TMK1-mediated auxin signalling regulates differential growth of the apical hook

Plants adjust their architecture to a constantly changing environment, requiring adaptation of differential growth. Despite their importance, molecular switches, which define growth transitions, are largely unknown. Apical hook development in dark grown Arabidopsis thaliana (A. thaliana) seedlings serves as a suitable model for differential growth transition in plants. Here, we show that the phytohormone auxin counteracts the light-induced growth transition during apical hook opening. We, subsequently, identified genes which are inversely regulated by light and auxin. We used in silico analysis of the regulatory elements in this set of genes and subsequently used natural variation in gene expression to uncover correlations between underlying transcription factors and the in silico predicted target genes. This approach uncovered that MADS box transcription factor AGAMOUS-LIKE 8 (AGL8)/FRUITFULL (FUL) modulates apical hook opening. Our data shows that transient FUL expression represses the expression of growth stimulating genes during early phases of apical hook development and therewith guards the transition to growth promotion for apical hook opening. Here, we propose a role for FUL in setting tissue identity, thereby regulating differential growth during apical hook development.

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Differential growth at the apical hook: all roads lead to auxin

Frontiers in Plant Science ◽

10.3389/fpls.2013.00441 ◽

2013 ◽

Vol 4 ◽

Cited By ~ 52

Author(s):

Mohamad Abbas ◽

David Alabadí ◽

Miguel A. Blázquez

Keyword(s):

Differential Growth ◽

Apical Hook

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Cytoskeleton dynamics control early events of lateral root initiation in Arabidopsis

10.1101/559443 ◽

2019 ◽

Author(s):

Amaya Vilches Barro ◽

Dorothee Stöckle ◽

Martha Thellmann ◽

Paola Ruiz-Duarte ◽

Lotte Bald ◽

...

Keyword(s):

Lateral Root ◽

Lateral Roots ◽

Asymmetric Division ◽

List Type ◽

Radial Expansion ◽

Cellular Mechanisms ◽

Differential Growth ◽

Auxin Signalling ◽

Genetic Perturbations ◽

Founder Cells

SUMMARYHow plant cells re-establish differential growth to initiate organs is poorly understood. Morphogenesis of lateral roots relies on the tightly controlled radial expansion and asymmetric division of founder cells. The cellular mechanisms that license and ensure these features are unknown. Here, we quantitatively analyse F-actin and microtubule dynamics during LR initiation. Using mutants, pharmacological and tissue-specific genetic perturbations, we show that dynamic reorganisation of both microtubule and F-actin networks is required for the asymmetric expansion of the founder cells. This cytoskeleton remodelling intertwine with auxin signalling in the pericycle and endodermis in order for founder cells to acquire a basic polarity required for initiating LR development. Our results reveal the conservation of cell remodelling and polarisation strategies between the Arabidopsis zygote and lateral root founder cells. We propose that coordinated, auxin-driven reorganisation of the cytoskeleton licenses asymmetric cell growth and divisions during embryonic and post-embryonic organogenesis.HIGHLIGHTSFailure for lateral root founder cells to undergo asymmetric radial expansion before division, leads to aberrant organ formation.Cortical microtubules arrays reorganise to facilitate this asymmetric expansion and F-actin the asymmetric division.Cytoskeletal reorganisation depends on auxin signalling.New genetic tools allow to perturb microtubules or actin in an inducible and cell-type specific manner.

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A Model of Differential Growth-Guided Apical Hook Formation in Plants

The Plant Cell ◽

10.1105/tpc.15.00569 ◽

2016 ◽

Vol 28 (10) ◽

pp. 2464-2477 ◽

Cited By ~ 22

Author(s):

Petra Žádníková ◽

Krzysztof Wabnik ◽

Anas Abuzeineh ◽

Marçal Gallemi ◽

Dominique Van Der Straeten ◽

...

Keyword(s):

Differential Growth ◽

Apical Hook

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Regulation of differential growth in the apical hook of Arabidopsis

Development ◽

10.1242/dev.126.16.3661 ◽

1999 ◽

Vol 126 (16) ◽

pp. 3661-3668 ◽

Cited By ~ 1

Author(s):

V. Raz ◽

J.R. Ecker

Keyword(s):

Apical Part ◽

Time Dependent ◽

Outer Side ◽

Acid Oxidase ◽

Differential Growth ◽

Oxidase Gene ◽

Apical Hook ◽

Distinct Process ◽

Differential Cell ◽

Sequential Phase

Arabidopsis seedlings develop a hook-like structure at the apical part of the hypocotyl when grown in darkness. Differential cell growth processes result in the curved hypocotyl hook. Time-dependent analyses of the hypocotyl showed that the apical hook is formed during an early phase of seedling growth and is maintained in a sequential phase by a distinct process. Based on developmental genetic analyses of hook-affected mutants, we show that the hookless mutants (hls1, cop2) are involved in an early aspect of hook development. From time-dependent analyses of ethylene-insensitive mutants, later steps in hook maintenance were found to be ethylene sensitive. Regulation of differential growth was further studied through examination of the spatial pattern of expression of two hormone-regulated genes: an ethylene biosynthetic enzyme and the ethylene receptor ETR1. Accumulation of mRNA for AtACO2, a novel ACC (1-aminocyclopropane-1-carboxylic acid) oxidase gene, occurred within cells predominantly located on the outer-side of the hook and was tightly correlated with ethylene-induced exaggeration in the curvature of the hook. ETR1 expression in the apical hook, however, was reduced by ethylene treatment. Based on the expression pattern of ETR1 and AtACO2 in the hook-affected mutants, a model for hook development and maintenance is proposed.

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