Project description:Infection of the chestnut blight fungus, Cryphonectria parasitica, by hypovirus CHV1-EP713 or by reoviruses MYRV1-Cp9B21 or MYRV2-CpC18 results in reduced fungal virulence (hypovirulence). However, additional phenotypic changes caused by the two groups of mycoviruses are quite different. CHV1-EP713 infection results in depressed pigmentation and conidiation while reovirus infection has little effect on these processes. We now report that loss of female fertility and resulting absence of virus transmission through sexual spores observed after hypovirus infection was not observed for reovirus infected C. parasitica. Reovirus-infected strains were male and female fertile and able to transmit virus to ascospore progeny at a high rate when serving as a female parent. Consistent with this result, real-time RT-PCR revealed that expression of two genes involved in sexual reproduction, the pheromone precursor gene, mf2-1 and yeast Ste12-like transcriptional factor gene, Cpst12, were less reduced in reovirus-infected strains than in hypovirus-infected strains. Analysis with a custom microarray cDNA chip containing EST clones representing ca 2,200 unique C. parasitica genes identified 140 and 128 host genes that were responsive to MYRV1-Cp9B21 and MYRV2-CpC18 infection, respectively. Comparison of these virus-responsive genes revealed an overlap of 85 genes even though the overall degree of nucleotide sequence identity of the two reoviruses is less than 50%. Significantly, 84 of the 85 genes were altered in the same direction. Further comparison revealed that 51 % and 48% of the genes that were responsive to reoviruses MYRV1-Cp9B21 and MYRV2-CpC18 infection were also responsive to CHV1-EP713 infection. Finally, similar to results reported for hypovirus infection, a high percentage (59% and 66%) of the mycoreovirus responsive genes were also differentially expressed following disruption of the cellular G-protein signal transduction pathway. These data support the hypothesis that hypovirus and reovirus infections perturb common and specific C. parasitica regulatory pathways to cause hypovirulence and distinct sets of phenotypic changes. Keywords: Mycoreovirus, hypovirus, gene expression, microarray.

Project description:Cryphonectria parasitica, the chestnut blight fungus, can be infected by virulence-attenuating mycoviruses of the family Hypoviridae. Previous studies have led to the hypothesis that the hypovirus-infected phenotype is partly due to metabolic changes induced by the viral infection. To investigate this, we measured the metabolic rate and respiration of C. parasitica colonies grown on solid medium. These experiments supported historical observations of other fungal species done in liquid cultures that the metabolic rate steadily declines with age and differentiation of the mycelium. Hypovirus infection increased metabolic rate in the youngest mycelium, but a subsequent decline was also observed as the mycelium aged. By measuring both CO(2) production and O(2) consumption, we also observed that changes occur in carbohydrate metabolism as a result of ageing in both infected and uninfected mycelium. Mycelium on the periphery of the colony exploited fermentation pathways extensively, before transitioning to aerobic carbohydrate metabolism and finally lipid metabolism in the interior regions, despite abundant remaining glucose. However, the hypovirus affected the extent of these changes, with infected mycelium apparently unable to utilize lipid-related metabolic pathways, leading to an increased depletion of glucose. Finally, we used metabolic profi fi ling to determine the changes in accumulation of primary metabolites in wild-type and hypovirus-infected mycelium and found that approximately one-third of the 164 detected metabolites were affected. These results are consistent with those expected from the physiological measurements, with significant alterations noted for compounds related to lipid and carbohydrate metabolism. Additionally, we observed an increase in the accumulation of the polyamine spermidine in the presence of hypovirus. Polyamines have been implicated in antiviral responses of mammalian systems; therefore this may suggest a novel antiviral response mechanism in fungi.

Dataset Information

Controlled gene expression in the plant pathogen Cryphonectria parasitica by use of a copper-responsive element.

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Controlled gene expression in the plant pathogen Cryphonectria parasitica by use of a copper-responsive element.

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