Secretome analysis reveals effector candidates associated with broad host range necrotrophy in the fungal plant pathogen Sclerotinia sclerotiorum

Abstract

BackgroundThe white mold fungus Sclerotinia sclerotiorum is a devastating necrotrophic plant pathogen with a remarkably broad host range. The interaction of necrotrophs with their hosts is more complex than initially thought, and still poorly understood.ResultsWe combined bioinformatics approaches to determine the repertoire of S. sclerotiorum effector candidates and conducted detailed sequence and expression analyses on selected candidates. We identified 486 S. sclerotiorum secreted protein genes expressed in planta, many of which have no predicted enzymatic activity and may be involved in the interaction between the fungus and its hosts. We focused on those showing (i) protein domains and motifs found in known fungal effectors, (ii) signatures of positive selection, (iii) recent gene duplication, or (iv) being S. sclerotiorum-specific. We identified 78 effector candidates based on these properties. We analyzed the expression pattern of 16 representative effector candidate genes on four host plants and revealed diverse expression patterns.ConclusionsThese results reveal diverse predicted functions and expression patterns in the repertoire of S. sclerotiorum effector candidates. They will facilitate the functional analysis of fungal pathogenicity determinants and should prove useful in the search for plant quantitative disease resistance components active against the white mold.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-336) contains supplementary material, which is available to authorized users.

High-Resolution Transcript Profiling of the Atypical Biotrophic Interaction betweenTheobroma cacaoand the Fungal PathogenMoniliophthora perniciosa

“…Moreover, we demonstrate that the majority of these CSEPs are among the most highly expressed fungal genes in green brooms (Table 2), whereas essentially no expression of these effectors is observed under in vitro conditions or in the necrotrophic stage of the disease (Figure 10). In agreement with these findings, high transcript levels in planta have been used as a filter to identify effectors in other filamentous pathogens (Pedersen et al, 2012;Guyon et al, 2014). This high abundance of effectors may allow these proteins to efficiently interact and interfere with their host targets.…”

The Arabidopsis Mediator Complex Subunit16 Is a Key Component of Basal Resistance against the Necrotrophic Fungal Pathogen Sclerotinia sclerotiorum

“…S. sclerotiorum may also secrete effector proteins, such as S. sclerotiorum INTEGRIN-LIKE and S. sclerotiorum CHORISMATE MUTASE1, to diminish plant defense responses (Kabbage et al, 2013;Zhu et al, 2013). A recent bioinformatic study revealed that the S. sclerotiorum genome encodes a large set of candidate effector proteins (Guyon et al, 2014), which may have functions in Sclerotinia spp. pathogenesis.…”

Ss-Bi1 encodes a putative BAX inhibitor-1 protein that is required for full virulence of Sclerotinia sclerotiorum

“…As one of the most devastating and cosmopolitan fungal pathogens, S. sclerotiorum has developed various effective ways to invade host plants that mainly involve the secretion of oxalic acid [4e9] and enzymes that degrade the cell wall [10e16]. In recent years, S. sclerotiorum has been predicted and proven to secrete low-molecular-weight proteins that function as potential effectors and suppress host resistance [17] and [18]. In addition to these important pathogenicity factors, many others involved in the development and pathogenicity of S. sclerotiorum have been identified and characterized at the molecular level [19e27].…”