After a pre-heat shock at 36[o]C, Hsf4 mutants show substantial synaptic thermoprotection (as measured by the percentage of boutons responding) - thermoprotection is less than in pre-heat shocked wild type controls, but is greater than in Hsf4 mutants that did not receive a pre-heat shock treatment.
Homozygotes are viable at temperatures of 25oC or below. Homozygotes arrest at the 1st or 2nd larval instar stage and die after 2-3 days without any further growth or development at the non-permissive temperature of 29oC. Viability is rescued in homozygous or hemizygous Hsf2/Df(2R)PclP2 flies carrying Hsf+t8. Homozygous adults show reduced survival after a 40 minute heat treatment at temperatures of 38oC and above, when compared to wild-type flies or homozygous Hsf4 flies carrying two copies of Hsf+t8. The temperature-sensitive period is at approximately 1.5-2.5 days of development. Homozygous adults are viable and fertile when kept at 29oC upon eclosion. Females mosaic for homozygous clones in the germ line are fertile at both permissive and restrictive temperatures.