Differentiation zones of tan1 air9 roots expressing full-length TAN1-YFP, TAN1-∆I-YFP, and TAN1-∆II-YFP. A to D, Maximum projections of 10 Z-stacks of 0.2 µm of propidium iodide-stained roots of tan1 air9 plants (A) and tan1 air9 plants expressing TAN1-YFP (B), TAN1-∆I-YFP (C), and TAN1-∆II-YFP (D). Bar = 200 µm. E, Cell file rotation angles of double mutant tan1 air9 plants expressing TAN1-YFP, TAN1-∆I-YFP, or TAN1-∆II-YFP and the corresponding nontransformed sibling plants (-sib). Angles greater than 90° are left twisting and angles less than 90° are right twisting. The asterisk indicates a significantly smaller variance (P < 0.001 by Levene’s test; n = 330).