infected isolate, while pathogenesis-related proteins, chitinases and WRKY transcription factors are differentially expressed. These results illustrate the potential for deliberate inoculation of plants with hypervirulent L. biglobosa to decrease the severity of phoma stem canker later in the growing season.
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Identification, Molecular Characterization, and Biology of a Novel Quadrivirus Infecting the Phytopathogenic Fungus Leptosphaeria biglobosa
MDPI AG, 2018Co-Authors: Unnati A. Shah, Bruce D L Fitt, Ioly Kotta-loizou, Robert H. A. CouttsAbstract:Here we report the molecular characterisation of a novel dsRNA virus isolated from the filamentous, plant pathogenic fungus Leptosphaeria biglobosa and known to cause significant alterations to fungal pigmentation and growth and to result in hypervirulence, as illustrated by comparisons between virus-infected and -cured isogenic fungal strains. The virus forms isometric particles approximately 40–45 nm in diameter and has a quadripartite dsRNA genome structure with size ranges of 4.9 to 4 kbp, each possessing a single ORF. Sequence analysis of the putative proteins encoded by dsRNAs 1–4, termed P1–P4, respectively, revealed modest similarities to the amino acid sequences of equivalent proteins predicted from the nucleotide sequences of known and suspected members of the family Quadriviridae and for that reason the virus was nominated Leptosphaeria biglobosa quadrivirus-1 (LbQV-1). Sequence and phylogenetic analysis using the P3 sequence, which encodes an RdRP, revealed that LbQV-1 was most closely related to known and suspected quadriviruses and monopartite totiviruses rather than other quadripartite mycoviruses including chrysoviruses and alternaviruses. Of the remaining encoded proteins, LbQV-1 P2 and P4 are structural proteins but the function of P1 is unknown. We propose that LbQV-1 is a novel member of the family Quadriviridae