February 15-18, 2009 Washington State Convention Center Seattle ...

DIFFRENTLY EXPRESSED ANTIOXIDANT GENES IN DISK ABALONE EXPOSED TO
HEAT STRESS
Mahanama De Zoysa* and Jehee Lee
Department of Marine Biotechnology
College of Ocean Science
Cheju National University
Jeju Special Self Governing Province
690-756, Republic of Korea
mahanama_dezoysa@yahoo.com
High temperatures represent one of the main physiological stresses, which foster elevated ROS levels and induced antioxidant
enzymes in marine organisms. Overall antioxidant defense in an organism is a combination of multiple responses of these
enzymes. Therefore, it is important to understand the functional relationship between different antioxidant enzymes against
heat stress.
This study was conducted to investigate responses of different antioxidant enzymes in mollusk disk abalone (Haliotis
discus discus) against oxidative stress upon exposure to high temperature above the habitat temperature. Disk abalones were
exposed to heat stress at 28 0 C for 48 h and control group was maintained at 20 0 C separately. Gill tissue was isolated in
different time points (1 h, 2 h, 4 h, 8 h, 12 h and 24 h) from both heat stress and control animals. Quantitative real time PCR was
conducted to analysis the heat stress responses of six anitioxidant enzymes including Mn-superoxide dismutase (Mn-SOD),
CuZn-superoxide dismutase (CuZn-SOD), catalase, thioredoxin peroxidase (TPx), mitochondrial thioredoxin-2 (MtTRx-2)
and Selenium dependant glutathione peroxidases (SeGPx).
Transcripts of the all six antioxidant enzymes were expressed in untreated abalone gill, mantle, abductor muscle, gonad,
digestive tract tissues and hemocytes with tissue specific manner. Time frame heat stress experiment results showed that
transcriptional responses were varied in different antioxidant enzymes. Transcriptional up-regulation of MnSOD (2.07-fold at
1 h), catalse (3.07-fold at 8 h), TPx (2.8-fold at 12 h) and SeGPx (13.2-fold at 24 h) were observed in abalone gill tissue after
heat stress at 28 0 C compared to control animal at 20 0 C. In contrast CuZnSOD and Mit-TRx-2 transcripts were initially down
regulated until 4 h and then reached to basal level at 24 h.
Our results revealed that MnSOD has immediate heat stress response at 1 h, while SeGPx has slow response at early stage
however it showed the highest expression (13.2-fold) at 24 h compared to other antioxidant enzymes in abalone. Finally, our
preliminary results suggest that abalone antioxidant enzymes can corporately response to the oxidative stress generated high
heat condition, however exact interrelations of these enzymes need to be clarified in future.
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