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

Pieter van West, Irene de Bruijn, Kirsty L Minor, Andrew J Phillips, Emma J Robertson, Stephan Wawra, Judith Bain, Victoria L Anderson, Chris J Secombes

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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.
Original languageEnglish
Pages (from-to)127-137
Number of pages11
JournalFEMS Microbiology Letters
Issue number2
Early online date9 Jul 2010
Publication statusPublished - Sep 2010



  • amino acid sequence
  • animals
  • cell line
  • fish diseases
  • gene expression profiling
  • gene expression regulation
  • host-parasite interactions
  • infection
  • molecular sequence data
  • Oncorhynchus mykiss
  • protein transport
  • protozoan proteins
  • saprolegnia

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