Localization of mitochondrial large ribosomal RNA in germ plasm of Xenopus embryos

• Published in: Current biology 1998-10, Vol.8 (20), p.1117-1120
• Main Authors: Kobayashi, Satoru, Amikura, Reiko, Mukai, Masanori
• Format: Article
• Language: English
• Subjects: Animals; Cell Polarity; Cytoplasm - metabolism; Drosophila; Freshwater; Germ Cells; Mitochondria - genetics; RNA - metabolism; RNA, Mitochondrial; RNA, Ribosomal - metabolism; Xenopus; Xenopus laevis
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/S0960-9822(98)70466-X

In Xenopus, factors with the ability to establish the germ line are localized in the vegetal pole cytoplasm, or germ plasm, of the early embryo [1–3]. The germ plasm of Xenopus, and of many other animal species including Drosophila, contains electron-dense germinal granules which may be essential for germ-line formation [4,5]. Several components of the germinal granules have so far been identified in Drosophila[6–10]. One of these is mitochondrial large ribosomal RNA (mtlrRNA), which is present in the germinal granules (polar granules) during the cleavage stage until the formation of the germ-line progenitors or pole cells [8,9]. MtlrRNA has been identified as a factor that induces pole cells in embryos that have been sterilized by ultraviolet radiation [11]. The reduction of mtlrRNA in germ plasm by injecting anti-mtlrRNA ribozymes into embryos leads to the inability of these embryos to form pole cells [12]. These observations clearly show that mtlrRNA is essential for pole cell formation in Drosophila. Here, we report that mtlrRNA is enriched in germ plasm of Xenopus embryos from the four-cell stage to the blastula. Furthermore, our electron microscopic studies show that this mtlrRNA is present in the germinal granules during these stages. Thus, mtlrRNA is a common component of germinal granules in Drosophila and Xenopus, suggesting that the mtlrRNA has a role in germ-line development across phylogenetic boundaries.