<i>OBE3</i> gene structure and mutant phenotypes.

<p>(A) Structure of the <i>OBE3</i> gene. The upstream region used for the complementation is shown in green. (B-D) Phenotypes of the denoted genotypes of 10-day-old seedlings (B), shoots (C), and flowers (D). Scale bars: 1 mm (B, D), 2 cm (C).</p

<i>obe3-2</i> enhances the meristem defects of weak and intermediate <i>wus</i> alleles.

<p><i>obe3-2</i> enhances the meristem defects of weak and intermediate <i>wus</i> alleles.</p

Changes of transcripts in <i>obe3-2</i> and <i>obe4-2</i>.

<p>(A) Transcript levels of 7-day-old seedlings as indicated. Error bars represent SE. (B) After induction of <i>OBE3</i> overexpression, mRNA levels of <i>WUS</i> are increased, whereas mRNA levels of <i>CLV3</i>, <i>STM</i>, and <i>ARR7</i> are unchanged in 7-day-old seedling. Error bars represent SD. (C) <i>pWUS</i>:<i>GUS</i> expression in 6-day-old <i>obe3-1 obe4-1/+</i> seedlings is confined to the OC as in the wild type. (D) <i>WUS</i> mRNA is undetectable by <i>in situ</i> hybridization in <i>obe3-1 obe4-1/+</i> floral meristems of 30-day-old plants. (E) <i>WUS</i> overexpression upregulates <i>OBE3</i> and <i>OBE4</i> mRNA levels in 7-day-old seedlings. <i>ARR7</i> expression is used as a control. Error bars represent SD. Relative mRNA levels compared to the mock control are shown.*,p<0.05, calculated from Cp’ values; ***, p<0.001, calculated from Cp’ values.</p

Flower phenotypes of <i>obe3-2 wus-1</i>, <i>obe3-2 wus-7</i> and <i>obe3-2 wus-6</i>.

<p>Flower phenotypes of <i>obe3-2 wus-1</i>, <i>obe3-2 wus-7</i> and <i>obe3-2 wus-6</i>.</p

<i>p35S</i>:<i>cOBE3</i> expression partially suppresses <i>wus-1</i> defects.

<p>(A) Phenotypes of segregating seedlings in the progeny of a <i>p35S</i>:<i>cOBE3 wus-1/+</i> mother plant. (B) <i>p35s</i>:<i>cOBE3 wus-1</i> plants produce <i>wus-1</i>-like flowers. (C) Model for <i>WUS-OBE3</i> interaction. Scale bars: 1 mm.</p

Additional file 11: Figure S3. of ZLL/AGO10 maintains shoot meristem stem cells during Arabidopsis embryogenesis by down-regulating ARF2-mediated auxin response

Expression of ARF2 but not ARF3 and ARF4 is negatively regulated by AGO10 and REV. ARF mRNA levels in torpedo stage embryos of the indicated genotypes relative to wild type. Transcription levels are normalized to the reference gene At4g26410. Significance tested by Student’s t-test is indicated. **p < 0.01, ***p < 0.001. All other comparisons did not show a significant difference. (PPT 123 kb

Petal phenotypes of <i>atkin13a</i> and <i>atkin13b</i> loss-of-function mutants.

<p>(A) Photographs of petals of the indicated genotypes. Scale bar is 1 mm. (B) Schematic representation of the <i>AtKIN13A</i> and <i>AtKIN13B</i> loci and position of mutant alleles. Open rectangles represent UTRs, filled rectangles show the protein-coding region, and thick connecting lines show introns. (C–I) Measurements of petal parameters for the indicated genotypes. Numbers in C and D indicate relative parameter values with respect to the corresponding wild-type values. Asterisk indicates significant difference from wild-type at p<0.05 (with Bonferroni correction for comparisons to Col-0). (C) Petal size. (D) Petal-cell size. (E) Petal length. (F) Petal cell number in the longitudinal direction. (G) Petal width. (H) Petal cell number along the petal width. (I) Petal index, i.e. length divided by width. (J) Gel prints (top) and representative cells (bottom) from petals of the indicated genotypes. Scale bars are 1 mm (top panel) and 100 µm (bottom panel). Values are mean + SD of 12 petals (C,E–I) or of 50 petal cells each from more than 10 petals (D).</p

Excess cell expansion in <i>atkin13a</i> mutants requires <i>THE1</i> activity.

<p>(A,D–I) Measurements of petal parameters for the indicated genotypes. (A) Petal size. (B) Whole-flower photographs of the indicated genotypes. (C) Photographs of petals of the indicated genotypes. Scale bars are 1 mm in (B,C). (D) Petal-cell size. (E) Petal index, i.e. length divided by width. (F) Petal length. (G) Petal cell number in the longitudinal direction. (H) Petal width. (I) Petal cell number along the petal width. Values are mean ± SD of more than 12 petals from 8 plants (A,E–I) or of 50 petal cells from more than 8 petals (D). Asterisk indicates significant difference at p<0.05.</p

Atkinesin-13A Modulates Cell-Wall Synthesis and Cell Expansion in <i>Arabidopsis thaliana</i> via the THESEUS1 Pathway

<div><p>Growth of plant organs relies on cell proliferation and expansion. While an increasingly detailed picture about the control of cell proliferation is emerging, our knowledge about the control of cell expansion remains more limited. We demonstrate here that the internal-motor kinesin AtKINESIN-13A (AtKIN13A) limits cell expansion and cell size in <i>Arabidopsis thaliana</i>, with loss-of-function <i>atkin13a</i> mutants forming larger petals with larger cells. The homolog, AtKINESIN-13B, also affects cell expansion and double mutants display growth, gametophytic and early embryonic defects, indicating a redundant role of the two genes. <i>AtKIN13A</i> is known to depolymerize microtubules and influence Golgi motility and distribution. Consistent with this function, <i>AtKIN13A</i> interacts genetically with <i>ANGUSTIFOLIA</i>, encoding a regulator of Golgi dynamics. Reduced <i>AtKIN13A</i> activity alters cell wall structure as assessed by Fourier-transformed infrared-spectroscopy and triggers signalling via the <i>THESEUS1</i>-dependent cell-wall integrity pathway, which in turn promotes the excess cell expansion in the <i>atkin13a</i> mutant. Thus, our results indicate that the intracellular activity of AtKIN13A regulates cell expansion and wall architecture via THESEUS1, providing a compelling case of interplay between cell wall integrity sensing and expansion.</p></div

Increased postmitotic cell expansion in <i>atkin13a</i> mutants.

<p>(A) Developmental series of petal size for the indicated genotypes. Flower 1 represents the youngest open flower, while flower −1 is the oldest unopened flower bud. Values are normalized to the size of the wild-type petals from the oldest measured flowers. Values represent mean ± SEM (n<10 petals). (B) Gel-print images of wild-type petal cells from the indicated flower stages (after <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004627#pgen.1004627-Smyth1" target="_blank">[71]</a>). (C) Petal-cell size from stage 10–11 buds is not different between wild type and <i>atkin13a-3</i> mutants. Values are mean ± SD of 50 petal cells each from more than 6 petals. (D) Etiolated hypocotyls are longer in <i>atkin13a-3</i> mutants than in wild type. Values are mean ±SD of 10 plants. 8-day old seedlings were measured. (E) Toluidine-blue stained cross section through a mature wild-type (left) and a mature mutant petal (right). Adaxial side is to the right in both images. (F) Cross-sectional cell area, cell height and cell width from petals of wild type and <i>atkin13a-3^EMS</i> mutants. Values are normalized to wild-type values and represent mean ± SD of 50 petal cells. (G) Thickness of petal-cell walls as measured from scanning-electron micrographs. Values are mean ± SEM of 100 petal cells from 10 petals, normalized to the wild-type value. (H) Scanning-electron micrographs of wild-type petals before (top left) and after (top right and bottom) freeze fracturing. Bottom image also indicates how measurements of cell-wall thickness were taken (pairs of white crosses). Length of scale bars is indicated. (I) Petal dry weight of the indicated genotypes. Values are mean + SD from 3 replicates of 50 petals each, normalized to the respective wild-type values. Differences between the three <i>atkin13a</i> mutant alleles are not statistically significant (n.s.). Asterisk indicates significant difference from wild-type at p<0.05 (with Bonferroni correction where appropriate).</p