Sclerotinia sclerotiorum Thioredoxin Reductase Is Required for Oxidative Stress Tolerance, Virulence, and Sclerotial Development

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 H 2 O 2 . 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 .

Antifungal, Plant Growth-Promoting, and Genomic Properties of an Endophytic Actinobacterium Streptomyces sp. NEAU-S7GS2

“…Sclerotia are hard, asexual, resting structures that are produced by many phytopathogenic fungi in Ascomycota and Basidiomycota . They are important dormant bodies that can survive for several years in soil and play a key role in the disease cycle (Zhang et al, 2019). Although chemical fungicides have played important roles in the control of disease caused by S. sclerotiorum , they could not continuously prevent the disease in future crop seasons due to the presence of sclerotia in the soils (Sabaté et al, 2018).…”

Sclerotinia sclerotiorum Thioredoxin1 (SsTrx1) is required for pathogenicity and oxidative stress tolerance

“…These reduce oxidized proteins via cysteine thiol-disulphide exchange (Hanschmann et al, 2013;Liebthal et al, 2018;Meyer et al, 2012;Montrichard et al, 2009). Many fungal genes that encode TrrR have been cloned and functionally analysed in Saccharomyces cerevisiae (Pedrajas et al, 1999), Alternaria alternata (Ma et al, 2018), B. cinerea (Viefhues et al, 2014), and S. sclerotiorum (Zhang et al, 2019). Their suppression impaired the virulence and antioxidant capabilities of the host species.…”

“…Trx, Trx reductase (TrrR), and nicotinamide adenine dinucleotide phosphate (NADPH) are key elements of the Trx system, which is associated with redox regulation and antioxidant defence in all living beings (Arnér & Holmgren, 2000;Zhang et al, 2019). These act at both intracellular and extracellular levels and are localized in the cytosol, mitochondrion, plastid, and nucleus (Hofmann, 2010;Liebthal et al, 2018).…”

The Notorious Soilborne Pathogenic Fungus Sclerotinia sclerotiorum: An Update on Genes Studied with Mutant Analysis

“…Interestingly, reduced OA production and virulence was only observed in nox1, but not nox2, which suggests that these two genes are not fully redundant, likely due to their different expression patterns. Consistently, when the thioredoxin reductase (Trr1) gene that is partly responsible for ROS detoxification is silenced, less and larger sclerotia are formed [47]. However, virulence is attenuated in Trr1 silenced strains, suggesting that an optimum ROS is needed for virulence.…”