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. 1999 Oct 12;96(21):12186–12191. doi: 10.1073/pnas.96.21.12186

Figure 3.

Figure 3

Characterization of the transcriptional induction of ZMK1 by auxin. (A) Kinetics of auxin-induced coleoptile growth. Representative growth curves of abraded coleoptile segments in K+-containing medium in the presence and absence of 5 μM NAA (♦ and ○, respectively). (B) Kinetics of auxin-induced ZMK1 expression. Transcript abundance of ZMK1 in coleoptile segments in the presence and absence of 5 μM NAA (solid and open bars, respectively). The content of ZMK1 mRNA at the given times [n = 3, 75 min (■); n = 1, 90 and 105 min □)] was analyzed by Northern dot blots and quantified as described in Materials and Methods. The transcript contents were normalized to the ZMK1 mRNA level at t = 0 min, which was set to 1.0 (arbitrary units). According to a t test the ZMK1 mRNA content in auxin-treated coleoptiles was significantly different from untreated tissue after 45 min (5% level). The statistical significance is indicated by asterisks (∗, 5% level; ∗3, 0.1% level). (C) Concentration dependence of the auxin-induced ZMK1 expression. Half-logarithmic plot of ZMK1 mRNA content (●) in coleoptile segments after 60 min of incubation with different IAA concentrations (n = 2). The relative content of ZMK1 mRNA was analyzed as described, and the background level of ZMK1 mRNA (0 μM IAA) was set to 1.0 (arbitrary units). The concentration dependence of ZMK1 expression can be fitted with a saturation function (gray line), characterized by a KM of about 0.1 μM IAA. (D) ZMK1 transcription is induced specifically by the active auxin 1-NAA. Shown are Northern dot blots of 0.5 μg mRNA from nontreated (–) coleoptiles and tissues treated for 60 min with 5 μM 1-NAA, 5 μM 2-NAA, and 1 μM FC and incubated in pH 3.7, which were hybridized against a radiolabeled ZMK1 probe. (E) Auxin-induced transcription of ZMK1 is cycloheximide-independent. Shown are Northern dot blots of 0.5 μg mRNA from coleoptiles treated for 60 min with 5 μM IAA (IAA), 5 μM IAA, 70 μM CHX (IAA CHX), and 70 μM CHX (CHX) and nontreated tissue (–), which were hybridized against a radiolabeled ZMK1 probe.