CELL-SPECIFIC EXPRESSION AND HEAT-SHOCK INDUCTION OF HSPS DURING SPERMATOGENESIS IN DROSOPHILA-MELANOGASTER

The developmental and heat-shock-induced expression of two small heat- shock proteins (Hsp23 and Hsp27) was investigated during spermatogenes is in Drosophila melanogaster. Both of these Hsps were expressed in un stressed and stressed male gonads as shown by immunoblotting, Immunost aining of whole-mount organs and thin sections of testes showed that a n anti-Hsp23 antibody specifically decorated cells of the somatic line age, such as the cyst cells and the epithelial cells of the testis and of the seminal vesicle. Hsp27 was expressed in some somatic cells (cy st cells and epithelial cells of the accessory glands) and, in additio n, was also visible in the maturing spermatocytes of the germline, The same cell-specific pattern of expression was observed after heat shoc k, and cells which did not express Hsp23 and Hsp27 in the absence of s tress were similarly unable to mount a heat shock response for these s -Hsps. However other Hsps such as Hsp70 and Hsp22 were induced under h eat-shock conditions in testes. Actinomycin D prevented the heat-induc ed accumulation of these Hsps indicating that the induction of Hsps wa s regulated at the transcriptional level, The heat shock transcription al factor of Drosophila (DmHSF), present in significantly lower amount in testes when compared to other tissues such as the head, was shown to be required for the heat activation of Hsp22 and Hsp70. Immunostain ing revealed that HSF expression was restricted to specific cells such as cyst cells, epithelial pigment cells, spermatogonia and spermatids but not the primary spermatocytes. These data show that the expressio n and induction of the different small Hsps is regulated in a cell-spe cific manner under both normal and heat shock conditions and suggest t hat factors other than the DmHSF are involved in this regulation in ma le gonads.