engleski

Variable effect of Cryphonectria hypovirus 1 infection on laccase activity in chestnut blight fungus

Cryphonectria hypovirus 1 (CHV1) is a well-known viral biocontrol agent of chestnut blight fungus Cryphonectria parasitica. Infection with CHV1 leads to the hypovirulence of the fungus, reducing its growth, sexual and asexual reproductive ability, and virulence toward the host, leading to its debilitation, and subsequent recovery of the diseased chestnuts. Reduced activity of fungal laccases, enzymes involved in chestnut blight pathogenic process, has also been considered as one of the traits of hypovirulence. However, the data on laccase activity was based predominantly on the observations on the prototypic laboratory experimental system, supported by limited experiments with field isolates of the fungus and its associated virus. Different methods utilized for assessing this phenomenon (analysis of the fungal transcriptome and secretome, different cultivation conditions, etc.) have produced varied and often conflicting results. Thus, our goal was to ascertain if the variability in laccase activity of CHV1-infected C. parasitica is affected by (1) growth conditions, and (2) variability of C. parasitica isolates and CHV1 strains used in our experimental systems. The effect of growth conditions was tested by using two growth media (potato dextrose and malt extract) in two different forms (solid and liquid) and cultivation for either five or ten days. The effect of fungal isolate/virus strain was tested by using three fungal isolates and four viral strains and their combinations. We have demonstrated that some CHV1 strains, contrary to previous assumptions, increase the activity of C. parasitica laccases. Furthermore, the specific fungal isolates used in the experiments, as well as culture conditions also affected the results. We evaluated the suitability of two substrates (ABTS and DMOP) commonly used for laccases’ activities measurement as well, and demonstrated that they cannot be used interchangeably in C. parasitica laccase activity assays. Thus, we conclude that experimental design, growing conditions and analytical procedures can drastically affect the outcome of enzymes’ activities measurements, making the planning of such experiments of the utmost importance if the most relevant conclusions applicable to natural populations are to be achieved.

chestnut blight ; Cryphonectria hypovirus 1 ; virus effect

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