Fig. 3.

Seryp is proteolyzed prior to Vitellogenin. (A) By bulk measurement (western blotting), Vitellogenin derivatives (LV1, LV2) and Seryp species (p50, p48, p30) decline at later stages of development. Extracts are ordered by time post-fertilization (pf) and Nieuwkoop-Faber stage (NF). Load: 1/500 (top blot) or 1/50 (bottom blot) of single embryos. (B) Quantitative dot blotting of extracts prepared from single embryos confirms that Seryp is consumed prior to Vitellogenin during development. Absolute levels of LV1 and Seryp p50 were obtained from standard curves relating antibody binding (fluorescence intensity) to absolute amounts of each protein. Each dot is the average for a single embryo ±1 s.d. (C) Seryp could not be detected in many YPs in tailbud embryos. Notochord (1) and prosencephalon (2) (yellow boxes) from a sagittal section of a tailbud embryo (top, stage 26, scale bar: 100 μm) were immunostained with anti-Vtg and anti-Seryp and imaged by confocal microscopy (bottom, scale bars: 10 μm). Blue arrows highlight YPs without detectable Seryp.