Immunofluorescence localization of DNA:RNA hybrids in Drosophila melanogaster polytene chromosomes

Abstract

Sites of transcriptional activity in the whole set of Drosophila melanogaster polytene chromosomes have been localized by means of fluorescent antibodies against DNA:RNA hybrid molecules and compared with results on 3H-uridine incorporation obtained earlier. The majority of large and small puffs with intensive 3H-uridine incorporation demonstrate bright fluorescence. Moreover, bright fluorescence is also observed for a large number of small puffs though the intensity of 3H-uridine incorporation is low. Some prominent puffs with high levels of 3H-uridine incorporation show weak fluorescence. Condensed bands, as a rule, do not show fluorescence. The regions that look like interbands under the light microscope are not real interbands, but consist of minibands visible only in the electron microscope (EM). However, a region that has been previously studied by EM and proven to be a real interband between two thick dark bands (100B3-100B4-5) showed fluorescence. These data support previous suggestions indicating a substantial contribution of transcriptional products from small puffs and interbands to the whole transcriptional system of polytene chromosomes.

High order structure of Chironomus polytene chromosomes by scanning electron microscopy.

“…Some recent studies have claimed the transcriptional activity of interbands (Jamrich et al 1977, Semenshin et al 1979, Vlassova et al 1985. This seems quite probable since decondensation of chromatin fibers should be at least related to transcriptional activity.…”

“…It is, therefore, impossible to exactly correlate band and interband configurations in the stained preparations with those from TEM images. The necessity of TEM for the detection of "real" interbands in the sectioned materials has been claimed by Vlassova et al (1985).…”

Developmental puffing activity in the salivary gland and Malpighian tubule chromosomes ofAcricotopus lucidus (Diptera, Chironomidae)

“…Thus, A. lucidus falls within the range that has been ascertained from the salivary glands of other Diptera studied intensively. The range includes C. tentans with 277 (Pelling 1964), C. thummi with 336 (Kiknadze 1981), D. melanogaster with 341 (Zhimulev 1974) or 355 (Vlassova et al 1985) and D. virilis with 348 active loci (Kress 1972).…”

Chromomeric organization of polytene chromosomes

“…These interbands are transcribed during the whole period of analysis from the third instar until 4-6 h prepupa (Vlassova et al, 1985;Umbetova et al, 1991b).…”