Abstract
Sclerotinia sclerotiorum is a destructive ascomycete plant pathogen with worldwide distribution. Extensive research on different aspects of this pathogen’s capability to cause disease will help to uncover clues about new ways to safely control Sclerotinia diseases. The thioredoxin (Trx) system consists of Trx and thioredoxin reductase (TrxR), which play critical roles in maintenance of cellular redox homeostasis. In this study, we functionally characterized a gene encoding a TrxR (SsTrr1) in S. sclerotiorum. The amino acids of SsTrr1 exhibited high similarity with reported TrxRs in plant pathogens and targeted silencing of SsTrr1 lead to a decrease in TrxR activities of mycelium. SsTrr1 showed high expression levels during hyphae growth, and the levels decreased at the different stages of sclerotial development. SsTrr1 gene-silenced strains produced a smaller number of larger sclerotia on potato dextrose agar medium. The observations were consistent with the inhibitory effects on sclerotial development by the TrxR inhibitor, anrunofin. The expression of SsTrr1 showed a dramatic increase under the oxidative stress and the hyphal growth of gene-silenced strains showed more sensitivity to H2O2. SsTrr1 gene-silenced strains also showed impaired virulence in different hosts. Taken together, our results suggest that SsTrr1 encodes a TrxR that is of great important for oxidative stress tolerance, virulence, and sclerotial development of S. sclerotiorum.
Highlights
Sclerotinia sclerotiorum is an ascomycete plant pathogen with a worldwide distribution (Bolton et al, 2006)
The number of sclerotia was negatively correlated with increasing concentrations of auranofin (Figure 1B), suggesting that auranofin inhibited S. sclerotiorum sclerotial formation. These results reveal the inhibitory effect of auranofin on S. sclerotiorum and support the possibility that thioredoxin reductase (TrxR) is required for the hyphal growth and sclerotial development of this fungus
SsTrr1 was shown to have an effect on the oxidative stress tolerance, sclerotial development, and pathogenicity of S. sclerotiorum
Summary
Sclerotinia sclerotiorum is an ascomycete plant pathogen with a worldwide distribution (Bolton et al, 2006). This fungus infects more than 400 known plants and is the causal agent of stem rot in oilseed rape. Sclerotia may germinate carpogenically to produce millions of airborne ascospores, which are the primary sources of inocula in most Sclerotinia diseases. Sclerotia germinate myceliogenically to produce hyphae, which can directly infect the hosts’ stem or leaves (Schwartz and Steadman, 1978; Bardin and Huang, 2001)
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