Dataset Information

Molecular Characterization of a Novel Strain of Fusarium graminearum Virus 1 Infecting Fusarium graminearum.

ABSTRACT: Fungal viruses (mycoviruses) have attracted more attention for their possible hypovirulence (attenuation of fungal virulence) trait, which may be developed as a biocontrol agent of plant pathogenic fungi. However, most discovered mycoviruses are asymptomatic in their hosts. In most cases, mycovirus hypovirulent factors have not been explored clearly. In this study, we characterized a ssRNA mycovirus in Fusarium graminearum strain HB56-9. The complete nucleotide genome was obtained by combining random sequencing and rapid amplification of cDNA ends (RACE). The full genome was 6621-nucleotides long, excluding the poly(A) tail. The mycovirus was quite interesting because it shared 95.91% nucleotide identities with previously reported Fusarium graminearum virus 1 strain DK21 (FgV1-DK21), while the colony morphology of their fungal hosts on PDA plates were very different. The novel virus was named Fusarium graminearum virus 1 Chinese isolate (FgV1-ch). Like FgV1-DK21, FgV1-ch also contains four putative open reading frames (ORFs), including one long and three short ORFs. A phylogenetic analysis indicated that FgV1-ch is clustered into a proposed family Fusariviridae. FgV1-ch, unlike FgV1-DK21, had mild or no effects on host mycelial growth, spore production and virulence. The nucleotide differences between FgV1-ch and FgV1-DK21 will help to elucidate the hypovirulence determinants during mycovirus-host interaction.

SUBMITTER: Zhang L

PROVIDER: S-EPMC7150806 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Molecular Characterization of a Novel Strain of Fusarium graminearum Virus 1 Infecting <i>Fusarium graminearum</i>.

Zhang Lihang L Chen Xiaoguang X Bhattacharjee Pallab P Shi Yue Y Guo Lihua L Wang Shuangchao S

Viruses 20200324 3

Fungal viruses (mycoviruses) have attracted more attention for their possible hypovirulence (attenuation of fungal virulence) trait, which may be developed as a biocontrol agent of plant pathogenic fungi. However, most discovered mycoviruses are asymptomatic in their hosts. In most cases, mycovirus hypovirulent factors have not been explored clearly. In this study, we characterized a ssRNA mycovirus in <i>Fusarium graminearum</i> strain HB56-9. The complete nucleotide genome was obtained by comb ...[more]

PMID: 32213895

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Project description:Fusarium graminearum virus 1 (FgV1) is a positive-sense ssRNA virus that confers hypovirulence in its fungal host, Fusarium graminearum. Like most mycoviruses, FgV1 exists in fungal cells, lacks an extracellular life cycle, and is therefore transmitted during sporulation or hyphal anastomosis. To understand FgV1 evolution and/or adaptation, we conducted mutation accumulation (MA) experiments by serial passage of FgV1 alone or with FgV2, 3, or 4 in F. graminearum. We expected that the effects of positive selection would be highly limited because of repeated bottleneck events. To determine whether selection on the virus was positive, negative, or neutral, we assessed both the phenotypic traits of the host fungus and the RNA sequences of FgV1. We inferred that there was positive selection on beneficial mutations in FgV1 based on the ratio of non-synonymous to synonymous substitutions (d N /d S ), on the ratio of radical to conservation amino acid replacements (p NR /p NC ), and by changes in the predicted protein structures. In support of this inference, we found evidence of positive selection only in the open reading frame 4 (ORF4) protein of DK21/FgV1 (MA line 1); mutations at amino acids 163A and 289H in the ORF4 of MA line 1 affected the entire structure of the protein predicted to be under positive selection. We also found, however, that deleterious mutations were a major driving force in viral evolution during serial passages. Linear relationships between changes in viral fitness and the number of mutations in each MA line demonstrated that some deleterious mutations resulted in fitness decline. Several mutations in MA line 1 were not shared with any of the other four MA lines (PH-1/FgV1, PH-1/FgV1 + 2, PH-1/FgV1 + 3, and PH-1/FgV1 + 4). This suggests that evolutionary pathways of the virus could differ with respect to hosts and also with respect to co-infecting viruses. The data also suggested that the differences among MA lines might also be explained by mutational robustness and other unidentified factors. Additional research is needed to clarify the effects of virus co-infection on the adaptation or evolution of FgV1 to its environments.

Project description:BackgroundFusarium graminearum virus 1 strain-DK21 (FgV1-DK21) is a mycovirus that confers hypovirulence to F. graminearum, which is the primary phytopathogenic fungus that causes Fusarium head blight (FHB) disease in many cereals. Understanding the interaction between mycoviruses and plant pathogenic fungi is necessary for preventing damage caused by F. graminearum. Therefore, we investigated important cellular regulatory processes in a host containing FgV1-DK21 as compared to an uninfected parent using a transcriptional approach.ResultsUsing a 3'-tiling microarray covering all known F. graminearum genes, we carried out genome-wide expression analyses of F. graminearum at two different time points. At the early point of growth of an infected strain as compared to an uninfected strain, genes associated with protein synthesis, including ribosome assembly, nucleolus, and ribosomal RNA processing, were significantly up-regulated. In addition, genes required for transcription and signal transduction, including fungal-specific transcription factors and cAMP signaling, respectively, were actively up-regulated. In contrast, genes involved in various metabolic pathways, particularly in producing carboxylic acids, aromatic amino acids, nitrogen compounds, and polyamines, showed dramatic down-regulation at the early time point. Moreover, genes associated with transport systems localizing to transmembranes were down-regulated at both time points.ConclusionThis is the first report of global change in the prominent cellular pathways in the Fusarium host containing FgV1-DK21. The significant increase in transcripts for transcription and translation machinery in fungal host cells seems to be related to virus replication. In addition, significant down-regulation of genes required for metabolism and transporting systems in a fungal host containing the virus appears to be related to the host defense mechanism and fungal virulence. Taken together, our data aid in the understanding of how FgV1-DK21 regulates the transcriptional reprogramming of F. graminearum.

Project description:BackgroundThe soil dwelling saprotrophic non-pathogenic fungus Fusarium venenatum, routinely used in the commercial fermentation industry, is phylogenetically closely related to the globally important cereal and non-cereal infecting pathogen F. graminearum. This study aimed to sequence, assemble and annotate the F. venenatum (strain A3/5) genome, and compare this genome with F. graminearum.ResultsUsing shotgun sequencing, a 38,660,329 bp F. venenatum genome was assembled into four chromosomes, and a 78,618 bp mitochondrial genome. In comparison to F. graminearum, the predicted gene count of 13,946 was slightly lower. The F. venenatum centromeres were found to be 25% smaller compared to F. graminearum. Chromosome length was 2.8% greater in F. venenatum, primarily due to an increased abundance of repetitive elements and transposons, but not transposon diversity. On chromosome 3 a major sequence rearrangement was found, but its overall gene content was relatively unchanged. Unlike homothallic F. graminearum, heterothallic F. venenatum possessed the MAT1-1 type locus, but lacked the MAT1-2 locus. The F. venenatum genome has the type A trichothecene mycotoxin TRI5 cluster, whereas F. graminearum has type B. From the F. venenatum gene set, 786 predicted proteins were species-specific versus NCBI. The annotated F. venenatum genome was predicted to possess more genes coding for hydrolytic enzymes and species-specific genes involved in the breakdown of polysaccharides than F. graminearum. Comparison of the two genomes reduced the previously defined F. graminearum-specific gene set from 741 to 692 genes. A comparison of the F. graminearum versus F. venenatum proteomes identified 15 putative secondary metabolite gene clusters (SMC), 109 secreted proteins and 38 candidate effectors not found in F. venenatum. Five of the 15 F. graminearum-specific SMCs that were either absent or highly divergent in the F. venenatum genome showed increased in planta expression. In addition, two predicted F. graminearum transcription factors previously shown to be required for fungal virulence on wheat plants were absent or exhibited high sequence divergence.ConclusionsThis study identifies differences between the F. venenatum and F. graminearum genomes that may contribute to contrasting lifestyles, and highlights the repertoire of F. graminearum-specific candidate genes and SMCs potentially required for pathogenesis.

Dataset Information

Molecular Characterization of a Novel Strain of Fusarium graminearum Virus 1 Infecting Fusarium graminearum.

Publications

Molecular Characterization of a Novel Strain of Fusarium graminearum Virus 1 Infecting <i>Fusarium graminearum</i>.

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