Fig. 4. The nature of the kan1 kan2 blade outgrowths. (A) The outgrowths developing on the abaxial side of kan1-2 kan2-1 leaves appear nearly radial, with cell types normally found on leaf margins positioned around their entire circumference. (B) In wild-type seedlings, these cells show blue staining when the GUS reporter is driven by the enhancer trap YJ158. (C) This reporter drives GUS throughout the epidermis of the kan1 kan2 blade outgrowths and in scattered cells on the abaxial leaf surface. (D) Transverse section through a mature wild-type leaf displaying an asymmetric anatomy both within the leaf and in the vascular bundle. (E,F) In mature kan1 kan2 leaves, numerous vascular bundles are formed, connecting the outgrowths to leaf main bundles (E). The radial outgrowths have nearly radial anatomy, with a large bundle (arrow) found in their center (F). (G) Close-up of a wild-type minor leaf bundle showing xylem vessel members (arrow) positioned adaxially, while phloem sieve tube elements (arrow) are located abaxially. (H) In kan1 kan2 the central bundles of the outgrowths have clusters of phloem tissue surrounding xylem vessel members. (I,J) The prolonged period of cell division in the abaxial region of kan1 kan2 leaves is responsible for the formation of outgrowths, reflected by the maintenance of the densely cytoplasmic appearance of these cells (I), and correlated with prolonged localized FIL mRNA expression (J). (K) Earlier in leaf development, high levels of FIL expression demarcate presumptive outgrowths (arrow) while a lower level of FIL expression is throughout the abaxial region of the leaves. ab, abaxial; ad, adaxial; ph, phloem; xy, xylem. Scale bars: 1 mm (A), 50 µm (B-K).