Fig. 3. Expression of the meristem marker genes LeWUS and LeT6 in the meristem after ablation of the CZ. Gene expression was visualised by in situ hybridisation with ³⁵S-labelled riboprobes. Signal appears as yellow grains. All images are transverse sections, except for I and J which are longitudinal sections. Position of the lesion is indicated by yellow arrowheads. (A-G) Expression of LeWUS. (H-L) Expression of LeT6. (A) Expression of LeWUS in a control meristem. (B) Expression of LeWUS immediately after ablation of the CZ (yellow arrowhead). No LeWUS expression can be detected. (C) Expression of LeWUS 1 day after ablation of the CZ. A ring-shaped area around the lesion expresses LeWUS at low levels (arrows). (D) Expression of LeWUS 2 days after ablation of the CZ. The lesion (arrowhead) is closed, and the LeWUS signal becomes confined to one side of the lesion. (E) Expression of LeWUS 4 days after ablation of the CZ. The LeWUS-expressing zone at the flank has resolved into a new WUS centre with normal dimensions (compare with A). (F) Expression of LeWUS 6 days after ablation of the CZ. A new functional meristem centre with a normal WUS centre has been re-established. (G) Expression of LeWUS 4 days after ablation of the CZ. Two new WUS centres are evident at opposite sides of the lesion. (H) Expression of LeT6 in a control meristem. Note down-regulation of LeT6 in the youngest primordium (P₁) and at the site of incipient leaf formation (I₁). (I) Expression of LeT6 in a control meristem. Note down-regulation of LeT6 in the youngest (P₁) and second youngest primordium (P₂). (J) Expression of LeT6 6 hours after ablation of the CZ. LeT6 remains active at the periphery of the meristem and is only decreased in the vicinity of the lesion. (K) Expression of LeT6 5 days after ablation of the CZ. The lesion is displaced, and LeT6 is expressed in the new meristem centre and excluded from leaf primordia. (L) Expression of LeT6 4 days after ablation of the CZ. Two new LeT6-expressing meristems are induced on opposite sides of the lesion. P₃, P₂, and P₁ indicate leaf primordia that were present at the beginning of the experiment; I₁, I₂, I₃, and I₄ indicate primordia formed after the ablation. Scale bars: 100 µm.