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Ss-Rhs1, a secretory Rhs repeat-containing protein, is required for the virulence of Sclerotinia sclerotiorum.

ABSTRACT: Sclerotinia sclerotiorum is a devastating necrotrophic plant pathogen with a worldwide distribution. Cell wall-degrading enzymes and oxalic acid are important to the virulence of this pathogen. Here, we report a novel secretory protein, Ss-Rhs1, which is essential for the virulence of S. sclerotiorum. Ss-Rhs1 is believed to contain a typical signal peptide at the N-terminal and eight rearrangement hotspot (Rhs) repeats. Ss-Rhs1 exhibited a high level of expression at the initial stage of sclerotial development, as well as during the hyphal infection process. Targeted silencing of Ss-Rhs1 resulted in abnormal colony morphology and reduced virulence on host plants. Microscopic observations indicated that Ss-Rhs1-silenced strains exhibited reduced efficiency in compound appressoria formation.

SUBMITTER: Yu Y

PROVIDER: S-EPMC6638210 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Ss-Rhs1, a secretory Rhs repeat-containing protein, is required for the virulence of Sclerotinia sclerotiorum.

Yu Yang Y Xiao Jifen J Zhu Wenjun W Yang Yuheng Y Mei Jiaqin J Bi Chaowei C Qian Wei W Qing Ling L Tan Wanzhong W

Molecular plant pathology 20160908 8

Sclerotinia sclerotiorum is a devastating necrotrophic plant pathogen with a worldwide distribution. Cell wall-degrading enzymes and oxalic acid are important to the virulence of this pathogen. Here, we report a novel secretory protein, Ss-Rhs1, which is essential for the virulence of S. sclerotiorum. Ss-Rhs1 is believed to contain a typical signal peptide at the N-terminal and eight rearrangement hotspot (Rhs) repeats. Ss-Rhs1 exhibited a high level of expression at the initial stage of sclerot ...[more]

PMID: 27392818

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Project description:UnlabelledA recombinant strain of Sclerotinia sclerotiorum hypovirus 2 (SsHV2) was identified from a North American Sclerotinia sclerotiorum isolate (328) from lettuce (Lactuca sativa L.) by high-throughput sequencing of total RNA. The 5'- and 3'-terminal regions of the genome were determined by rapid amplification of cDNA ends. The assembled nucleotide sequence was up to 92% identical to two recently reported SsHV2 strains but contained a deletion near its 5' terminus of more than 1.2 kb relative to the other SsHV2 strains and an insertion of 524 nucleotides (nt) that was distantly related to Valsa ceratosperma hypovirus 1. This suggests that the new isolate is a heterologous recombinant of SsHV2 with a yet-uncharacterized hypovirus. We named the new strain Sclerotinia sclerotiorum hypovirus 2 Lactuca (SsHV2L) and deposited the sequence in GenBank with accession number KF898354. Sclerotinia sclerotiorum isolate 328 was coinfected with a strain of Sclerotinia sclerotiorum endornavirus 1 and was debilitated compared to cultures of the same isolate that had been cured of virus infection by cycloheximide treatment and hyphal tipping. To determine whether SsHV2L alone could induce hypovirulence in S. sclerotiorum, a full-length cDNA of the 14,538-nt viral genome was cloned. Transcripts corresponding to the viral RNA were synthesized in vitro and transfected into a virus-free isolate of S. sclerotiorum, DK3. Isolate DK3 transfected with SsHV2L was hypovirulent on soybean and lettuce and exhibited delayed maturation of sclerotia relative to virus-free DK3, completing Koch's postulates for the association of hypovirulence with SsHV2L.ImportanceA cosmopolitan fungus, Sclerotinia sclerotiorum infects more than 400 plant species and causes a plant disease known as white mold that produces significant yield losses in major crops annually. Mycoviruses have been used successfully to reduce losses caused by fungal plant pathogens, but definitive relationships between hypovirus infections and hypovirulence in S. sclerotiorum were lacking. By establishing a cause-and-effect relationship between Sclerotinia sclerotiorum hypovirus Lactuca (SsHV2L) infection and the reduction in host virulence, we showed direct evidence that hypoviruses have the potential to reduce the severity of white mold disease. In addition to intraspecific recombination, this study showed that recent interspecific recombination is an important factor shaping viral genomes. The construction of an infectious clone of SsHV2L allows future exploration of the interactions between SsHV2L and S. sclerotiorum, a widespread fungal pathogen of plants.

Project description:Small, secreted proteins have been found to play crucial roles in interactions between biotrophic/hemi-biotrophic pathogens and plants. However, little is known about the roles of these proteins produced by broad host-range necrotrophic phytopathogens during infection. Here, we report that a cysteine-rich, small protein SsSSVP1 in the necrotrophic phytopathogen Sclerotinia sclerotiorum was experimentally confirmed to be a secreted protein, and the secretion of SsSSVP1 from hyphae was followed by internalization and cell-to-cell movement independent of a pathogen in host cells. SsSSVP1∆SP could induce significant plant cell death and targeted silencing of SsSSVP1 resulted in a significant reduction in virulence. Through yeast two-hybrid (Y2H), coimmunoprecipitation (co-IP) and bimolecular fluorescence complementation (BiFC) assays, we demonstrated that SsSSVP1∆SP interacted with QCR8, a subunit of the cytochrome b-c1 complex of mitochondrial respiratory chain in plants. Double site-directed mutagenesis of two cysteine residues (C38 and C44) in SsSSVP1∆SP had significant effects on its homo-dimer formation, SsSSVP1∆SP-QCR8 interaction and plant cell death induction, indicating that partial cysteine residues surely play crucial roles in maintaining the structure and function of SsSSVP1. Co-localization and BiFC assays showed that SsSSVP1∆SP might hijack QCR8 to cytoplasm before QCR8 targeting into mitochondria, thereby disturbing its subcellular localization in plant cells. Furthermore, virus induced gene silencing (VIGS) of QCR8 in tobacco caused plant abnormal development and cell death, indicating the cell death induced by SsSSVP1∆SP might be caused by the SsSSVP1∆SP-QCR8 interaction, which had disturbed the QCR8 subcellular localization and hence disabled its biological functions. These results suggest that SsSSVP1 is a potential effector which may manipulate plant energy metabolism to facilitate the infection of S. sclerotiorum. Our findings indicate novel roles of small secreted proteins in the interactions between host-non-specific necrotrophic fungi and plants, and highlight the significance to illuminate the pathogenic mechanisms of this type of interaction.

Dataset Information

Ss-Rhs1, a secretory Rhs repeat-containing protein, is required for the virulence of Sclerotinia sclerotiorum.

Publications

Ss-Rhs1, a secretory Rhs repeat-containing protein, is required for the virulence of Sclerotinia sclerotiorum.

Similar Datasets

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