Laccase Activity in Fungus Cryphonectria parasitica Is Affected by Growth Conditions and Fungal–Viral Genotypic Interactions

Abstract

Laccase activity reduction in the chestnut blight fungus Cryphonectria parasitica usually accompanies the hypovirulence caused by the infection of fungus with Cryphonectria hypovirus 1 (CHV1). However, the different methods utilized for assessing this phenomenon has produced varied and often conflicting results. Furthermore, the majority of experimental setups included only one prototypic system, further confounding the results. Considering the diversity of fungal isolates, viral strains, and variability of their effects on the phytopathogenic process observed in nature, our goal was to ascertain if laccase activity variability is affected by (1) different C. parasitica isolates infected with several CHV1 strains, and (2) growth conditions. We have demonstrated that some CHV1 strains, contrary to previous assumptions, increase the activity of C. parasitica laccases. The specific fungal isolates used in the experiments and culture conditions also affected the results. Furthermore, we showed that two commonly used laccase substrates, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and 2,4-dimethoxyphenol, cannot be used interchangeably in C. parasitica laccase activity measurements. Our results illustrate the importance of conducting this type of study in experimental systems and culture conditions that resemble natural conditions as much as possible to be able to infer the most relevant conclusions applicable to natural populations.

Diversity and impact of single-stranded RNA viruses in CzechHeterobasidionpopulations

“…In all three virus-infected isolates, an enzyme laccase showed a significant increase in abundance. This finding aligns with prior observations of viral influence on fungal laccase production (Nuskern et al 2021). Proteins that possibly participated in the fungal response to viruses and showed a significant decrease in abundance included (among others) nine isoforms of glycoside hydrolases, which are believed to play a role in biotic interactions (Bradley et al 2022), two protein kinases, PKS_ER domain-containing proteins that are involved in secondary metabolism, cytochrome P450 monooxygenases, an enzyme in chitin biosynthesis glutamine-fructose-6-phosphate aminotransferase, proteases, and several proteins with an unknown function.…”

Physiological variations in hypovirus-infected wild and model long-term laboratory strains of Cryphonectria parasitica

“…The absolute values of laccase activity in samples of C. parasitica naturally infected with CHV1 measured in this study fell exclusively within the lower end of the range of values observed by Nuskern et al (2021) in samples which have been infected with CHV1 by laboratory transmissions ( Supplementary Table 2 ). It was possible to directly compare these two studies as the experimental setup was the same.…”

“…Consequently, some conclusions about fungal physiology derived from the experiments on long-term C. parasitica model strains and prototypic hypovirus strains may not accurately reflect natural populations. For example, fungal enzymes such as laccases, considered a hallmark of pathogenic potential of C. parasitica, are important in many other biological processes including development of fungal structures, pigment synthesis, lignin decomposition and fungal/plant interactions ( Baldrian, 2006 ) but previous studies have shown inconsistent results regarding changes in the laccase activity across different strains and experimental settings ( Rigling et al, 1989 ; Rigling and Van Alfen, 1991 ; Allen et al, 2003 ; Gong et al, 2017 ; Nuskern et al, 2021 ). Most recently the intra-host populations of CHV1 from naturally infected Swiss and Croatian C. parasitica isolates were characterised ( Leigh et al, 2021 ).…”

Applying molecular and genetic methods to trees and their fungal communities

“…With regard to virulence, a complex picture emerges of different signaling pathways acting in coherent but also opposing directions, independent of or with parallel effects on growth traits, cell wall qualities, perceptions of different types of stress, and defense strategies against toxic plant metabolites and other host measures (Table 2 ). While variations in genotypes of pathogens, viruses, and chestnut hosts play a role in the severity of responses (Ježić et al 2021 ; Krstin et al 2017 ; Nuskern et al 2021 ), and there may be no simple unifying rules recognizable from the mutant data (Table 2 ), understanding better the processes of fungal virulence could be useful to find potential novel targets and breeding strategies to combat the disease.…”