EFFECT OF ENGINEERING HSP70 COPY NUMBER ON HSP70 EXPRESSION AND TOLERANCE OF ECOLOGICALLY RELEVANT HEAT-SHOCK IN LARVAE AND PUPAE OF DROSOPHILA-MELANOGASTER

To determine how the accumulation of the major Drosophila melanogaster heat-shock protein, Hsp70, affects inducible thermotolerance in larva e and pupae, we have compared two sister strains generated by site-spe cific homologous recombination, One strain carried 12 extra copies of the Hsp70 gene at a single insertion site (extra-copy strain) and the other carried remnants of the transgene construct but Lacked the extra copies of Hsp70 (excision strain), Hsp70 levels in whole-body lysates of larvae and pupae were measured by ELISA with an Hsp70-specific ant ibody, In both extra-copy and excision strains, Hsp70 was undetectable prior to heat shock, Hsp70 concentrations were higher in the extra-co py strain than in the excision strain at most time points during and a fter heat shock. Pretreatment (i.e. exposure to 36 degrees C before he at shock) significantly improved thermotolerance, and this improvement was greater and more rapid in larvae and pupae of the extra-copy stra in than in those of the excision strain, The experimental conditions r esemble thermal regimes actually experienced by Drosophila in the fiel d. Thus, these findings represent the best evidence to date that the a mount of a heat-shock protein affects the fitness of a complex animal in the wild.