Fig. 4. UFO expression pattern during flower development. The expression pattern of UFO was examined by RNA in situ hybridisation in wild type (A-G) and in ufo-2 35S::UFO_ind before ethanol induction (H,I) and 24 hours after the beginning of an 8-hour ethanol pulse (J,K). (A-E) Transverse sections, (F-K) longitudinal sections. (A-E) UFO is expressed in four discrete spots corresponding to expected positions of the petals. The expression subsists weakly in the petal primordia after their initiation in a stage 6 flower (arrowheads). ^*, stamens. (F) In wild-type early stage 3 flowers, UFO is expressed in a cup-shaped domain. (G) A stage 4 wild-type flower with UFO expressed at the boundary of the meristem and the sepals. (H) UFO is expressed in a non-induced ufo-2 35S::UFO_ind early stage 3 flower in a cup-shaped domain similar to the wild-type. (I) In a non-induced ufo-2 35S::UFO_ind stage 4/5 flower, UFO is expressed at the axils of the sepals. (J,K) 24 hours after an 8-hour ethanol vapour treatment, UFO is uniformly expressed in a ufo-2 35S::UFO_ind early stage 4 flower (J) or in a stage 4/5 flower (L). A-E are at the same magnification and F-K are at the same magnification. Bars: 100 µm.