Thermal adaptation and heat shock response of Tilapia ovary cells

Abstract
The growth of tissue culture TO-2 cells derived from the warm water fish Tilapia, the induction of thermotolerance, and protein synthesis profiles of these cells in response to temperature changes were examined. TO-2 cells can grow between 15 to 34°, with an optimal growth temperature of 31°. There is no apparent killing of the cells when the temperature is lowered to 4° for up to 3 days. Survival of TO-2 cells at 43° was studied after various preheat treatments: (1) acute heating at 40° for 15 min followed by 31° incubation, (2) chronic exposure at 37° for several hr, or (3) long-term thermal adaptation at 34°. The cells acquire thermotolerance from pre-exposure to 37° for as short as 6 hr. Preheating at 40° followed by incubation at 31° also induces thermotolerance against a subsequent 43° heat challenge. In addition, 34° thermal adapted cells are resistant to 43° heating. One- and two-dimensional gel electrophoresis of proteins after heat treatments show that three major heat shock proteins with molecular weights around 87, 70, and 27 kD are preferentially synthesized. The synthesis of two additional proteins with an isoelectric point of 6.9 and molecular weights of 60 and 44 kD are significantly enhanced in 34° thermal-adapted and 37° chronic heated cells, but not in cells subjected to an acute heat shock at either 40° or 43°. On the other hand, the 27 kD heat shock proteins are mainly present in the 43°, 40°, and 37° heat-shocked cells, but not in the 34° thermal-adapted cells.

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