12 research outputs found
Clonality, recombination, and hybridization in the plumbing-inhabiting human pathogen Fusarium keratoplasticum inferred from multilocus sequence typing
Sammanfattning/AbstractHelene Erös och Jennie Karlsson (2013). Action programs as tool for learning.Specialpedagogprogrammet 90hp Skolutveckling och ledarskap LĂ€rande och samhĂ€lle, Malmö högskolaProblemomrĂ„de: Skolverket (2012) presenterade nyligen de senaste resultaten frĂ„n PIRLS och TIMMS. De visade att Sveriges elever i Ă„rskurs 4 hade försĂ€mrats inom lĂ€sning och i matematik hade de lĂ€gre resultat Ă€n andra EU/OECD lĂ€nder. Detta Ă€r alarmerande och mĂ„ste tas pĂ„ allvar. SĂ€mre resultat leder pĂ„ sikt till att fler och fler Ă„tgĂ€rdsprogram behöver utfĂ€rdas. Det Ă€r viktigt att Ă„tgĂ€rdsprogrammen fungerar som redskap för att motverka de negativa utvecklingstrenderna.Syfte: Syftet med vĂ„r undersökning var att undersöka Ă„tgĂ€rdsprogram som verktyg för lĂ€rande. Med hjĂ€lp av vĂ„ra frĂ„gestĂ€llningar belyste vi Ă„tgĂ€rdsprogram ur flera perspektiv. De var blanketternas utformning och innehĂ„ll, synen pĂ„ lĂ€rande i Ă„tgĂ€rderna och hur lĂ€rare arbetar med Ă„tgĂ€rdsprogram i undervisningen. Teoretisk ram: I arbetet utgick vi frĂ„n tvĂ„ teorier om lĂ€rande, kognitiv konstruktivism och social konstruktivism. Vi anvĂ€nde Ă€ven teori utifrĂ„n det sociokulturella perspektivet. Tidigare forskning kring Ă„tgĂ€rdsprogram och riktlinjer frĂ„n lagar, lĂ€roplaner och allmĂ€nna rĂ„d bildade en bakgrund.Metod: Vi valde att göra en kvalitativ innehĂ„llsanalys av Ă„tgĂ€rdsprogram och halvstrukturerade intervjuer med fyra lĂ€rare frĂ„n tvĂ„ kommuner.Resultat med analys: VĂ„ra resultat visar att begrepp i Ă„tgĂ€rdsprogrammen som styrkor eller organisation, grupp och individ tolkas olika av lĂ€rare. MĂ„len Ă€r överlag svĂ„ra för eleven att uppnĂ„ inom en rimlig tid och det Ă€r vanligt att mĂ„lformuleringarna Ă€r otydliga. Ă
tgÀrderna ligger mycket pÄ individnivÄ och omfattas mest av fÀrdighetstrÀning. FörÀldrars och elevers delaktighet vid utformningen av ÄtgÀrdsprogrammen varierar. I intervjuerna framkommer att lÀrarna ser elevernas svÄrigheter som nÄgot utöver och utanför den ordinarie undervisningen. LÀrarna förlÀgger ÄtgÀrderna under eget arbete i eller utanför klassrummet och ibland till och med innan eller efter skoltid. Konklusion: Formuleringarna av mÄl och ÄtgÀrder varierar beroende pÄ vem som skriver. För att ÄtgÀrdsprogram ska fungera som verktyg för lÀrande mÄste pedagogerna först förstÄ begreppen i ÄtgÀrdsprogrammen. De mÄste Àven ha kunskaper om var eleverna befinner sig i sin utveckling och framförallt vart de Àr pÄ vÀg sÄ att mÄl och ÄtgÀrder blir kortsiktiga, konkreta och mÀtbara. Blanketternas utformning och ordval kan förvilla pedagogerna och bidra till feltolkningar. Detta Àr ett omrÄde som vi inte hittat nÄgon forskning kring. UtifrÄn ett sociokulturellt perspektiv drar vi slutsatsen att fler ÄtgÀrder bör ligga pÄ gruppnivÄ dÀr dialogen blir ett viktigt redskap.Implementering: Specialpedagogens roll blir att föra en regelbunden dialog med lÀrarna ute pÄ skolorna om ÄtgÀrdsprogrammens begrepp och vad som ska ingÄ i programmen. En annan uppgift för specialpedagogen blir att fÄ lÀrarna att anvÀnda sig av gruppen och fÄ arbetet med ÄtgÀrdsprogrammen integrerat i den ordinarie undervisningen. FÄr vi till detta blir ÄtgÀrdsprogrammen fungerande verktyg för lÀrande. VÄra resultat stÀmmer med tidigare forskning kring formuleringen av innehÄllet i ÄtgÀrdsprogrammen. Implikationerna gÀller dÀrför bÄde för oss specifikt men Àven i vidare mening
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Cu/Zn superoxide dismutase (VdSOD1) mediates reactive oxygen species detoxification and modulates virulence in Verticillium dahliae.
The accumulation of reactive oxygen species (ROS) is a widespread defence mechanism in higher plants against pathogen attack and sometimes is the cause of cell death that facilitates attack by necrotrophic pathogens. Plant pathogens use superoxide dismutase (SOD) to scavenge ROS derived from their own metabolism or generated from host defence. The significance and roles of SODs in the vascular plant pathogen Verticillium dahliae are unclear. Our previous study showed a significant upregulation of Cu/Zn-SOD1 (VdSOD1) in cotton tissues following V. dahliae infection, suggesting that it may play a role in pathogen virulence. Here, we constructed VdSOD1 deletion mutants (ÎSOD1) and investigated its function in scavenging ROS and promoting pathogen virulence. ÎSOD1 had normal growth and conidiation but exhibited significantly higher sensitivity to the intracellular ROS generator menadione. Despite lacking a signal peptide, assays in vitro by western blot and in vivo by confocal microscopy revealed that secretion of VdSOD1 is dependent on the Golgi reassembly stacking protein (VdGRASP). Both menadione-treated ÎSOD1 and cotton roots infected with ÎSOD1 accumulated more O2- and less H2 O2 than with the wildtype strain. The absence of a functioning VdSOD1 significantly reduced symptom severity and pathogen colonization in both cotton and Nicotiana benthamiana. VdSOD1 is nonessential for growth or viability of V. dahliae, but is involved in the detoxification of both intracellular ROS and host-generated extracellular ROS, and contributes significantly to virulence in V. dahliae
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Verticillium dahliae transcription factor VdFTF1 regulates the expression of multiple secreted virulence factors and is required for full virulence in cotton
Fungal transcription factors (TFs) implicated in the regulation of virulence gene expression have been identified in a number of plant pathogens. In Verticillium dahliae, despite its agricultural importance, few regulators of transcription have been characterized. In this study, a T-DNA insertion mutant with significantly reduced virulence towards cotton was identified. The T-DNA was traced to VdFTF1, a gene encoding a TF containing a Fungal_trans domain. Transient expression in onion epidermal cells indicated that VdFTF1 is localized to the nucleus. The VdFTF1-deletion strains displayed normal vegetative growth, mycelial pigmentation and conidial morphology, but exhibited significantly reduced virulence on cotton, suggesting that VdFTF1 is required exclusively for pathogenesis. Comparisons of global transcription patterns of wild-type and VdFTF1-deletion strains indicated that VdFTF1 affected the expression of 802 genes, 233 of which were associated with catalytic processes. These genes encoded 69 potentially secreted proteins, 43 of which contained a carbohydrate enzyme domain known to participate in pathogenesis during infection of cotton. Targeted gene deletion of one VdFTF1-regulated gene resulted in significantly impaired vascular colonization, as measured by quantitative polymerase chain reaction, as well as aggressiveness and symptom severity in cotton. In conclusion, VdFTF1, which encodes a TF containing a Fungal_trans domain, regulates the gene expression of plant cell wall degradation enzymes in V. dahliae, which are required for full virulence on cotton
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The island cotton NBSâLRR gene GbaNA1 confers resistance to the nonârace 1 Verticillium dahliae isolate Vd991
Wilt caused by Verticillium dahliae significantly reduces cotton yields, as host resistance in commercially cultivated Gossypium species is lacking. Understanding the molecular basis of disease resistance in non-commercial Gossypium species could galvanize the development of Verticillium wilt resistance in cultivated species. Nucleotide-binding site leucine-rich repeat (NBS-LRR) proteins play a central role in plant defence against pathogens. In this study, we focused on the relationship between a locus enriched with eight NBS-LRR genes and Verticillium wilt resistance in G. barbadense. Independent virus-induced gene silencing of each of the eight NBS-LRR genes in G. barbadense cultivar Hai 7124 revealed that silencing of GbaNA1 alone compromised the resistance of G. barbadense to V. dahliae isolate Vd991. In cultivar Hai 7124, GbaNA1 could be induced by V. dahliae isolate Vd991 and by ethylene, jasmonic acid and salicylic acid. Nuclear protein localization of GbaNA1 was demonstrated by transient expression. Sequencing of the GbaNA1 orthologue in nine G. hirsutum accessions revealed that all carried a non-functional allele, caused by a premature peptide truncation. In addition, all 10 G. barbadense and nine G. hirsutum accessions tested carried a full-length (âŒ1140 amino acids) homologue of the V. dahliae race 1 resistance gene Gbve1, although some sequence polymorphisms were observed. Verticillium dahliae Vd991 is a non-race 1 isolate that lacks the Ave1 gene. Thus, the resistance imparted by GbaNA1 appears to be mediated by a mechanism distinct from recognition of the fungal effector Ave1
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Heterologous Expression of the Cotton NBS-LRR Gene GbaNA1 Enhances Verticillium Wilt Resistance in Arabidopsis.
Verticillium wilt caused by Verticillium dahliae results in severe losses in cotton, and is economically the most destructive disease of this crop. Improving genetic resistance is the cleanest and least expensive option to manage Verticillium wilt. Previously, we identified the island cotton NBS-LRR-encoding gene GbaNA1 that confers resistance to the highly virulent V. dahliae isolate Vd991. In this study, we expressed cotton GbaNA1 in the heterologous system of Arabidopsis thaliana and investigated the defense response mediated by GbaNA1 following inoculations with V. dahliae. Heterologous expression of GbaNA1 conferred Verticillium wilt resistance in A. thaliana. Moreover, overexpression of GbaNA1 enabled recovery of the resistance phenotype of A. thaliana mutants that had lost the function of GbaNA1 ortholog gene. Investigations of the defense response in A. thaliana showed that the reactive oxygen species (ROS) production and the expression of genes associated with the ethylene signaling pathway were enhanced significantly following overexpression of GbaNA1. Intriguingly, overexpression of the GbaNA1 ortholog from Gossypium hirsutum (GhNA1) in A. thaliana did not induce the defense response of ROS production due to the premature termination of GhNA1, which lacks the encoded NB-ARC and LRR motifs. GbaNA1 therefore confers Verticillium wilt resistance in A. thaliana by the activation of ROS production and ethylene signaling. These results demonstrate the functional conservation of the NBS-LRR-encoding GbaNA1 in a heterologous system, and the mechanism of this resistance, both of which may prove valuable in incorporating GbaNA1-mediated resistance into other plant species
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Diversity and function of fungi associated with the fungivorous millipede, Brachycybe lecontii.
Fungivorous millipedes (subterclass Colobognatha) likely represent some of the earliest known mycophagous terrestrial arthropods, yet their fungal partners remain elusive. Here we describe relationships between fungi and the fungivorous millipede, Brachycybe lecontii. Their fungal community is surprisingly diverse, including 176 genera, 39 orders, four phyla, and several undescribed species. Of particular interest are twelve genera conserved across wood substrates and millipede clades that comprise the core fungal community of B. lecontii. Wood decay fungi, long speculated to serve as the primary food source for Brachycybe species, were absent from this core assemblage and proved lethal to millipedes in pathogenicity assays while entomopathogenic Hypocreales were more common in the core but had little effect on millipede health. This study represents the first survey of fungal communities associated with any colobognath millipede, and these results offer a glimpse into the complexity of millipede fungal communities
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Diversity and function of fungi associated with the fungivorous millipede, Brachycybe lecontii.
Fungivorous millipedes (subterclass Colobognatha) likely represent some of the earliest known mycophagous terrestrial arthropods, yet their fungal partners remain elusive. Here we describe relationships between fungi and the fungivorous millipede, Brachycybe lecontii. Their fungal community is surprisingly diverse, including 176 genera, 39 orders, four phyla, and several undescribed species. Of particular interest are twelve genera conserved across wood substrates and millipede clades that comprise the core fungal community of B. lecontii. Wood decay fungi, long speculated to serve as the primary food source for Brachycybe species, were absent from this core assemblage and proved lethal to millipedes in pathogenicity assays while entomopathogenic Hypocreales were more common in the core but had little effect on millipede health. This study represents the first survey of fungal communities associated with any colobognath millipede, and these results offer a glimpse into the complexity of millipede fungal communities
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Comparative genomics reveals cotton-specific virulence factors in flexible genomic regions in Verticillium dahliae and evidence of horizontal gene transfer from Fusarium.
Verticillium dahliae isolates are most virulent on the host from which they were originally isolated. Mechanisms underlying these dominant host adaptations are currently unknown. We sequenced the genome of V. dahliae Vd991, which is highly virulent on its original host, cotton, and performed comparisons with the reference genomes of JR2 (from tomato) and VdLs.17 (from lettuce). Pathogenicity-related factor prediction, orthology and multigene family classification, transcriptome analyses, phylogenetic analyses, and pathogenicity experiments were performed. The Vd991 genome harbored several exclusive, lineage-specific (LS) genes within LS regions (LSRs). Deletion mutants of the seven genes within one LSR (G-LSR2) in Vd991 were less virulent only on cotton. Integration of G-LSR2 genes individually into JR2 and VdLs.17 resulted in significantly enhanced virulence on cotton but did not affect virulence on tomato or lettuce. Transcription levels of the seven LS genes in Vd991 were higher during the early stages of cotton infection, as compared with other hosts. Phylogenetic analyses suggested that G-LSR2 was acquired from Fusarium oxysporum f. sp. vasinfectum through horizontal gene transfer. Our results provide evidence that horizontal gene transfer from Fusarium to Vd991 contributed significantly to its adaptation to cotton and may represent a significant mechanism in the evolution of an asexual plant pathogen
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Population genomics demystifies the defoliation phenotype in the plant pathogen Verticillium dahliae.
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