Fig. 3.

SA potentiates hsp70 gene expression at different time intervals during and after heat shock (HS). Real-time PCR analysis of RNA isolated from tomato seedlings maintained at room temperature (Control, –SA) or treated with 0.1 mM SA (Control, +SA), HS (40 °C, 30 min) in the presence (+SA) or absence (–SA) of SA. RNA was isolated during HS (10, 20, and 30 min, no recovery period), or after 30 min HS followed by a 30, 60, or 120 min recovery period. SA alone had no effect on hsp70 gene expression (Control, +SA). Increased hsp70 gene expression was already observed after 10 min HS, reaching a maximum after 1 h (30 min HS+30 min recovery) followed by a decline during the 60 min recovery period. The presence of SA caused increased heat-induced expression of hsp70 during and following HS to be significantly potentiated. Bars represent average values (n=10) and the error bars indicate the SEM. Symbols indicate significant differences (least significant difference) at P <0.001: * indicates a difference between each treated sample and the non-treated control (Control –SA); the filled circle • indicates the difference between the SA treated sample versus the non-SA treated sample at that specific time point (HS plus recovery period).