Figure 7. In situ hybridization- pool B transcripts.

Genes up-regulated post-settlement. (A) B1 (unknown function) is sharply up-regulated at settlement and is expressed in aboral ectodermal cells in the future calicoblast layer except at the rim of the base. (1, 2). Expression then fades centrally, leaving a circle of expressing cells just inside the rim (3). Slightly later this circle of expressing cells is maintained and expression is also detected along the developing septa. (B) B5 (DOMON domain protein) is initially expressed orally at the time of settlement (1, 2), with post-settlement expression limited to the rim, in a pattern almost complementary to B1. (C) B14 (carbonate transporter) is expressed immediately post-settlement in the aboral ectoderm of the future calicoblast layer (1–4). (D) B2 (a SCRiP) is expressed in the planula as a ring around the oral pore (1, 2). At the time of settlement it becomes delimited to the oral ectoderm (3–5). Post-settlement it continues to be expressed orally in addition to being expressed along the septa (6–9, arrows in 6,9). In (10) the main expression is in a more central ring and between the tentacle bases of the central polyp. (E) B26 (ZP domain) is first expressed orally at settlement (1, 2) and later along the developing septa (3–5, arrows 3, 4). Where available, the virtual northern blots are reproduced in this figure.