a, Identification of TMK1 C terminus. Full-length TMK1 and TMK1C-terminus were immunoprecipitated from gTMK1-GFP seedlings and separated by SDS–PAGE. Three biological repeats were performed with similar results. b, Mass spectrometry analysis of the TMK1C-terminus band. Results are displayed as spectral counts of the peptide fragment (y axis) along the TMK1 amino acid position (x axis). c, Quantification of western blotting results shown in Fig. 1f. d, Treatment with yucasin and auxin affects TMK1 cleavage. e, Quantification of western blotting results shown in d. f, Quantification of western blotting results shown in Fig. 1g. n = 3. g, The effect of treatment with PEO-IAA was tested by the inhibition of auxin-mediated IAA28 degradation by 35S-IAA28-MYC transgenic line. Col-0 was used as a negative control; the asterisk indicates a non-specific band. h, The effect of treatment with PEO-IAA on auxin-mediated TMK1 cleavage. Three biological repeats. i, The effect on TMK1 cleavage of treatment with 10 μM ACC for a short period. Three biological repeats. For d, g–i, the same membrane was stripped and blotted with anti-actin antibodies as a loading control. j, Apical-hook development in the presence and absence of ACC in both Col-0 and tmk1-1 plants. n = 20. Data are mean ± s.e.m.; dots show data distribution. n denotes the number of biologically independent seedlings.