The putative RxLR effector protein SpHtp1 from the fish pathogenic oomycete Saprolegnia parasitica is translocated into fish cells

Authors

  • Pieter Van West,

    1. Aberdeen Oomycete Laboratory, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen – School of Medical Sciences, Foresterhill, Aberdeen, UK
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  • Irene De Bruijn,

    1. Aberdeen Oomycete Laboratory, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen – School of Medical Sciences, Foresterhill, Aberdeen, UK
    2. Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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  • Kirsty L. Minor,

    1. Aberdeen Oomycete Laboratory, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen – School of Medical Sciences, Foresterhill, Aberdeen, UK
    2. Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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  • Andrew J. Phillips,

    1. Aberdeen Oomycete Laboratory, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen – School of Medical Sciences, Foresterhill, Aberdeen, UK
    2. Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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  • Emma J. Robertson,

    1. Aberdeen Oomycete Laboratory, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen – School of Medical Sciences, Foresterhill, Aberdeen, UK
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  • Stephan Wawra,

    1. Aberdeen Oomycete Laboratory, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen – School of Medical Sciences, Foresterhill, Aberdeen, UK
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  • Judith Bain,

    1. Aberdeen Oomycete Laboratory, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen – School of Medical Sciences, Foresterhill, Aberdeen, UK
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  • Victoria L. Anderson,

    1. Aberdeen Oomycete Laboratory, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen – School of Medical Sciences, Foresterhill, Aberdeen, UK
    2. Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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  • Chris J. Secombes

    1. Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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  • Editor: Craig Shoemaker

  • Present address: Emma J. Robertson, Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.

Correspondence: Pieter van West, Aberdeen Oomycete Laboratory, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen – School of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK. Tel.: +01224 555 848; fax: +44 1224 555844; e-mail: p.vanwest@abdn.ac.uk

Abstract

The fish pathogenic oomycete Saprolegnia parasitica causes the disease Saprolegniosis in salmonids and other freshwater fish, resulting in considerable economic losses in aquaculture. Very little is known about the molecular and cellular mechanisms underlying the infection process of fish pathogenic oomycetes. In order to investigate the interaction in detail, an in vitro infection assay using an Oncorhynchus mykiss (rainbow trout) cell line (RTG-2) was developed. In a zoospore/cyst cDNA library, we identified the ORF SpHtp1, which encodes a secreted protein containing an RxLR motif. Detailed expression analysis indicated that SpHtp1 is highly expressed in zoospores/cysts from S. parasitica and in the very early stages of infection on RTG-2 cells, when compared with in vitro-grown mycelium. Moreover, the protein, SpHtp1, was found to translocate into the RTG-2 trout cells, during the interaction with S. parasitica, and also when the RTG-2 cells were treated with recombinant SpHtp1 fused to a C-terminal His-tag. These findings suggest that protein translocation could play an important role in Saprolegniosis.

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