RNA synthesis during early embryogenesis of mass cultured highly synchronized coleopteran embryos.

Bruchidius embryos are shown to be well suited for biochemical studies during early embryogenesis. Mass cultivation is easy, and highly synchronized embryos can be obtained in large numbers (104-105 eggs). A method for in vivo incubation is described which allows the labelling of newly synthesized RNA. The kinetics of3H-ruidine uptake, phosphorylation and incorporation into RNA are presented. By autoradiography, the distribution of newly synthesized RNA is shown. Thereby, stage-specific differences were found in the labelling pattern of vitellophage nuclei, of blastoderm nuclei and of the nuclei of pole cells. The labelling of the cytoplasm remains weak until cellular blastoderm is formed. During late blastoderm and at gastrulation this label increases markedly. Gel electrophoresis of isolated RNA shows that at cellular blastoderm formation most of the label occurs in a region between 18 S and 7 S. Later on, at the onset of gastrulation, the3H-uridine incorporation found in isolated RNA is raised about 10 fold and rRNA synthesis becomes prominent. In a "chase" experiment, the processing of precursor RNA molecules into shorter RNA species, especially into mature rRNA and 5S RNA, is shown. The advantages of theBruchidius embryo for the biochemical analysis of early RNA synthesis and the regulation of rRNA synthesis in insect embryos are discussed.