Fusarium: Genomics, Molecular and Cellular Biology | Book
Caister Academic Press
Daren W. Brown and Robert H. Proctor Bacterial Foodborne Pathogens and Mycology Research, USDA-ARS-NCAUR, USA
viii + 182 (plus colour plates)
August 2013Buy hardbackAvailable now!
GB £159 or US $319
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The fungus Fusarium is a major plant pathogen that causes disease in nearly every agriculturally important plant. In addition, some strains produce mycotoxins that can cause serious illness in humans and livestock. The enormous economic importance of and health hazards posed by Fusarium have fuelled research into its biochemistry, genetics, genomics, proteomics and metabolomics by scientists worldwide. The primary aim of this research is the identification of strategies to reduce crop diseases and the risks posed to human and animal health. The wealth of information derived from this research has allowed Fusarium to serve as a model system for eukaryotic biology, permitting tremendous advances in our understanding of the genetic and biochemical processes involved in the fungus-plant interaction, fungal pathogenesis, toxin biosynthesis, genome plasticity and adaptive evolution to ecological niches.
In this book, an international group of researchers critically reviews the most important current research on the genomics and molecular and cellular biology of Fusarium. The opening chapter provides a fascinating introduction to the organism. Subsequent chapters deal with: sex and fruiting; genome structural dynamics; molecular genetics and genomic approaches to study pathogenesis in wheat; proteomic analysis of the fungus-host interaction; Repeat-induced point mutation, DNA methylation and heterochromatin in Fusarium graminearum (Gibberella zeae); nitrogen regulation network and its impact on secondary metabolism and pathogenicity; diversity of polyketide synthases; and plant responses to Fusarium metabolites. This volume is essential for everyone working with Fusarium and other filamentous fungi. A recommended book for all biology, agriculture and medical libraries.
An Overview of Fusarium
John F. Leslie and Brett A. Summerell
There is no Abstract Section in this chapter. The following is the first paragraph of the introduction: Fusarium is a form genus of ascomycete fungi first described by Link in 1809 as Fusisporium. Members of the genus are numerous and can be recovered from plants and soil worldwide as pathogens, endophytes and saprophytes. Members of the genus are notorious for their capabilities as plant pathogens, although work with native plants and soil in undisturbed areas suggests that the number of species not associated with known diseases may far outnumber those that cause disease. Most members of the genus produce an array of secondary metabolites, which vary widely in chemical form. A number of the secondary metabolites are important as mycotoxins that are toxic and/or carcinogenic to humans and domesticated animals, may have a role in plant disease, and may be regulated in commercial and international trade.
Sex and Fruiting in Fusarium
Fusarium spp. represent an array of sexual life styles: asexual, homothallic, and heterothallic. The recent availability of genomic resources for several Fusarium species has inspired intense research on these organisms, including a better understanding of sporulation. Although studies have clarified the arrangement of the MAT idiomorphs among these species, little is known about the role of MAT genes in sex and fruiting body development. For most Fusarium species, the sexual cycle does not predominate in the field. However, F. graminearum, a homothallic species, relies on sexual development for spore dissemination to host plants. Recent functional studies have revealed genes involved in many aspects of perithecium development in this species. This chapter will focus on morphogenic aspects of sexual development, summarize the function of genes that have been shown to affect development, and speculate about the ecological and evolutionary implications of sexual life styles.
Structural Dynamics of Fusarium Genomes
H. Corby Kistler, Martijn Rep and Li-Jun Ma
Fungi in the genus Fusarium have a great negative impact on the world economy, yet also hold great potential for answering many fundamental biological questions. The advance of sequencing technologies has made possible the connection between phenotypes and genetic mechanisms underlying the acquisition and diversification of such traits with economic and biological significance. This chapter provides a historical view of our understanding of genomic structural variation among Fusarium species. Prior to the genomic era, chromosomal variation was observed between Fusarium species and among isolates of F. oxysporum and F. solani (teleomorph Nectria haematococca). Such observations led to the discovery of supernumerary chromosomes in Nectria haematococca MPVI and have established their role in fungal-plant interactions. Contemporary comparative genomic studies not only have confirmed the existence of supernumerary chromosomes in the F. oxysporum and F. solani genomes, but also have provided strong evidence for the horizontal transmission of these chromosomes and their role as genetic determinants of host specific virulence. Overall, knowledge of the highly dynamic Fusarium genomes establishes them as eukaryotic models allowing greater understanding of genome plasticity and adaptive evolution to ecological niches.
Molecular Genetics and Genomic Approaches to Explore Fusarium Infection on Wheat Floral Tissue
Martin Urban and Kim E. Hammond-Kosack
The most destructive phase of the wheat-Fusarium interaction commences at anthesis and results in lower grain yields, reduced grain quality and the contamination of grain with harmful mycotoxins. Current control strategies are often inadequate. Globally, F. graminearum is the most problematic species. A recent microscopic study has revealed a hitherto unsuspected latent phase where hyphae symptomlessly advance the infection through living wheat floral tissues prior to host cell death. Various forward and reverse genetic methods have been developed to explore the repertoire of Fusarium genes contributing to disease formation, mycotoxin production and sporulation. At the time of writing this chapter, 159 genes are known to contribute to virulence. A newly devised seven-stage floral disease assessment key is described to assist in the inter-comparison of mutant phenotypes. Various innovative bioinformatics approaches are currently being used to predict additional virulence components, by taking advantage of the wealth of genomic, transcriptomic, metabolomic and phenotypic knowledge available. These include (1) InParanoid analyses to infer gene function by using the phenomics data sets available for ~100 pathogenic species in the Pathogen-Host Interaction database, (2) the prediction of protein-protein interaction networks, and (3) statistical analysis of the spatial distribution of specific gene types within the genomic landscape and via comparative phytopathogen genome analyses. Soon data arising from various next generation sequencing approaches will increase the precision of both experimental and predictive studies.
Applying Proteomics to Investigate the Interactions Between Pathogenic Fusarium Species and Their Hosts
Linda J. Harris, Thérèse Ouellet and Rajagopal Subramaniam
The recent technical advances in mass spectrometry (MS) such as tandem MS (MS/MS) and gel and non-gel-based methods of protein separation and quantification have galvanized research efforts to study the proteomes of pathogenic fungi. The acquisition of high quality genomic sequences has provided the species-specific protein databases essential for successful assignment of sequenced peptides to fungal proteins. Proteomics can be defined as defining the complete set of protein species present in a living organism. While transcriptomics describes the transcripts available for translation, proteomics tells us which proteins have actually been translated, modified, and are available for facilitating cellular processes. This review touches on how proteomics has been exploited to further explore biological questions involving Fusarium species.
Repeat-induced Point Mutation, DNA Methylation and Heterochromatin in Gibberella zeae (anamorph: Fusarium graminearum)
Kyle R. Pomraning, Lanelle R. Connolly, Joseph P. Whalen, Kristina M. Smith and Michael Freitag
Multiple mechanisms control genome stability in filamentous fungi. To limit the expansion of repeated DNA, e.g. transposable elements (TEs), a group of filamentous ascomycetes make use of a duplication-dependent mutator system, called "Repeat-Induced Point mutation" (RIP). This phenomenon was the first eukaryotic genome defense system identified and characterized in the 1980s by Selker and colleagues in pioneering studies with Neurospora crassa. RIP detects gene-sized duplications and aligns homologous copies by an unknown homology search mechanism during pre-meiosis. Transition mutations (C:G to T:A) are introduced, typically into both or all copies of the DNA segments. In 2007, RIP was first described in Gibberella zeae (anamorph: Fusarium graminearum) by Kistler and colleagues. Here we review previous experiments and add our recent data, which confirm that RIP occurs at relatively high frequencies in this homothallic species. We show that the G. zeae rid homologue is required for RIP, as had been found in N. crassa. In contrast to N. crassa, DNA methylation does not seem to be a common consequence of RIP. Lastly, we discuss potential evolutionary consequences of RIP in heterothallic and homothallic fungi.
The Nitrogen Regulation Network and its Impact on Secondary Metabolism and Pathogenicity
Philipp Wiemann and Bettina Tudzynski
Nitrogen is essential for fungal growth because it is a component of both nucleic acids and proteins. Fungi have two predominant mechanisms to incorporate ammonium into their metabolism: 1) the NADP-dependent, glutamate-dehydrogenase-catalyzed reductive amination of 2-oxoglutarate to form glutamate; and 2) the ATP-dependent, glutamine synthase-catalyzed fusion of ammonium and glutamate to form glutamine. Beside ammonium, fungi can also utilize a broad variety of other nitrogen sources, such as nitrate, proteins, amino acids, uric acid, allantoin and urea. Efficient control mechanisms are needed to coordinate activation/repression of genes and their products that are involved in sensing, transporting and/or metabolizing nitrogen-containing substances. Furthermore, nitrogen availability plays a critical role in how fungi interact with plants as pathogens and endophytes. Thus, nitrogen limitation has been proposed to be a key signal for activating the expression of virulence-associated genes in plant pathogens. Additionally, quality and quantity of nitrogen also affects the formation of a broad range of secondary metabolites. These secondary metabolites often contribute to virulence on the fungus' host and additionally can bare a threat to animal and human health when they occur as contaminants of food and feed. This Chapter will review the genetic basis of the nitrogen regulation network with the focus on the genus Fusarium which contains some of the most devastating plant pathogens.
Diversity of Polyketide Synthases in Fusarium
Daren W. Brown and Robert H. Proctor
Fusarium can produce a structurally diverse array of secondary metabolites (SMs) with a range of biological activities, including pigmentation, plant growth regulation, and toxicity to humans and other animals. Contamination of grain-based food and feed with toxic SMs produced by Fusarium is associated with a variety of diseases in plants and animals and results in loss of millions of dollars in grain commodities each year. Many SMs are formed via the activities of a family of large enzymes called polyketide synthases (PKSs) that consist of between five and eight functional domains. This Chapter reviews the structures and functions of Fusarium PKSs present in four species, Fusarium verticillioides, Fusarium graminearum, Fusarium solani and Fusarium oxysporum. Each genome has between 11 and 16 PKS genes. Re-examination of inferred phylogenetic relationships of deduced amino acid sequences provides insight into how this gene family evolved. The geneaologies suggest that collectively the Fusarium PKSs represent 36 distinct sets of PKS homologs, where each set catalyzes synthesis of a structurally distinct polyketide. Variation in Fusarium PKS genes is due to both ancient and recent gene duplications, gene loss events, gain-of-function due to the acquisition of new domains, and of loss-of-function due to nucleotide mutations. The significant number and variety of evolutionary changes reflects a vast biosynthetic potential this gene family provides fungi and that may help them adapt to changing environmental conditions. Understanding how fungal polyketides are synthesized should lead to better methods to control their production and thereby reduce their negative impact on human endevors.
Plant Responses to Fusarium Metabolites
Plant pathogenic species of Fusarium produce numerous secondary metabolites during infection of host plants. These metabolites often perturb host defense responses and suppress plant growth. Plant responses to Fusarium metabolites can be classified as follows: (1) inhibition of root or shoot growth; (2) inhibition of seed germination; (3) changes in leaf color such as chlorosis; (4) cell death; and (5) suppression or activation of defense responses. These phytotoxic effects of Fusarium metabolites have been reported in various plant species. Two major Fusarium metabolites, fumonisins and trichothecenes, induce apoptosis-like programmed cell death and can contribute to virulence of fusaria on some plants. Recently, signaling events have been implicated in plant responses to Fusarium metabolites. In contrast, production of the growth-promoting metabolites gibberellins by the rice pathogen Fusarium fujikuroi results in the seedling elongation symptom characteristic of bakanae disease of rice. Thus, Fusarium secondary metabolites have various effects in host plants. This chapter reviews Fusarium secondary metabolites and how plant respond to them.
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(EAN: 9781908230256 Subjects: [microbiology] [medical microbiology] [molecular microbiology] [mycology])