Analysis of the expression level of K31 gene at different developmental stages in zebrafish. (A) Real time RT-PCR analysis of K31 transcription during development. K31 transcripts are expressed maternally in the ovum. From zygote to pharyngula period, K31 has a characteristic of constitutive expression gene. GAPDH was used as endogenous reference. (B-J) Expression of K31 transcripts as detected by WISH during embryogenesis in zebrafish. (B) ovary, (C) 8-cell stage (1.25 hpf, hours post-fertilization), (D) sphere stage (4 hpf), (E) 75% epiboly (8 hpf), (F) 10-somite stage (13 hpf), (G) 1 dpf (day post-fertilization), (F) 2 dpf, (I) 2 dpf embryo with arrow indicating the hatching gland, (J) 2 dpf embryo with arrow indicating the pectoral fin. Embryos in C-I are lateral views, C-E with the animal pole to the top, and the dorsal to the right, F-I with dorsal to the top and anterior to the left; embryo in J is dorsal view, with anterior to the left.