Fig. 5. PP2C.D1 is required for asymmetric acid growth during apical hook development.

(A) Immunolabeling and signal quantification of PM H⁺-ATPase and Thr⁹⁴⁷-phosphorylated PM H⁺-ATPase in WT and pp2c.d1-1 mutant. Scale bars, 50 μm. (B) Apoplast pH and signal quantification at the hook region using the Apo-pHusion marker line in WT and pp2c.d1-1 backgrounds. Scale bars, 50 μm. (A and B) Details of the signal quantification can be found in Materials and Methods. (C) Proposed model for hypocotyl elongation and apical hook development during etiolated seedling development. A molecular signaling pathway underlying auxin-mediated inhibition of cell elongation at the concave side of the hook is shown at the bottom.