Persistence of maternal RNA in Engystomops embryos

Females of the neotropic anuran Engystomops pustulosus were injected with 3H‐uridine and produced eggs containing RNA labeled during synchronous oogenesis. The >4S, labeled RNA extracted from these eggs, and from embryos which developed from them, was hybridized with an isolated repetitive fraction of Engystomops DNA, and the hybrids were assayed on hydroxyapatite columns. About 1% of the egg RNA is transcribed from DNA sequences included in this fraction. Hybridization of labeled ribosomal RNA was minimized by the addition of excess unlabeled ribosomal RNA extracted from Xenopus ovaries. The labeled RNA of embryos up to the tadpole stage was identified as maternal transcript by competition experiments with unlabeled Engystomops oocyte RNA. It was found that maternally‐labeled RNA is retained in embryos at least up to the tadpole stage.