Seasonal variation in the Heat Shock response in the oyster Crassotrea gigas

Titre du congrès :SETAC Europe 16th Annual Meeting Ville du congrès :La Hague Date du congrès :11/05/2006

The oyster Crassostrea gigas is commonly used for ecotoxicological studies. Its physiology is strongly influenced by the reproductive cycle and its response to stress is likely to fluctuate with the seasonal cycle. In the present work, we recorded the mRNA level of stress-induced genes in order to characterize their natural variations. On the basis of the observed expression pattern, a one hour heat shock at 37°C was performed at two opposed periods of the annual cycle, April and September, and the responses were compared. The genes addressed were Hsc72, Hsp70, Hsp90, involved in the chaperone proteins function and more generally in cell stress regulation. Real time PCR was used to quantify mRNA encoding for those markers and for actin as a reference gene. The results showed that environmental levels of mRNA encoding for Hsp family genes in oyster vary throughout the annual cycle. In March and September, the response to an acute though ecologically relevant heat shock was clearly different, regarding the magnitude and the kinetics.