Fig. 3. Opposite effects of NvFGFa1 and NvFGFa2 morpholinos on apical organ formation. (A) Autoradiograph of transcription-translation reactions in the presence of ³⁵S-labeled methionine. Plasmids and MOs added to the reaction are indicated above the lanes. Tested MOs only inhibit translation of the corresponding transcripts. (B-D) Scanning electron microscopy of 4-day-old planulae injected with the MOs indicated. The aboral pole is marked by asterisks; arrows in B point to the apical tuft. NvFGFa1 MO leads to loss, NvFGFa2 MO to expansion of the apical organ. (E-G) Visualisation of the ciliary tuft by anti-acetylated tubulin antibody staining of 48-hpf planulae injected with MOs indicated. Lateral views, aboral pole to the left. The NvFGFa2 MO causes premature formation of an expanded apical tuft. (H,I) Animals with a differentiated apical organ treated from 72 hpf to 120 hpf with 0.1% DMSO or 20 µM SU5402/0.1% DMSO. SU5402 causes loss of the apical organ.