Fig. 5.

The PPI active site is required for SlCyp1 function in the phloem to control auxin response. (A) 3D structure of HsCypA (left) and a homology-based model of SlCyp1 (right). The shaded areas at the end of the arrows indicate the active-site residues that were targeted for mutagenesis in HsCypA (Zydowsky et al., 1992) and the corresponding amino-acids in SlCyp1. 3D modeling was performed according to Arnold et al. (2006). (B) Primary root length of VFN8, dgt, SlCyp1-PX-9, SlCyp1-PX-R62A, SlCyp1-PX-H133Q, and SlCyp1-PX-W128A tomato seedlings grown on various concentrations of NAA: 0 µM (white bars), 0.5 µM (grey bars), or 1 µM (black bars). Tomato seeds were sown on standard germination paper soaked with distilled water containing each of the indicated NAA concentrations. Root length measurements were taken 14 d after sowing. (C) Images showing the gravitropic response of VFN8, dgt, and SlCyp1-PX-9 seedlings 48 h after a gravity stimulus. Soon after the emergence of the radicle (2–5 mm) seedlings were oriented horizontal to the gravity axis (represented by the dashed lines) and allowed to grow for 48 h, after which the angle of curvature (represented by the dashed arrows) was measured. Scale bar = 1 cm. (D) Gravitropic curvature angles of VFN8, dgt, SlCyp1-PX-9, SlCyp1-PX-R62A, SlCyp1-PX-H133Q, and SlCyp1-PX-W128A 48 h after the gravity stimulus. The data represent the means of six biological replications (±SE). Identical letters indicate no significant differences between each replicate at P<0.05 by Tukey’s HSD-test. (This figure is available in colour at JXB online.)