ALBERT

Beschreibung: How biological systems generate reproducible patterns with high precision is a central question in science. The shoot apical meristem (SAM), a specialized tissue producing plant aerial organs, is a developmental system of choice to address this question. Organs are periodically initiated at the SAM at specific spatial positions and this spatiotemporal pattern defines phyllotaxis. Accumulation of the plant hormone auxin triggers organ initiation, whereas auxin depletion around organs generates inhibitory fields that are thought to be sufficient to maintain these patterns and their dynamics. Here we show that another type of hormone-based inhibitory fields, generated directly downstream of auxin by intercellular movement of the cytokinin signalling inhibitor ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN 6 (AHP6), is involved in regulating phyllotactic patterns. We demonstrate that AHP6-based fields establish patterns of cytokinin signalling in the meristem that contribute to the robustness of phyllotaxis by imposing a temporal sequence on organ initiation. Our findings indicate that not one but two distinct hormone-based fields may be required for achieving temporal precision during formation of reiterative structures at the SAM, thus indicating an original mechanism for providing robustness to a dynamic developmental system.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Besnard, Fabrice -- Refahi, Yassin -- Morin, Valerie -- Marteaux, Benjamin -- Brunoud, Geraldine -- Chambrier, Pierre -- Rozier, Frederique -- Mirabet, Vincent -- Legrand, Jonathan -- Laine, Stephanie -- Thevenon, Emmanuel -- Farcot, Etienne -- Cellier, Coralie -- Das, Pradeep -- Bishopp, Anthony -- Dumas, Renaud -- Parcy, Francois -- Helariutta, Yka -- Boudaoud, Arezki -- Godin, Christophe -- Traas, Jan -- Guedon, Yann -- Vernoux, Teva -- England -- Nature. 2014 Jan 16;505(7483):417-21. doi: 10.1038/nature12791. Epub 2013 Dec 15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Laboratoire de Reproduction et Developpement des Plantes, CNRS, INRA, ENS Lyon, UCBL, Universite de Lyon, 69364 Lyon, France [2] IBENS, ENS, 75005 Paris, France (F.B.); UMR CNRS 5534, Universite Claude Bernard Lyon I, Batiment Gregor Mendel, 16 rue Raphael Dubois, 69622 Villeurbanne, France (V.M.); University of Nottingham, University Park, Nottingham NG7 2RD, UK (E.F); University of Nottingham, Sutton Bonington LE12 5RD, UK (A.Bi.). ; Virtual Plants INRIA/CIRAD/INRA Project Team, UMR AGAP, Institut de Biologie Computationelle, 34095 Montpellier, France. ; 1] Laboratoire de Reproduction et Developpement des Plantes, CNRS, INRA, ENS Lyon, UCBL, Universite de Lyon, 69364 Lyon, France [2] IBENS, ENS, 75005 Paris, France (F.B.); UMR CNRS 5534, Universite Claude Bernard Lyon I, Batiment Gregor Mendel, 16 rue Raphael Dubois, 69622 Villeurbanne, France (V.M.); University of Nottingham, University Park, Nottingham NG7 2RD, UK (E.F); University of Nottingham, Sutton Bonington LE12 5RD, UK (A.Bi.). [3]. ; 1] Laboratoire de Reproduction et Developpement des Plantes, CNRS, INRA, ENS Lyon, UCBL, Universite de Lyon, 69364 Lyon, France [2]. ; Laboratoire de Reproduction et Developpement des Plantes, CNRS, INRA, ENS Lyon, UCBL, Universite de Lyon, 69364 Lyon, France. ; 1] Laboratoire de Reproduction et Developpement des Plantes, CNRS, INRA, ENS Lyon, UCBL, Universite de Lyon, 69364 Lyon, France [2] Laboratoire Joliot-Curie, CNRS, ENS Lyon, Universite de Lyon, 69364 Lyon, France. ; 1] Laboratoire de Reproduction et Developpement des Plantes, CNRS, INRA, ENS Lyon, UCBL, Universite de Lyon, 69364 Lyon, France [2] Virtual Plants INRIA/CIRAD/INRA Project Team, UMR AGAP, Institut de Biologie Computationelle, 34095 Montpellier, France [3] Laboratoire Joliot-Curie, CNRS, ENS Lyon, Universite de Lyon, 69364 Lyon, France. ; Laboratoire Physiologie Cellulaire et Vegetale, CEA, CNRS, INRA, UJF, 38041 Grenoble, France. ; 1] Virtual Plants INRIA/CIRAD/INRA Project Team, UMR AGAP, Institut de Biologie Computationelle, 34095 Montpellier, France [2] IBENS, ENS, 75005 Paris, France (F.B.); UMR CNRS 5534, Universite Claude Bernard Lyon I, Batiment Gregor Mendel, 16 rue Raphael Dubois, 69622 Villeurbanne, France (V.M.); University of Nottingham, University Park, Nottingham NG7 2RD, UK (E.F); University of Nottingham, Sutton Bonington LE12 5RD, UK (A.Bi.). ; 1] Institute of Biotechnology/Department of Biosciences, University of Helsinki, FIN-00014, Finland [2] IBENS, ENS, 75005 Paris, France (F.B.); UMR CNRS 5534, Universite Claude Bernard Lyon I, Batiment Gregor Mendel, 16 rue Raphael Dubois, 69622 Villeurbanne, France (V.M.); University of Nottingham, University Park, Nottingham NG7 2RD, UK (E.F); University of Nottingham, Sutton Bonington LE12 5RD, UK (A.Bi.). ; Institute of Biotechnology/Department of Biosciences, University of Helsinki, FIN-00014, Finland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24336201" target="_blank"〉PubMed〈/a〉

Beschreibung: Auxin is a key plant morphogenetic signal but tools to analyse dynamically its distribution and signalling during development are still limited. Auxin perception directly triggers the degradation of Aux/IAA repressor proteins. Here we describe a novel Aux/IAA-based auxin signalling sensor termed DII-VENUS that was engineered in the model plant Arabidopsis thaliana. The VENUS fast maturing form of yellow fluorescent protein was fused in-frame to the Aux/IAA auxin-interaction domain (termed domain II; DII) and expressed under a constitutive promoter. We initially show that DII-VENUS abundance is dependent on auxin, its TIR1/AFBs co-receptors and proteasome activities. Next, we demonstrate that DII-VENUS provides a map of relative auxin distribution at cellular resolution in different tissues. DII-VENUS is also rapidly degraded in response to auxin and we used it to visualize dynamic changes in cellular auxin distribution successfully during two developmental responses, the root gravitropic response and lateral organ production at the shoot apex. Our results illustrate the value of developing response input sensors such as DII-VENUS to provide high-resolution spatio-temporal information about hormone distribution and response during plant growth and development.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brunoud, Geraldine -- Wells, Darren M -- Oliva, Marina -- Larrieu, Antoine -- Mirabet, Vincent -- Burrow, Amy H -- Beeckman, Tom -- Kepinski, Stefan -- Traas, Jan -- Bennett, Malcolm J -- Vernoux, Teva -- BB/F007418/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- BB/F013981/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- England -- Nature. 2012 Jan 15;482(7383):103-6. doi: 10.1038/nature10791.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Reproduction et Developpement des Plantes, CNRS, INRA, ENS Lyon, UCBL, Universite de Lyon, 69364 Lyon, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22246322" target="_blank"〉PubMed〈/a〉

Beschreibung: Gravity profoundly influences plant growth and development. Plants respond to changes in orientation by using gravitropic responses to modify their growth. Cholodny and Went hypothesized over 80 years ago that plants bend in response to a gravity stimulus by generating a lateral gradient of a growth regulator at an organ's apex, later found to be auxin. Auxin regulates root growth by targeting Aux/IAA repressor proteins for degradation. We used an Aux/IAA-based reporter, domain II (DII)-VENUS, in conjunction with a mathematical model to quantify auxin redistribution following a gravity stimulus. Our multidisciplinary approach revealed that auxin is rapidly redistributed to the lower side of the root within minutes of a 90° gravity stimulus. Unexpectedly, auxin asymmetry was rapidly lost as bending root tips reached an angle of 40° to the horizontal. We hypothesize roots use a “tipping point” mechanism that operates to reverse the asymmetric auxin flow at the midpoint of root bending. These mechanistic insights illustrate the scientific value of developing quantitative reporters such as DII-VENUS in conjunction with parameterized mathematical models to provide high-resolution kinetics of hormone redistribution.