TISSUE-SPECIFIC VARIATION IN HSP70 EXPRESSION AND THERMAL-DAMAGE IN DROSOPHILA-MELANOGASTER LARVAE

All tissues of larval Drosophila melanogaster express Hsp70, the major heat-shock protein of this species, after both mild (36 degrees C) an d severe (38.5 degrees C) heat shock, We used Hsp70-specific immunoflu orescence to compare the rate and intensity of Hsp70 expression in var ious tissues after these two heat-shock treatments, and to compare thi s with related differences in the intensity of Trypan Blue staining sh own by the tissues, Trypan Blue is a marker of tissue damage, Hsp70 wa s rarely detectable before heat shock, Brain, salivary glands, imagina l disks and hindgut expressed Hsp70 within the first hour of heat shoc k, whereas gut tissues, fat body and Malpighian tubules did not expres s Hsp70 until 4-21 h after heat shock, Differences in Hsp70 expression between tissues were more pronounced at the higher heat-shock tempera ture, Tissues that expressed Hsp70 slowly stained most intensely with Trypan Blue. Gut stained especially intensely, which suggests that its sensitivity to heat shock may limit larval thermotolerance, These pat terns further suggest that some cells respond primarily to damage caus ed by heat shock rather than to elevated temperature per se and/or tha t Hsp70 expression is itself damaged by heat and requires time for rec overy in some tissues.