Mitochondrial small ribosomal RNA is a component of germinal granules in Xenopus embryos

Mitochondrial large rRNA (mtlrRNA) and small rRNA (mtsrRNA) have been ident ified as components of germinal granules in Drosophila. We have previously reported that mtlrRNA is present on the germinal granules in Xenopus embryo s. Here we report that mtsrRNA is also a common component of the germinal g ranules. Extra-mitochondrial mtsrRNA is localized on the surface of germina l granules in germ plasm from four-cell to blastula stags, then disappears until the completion of gastrulation. This temporal and spatial distributio n pattern is identical to that of mtlrRNA. During the stages when both mito chondrial rRNAs are present around the germinal granules, mitochondrial typ e ribosomes, typified by their smaller size, were also present on the surfa ce of the germinal granules. (C) 2001 Elsevier Science Ireland Ltd. All rig hts reserved.