Figure 4.

Ectopic expression of p38a rescues heat-shock sensitivity. D-p38a¹ mutants are sensitive to 37°C heat shock, as previously shown. Expression of D-p38a with one copy of the transgene in a wild-type background has no effect. Expression of D-p38a in one copy in a D-p38a¹ background rescues heat sensitivity to 86.8% of wild type, demonstrating that the D-p38a¹ heat-shock sensitivity phenotype is due to the loss of D-p38a. However, expression of D-p38a with two copies of the transgene in a D-p38a¹ background rescues heat sensitivity to only 75.4% of wild type. Expressing D-p38a with two copies of the transgene in a wild-type background reduced the survival rate to just 33.6% of control, suggesting that high levels of D-p38a also inhibit the ability of flies to adapt to heat shock. An average of 200 flies was tested for each genotype.