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Fig. 2. Upstream genomic Xag1 sequence drives cement gland-specific expression. In situ hybridization for endogenous Xag1 (A,B) or gfp transcripts (C,E-J) in early neurula (A,C,E,G) or tailbud (B,F,H-J) embryos. (D) GFP fluorescence in a transgenic tailbud embryo. Endogenous Xag1 is expressed at the anterior of the embryo from the end of gastrulation (A) in the cement gland (black arrowhead) and hatching gland primordia (black arrow), and in the cement gland (white arrowhead) and hatching gland (white arrow) in the tailbud embryo (B). This expression pattern is replicated by 8 kb of Xag1 genomic sequence driving a GFP reporter gene (C,D). (E-H) Cement gland-specific gfp expression is driven from early neurula stages by –275 bp (E,F) and –102 bp (G,H), but not 73 bp of upstream sequence (I) or the Xag1 TATA box (J) (arrowheads indicate location of cement gland). Expression is weaker with the –102 bp construct (G,H) than with the longer –275 bp construct (E,H), especially at neurula stages (arrowheads). Po, posterior; np, neural plate. |
