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Fig. 2. X-twi expression at stages 6' /2-7 and 11 1/2. (A-1 and A-2) Transverse sections of a stage 6'/} embryo (A-I) and through a stage 7 embryo (A-2) which had been hybridized with the antisense digoxigenin-labeled probe. The X-twi transcripts are detected in bfastomeres from animal region. Notice that the transcripts are restricted towards the ventral part of the outermost animal blastomeres, and in the facing cytoplasm of the blastomeres that form the second row of eel/s. (A-3) Transverse section of a stage 6/7 embryo which had been hybridized in parallel with the sense digoxigenin-Iabeled probe. No meaningful staining could be detected within all the sections. (B.1) On a stage 11' 1/2 whole embryo, Xtwi transcripts are seen in the dorsal/posterior region above the dorsal blastopore (antisense probe: embryo to the left). The control embryo (sense probe) is shown on the right: no signal is detected in it. (B-1') Schematic drawing of the embryo hybridized with the antisense probe, with the plan of the sections. (B-2 and B.2') Sagittal sections show the detectable X-twi RNA in the involuted presumptive chorda-mesoderm cells. ani, animal pole; Arc. F., archenteron floor; Arc. R., archenteron roof. 0, dorsal region; Mes., involuted presumptive chordo-mesodermal cells,- SLN, sensorial layer of the neurectoderm; V, ventral region; veg, vegetative pole. Bar, 100 mm. |