Expressed sequence tags from the oomycete fish pathogen Saprolegnia parasitica reveal putative virulence factors.
BACKGROUND
The oomycete Saprolegnia parasitica is one of the most economically important fish pathogens. There is a dramatic recrudescence of Saprolegnia infections in aquaculture since the use of the toxic organic dye malachite green was banned in 2002. Little is known about the molecular mechanisms underlying pathogenicity in S. parasitica and other animal pathogenic oomycetes. In this study we used a genomics approach to gain a first insight into the transcriptome of S. parasitica.


RESULTS
We generated 1510 expressed sequence tags (ESTs) from a mycelial cDNA library of S. parasitica. A total of 1279 consensus sequences corresponding to 525944 base pairs were assembled. About half of the unigenes showed similarities to known protein sequences or motifs. The S. parasitica sequences tended to be relatively divergent from Phytophthora sequences. Based on the sequence alignments of 18 conserved proteins, the average amino acid identity between S. parasitica and three Phytophthora species was 77% compared to 93% within Phytophthora. Several S. parasitica cDNAs, such as those with similarity to fungal type I cellulose binding domain proteins, PAN/Apple module proteins, glycosyl hydrolases, proteases, as well as serine and cysteine protease inhibitors, were predicted to encode secreted proteins that could function in virulence. Some of these cDNAs were more similar to fungal proteins than to other eukaryotic proteins confirming that oomycetes and fungi share some virulence components despite their evolutionary distance


CONCLUSIONS
We provide a first glimpse into the gene content of S. parasitica, a reemerging oomycete fish pathogen. These resources will greatly accelerate research on this important pathogen. The data is available online through the Oomycete Genomics Database.
Torto-Alalibo
Trudy
T
Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, Ohio, USA. trutot@gmail.com
Tian
Miaoying
M
Gajendran
Kamal
K
Waugh
Mark E
ME
van West
Pieter
P
Kamoun
Sophien
S
D000818:Animals; D001665:Binding Sites; D002482:Cellulose / Q000378:metabolism; D016384:Consensus Sequence; D018076:DNA, Complementary / Q000235:genetics; D020224:Expressed Sequence Tags; D005393:Fish Diseases / Q000382:microbiology*; D005399:Fishes; D015723:Gene Library; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics; D044762:Saprolegnia / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity; D014774:Virulence
D018076:DNA, Complementary; D012333:RNA, Messenger; D002482:Cellulose