Ethylene Modulates Stem Cell Division in the Arabidopsis thaliana Root

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Science  27 Jul 2007:
Vol. 317, Issue 5837, pp. 507-510
DOI: 10.1126/science.1143409

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  1. Fig. 1.

    Identification of mutants in which the QC cells divide. (A) Wild-type stem cell niche organization (schematic). (B) Wild-type, (C) E6263, and (D) E4510 root morphologies. Cellular organization of the stem cell niche region (a pair of cells in longitudinal section) in (E) 4-day-old, (G) 8-day-old, and (I) 12-day-old wild-type roots, as revealed by propidium iodide staining. Red lines show the outline of the two QC cells that are visible. Cellular organization in (F) 4-day-old, (H) 8-day-old, and (J) 12-day-old E6263 mutant roots showing supernumerary divisions in the QC (red arrowheads). Scale bars, 25 μm.

  2. Fig. 2.

    Ethylene promotes QC cell division. Stem cell niche organization of (A) wild-type, (B) eto1-11 mutant, (C) eto1-11 treated with AVG (0.5 μM), (D) wild-type treated with ACC (50 μM), (E) eto2 mutant, and (F) ctr1 mutant roots. Red arrowheads, extra cell division in the QC. Scale bars, 50 μm.

  3. Fig. 3.

    QC cell identity and function are maintained in eto1 mutants. SCRpro::GFP expression is present in (A) the QC cells of wild type, (B) the new cells derived from the extra divisions (white arrow) in the QC of ACC-treated wild type, and (C) eto1-11 mutant. The enhancer trap J0571 is expressed in (D) the QC cells in wild-type, (E) the extra QC cells that develop in wild-type roots treated with ACC (50 μM), and (F) eto1-11 mutant. The QC-25 marker line expresses β-glucuronidase (GUS) activity (blue) in the QC, and lugol staining marks the differentiated columella cells. (G and I) In wild type, there is a single nonstaining layer of initials (arrow) between the QC and the columella. (I) is a higher-magnification view of (G). (H and J) The presence of functioning initials is revealed by the absence of lugol staining (arrow) in wild type treated with ACC (50 μM), where there is an increase in the number of blue-stained QC cells (arrowheads). (J) is a higher-magnification view of (H). Scale bars, 50 μm [(G) and (H)], 25 μm [(I) and (J)].

  4. Fig. 4.

    Ethylene stimulates cell division leading to the formation of additional columella cell layers. (A) Phenotype of wild-type root. There is a decrease in the number of columella layers (red dots) in (B) wild-type roots that have been treated with AVG, (C) plants harboring 35S::ETO1, and (D) ein2 mutants. Scale bars, 50 μm.