A Comparison of Transcriptional Patterns and Mycological Phenotypes following Infection of Fusarium graminearum by Four Mycoviruses

Abstract

Many fungi-infecting viruses, which are termed mycoviruses, have been identified, and most do not cause any visible symptoms. Some mycoviruses, however, can attenuate the virulence of the infected fungi, a phenomenon referred to as hypovirulence. To study fungus responses to virus infection, we established a model system composed of Fusarium graminearum and four mycoviruses including FgV1 (Fusarium graminearum virus 1), FgV2, FgV3, and FgV4. FgV1 and FgV2 infections caused several phenotypic alterations in F. graminearum including abnormal colony morphology, defects in perithecium development, and reductions in growth rate, conidiation, and virulence. In contrast, FgV3 and FgV4 infections did not cause any phenotypic change. An RNA-Seq-based analysis of the host transcriptome identified four unique Fusarium transcriptomes, one for each of the four mycoviruses. Unexpectedly, the fungal host transcriptome was more affected by FgV1 and FgV4 infections than by FgV2 and FgV3 infections. Gene ontology (GO) enrichment analysis revealed that FgV1 and FgV3 infections resulted in down-regulation of host genes required for cellular transport systems. FgV4 infection reduced the expression of genes involved in RNA processing and ribosome assembly. We also found 12 genes that were differentially expressed in response to all four mycovirus infections. Unfortunately, functions of most of these genes are still unknown. Taken together, our analysis provides further detailed insights into the interactions between mycoviruses and F. graminearum.

Molecular characterization of a novel hypovirus from the plant pathogenic fungus Fusarium graminearum

“…As previously reported, the expression of genes involved in dsRNA-mediated gene silencing is strongly induced in response to viral infection Lee et al, 2014). Thirteen F. graminearum genes responsible for PTGS were selected to examine the effect of FgHV2/JS16 on the expression of these genes.…”

“…Total RNAs were extracted with a Fungal RNA kit (OMEGA) according to the manufacturer's instructions, treated with DNase I (TaKaRa Bio Inc.) to completely remove genomic DNA, and suspended in DEPC-treated water. The synthesis of cDNAs was performed with M-MLV reverse transcriptase (Promega) and an oligo d (T) primer to quantify mRNA expression (Lee et al, 2014). Relative quantitative real-time RT-PCR (qRT-PCR) was performed on a CFX96 Real-Time PCR System (Bio-Rad, Herculess, U. S.A.) using the TransStart s Green qPCR SuperMix UDG (TransGen) according to the manufacturer's instructions.…”

“…Relative quantitative real-time RT-PCR (qRT-PCR) was performed on a CFX96 Real-Time PCR System (Bio-Rad, Herculess, U. S.A.) using the TransStart s Green qPCR SuperMix UDG (TransGen) according to the manufacturer's instructions. Two endogenous reference genes encoding cyclophilin 1 (CYP1, locus FGSG_07439) and elongation factor 1α (EF1α, locus FGSG_08811) were selected as reference genes to normalize the real time RT-PCR results (Lee et al, 2014). Another 9 F. graminearum genes that are predicted to be responsible for PTGS were selected (Lee et al, 2014).…”

“…Two endogenous reference genes encoding cyclophilin 1 (CYP1, locus FGSG_07439) and elongation factor 1α (EF1α, locus FGSG_08811) were selected as reference genes to normalize the real time RT-PCR results (Lee et al, 2014). Another 9 F. graminearum genes that are predicted to be responsible for PTGS were selected (Lee et al, 2014). Of the 9 F. graminearum genes, 2 (FGSG_08752; are Argonaute-like genes, 2 (FGSG_09025; FGSG_04408) are Dicer-like genes, and 5 (FGSG_ 04619; FGSG_06504; FGSG_08716; FGSG_09076; FGSG_01582) are RdRP-like genes.…”

Transcriptome-Based Discovery of Fusarium graminearum Stress Responses to FgHV1 Infection

“…Although CHV1-Euro7 shares a high level of sequence identity at both the nucleotide (87% to 93%) and the amino acid (90% to 98%) levels with CHV1-EP713, significant differences in the C. parasitica transcriptome were observed. Based on the application of next-generation sequencing technology, Lee et al recently reported transcriptional changes following the infection of F. graminearum with four mycoviruses from four different families [16]. There has been extensive research on the gene expression changes that occur in C. parasitica infected with hypoviruses such as CHV1/EP713 and CHV1-Euro7 compared with the wild-type strain.…”