Fig. 2. Local induction of Nicta;CycA3;2 and Sp;cdc25 gene expression leads to cell proliferation on the leaf margin. (A) Cross section through a tobacco shoot apex to show site of Ahtet application (red spot) on the abaxial flank of a P2 primordium. (B) Cross section of a P2 primordium from a Tet::Sp:cdc25 plant 24 hours after local induction on one flank (red line). (C) Cross section of a P2 primordium from a Tet::Nicta;CycA3;2 plant 24 hours after local induction on one flank (red line). (D) Tangential section through a primordium from a Tet::Nicta.CycA3;2 plant 72 hours after Ahtet induction on one flank. An accumulation of small cytoplasmically dense cells is apparent on the induced flank (i) compared with the non-induced flank (ni). (E,F) Magnifications of the induced flank (E) and non-induced flank (F) shown in D. Cells in E are small, dense and meristematic. Cells in F have undergone vacuolation. (G) In situ hybridisation of a section of a P2 primordium from a Tet::Nicta;CycA3;2 plant 72 hours after Ahtet induction on one flank. The section has been hybridised with a probe for Nicta;CycA3;2. A larger area of signal (blue/purple) is present in the induced flank (i) compared with the non-induced flank (ni). (H) As in G except that the primordium was mock-induced (i) with buffer on one flank. (I) Cross section of primordium of Tet::Sp:cdc25 plant 72 hours after Ahtet induction on one flank. The induced flank (i) is slightly thicker than the non-induced (ni) and the lateral vein (v) differentiation in the non-induced flank is not apparent in the induced flank. (J,K) Examples of Ahtet-induced flanks of Tet::Sp:cdc25 primordia. Note the disorganised cellular patterns leading in some areas to apparent cell death and compression and poorly developed vascular tissue (v). (L) Cross section of leaf blade from a non-induced flank showing highly ordered cellular structure and appropriate vascular differentiation (v). Bars: 40 µm in E and F; 60 µm in G and H; 75 µm in B and C; 100 µm in D, J, K, and L; 120 µm in I.
