Article Figures & Data
Figures
- Figure 1.
Capitulum morphology and development. A–C, Nontreated M. inodora capitula (A and B), and phyllaries and florets (C). D–H, SEM images of developing nontreated M. inodora capitula. I to K, GUS expression in DR5::GUS S. vulgaris capitula. A young capitulum (I, stage 1). Clusters of capitula showing different developmental stages (J and K, stages 2 to 6). M–P, Sections of DR5::GUS S. vulgaris capitula at different stages of development. GUS concentration decreases as the capitulum develops in DR5::GUS lines. L and Q–S, IAA immunolocalization in developing S. vulgaris (L) and M. inodora (Q–S) capitula. T, Negative control (no primary antibody). Scale bars = 5 mm (A and B), 2 mm (C), 100 μm (D–F, M–T), and 500 µm (G and H, I–L). P, phyllary; Pi, incipient phyllary primordium; R, ray floret; Ri, incipient ray floret primordium; D, disc floret; Di, incipient disc floret primordia.
- Figure 2.
Auxin application induced homeotic conversions in the capitulum. Phenotypes of capitula sprayed with 3-μM (A–I) and 10-μM (J–L) IAA, showing conversion of disc florets into both ray florets and phyllaries (A–I) or solely into phyllaries (J–L). A–D, Capitula with fully developed converted phyllaries and ray florets. E–H, Initial developing stages of converted phyllaries and ray florets after IAA treatments. H, Close-up of (G) showing the order of converted phyllaries and ray florets. Scale bars = 5 mm (A–D, I–J), 2 mm (E–H, K and L). M, Quantification of phyllary and ray floret conversion after IAA treatments. Each error bar represents the mean ± SE. Values marked by asterisk are significantly different (P = 0.04 for ray florets and P = 0.04 for phyllaries; two-tailed t-test analysis). Pc, converted phyllary; Rc, converted ray floret.
- Figure 3.
Auxin regulates floret identity genes in M. inodora capitula. A–F, RT-qPCR of MiRAY2 (A–C) and MiLFY (D–F) on untreated dissected leaves, phyllarys, and florets (A and D) and on stage-3 whole capitula treated with 3-μM (B and E) and 10-μM (C and F) IAA. The X axes in (A) and (D) represent dissected organs and in (B), (C), (E), and (F), “6” and “18” represent hours after auxin application. The Y axes indicate the relative expression of MiRAY2 and MiLFY. Each bar represents the mean ± SE. Values marked by asterisk are significantly different (*P < 0.05, ****P < 0.0001), with “n.s.” as non-significant, at P > 0.05 (one-way analysis of variance with post-hoc Tukey’s multiple comparison test). G to L, M. inodora in situ hybridizations using MiRAY2 (G, I, and K) and MiLFY (H, J, and L) probes in mock-treated (G and H) and 3-μM (I) or 10-μM (J) IAA-treated stage-3 capitula. K and L, Sense probe control. Scale bars = 50 μm. L, leaves.
- Figure 4.
Schematic models of how auxin gradients determine capitulum patterning. A, Wild-type M. inodora capitula from young to mature stages and their respective auxin concentrations (in shades of blue) as well as the expressions of MiLFY (in orange) and MiRAY2 (in purple). Brackets represent the meristematic regions where phyllaries, ray florets, and disc florets will be initiated (Pi, Ri, and Di). B, Capitulum showing superimposed auxin gradients of different developmental stages and downstream gene regulation. C–F, Schematic models representing the homeotic conversion phenotypes shown in Fig. 2 and the respective auxin gradients. Exogenous auxin application to stage-3 capitulum induces an ectopic auxin gradient in the center of the capitulum, which promotes the reappearance of phyllaries and ray florets (C–E). Moreover, a range of auxin levels within the ectopic gradient will determine the final capitulum morphology. An ectopic gradient consisting of all the auxin levels represented in stages 1, 2, and 3 (A) will generate phyllaries, ray florets, and disc florets sequentially in the center of the capitulum (C; and see Fig. 2, B and C). An ectopic gradient consisting of the auxin levels of stages 1 and 2 will generate phyllaries and ray florets in the center of the capitulum (D; and see Fig. 2, A, E, and I), whereas a gradient consisting of stage-1 auxin levels will generate only phyllaries (E and F; and see Fig. 2, J–L).
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Supplemental Figures and Tables
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- Supplemental Data - Supplemental Figures 1 and 2 and Supplemental Tables 1-4
