from Martin Urban and Kim E. Hammond-Kosack writing in Fusarium: Genomics, Molecular and Cellular Biology:

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.

Further reading: Fusarium: Genomics, Molecular and Cellular Biology

from Takumi Nishiuchi writing in Fusarium: Genomics, Molecular and Cellular Biology:

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.

Further reading: Fusarium: Genomics, Molecular and Cellular Biology

from Kyle R. Pomraning, Lanelle R. Connolly, Joseph P. Whalen, Kristina M. Smith and Michael Freitag writing in Fusarium: Genomics, Molecular and Cellular Biology:

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.

Further reading: Fusarium: Genomics, Molecular and Cellular Biology

from Francis Trail writing in Fusarium: Genomics, Molecular and Cellular Biology:

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.

Further reading: Fusarium: Genomics, Molecular and Cellular Biology

from H. Corby Kistler, Martijn Rep and Li-Jun Ma writing in Fusarium: Genomics, Molecular and Cellular Biology:

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.

Further reading: Fusarium: Genomics, Molecular and Cellular Biology

from Philipp Wiemann and Bettina Tudzynski writing in Fusarium: Genomics, Molecular and Cellular Biology:

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.

Further reading: Fusarium: Genomics, Molecular and Cellular Biology