Differential expression of genes encoding anti-oxidant enzymes in Sydney rock oysters,Saccostrea glomerata (Gould) selected for disease resistance |
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| Authors: | Timothy J. Green Tom J. Dixon Emilie Devic Robert D. Adlard Andrew C. Barnes |
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| Affiliation: | 1. The University of Queensland, Centre for Marine Studies, Brisbane, Queensland 4072, Australia;2. CSIRO Livestock Industries, QLD Biosciences Precinct, St Lucia 4072, Australia;3. CSIRO Food Futures National Research Flagship, 5 Julius Avenue, North Ryde, NSW 2113, Australia;4. Biodiversity Program, Queensland Museum, South Bank 4101, Australia;5. The University of Queensland, School of Molecular & Microbial Sciences, Brisbane, Queensland 4072, Australia;6. The University of Queensland, School of Biological Sciences, Queensland 4072, Australia;1. School of Life Sciences and Food Engineering, Nanchang University, No. 999 Xuefu Road, Hong Gu Tan New District, Nanchang, Jiangxi 330031, China;2. Key Laboratory of Molecular Biology and Genetic Engineering of Jiangxi, Nanchang University, Jiangxi 330031, China;1. Department of Biological Sciences, Macquarie University, NSW 2109, Australia;2. Sydney Institute of Marine Science, NSW 2088, Australia;1. School of Marine Biomedical Science (BK 21 PLUS), Jeju National University, 102 Jejudaehakno, Jeju 690-756, Republic of Korea;2. Department of Fisheries, University of Rajshahi, Bangladesh;3. Marine Living Resources Research Division, Korea Institute of Ocean Science and Technology (KIOST), Ansan, Republic of Korea;4. School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea;1. School of Marine Biomedical Science (BK21 PLUS), Jeju National University, Jeju, 63243, Republic of Korea;2. Marine Science Institute, Jeju National University, Jeju, 63333, Republic of Korea;3. Tidal Flat Research Center, National Institute of Fisheries Science (NIFS) of Korea, Gunsan, 54001, Republic of Korea;4. Southeast Sea Fisheries Research Institute, NIFS of Korea, Tongyeong, 53085, Republic of Korea;1. Department of Environmental Pollution, Science and Research Branch, Islamic Azad University, Khouzestan, Iran;2. Department of Environmental Sciences, Faculty of Natural Resource and Marine Science, Tarbiat Modares University, P.O. Box 46414-356, Noor, Mazandaran, Iran;1. Université de Brest, Institut Universitaire de Technologie, Laboratoire Universitaire de Biodiversité et d''Ecologie Microbienne EA3882, Université Européenne de Bretagne, 6 rue de l''université, 29334 Quimper Cedex, France;2. Université de Bretagne Sud, Centre d''Enseignement et de Recherche Yves Coppens, Laboratoire de Biotechnologie et Chimie Marines EA3884, Université Européenne de Bretagne, Campus de Tohannic, BP573, 56017 Vannes Cedex, France;3. Université de Caen Basse Normandie, CNRS INEE – FRE3484 BioMEA – IBFA, 14032 Caen Cedex, France;4. Université de Rennes 1, Sciences Chimiques de Rennes U.M.R. 6226, Campus de Beaulieu, Bat. 10A, 10C, Avenue du Général Leclerc, 35042 Rennes Cedex, France |
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| 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. |
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