In situ transcription analysis of chromatin template activity of the S-chromosome of Drosophila following high molar NaCl treatment.

The chromatin template activity of the polytene chromosomes in larval salivary glands of Drosophila hydei has been assayed by in situ transcription, on the fixed chromatin using E. coli RNA polymerase holoenzyme and 3H-UTP as the monitoring substrate, both with optimal salt and high salt concentration (1 M NaCl). Results reveal an increase in the net transcription of all chromosomes in the high salt treatment series in comparison with the control. The X-chromosomes of the male larval gland also shows an increase in the labelling following the high salt treatment, but the increase is significantly less than that of the autosomes of the same nucleus. On the basis of these findings it has been suggested that the X-chromosomal hyperactivity of the male, as normally known to exist, might be guided by an inherent modulation of the structure of the X-chromatin.