Fig. 6. Maize yabby genes are expressed on the adaxial side of incipient leaf primordia. (A) In situ hybridization with a knotted1 (kn1) specific probe shows expression in the meristematic cells of the SAM. (B-E) Hybridization of adjacent longitudinal sections with kn1 (B) and zyb14 (C), or kn1 (D) and zyb9 (E), shows that incipient leaf primordia defined by lack of kn1 expression comprise around six tiers of cells (indicated by arrowheads), and that zyb9 and zyb14 expression is limited to the adaxial side.