Differential sex chromosome replication and dosage compensation in polytene trichogen cells of Lucilia cuprina (Diptera: Calliphoridae)

Abstract

Non banded sex chromosome elements have been identified in polytene trichogen cells of Lucilia cuprina using Y-autosome translocations, C-banding and Quinacrine fluorescence. The X chromosome is an irregular granular structure while the much smaller Y chromosome has both a dense darkly stained and a loosely organised segment. The X and Y chromosomes are under-replicated in polytene cells but comparison of C- and Q-banding characteristics of sex chromosomes in diploid and polytene tissues indicates that selective replication of non C-banding material occurs in both the sex chromosomes. Brightly fluorescing material in the Y chromosome is replicated to such an extent that it consists of half the polytene element, while the C-banding material, which makes up most of the diploid X chromosome, is virtually unreplicated. Differential replication also occurs in autosomes. In XXY males, and in males carrying a duplication of the X euchromatic region, a short uniquely banded polytene chromosome is formed. It is suggested that in males carrying two doses of X euchromatin a dosage compensation mechanism operates in which genes in one copy are silenced by forming a banded polytene chromosome.

Cytogenetic analysis of the Ethiopian fruit fly Dacus ciliatus (Diptera: Tephritidae)

“…The arms of each individual chromosome are unequal in length, corresponding to the submetracentric mitotic arms. No banded sex chromosomes were identified in the polytene complement of D. ciliatus, consistent with previous reports on C. capitata (Bedo 1986(Bedo , 1987Zacharopoulou 1987Zacharopoulou , 1990, B. oleae (Mavragani-Tsipidou et al 1992;Zambetaki et al 1995), B. tryoni (Zhao et al 1998), B. cucurbitae (Shahjahan and Yesmin 2002), B. dorsalis (Zacharopoulou et al 2011), R. cerasi (Kounatidis et al 2008) and R. completa (Drosopoulou et al 2010) and on the califorids, Lucilia cuprina (Childress 1969;Foster et al 1980;Bedo 1982) and Chrysomya bezziana (Bedo 1992). The heterochromatic network found in all polytene nuclei of D. ciliatus individuals (Fig.…”

“…2f-g) may represent the underreplicated XX and XY sex chromosomes. Even though this correspondence is proposed for other Diptera as well (Childress 1969;Bedo 1982Bedo , 1987Bedo and Zacharopoulou 1988;Mavragani-Tsipidou et al 1992;Shahjahan and Yesmin 2002;Kounatidis et al 2008;Drosopoulou et al 2010;Zacharopoulou et al 2011), further analysis is needed to establish the exact correlation between the two sets of chromosomal elements (mitotic and polytene) and to elucidate the fate of the sex chromosomes of the mitotic complement.…”

Genetic and cytogenetic analysis of the American cherry fruit fly, Rhagoletis cingulata (Diptera: Tephritidae)

“…The absence of banded sex chromosomes is consistent with previous reports on C. capitata (Bedo 1986(Bedo , 1987Zacharopoulou 1987Zacharopoulou , 1990, B. oleae (Mavragani-Tsipidou et al 1992;Zambetaki et al 1995), B. tryoni (Zhao et al 1998), B. curcubitae (Shahjahan and Yesmin 2002), R. pomonella (Procunier and Smith 1993) R. cerasi (Kounatidis et al 2008), R. completa (Drosopoulou et al 2010), Dacus ciliatus ) and on the califorids Lucilia cuprina (Childress 1969;Foster et al 1980;Bedo 1982) and Chrysomya bezziana (Bedo 1992).…”

Mitotic and salivary gland chromosome analyses in the Musca domestica L. (house fly) (Diptera: Muscidae)

“…These results suggest that, like Simulium ornatipes (Bedo, 1982b) and Chironomus melanotus (Steinemann, 1978), X liëtero-chromatin in the Musca domestica is underreplicated in a pronounced pattern. Similar results were obtained in Drosophila (Heitz, 1934;Gall, 1973), Sarcophaga bullata (Samols & Swift, 1979) and Lucilia cuprina (Bedo, 1982a). Thus it would now be interesting to undertake comparative studies to find the correlation that may exist between the sequence arrangement pattern of DNA organization and the under-replication of X heterochromatin in order to understand the evolution within the Diptera order.…”

“…Sciara coprophila (Gabrusewycz-Garcia, 1964). Chironomus melanotus (Steinemann, 1978), Sarcophaga bullata (Samols & Swift, 1979) and Lucilia cuprina (Bedo, 1982a), M. domestica heterosomes (X and Y) have polytene counterparts. In our studies, the size of the X chromosome in the diploid tissues was similar to that of the other autosomes, while it was much smaller in the salivary gland cells.…”