Fig. 6.
S-nitrosylation of IAA17 at Cys-70 attenuates auxin responsiveness. A: Seeds with the indicated genotypes were germinated and grown on 1/2 MS media with sucrose for 5 days. Seedlings were then transferred onto media containing 10 nM 2,4-D and cultured for additional 6 days. Representative seedlings were photographed. B and C: The primary root length and the lateral root density of seedlings shown in (A). n = 50 and n = 20 seedlings are used for the analysis of the root length and the lateral root density, respectively. Data are mean ± SD from three independent experiments and gray dots represent the individual values. The statistical significance is determined by a two-sided Student’s t-test (Paired two samples for means). **, P < 0.01 when compared to Col-0. D: A proposed model of NO-regulated auxin signaling. NO-mediated S-nitrosylation of IAA17 at Cys-70 may cause its structural alterations, resulting in the inhibition of its interaction with the SCFTIR1 complex and consequently its proteasomal degradation induced by auxin. The increased accumulation of IAA17 protein thus attenuates auxin responsiveness. Scale bar, 1 cm (A).