Article Figures & Data
Figures
- Fig. 1.
DR5::GUS reporter gene expression in leaf primordia exposed to 2,4-D. First rosette leaf primordia were incubated in culture medium containing 1 μm 2,4-D for 5 h, followed by histochemical detection of GUS activity. Age in DAG: A, 2; B, 3; C, 4. Scale bars = 50 μm in A and B, 100 μm in C. DIC optics.
- Fig. 2.
Expression pattern of DR5::GUS in developing leaf primordia. First rosette leaf primordia, stages given in days after germination (DAG). A, Lateral view of 2-DAG primordia, with limited growth. Arrows point at DR5::GUS expression. B, Lateral view of 2-DAG primordia, somewhat older than in A. DF of expression in subepidermal cells and faint expression at the site of incipient primary vein (I1°). Note the absence of expression in the central apical dome of the shoot meristem. C, Abaxial view of 2-DAG primordium, with DF and I1°. D, Primordium at 3 DAG. Note diminished DR5::GUS expression in the basal part of I1°, whereas expression is visible in incipient secondary veins (I2°). E, Primordium at 3 DAG. Arrow indicates appearance of additional I2° in the basal region. F, Primordium at 4 DAG. Expression in basal I2°s and in incipient tertiary veins (I3°). G, Primordium at 4 DAG. Another I2° is appearing in a basal position. Expression is also seen at site of future hydathode (H). H, Primordium at 5 DAG. The vascular pattern, as visualized by DR5 expression and overt differentiation of vessels, comprises veins of all classes. DR5 expression is especially high in I3°s and in lateral positions where hydathodes will appear. I, Primordium at 6 DAG. The levels of DR5 expression are subsiding. Residual GUS activity primarily in veins in the basal part of the leaf after doubled assay time. J, Primordium at 7 DAG. Differentiated vessels, DR5 expression is no longer detectable. Scale bars = 50 μm in A through G, 200 μm in H through J. DIC optics.
- Fig. 3.
DR5::GUS expression in pre-procambial and procambial cells. Four-DAG first rosette leaf primordium. A, Extremely low DR5 expression in elongated procambial cells of I1° in the basal part and somewhat stronger expression in younger apical sections of I1°. Frames indicate magnified areas in B and C. B, Low, heterogenous DR5 expression cells of I3°. Note that these cells are still isodiametric in shape and cannot anatomically be distinguished from surrounding cells. C, Strong, homogenous DR5 expression in cells of I2°s, some of which have divided to form double rows of narrow procambial cells (outlined). Scale bar = 50 μm. DIC optics.
- Fig. 4.
Pattern of DR5::GUS expression in primordia exposed to auxin transport inhibitors. Ages are 3 DAG in left column (A, D, G, and J), 4 DAG in middle column (B, E, H, and K), and 7 DAG in right column (C, F, I, and L). Levels of NPA are 0 μm (A–C), 0.1 μm (D–F), 1.0 μm (G–I), and 10 μm (J–L). Note that with increasing concentration of NPA, the expression is gradually confined to tips and margins of primordia (arrows in H and K) coinciding with the site of final vascularization (arrows in I and L). Scale bars = 50 μm in A, D, G, and J; 100 μm in B, E, H, and K; and 200 μm in C, F, I, and L. Dark-field illumination, low concentration of GUS product as red and higher levels as blue staining.
- Fig. 5.
Auxin responses in monopteros mutants. Genotypes: wild type (black), auxin-resistant 1-12 (gray), and monopteros G33 (white, mpG12 in A and B, mpG33 in C). A and B, Quantification of cotyledon area of seedlings grown for 10 d in the presence of 0 and 1 μm IAA (A) and in the presence of 0 and 1 μm 2,4-D (B). Size bars indicate se. Significance of genotype-dependent differences relative to wt type values as determined by Student t test analysis is indicated by asterisks (*, 0.01 ≤ P < 0.05; **, 0.001 ≤P < 0.01; and ***, P < 0.001). Sample sizes of 10 to 50 cotyledons. C, Adventitious root formation in cotyledons exposed to 0.3 mg L−1 indole-butyric acid (IBA). Sample sizes of 222 to 475 cotyledons.
- Fig. 6.
AtHB20::GUSexpression in leaves. A, First rosette leaf primordium at 3 DAG: diffuse expression with elevated levels along I1° and at the tip of the primordium. B, 4 DAG: strong expression along the differentiating midvein and weak expression along I2°s. C, Highly localized and strong expression at late stage of secondary vein differentiation. D, Cross section of a 7-DAG leaf primordium: Expression is confined to cells in vascular bundles. E, Higher magnification of midvein in D (arrow) shows strong expression in fascicular cambium (arrow in E).
- Fig. 7.
Expression of HD-ZIP genes and AUX/IAA genes. Transcript abundance of the HD-ZIP genesAtHB8 (A), AtHB9 (B), AtHB14 (C),IFL1/REV (D), and AtHB20 (E) and of the AUX/IAA genes IAA1 (F) andIAA19 (G) were determined by northern-blot hybridization to total RNA from wild type (wt), mpmutant, and 35S::MP plants exposed for 30 min to 0, 10, and 100 μm IAA (indicated onx axes, genotypes below). Transcript levels (yaxes) for each gene were calculated as multiples of the wild-type level at 0 μm IAA. Columns represent the mean ±se from 3 to 5 (A–D), and the results of two experiments (F and G). Significance of genotype-dependent differences between mp and35S::MP values relative towt type values under identical conditions as determined by Student's t test analysis is indicated by asterisks (*, 0.01 ≤ P < 0.05; **, 0.001 ≤P < 0.01; ***, P < 0.001). Note that the absolute induction levels of IAA1 and IAA19 appear extremely high because of extremely low expression at 0 μmIAA.
