LOCALIZATION OF RIBOSOMAL DNA WITHIN OOCYTES OF THE HOUSE CRICKET, ACHETA DOMESTICUS (ORTHOPTERA: GRYLLIDAE)

Abstract

A large DNA-containing body is present in addition to the chromosomes in oocytes of the house cricket Acheta domesticus. Large masses of nucleolar material accumulate at the periphery of the DNA body during the diplotene stage of meiotic prophase I . RNA-DNA hybridization analysis demonstrates that the genes which code for 18S and 28S ribosomal RNA are amplified in the ovary . In situ hybridization indicates that the amplified genes are localized within the DNA body of early prophase cells . As the cells proceed through diplotene the DNA which hybridizes with ribosomal RNA is gradually incorporated into the developing nucleolar mass .1933 ; Bayreuther, 1956 ;Urbani, 1969) . Such a structure, referred to as the DNA body, is present in oocytes of the house cricket, Acheta domesticus (Nilsson, 1966) . The DNA body is limited to the oocytes and is not present in the nuclei of somatic cells . Microphotometric determinations made on the nuclei of Feulgen-stained pachytene stage cells show that the DNA body is present in addition to chromosomal DNA and accounts for approximately 25% of the DNA in the pachytene stage oocyte (Cave and Allen, 1969 a) . During diplotene large masses of RNA-containing material accumulate at the periphery of the DNA body (Heinonen and Halkka, 1967 ;Lima-de-Faria et al ., 1968) . Electron microscope examination indicates that the RNA-containing material associated with the body is characteristically nucleolar in appearance, the granular elements measuring 200-250 A in diameter (Allen and Cave, 1968 ; Cave and Allen, 1969 b ;Kunz, 1969) . Treatment with actinomycin D causes a typical segregation of components into

The Three-Dimensional Organization of the Amplified Ribosomal DNA Complex in Acheta

“…The hybridization showed that the sequences homologous to the satellite DNA were mainly localized in the major chromomeres of chromosomes 6 and 11 (17). When labeled (8). Amplification for ribosomal genes in Acheta has been demonstrated by homologous DNA * RNA hybridization at saturation.…”

“…(iii) Xenopus laevis has a DNA "spacer" that is about '50% of the total ribosomal DNA (14,15), but in Acketa the "spacer" DNA is between 80 and 92% of the total ribosomal DNA (9)(10)(11). (iv) In Acheta at late diplotene the ribosomal DNA * RNA complex can be seen, in the electron microscope, to be transferred to the cytoplasm as a large mass (16 (8,17). In the present report we describe the three-dimensional structure of these major chromomeres, which contain the ribosomal DNA.…”

“…Amplification of ribosomal genes has mainly been studied in two organisms, Xenopus laevis (1)(2)(3)(4)(5) and Acheta domesticus (6)(7)(8)(9)(10)(11). Certain aspects of the amplification process are easier to investigate in one of these organisms than in the other.…”

Frequencies of Circular Units of Nucleolar DNA in Oocytes of Two Insects, Acheta domesticus and Dytiscus marginalis, and Changes of Nucleolar Morphology during Oogenesis

“…1c; cf. [2,[26][27][28][29][30][31]. The ultrastructure of the early phase of this DNA-containing aggregate body with its complex architecture has been sufficiently well described in a series of articles (see refs.…”

Localization of NORs in the nucleolus-DNA body complex of the oocyte from the nemertine Amphiporus lactifloreus.

“…During oogenesis in nemertines, successive cytological features of the nucleus differ greatly according to whether the species belongs to the hoplonemertines or heteronemertines (1,2). The nucleus of the premeiotic oocyte from the hoplonemertine Amphiporus lactifioreus contains a DNA-rich body that somewhat resembles the DNA body in the germ cells of insects (7,8,26,28,30). During early vitellogenesis, this DNA body generates a peculiar, highly developed nucleolar apparatus, the nucleolus-DNA body complex, which has been described elsewhere (38).…”