Figure 1.

Activation of rDNA transcription recruits fibrillarin from the CB. (A) Immunostaining for the CB marker coilin (green) and the snoRNP component fibrillarin (magenta) over a developmental time course from the 64-cell stage to 8 hours post-fertilization (hpf). Insets magnify (2x) 2 representative bodies in the same nucleus (indicated by gray and yellow arrowheads). All scale bars, 10 μm. A Gaussian blur filter was applied for display reasons. (B) Detection of the onset of rDNA transcription through RT-qPCR amplification of pre-rRNA. Primers complementary to the 5′ external transcribed spacer (ETS) of 18S RNA were used to amplify pre-rRNA; signal (y-axis) was normalized to RT-qPCR values for pre-mitochondrial RNA, which was previously shown to be constant over these time points.²⁷