Differential expression of genes encoding anti-oxidant enzymes in Sydney rock oysters, Saccostrea glomerata (Gould) selected for disease resistance

Green, Timothy J., Dixon, Tom J., Devic, Emilie, Adlard, Robert D. and Barnes, Andrew C. (2009) Differential expression of genes encoding anti-oxidant enzymes in Sydney rock oysters, Saccostrea glomerata (Gould) selected for disease resistance. Fish & Shellfish Immunology, 26 5: 799-810. doi:10.1016/j.fsi.2009.03.003


Author Green, Timothy J.
Dixon, Tom J.
Devic, Emilie
Adlard, Robert D.
Barnes, Andrew C.
Title Differential expression of genes encoding anti-oxidant enzymes in Sydney rock oysters, Saccostrea glomerata (Gould) selected for disease resistance
Formatted title
Differential expression of genes encoding anti-oxidant enzymes in Sydney rock oysters, Saccostrea glomerata (Gould) selected for disease resistance
Journal name Fish & Shellfish Immunology   Check publisher's open access policy
ISSN 1050-4648
1095-9947
Publication date 2009-05-01
Sub-type Article (original research)
DOI 10.1016/j.fsi.2009.03.003
Volume 26
Issue 5
Start page 799
End page 810
Total pages 12
Editor A. E. Ellis
C. J. Secombes
Place of publication London, UK
Publisher Elsevier
Collection year 2010
Language eng
Subject 0704 Fisheries Sciences
C1
830104 Aquaculture Oysters
070401 Aquaculture
Formatted abstract
Sydney rock oysters (Saccostrea glomerata) selectively bred for disease resistance (R) and wild-caught control oysters (W) were exposed to a field infection of disseminating neoplasia. Cumulative mortality of W oysters (31.7%) was significantly greater than R oysters (0.0%) over the 118 days of the experiment. In an attempt to understand the biochemical and molecular pathways involved in disease resistance, differentially expressed sequence tags (ESTs) between R and W S. glomerata hemocytes were identified using the PCR technique, suppression subtractive hybridisation (SSH). Sequencing of 300 clones from two SSH libraries revealed 183 distinct sequences of which 113 shared high similarity to sequences in the public databases. Putative function could be assigned to 64 of the sequences. Expression of nine ESTs homologous to genes previously shown to be involved in bivalve immunity was further studied using quantitative reverse-transcriptase PCR (qRT-PCR). The base-line expression of an extracellular superoxide dismutase (ecSOD) and a small heat shock protein (sHsP) were significantly increased, whilst peroxiredoxin 6 (Prx6) and interferon inhibiting cytokine factor (IK) were significantly decreased in R oysters. From these results it was hypothesised that R oysters would be able to generate the anti-parasitic compound, hydrogen peroxide (H2O2) faster and to higher concentrations during respiratory burst due to the differential expression of genes for the two anti-oxidant enzymes of ecSOD and Prx6. To investigate this hypothesis, protein extracts from hemolymph were analysed for oxidative burst enzyme activity. Analysis of the cell free hemolymph proteins separated by native-polyacrylamide gel electrophoresis (PAGE) failed to detect true superoxide dismutase (SOD) activity by assaying dismutation of superoxide anion in zymograms. However, the ecSOD enzyme appears to generate hydrogen peroxide, presumably via another process, which is yet to be elucidated. This corroborates our hypothesis, whilst phylogenetic analysis of the complete coding sequence (CDS) of the S. glomerata ecSOD gene is supportive of the atypical nature of the ecSOD enzyme. Results obtained from this work further the current understanding of the molecular mechanisms involved in resistance to disease in this economically important bivalve, and shed further light on the anomalous oxidative processes involved.
Keyword Oyster
Saccostrea
Neoplasia
Innate immunity
Gene expression
Superoxide dismutase
Peroxiredoxin
Q-Index Code C1
Q-Index Status Confirmed Code

 
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Created: Thu, 03 Sep 2009, 18:02:33 EST by Mr Andrew Martlew on behalf of Centre for Marine Studies