Figure 1.

leafbladeless1 (lbl1) establishes leaf polarity by demarcating the domains of hd-zipIII and miR166 expression. (A) lbl1-rgd1 seedling with thread-like abaxialized leaves. (B) Longitudinal section through a wild-type apex shows rld2 expression in the SAM, vasculature, and adaxially in leaf primordia (arrowheads). (C) In lbl1-rgd1, meristematic, and adaxial (arrowheads) rld2 expression is reduced. (D) Precursor levels for mir166i, mir166h, and mir166c are increased in lbl1-rgd1 compared with wild type, whereas expression of mir166a is reduced. (E) In wild type, miR166 is expressed below and on the abaxial side of the incipient leaf (arrow). (F) In lbl1-rgd1, miR166 is expressed at the base of the SAM and uniformly throughout the incipient (arrow) and P1 primordia. Arrowheads in E and F mark the base of the incipient leaf.