Global ETD Search

1	Comparison of the infection biology and transcriptome of wild-type and single gene deletion strains of Fusarium graminearum Brown, Neil Andrew January 2012 (has links) Fusarium Ear Blight is a devastating fungal disease of cereals and due to the contamination of the harvested grain with a range of trichothecene mycotoxins presents a risk to human and animal health. The re-emergence of Fusarium graminearum on wheat and maize, the evolution of more aggressive fungal strains and the lack of an effective control strategy, has increased the need for a greater understanding of the disease aetiology. This project aimed to enhance the understanding of the interaction between F. graminearum and wheat (Triticum aestivum), through the utilisation of microscopy and molecular pathogenomics. A detailed investigation of the infection process revealed a prolonged latent period of intercellular infection that preceded host cell death, intracellular colonisation and the onset of disease symptoms. Phenotypic differences in colonisation and mycotoxin gene expression implied that hyphae within the two phases of infection were transcriptionally distinct, while a bioinformatic analysis described the fungal secretome. The two fungal gene-deficient strains assessed, top1 and tri5, were unable to establish symptomless infection or spread throughout the wheat ear, in the presence or absence of mycotoxin production, suggesting the existence of additional virulence factors. Subsequently, a genome wide transcriptome investigation of the two phases of infection, using both Affymetrix and RNA-sequencing technologies, revealed the unique expression profile, and secretome, of the advancing hyphal front of the symptomless infections. This greater understanding of the biphasic interaction will provide a benchmark for comparison with the single gene deficient strains. Finally, a laser capture microdissection procedure was developed to enable future cell-type specific transcriptome experiments. Collectively, I have discovered and developed a model of how F. graminearum establishes symptomless and symptomatic infection. In doing so, this study has enhanced the understanding of this non-biotrophic pathosystem, providing many new lines of investigation, which could greatly improve crop protection strategies. 632 Fusarium ear blight ; wheat
2	An exploration of the function of specific components of the predicted secretome of Fusarium graminearum during wheat infection Machado, Ana Karla de Freitas January 2017 (has links) Fusarium graminearum is a major fungal pathogen of wheat and other small grain cereal crops globally, causing Fusarium ear blight (FEB) disease. Like many other plant pathogens, F. graminearum is predicted to produce in planta secreted effector proteins that modulate plant metabolism to suppress or re-programme plant defences. Understanding the molecular functions of Fg effectors will help to elucidate the processes underlying wheat spike colonisation and fungal pathogenicity. With the aim of identifying Fg effector proteins that can suppress host plant defences, I selected using next generation sequencing and bioinformatic analysis, a set of small secreted proteins (SSP) to express in planta using the Barley stripe mosaic virus over-expression system (BSMV-VOX). I then tested whether expression of any of these SSPs enhanced Fg fungal infection of susceptible wheat spikes. Amongst the set of Fg SSP tested, FgSSP8, which encodes a ribonuclease protein, induced strong symptoms of necrosis in N. benthamiana leaves when infiltrated via the BSMV:FgSSP8. Three other genes tested (FgSSP7, FgSSP6 and FgSSP5) enhance FEB disease formation in the majority of the experiments when overexpressed in wheat ears prior to infecting with F. graminearum. FgSSP6 and FgSSP7 belong to the cerato-platanin protein (CPP) family. In several other plant pathogenic fungi, CPPs have been implicated in a number of virulence and plant protection mechanisms, including induction of host plant cell death, binding specific polymers and/or expansin-like activity. FgSSP5 encodes a protein that possesses the pfam domain RALF (Rapid alkalinization factor; PF05498.6). RALF domain-containing proteins are predominately found in plants and play a role in plant development regulating tissue expansion and/or negatively regulating pollen tube elongation. BLAST analyses identified RALF domain containing proteins in a restricted range of different pathogen species. Based on the VOX results and biochemical tests, our hypothesis is that pre-elevated cerato-platanins (FgSSP6 and FgSSP7) levels in the apoplast/surrounding the hyphae could initially shield the hyphae from detection by the plant, but late induce an intense defence response culminating in cell death to benefit the necrotrophic phase of Fg by increasing nutrient availability. FgSSP5 may be a specific virulence factor that manipulates a key plant process, by alkalinising the plant environment during infection, and using the same plant receptor repertoire used to recognise plant proteins. Once the mechanisms are further understood, these genes/proteins could potentially be novel intervention targets either for conventional chemistries and/or for methods such as host-induced gene silencing to achieve FEB disease and/or mycotoxin control. The characterisation of single and double gene deletion F. graminearum mutants is in progress.
3	Functional evaluation of plant defence signalling against Fusarium graminearum and F. culmorum in Arabidopsis floral tissue Brewer, Helen Caroline January 2014 (has links) Fusarium Ear Blight (FEB) is a globally important floral disease of cereal crops such as wheat, maize and barley. The predominant causal agents of FEB disease of wheat in the UK are Fusarium culmorum and F. graminearum. Wheat infecting isolates of both of these fungal species infect the floral and silique tissues of the model plant Arabidopsis thaliana, providing a tractable model for analysis of factors determining plant susceptibility or resistance to Fusarium infection. The effect of F. culmorum infection on the metabolic composition (metabolome) of Arabidopsis pedicel tissue following silique inoculation was investigated in a collection of mutants with altered defence responses to F. culmorum and/or other plant pathogens, using a 1Â¬H-NMR/ESI-MS (+/-) triple fingerprinting approach. These mutants showed differing metabolomic fingerprints in the absence of F. culmorum infection, as well as differences in accumulation or depletion of metabolites in response to F. culmorum colonisation. A number of metabolites were also identified which were induced by F. culmorum infection irrespective of plant genotype. Quantitative differences in compound accumulation were also observed between genotypes in the Columbia and Landsberg erecta accessions following F. culmorum infection. One of the genotypes investigated was eds11, which has enhanced susceptibility to F. culmorum floral infection. Mapping of the mutation responsible for the eds11 phenotype was initiated using an isogenic mapping by sequencing approach. This resulted in a list of potential candidates for the EDS11 gene. Additional Arabidopsis mutants were investigated for altered defence responses to F. culmorum floral infection. Multiple mutant alleles of the Arabidopsis homoserine kinase gene DMR1 were found to have enhanced resistance to F. culmorum silique infection and rosette leaf colonisation, associated with accumulation of homoserine in siliques and delayed leaf senescence. Exogenous homoserine application enhanced resistance in wild type and dmr1 plants. Collectively, these findings form a novel contribution to current knowledge of the Fusarium-Arabidopsis interaction. This may have applications for improvement of FEB resistance in cereals. 570
4	Pathogenicity determinants of Fusarium graminearum on wheat ears Beacham, Andrew Mark January 2011 (has links) Some specialist microbes can deploy a range of mechanisms to cause disease on one or more host plant species. To identify entirely new classes of pathogenicity and virulence factors, a bioinformatics-reverse genetics approach has been applied to a plant pathogen where near complete genomic sequence information was available. A genomic region was identified on chromosome 1 of the important cereal pathogen Fusarium graminearum that contains a significant grouping of homologues of known virulence genes. Targeted deletion of these genes revealed a role for the neutral trehalase (NTH1) and protein kinase A regulatory subunit (PKAR) genes in the rate of disease symptom spread by F. graminearum, in addition to the previously reported SNF1 Ser/Thr protein kinase and STE7 MAP kinase kinase genes. Subsequent investigation of further genes at this locality revealed the presence of a gene, here named Fusarium graminearum Contributor to Virulence 1 (FCV1), which represent a novel class of gene required for a full rate of symptom spread. Targeted deletion of FCV1 led to a reduced rate of disease development by F. graminearum on wheat ears and Arabidopsis floral tissue, but did not affect trichothecene mycotoxin production. The fcv1 deletion mutant also exhibits altered hyphal growth, reduced asexual sporulation and altered sensitivity to oxidative and osmotic stress. In the complemented strain, wild-type traits were completely or partially restored. This micro-region of < 40 kb containing these five important genes represents a novel type of gene cluster containing genes required for a full rate of disease development. This micro-region is located in a genomic region of low recombination, is highly conserved in three other Fusarium species, but is less conserved in other plant pathogenic species. The micro-region is not defined by a distinct GC content or coordinated gene expression patterns, nor is it flanked by highly repetitive sequences. This micro-region is distinct from the previously identified fungal and bacterial virulence gene clusters and the clustered biosynthesis-associated genes required to synthesis metabolites which contribute to pathogenicity. This method for novel disease development-contributing gene identification is applicable to any sequenced pathogen species. 632
5	Establishment and application of real-time PCR-based methods to study the epidemiology of Fusarium Head Blight / Etablierung und Anwendung der Real-time PCR für epidemiologische Untersuchungen zu Ährenfusariosen Brandfaß, Christoph 13 July 2006 (has links) No description available. 630 Landwirtschaft, Veterinärmedizin YEK 181 Agricultural Sciences Methode Mais DNA DON Duplex PCR Partielle Weißährigkeit FHB Fusarium culmorum Fusarium graminearum Gibberella zeae Maisrückstände Schmelzkurvenanalyse Mykotoxine Pflanzenmaterial Quantifizierung Ährenspindeln Getreide Weizen assay corn DNA DON duplex PCR ear blight FHB Fusarium culmorum Fusarium graminearum Gibberella zeae maize debris melting curve analysis mycotoxins plant material quantification rachides small-grain cereals wheat scab 48.54

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