Accumulation of a specific subset of D. melanogaster heat shock mRNAs in normal development without heat shock.

During normal development in D. melanogaster, messenger RNAs for three of the seven heat shock proteins (hsp83, hsp28 and hsp26) accumulate in adult ovaries and are abundant in embryos until blastoderm. The three mRNAs appear to originate in nurse cells and subsequently pass, during stages 10-11, into the oocyte. Little if any of the four other heat shock mRNAs is present in unshocked ovaries or embryos at any time examined. Pre-blastoderm embryos fail to accumulate these heat shock mRNAs even if subjected to heat shock. The accumulation in normal oogenesis of mRNAs for only three of the seven heat shock proteins indicates the existence of differential, possibly multiple controls of heat shock gene expression, and suggests that heat shock proteins hsp83, hsp28 and hsp26 function in the oocyte or early embryo.