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. 2008 Jan 24:9:37.
doi: 10.1186/1471-2164-9-37.

Discovery of genes implicated in whirling disease infection and resistance in rainbow trout using genome-wide expression profiling

Melinda R Baerwald  1 , Amy B Welsh, Ronald P Hedrick, Bernie May
Affiliations

Discovery of genes implicated in whirling disease infection and resistance in rainbow trout using genome-wide expression profiling

Melinda R Baerwald et al. BMC Genomics. .

Abstract

Background: Whirling disease, caused by the pathogen Myxobolus cerebralis, afflicts several salmonid species. Rainbow trout are particularly susceptible and may suffer high mortality rates. The disease is persistent and spreading in hatcheries and natural waters of several countries, including the U.S.A., and the economic losses attributed to whirling disease are substantial. In this study, genome-wide expression profiling using cDNA microarrays was conducted for resistant Hofer and susceptible Trout Lodge rainbow trout strains following pathogen exposure with the primary objective of identifying specific genes implicated in whirling disease resistance.

Results: Several genes were significantly up-regulated in skin following pathogen exposure for both the resistant and susceptible rainbow trout strains. For both strains, response to infection appears to be linked with the interferon system. Expression profiles for three genes identified with microarrays were confirmed with qRT-PCR. Ubiquitin-like protein 1 was up-regulated over 100 fold and interferon regulating factor 1 was up-regulated over 15 fold following pathogen exposure for both strains. Expression of metallothionein B, which has known roles in inflammation and immune response, was up-regulated over 5 fold in the resistant Hofer strain but was unchanged in the susceptible Trout Lodge strain following pathogen exposure.

Conclusion: The present study has provided an initial view into the genetic basis underlying immune response and resistance of rainbow trout to the whirling disease parasite. The identified genes have allowed us to gain insight into the molecular mechanisms implicated in salmonid immune response and resistance to whirling disease infection.

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Figures

Figure 1
Figure 1
Experimental approach for gene expression analysis. Within strain comparisons were first conducted to identify genes responding to pathogen exposure. The expression profiles of these genes were then compared between resistant and susceptible strains to determine which genes are implicated in the whirling disease phenotype.
Figure 2
Figure 2
Quantitative RT-PCR expression results for genes responding to Myxobolus cerebralis infection in the skin tissue of both strains. A) Ubiquitin-like protein 1 is 100 – 134 fold up-regulated following pathogen exposure for both strains. B) Interferon regulating factor 1 (IRF-1) is up-regulated 16 – 18 fold up-regulated for both strains. C) Metallothionein B (MT-B) is up-regulated over 5 fold in the resistant Hofer but is unchanged in the susceptible Trout Lodge strain. Asterisks represent significance (** = P < 0.005; *** = P < 0.001). Abbreviations: HC = Hofer Control; HE = Hofer Exposed; TLC = Trout Lodge Control; TLE = Trout Lodge Exposed.
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References

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