Tissue-specific variations in the induction of Hsp70 and Hsp64 by heat shock in insects

The patterns of heat-induced synthesis (37 degrees C to 45 degrees C) of he at shock proteins (Hsps) in different tissues of grasshoppers and cockroach es from natural populations and in laboratory-reared gram-pest (Heliothis a rmigera) were examined by S-35-methionine labeling and sodium dodecyl sulfa te-polyacrylamide gel electrophoresis fluorography. Whereas 45 degrees C wa s lethal in most cases, optimal induction of Hsp synthesis was seen between 37 degrees C and 42 degrees C. The ongoing protein synthesis was not much affected at these temperatures, except in the tissues of adult H armigera e xposed to 42 degrees C. The profiles of the Hsps induced in the tissues of the insects, however, were different. From the relative abundance of the sy nthesis of 70-kDa (Hsp70) and 64-kDa (Hsp64) polypeptides, three categories of heat shock response were identified: (1) induction of abundant Hsp70 bu t little Hsp64 (malpighian tubules, male accessory glands, and ovaries of a dult grasshoppers), (2) abundant Hsp64 but little Hsp70 (testes of adult gr asshoppers, testes and malpighian tubules of adult cockroaches, and testes, malpighian tubules, and fat bodies of H armigera larvae), and (3) inductio n of both Hsp70 and Hsp64 in more of less equal abundance (ovaries of adult cockroaches, salivary glands of H armigera larvae, and malpighian tubules, male accessory glands, testes, and ovaries of adult H armigera). Cockroach es collected from storerooms showed detectable synthesis of Hsp64 and/or Hs p70 only after heat shock, but those collected from drains showed detectabl e synthesis of both Hsp70 and Hsp64 in different tissues without heat stres s. Western blotting showed that the 64-kDa polypeptide in these insects is a member of the Hsp60 family. Grasshopper testes, which synthesized negligi ble Hsp70 but abundant Hsp64 after heat shock, developed thermotolerance. T hus, heat shock response is modulated by developmental and environmental fa ctors in different tissues of insects.