In this paper we report a transcriptional and translational study of the hsp83 gene of Drosophila subobscura. This gene is located at the 18C region of the J chromosome. A monoclonal antibody raised against hsp83 was used for the immunological detection of this protein by Western blotting throughout the development of D. subobscura in control and heat-shock conditions. Our results indicate that puff 18C is not only heat-shock inducible but is also expressed during normal development and its level of expression increases at the end of the prepupa period. We detected hsp83 at normal temperatures, in particular developmental stages with the exception of the larval and the beginning of prepupa formation. Hsp83 was induced by heat shock in all stages studied with the exception of 1st instar larvae. We found that temperatures in excess of 26 degrees C were sufficient to induce hsp83. In addition, at temperatures from 26 to 34 degrees C, the increase in hsp83 synthesis was accompanied by increased transcription of the hsp83 gene; this positive correlation was not observed at 37 degrees C.

Immunofluorescent techniques have been used in the analysis of DNA-RNA hybrids occurrence and its relationship to transcriptional events on polytene chromosomes of Drosophila subobscura. We have studied the distribution of these hybrids on uninduced/induced chromosomes. Two different indirect immunofluorescence methods for the detection of DNA-RNA hybrids were used. Our data confirm the positive correlation between localization of DNA-RNA hybrids and transcriptional activity by following the Büsen et al procedure (1982). Using the other protocol, which allows chromosomal DNA-RNA to denature and renature, makes DNA-RNA hybrids detectable not exclusively in active chromosomal regions. Taking Büsen as method of choice, this technique allowed to localize the exact transcriptional active sites on puffs: hybrid fluorescence was restricted to marginal or central puff areas. Moreover, no correlation between fluorescence and puffs size was found. However, our studies on induced chromosomes indicate that: 1) the 15DE puff, previously described as t-puff, was not really a heat shock puff, since no transcriptional activity was detected; 2) hybrid fluorescence at 2C and 31CD regions was observed. No labelling was found in these loci in the autoradiography data, reported by other authors.

When individuals of Drosophila subobscura at 0 hr prepupa are submitted to anoxia (4 hr and 24 hr, respectively), their puffing pattern is very similar to that shown by individuals at the moment of development in which treatment began. The same expression of genes (the same puffing pattern and the same protein pattern) is induced in this species by recovery from anoxia as well as by heat shock treatment at 31 degrees C.