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1. MSK-Mediated Phosphorylation of Histone H3 Ser28 Couples MAPK Signalling with Early Gene Induction and Cardiac Hypertrophy

Author

Emma L. Robinson, Faye M. Drawnel, Saher Mehdi, Caroline R. Archer, Wei Liu, Hanneke Okkenhaug, Kanar Alkass, Jan Magnus Aronsen, Chandan K. Nagaraju, Ivar Sjaastad, Karin R. Sipido, Olaf Bergmann, J. Simon C. Arthur, Xin Wang, and H. Llewelyn Roderick

Subjects
cardiomyocyte, MSK, phosphorylated histone 3 serine 28, immediate early genes, hypertrophy, Cytology, QH573-671
Abstract

Heart failure is a leading cause of death that develops subsequent to deleterious hypertrophic cardiac remodelling. MAPK pathways play a key role in coordinating the induction of gene expression during hypertrophy. Induction of the immediate early gene (IEG) response including activator protein 1 (AP-1) complex factors is a necessary and early event in this process. How MAPK and IEG expression are coupled during cardiac hypertrophy is not resolved. Here, in vitro, in rodent models and in human samples, we demonstrate that MAPK-stimulated IEG induction depends on the mitogen and stress-activated protein kinase (MSK) and its phosphorylation of histone H3 at serine 28 (pH3S28). pH3S28 in IEG promoters in turn recruits Brg1, a BAF60 ATP-dependent chromatin remodelling complex component, initiating gene expression. Without MSK activity and IEG induction, the hypertrophic response is suppressed. These studies provide new mechanistic insights into the role of MAPK pathways in signalling to the epigenome and regulation of gene expression during cardiac hypertrophy.

Published
2022
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2. Modelling and experimental analysis of hormonal crosstalk in Arabidopsis

Author

Junli Liu, Saher Mehdi, Jennifer Topping, Petr Tarkowski, and Keith Lindsey

Subjects
hormonal crosstalk, mathematical model, POLARIS, gene, root development, Biology (General), QH301-705.5, Medicine (General), R5-920
Abstract

Abstract An important question in plant biology is how genes influence the crosstalk between hormones to regulate growth. In this study, we model POLARIS (PLS) gene function and crosstalk between auxin, ethylene and cytokinin in Arabidopsis. Experimental evidence suggests that PLS acts on or close to the ethylene receptor ETR1, and a mathematical model describing possible PLS–ethylene pathway interactions is developed, and used to make quantitative predictions about PLS–hormone interactions. Modelling correctly predicts experimental results for the effect of the pls gene mutation on endogenous cytokinin concentration. Modelling also reveals a role for PLS in auxin biosynthesis in addition to a role in auxin transport. The model reproduces available mutants, and with new experimental data provides new insights into how PLS regulates auxin concentration, by controlling the relative contribution of auxin transport and biosynthesis and by integrating auxin, ethylene and cytokinin signalling. Modelling further reveals that a bell‐shaped dose–response relationship between endogenous auxin and root length is established via PLS. This combined modelling and experimental analysis provides new insights into the integration of hormonal signals in plants.

Published
2010
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3. A novel Botrytis species is associated with a newly emergent foliar disease in cultivated Hemerocallis.

Author

Robert T Grant-Downton, Razak B Terhem, Maxim V Kapralov, Saher Mehdi, M Josefina Rodriguez-Enriquez, Sarah J Gurr, Jan A L van Kan, and Frances M Dewey

Subjects
Medicine, Science
Abstract

Foliar tissue samples of cultivated daylilies (Hemerocallis hybrids) showing the symptoms of a newly emergent foliar disease known as 'spring sickness' were investigated for associated fungi. The cause(s) of this disease remain obscure. We isolated repeatedly a fungal species which proved to be member of the genus Botrytis, based on immunological tests. DNA sequence analysis of these isolates, using several different phyogenetically informative genes, indicated that they represent a new Botrytis species, most closely related to B. elliptica (lily blight, fire blight) which is a major pathogen of cultivated Lilium. The distinction of the isolates was confirmed by morphological analysis of asexual sporulating cultures. Pathogenicity tests on Hemerocallis tissues in vitro demonstrated that this new species was able to induce lesions and rapid tissue necrosis. Based on this data, we infer that this new species, described here as B. deweyae, is likely to be an important contributor to the development of 'spring sickness' symptoms. Pathogenesis may be promoted by developmental and environmental factors that favour assault by this necrotrophic pathogen. The emergence of this disease is suggested to have been triggered by breeding-related changes in cultivated hybrids, particularly the erosion of genetic diversity. Our investigation confirms that emergent plant diseases are important and deserve close monitoring, especially in intensively in-bred plants.

Published
2014
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4. MSK-mediated phosphorylation of Histone 3 Ser28 couples MAPK signaling with early gene induction and cardiac hypertrophy

Author

Ivar Sjaastad, Caroline R. Archer, J. Simon C. Arthur, Jan Magnus Aronsen, H. Llewelyn Roderick, Emma L. Robinson, Hanneke Okkenhaug, Olaf Bergmann, Xin Wang, Kanar Alkass, Saher Mehdi, Faye M. Drawnel, Chandan K. Nagaraju, Wei Liu, and Karin R. Sipido

Subjects
MAPK/ERK pathway, Regulation of gene expression, Histone H3, Histone, biology, Mitogen-activated protein kinase, biology.protein, Phosphorylation, Epigenome, Immediate early gene, Cell biology
Abstract

Heart failure is a leading cause of death that develops subsequent to deleterious hypertrophic cardiac remodelling. MAPK pathways play a key role in coordinating the induction of gene expression during hypertrophy. Induction of the immediate early gene (IEG) response is a necessary and early event in this process. How MAPK and IEG expression are coupled during cardiac hypertrophy is not yet resolved. Here, in vitro, in rodent models and in human samples, we demonstrate that MAPK-stimulated IEG induction depends on the Mitogen and Stress activated protein Kinase (MSK) and its phosphorylation of histone H3 at serine 28 (pH3S28). pH3S28 in IEG promoters in turn recruits Brg1, a BAF60 ATP-dependent chromatin remodelling complex component, initiating gene expression. Without MSK activity and IEG induction, the hypertrophic response is suppressed. These studies provide new mechanistic insights and highlight the role of signalling to the epigenome in gene expression regulation during cardiac hypertrophy.Brief summary one sentenceMSK1/2 phosphorylation of Histone 3 Serine 28 couples MAPK signalling with chromatin remodelling and immediate early gene expression to induce pro-hypertrophic cardiac transcriptional responses.

Published
2020
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5. Dark-Induced Senescence Causes Localized Changes in DNA Methylation

Author

Minerva S. Trejo-Arellano, Lars Hennig, Saher Mehdi, Eva Dvořák Tomaštíková, Jennifer de Jonge, and Claudia Köhler

Subjects
0106 biological sciences, Senescence, Physiology, Heterochromatin, Arabidopsis, Chromatin silencing, Down-Regulation, Plant Science, Biology, 01 natural sciences, Epigenesis, Genetic, Histones, Epigenome, Gene Expression Regulation, Plant, Genetics, Chromatin maintenance, Epigenetics, Gene Silencing, Cellular Senescence, Research Articles, Gene Expression Profiling, DNA Methylation, Darkness, Chromatin, Cell biology, Droughts, Plant Leaves, DNA methylation, DNA Transposable Elements, Transcriptome, Reprogramming, Genome, Plant, 010606 plant biology & botany
Abstract

Senescence occurs in a programmed manner to dismantle the vegetative tissues and redirect nutrients towards metabolic pathways supporting reproductive success. External factors can trigger the senescence program as an adaptive strategy, indicating that this terminal program is controlled at different levels. It has been proposed that epigenetic factors accompany the reprogramming of the senescent genome; however, the mechanism and extent of this reprogramming remain unknown. Using bisulphite conversion followed by sequencing, we assessed changes in the methylome of senescent Arabidopsis (Arabidopsis thaliana) leaves induced by darkness and monitored their effect on gene and transposable element (TE) expression with transcriptome sequencing. Upon dark-induced senescence, genes controlling chromatin silencing were collectively down-regulated. As a consequence, the silencing of TEs was impaired, causing in particular young TEs to become preferentially reactivated. In parallel, heterochromatin at chromocenters was decondensed. Despite the disruption of the chromatin maintenance network, the global DNA methylation landscape remained highly stable, with localized changes mainly restricted to CHH methylation. Together, our data show that the terminal stage of plant life is accompanied by global changes in chromatin structure but only localized changes in DNA methylation, adding another example of the dynamics of DNA methylation during plant development.

Published
2019

6. Influence of Nitrogen and Phosphorus on Rhamnolipid Biosurfactant Production by Pseudomonas aeruginosa DS10-129 using Glycerol as Carbon Source

Author

Jesse S. Dondapati, Pattanathu K. S. M. Rahman, and Saher Mehdi

Subjects
Chemistry, Pseudomonas aeruginosa, Phosphorus, Rhamnolipid, chemistry.chemical_element, Factorial experiment, medicine.disease_cause, Nitrogen, General Biochemistry, Genetics and Molecular Biology, Microbiology, chemistry.chemical_compound, Critical micelle concentration, Carbon source, Glycerol, medicine, Food science
Published
2011
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7. The WD40 Domain Protein MSI1 Functions in a Histone Deacetylase Complex to Fine-Tune Abscisic Acid Signaling

Author

Lejon E. M. Kralemann, Margareta Ramström, Lars Hennig, Maria Derkacheva, Jonas Bergquist, and Saher Mehdi

Subjects
Arabidopsis, Plant Science, Biology, SAP30, Sodium Chloride, Genes, Plant, Models, Biological, Histone Deacetylases, Histones, Histone H3, Histone H1, Gene Expression Regulation, Plant, Stress, Physiological, Histone H2A, RNA, Messenger, Research Articles, Histone binding, Genetics, Histone deacetylase 5, Histone deacetylase 2, Arabidopsis Proteins, Lysine, fungi, food and beverages, Acetylation, Cell Biology, Adaptation, Physiological, Chromatin, Cell biology, Protein Structure, Tertiary, Up-Regulation, Protein Subunits, Histone deacetylase complex, Abscisic Acid, Protein Binding, Signal Transduction
Abstract

MSI1 belongs to a family of histone binding WD40-repeat proteins. Arabidopsis thaliana contains five genes encoding MSI1-like proteins, but their functions in diverse chromatin-associated complexes are poorly understood. Here, we show that MSI1 is part of a histone deacetylase complex. We copurified HISTONE DEACETYLASE19 (HDA19) with MSI1 and transcriptional regulatory SIN3-like proteins and provide evidence that MSI1 and HDA19 associate into the same complex in vivo. These data suggest that MSI1, HDA19, and HISTONE DEACETYLATION COMPLEX1 protein form a core complex that can integrate various SIN3-like proteins. We found that reduction of MSI1 or HDA19 causes upregulation of abscisic acid (ABA) receptor genes and hypersensitivity of ABA-responsive genes. The MSI1-HDA19 complex fine-tunes ABA signaling by binding to the chromatin of ABA receptor genes and by maintaining low levels of acetylation of histone H3 at lysine 9, thereby affecting the expression levels of ABA receptor genes. Reduced MSI1 or HDA19 levels led to increased tolerance to salt stress corresponding to the increased ABA sensitivity of gene expression. Together, our results reveal the presence of an MSI1-HDA19 complex that fine-tunes ABA signaling in Arabidopsis.

Published
2015

8. Interaction of PLS and PIN and hormonal crosstalk in Arabidopsis root development

Author

Keith Lindsey, Junli Liu, Jiri Friml, Saher Mehdi, and Jennifer F. Topping

Subjects
EXPRESSION, Ethylene, EFFLUX, root development, Mutant, Plant Science, Signaling network, EMERGENCE, chemistry.chemical_compound, Auxin, Arabidopsis, Botany, BIOSYNTHESIS, heterocyclic compounds, Original Research Article, PIN proteins, chemistry.chemical_classification, biology, THALIANA, PLANT DEVELOPMENT, fungi, Biology and Life Sciences, food and beverages, biology.organism_classification, ETHYLENE, Cell biology, auxin flux, Crosstalk (biology), hormonal crosstalk, chemistry, Cytokinin, CELLS, signaling network, PLS protein, GROWTH, Developmental biology, AUXIN TRANSPORT
Abstract

Understanding how hormones and genes interact to coordinate plant growth is a major challenge in developmental biology. The activities of auxin, ethylene, and cytokinin depend on cellular context and exhibit either synergistic or antagonistic interactions. Here we use experimentation and network construction to elucidate the role of the interaction of the POLARIS peptide (PLS) and the auxin efflux carrier PIN proteins in the crosstalk of three hormones (auxin, ethylene, and cytokinin) in Arabidopsis root development. In ethylene hypersignaling mutants such as polaris (pls), we show experimentally that expression of both PIN1 and PIN2 significantly increases. This relationship is analyzed in the context of the crosstalk between auxin, ethylene, and cytokinin: in pls, endogenous auxin, ethylene and cytokinin concentration decreases, approximately remains unchanged and increases, respectively. Experimental data are integrated into a hormonal crosstalk network through combination with information in literature. Network construction reveals that the regulation of both PIN1 and PIN2 is predominantly via ethylene signaling. In addition, it is deduced that the relationship between cytokinin and PIN1 and PIN2 levels implies a regulatory role of cytokinin in addition to its regulation to auxin, ethylene, and PLS levels. We discuss how the network of hormones and genes coordinates plant growth by simultaneously regulating the activities of auxin, ethylene, and cytokinin signaling pathways.

Published
2013
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9. Contributors

Author

Reidunn B. Aalen, Yasser H.A. Abdel-Wahab, Michael E. Adams, Roger A.H. Adan, Rexford S. Ahima, Naima Ahmed, Omar Al-Massadi, Miriam Altstein, Youssef Anouar, Laura Anselmi, Siegfried Ansorge, Nikolinka Antcheva, Yevgeniya Antonova-Koch, Jon R. Appel, Anam J. Arik, Alison L. Arter, Peter Arvan, Avraham Ashkenazi, P.W. Baas, André Bado, Andrew Baird, Monica Baiula, Lauren O. Bakaletz, Earl E. Bakken, Márta Balaskó, Graham S. Baldwin, William A. Banks, Donatella Barra, Jessica R. Barson, Magali Basille, Natalie N. Bauer, Andrea Bedini, Christine Beeton, David J. Begley, Margery C. Beinfeld, William G. Bendena, Stephen C. Benoit, Itay Bentov, Howard Bern, Gabriele Bierbaum, Charles J. Billington, Anna Blasiak, Norman L. Block, Stephen. R. Bloom, Iwona Bonney, John H. Bowie, Sunny K. Boyd, Susan D. Brain, Dag A. Brede, Jozef Vanden Broeck, Kelly L. Brown, Mark R. Brown, James M. Bugni, Jens R. Bundgaard, Delphine Burel, Melinka A. Butenko, Melissa J. Call, Girolamo Calò, Duncan John Campbell, Anna Carlsson, Daniel B. Carr, Robert E. Carraway, Marcos C. Carreira, Felipe F. Casanueva, Sarah N. Cassella, Stuart A. Casson, Justo P. Castaño, Marek Cebrat, Valerie Chappe, David Chatenet, Keqiang Chen, Chen Chen, Longchuan Chen, Duan Chen, Carrie Y.Y. Cheng, Sung Ki Cho, Billy K.C. Chow, Arthur Christopoulos, Shijian Chu, Iain J. Clarke, Geoffrey M. Coast, Vincent Compere, Gisela P. Concepcion, Roger D. Cone, J. Michael Conlon, Germaine Cornélissen, Maité Courel, Réjean Couture, W.A. Cramer, Nathan P. Croft, Ana B. Crujeiras, Frank Cuttitta, Holger Cynis, F. D’Acquisto, Jon F. Davis, Thomas P. Davis, Claire Barbier de La Serre, Guillaume de Lartigue, Luis de Lecea, Marcelo de Oliveira Santos, Michel De Waard, Carolyn F. Deacon Bolette Hartmann, Charlène Delestre, Mario Delgado, Hans-Ulrich Demuth, Xiaoming Deng, Palitha Dharmawardhana, Anna Di Cosmo, Simoni Campos Dias, Jonathan W. Dickerson, Dzung B. Diep, H. Dircksen, Jasmin Dischinger, Jean-Claude do Rego, Paul R. Dobner, Graham J. Dockray, Robert M. Dores, Robert Ducroc, Nadine L. Dudek, Yvan Dumont, Celine Duraffourd, Dominique Duterte-Boucher, Alex N. Eberlé, Richard D. Egleton, Betty A. Eipper, Jorg B. Engel, Ella W. Englander, Jacques Epelbaum, Charlotte Erlanson-Albertsson, S. Evangelista, Karen A. Fagan, Joshua M. Farber, Klára Farkasfalvi, Csaba Fekete, Peter R. Flatt, R.J. Flower, Wolf-Georg Forssmann, Alain Fournier, Kevin Chu Foy, Octávio Luiz Franco, Dan Frenkel, Lloyd D. Fricker, César de la Fuente-Núñez, Hiroo Fukuda, Gerd Gäde, Ludovic Galas, Patricia E. Gallagher, Pierrick Gandolfo, Maria A. Garcia-Espinosa, Josune García-Sanmartín, Nori Geary, Hua Geng, Patrizia M. Germano, Jens P. Goetze, Alexis A. Gonzalez, Ana Gonzalez, Blake A. Gosnell, Katsutoshi Goto, Guillaume Gourcerol, I. Gozes, Francisco Gracia-Navarro, Bernadette E. Grayson, George H. Greeley, Megan Greenwald-Yarnell, Pierre Gressens, John R. Grider, Jan Grünewald, Juliano R. Guerreiro, Remo Guerrini, Filomena Guida, Laure Guilhaudis, Sandra Guilmeau, Andrew L. Gundlach, Jolanta Gutkowska, Clifton Hackbarth, Y. Haim Ohana, Franz Halberg, Mathias Hallberg, Sayyed A. Hamidi, Song Han, Ji-Sheng Han, Robert E.W. Hancock, Samer-ul Haque, Ikuko Hara-Nishimura, Aliza Hariton, Wendy J. Hartsock, Alan L. Harvey, Itaru Hasunuma, Robert J. Henning, Kristy M. Heppner, Kate L. Hertweck, Herbert Herzog, Tetsuya Higashiyama, Shuji Hinuma, Stefan Hippenstiel, Yuki Hirakawa, Shuichi Hirose, Jochen R. Hirsch, Andreas C. Hocke, Robert S. Hodges, Werner Hoffmann, Tomas Hökfelt, Jens Juul Holst, Peter Holzer, Frank M. Horodyski, Hiroshi Hosoda, Xiaowen Hou, Alisa Huffaker, Norio Iijima, Momoko Ikeuchi, Julita S. Imperial, Giovanna Improta, Akio Inui, Nigel Irwin, Munehiro Ishii, Xavier Iturrioz, Ljubica Ivanisevic, Hiroshi Iwao, Takeo Iwata, Yasukatsu Izumi, Hajime Izumiyama, Marek Jankowski, Tom Janssen, Sylvie Jégou, Robert T. Jensen, Preeti H. Jethwa, Helene Johannessen, Conrad Johanson, Valeria Judkowski, Przemyslaw Kaczmarek, Haruaki Kageyama, Tatsuo Kakimoto, Ki Sung Kang, Kenji Kangawa, Abba J. Kastin, Johji Kato, Pravin T.P. Kaumaya, Richard F. Keep, William R. Kem, Tetyana Khomenko, Sakae Kikuyama, Young-Joon Kim, Sadao Kimura, Ross King, Paul Kiptoo, Ichiro Kishimoto, Kazuo Kitamura, Alicja Kluczyk, Hiroyuki Kobori, Yosuke Kodama, Masayasu Kojima, Yuki Kondo, Meike Körner, Piotr Kosson, Catherine M. Kotz, Bhavani Krishnan, Bård Kulseng, Robert Kumpf, Marc Laburthe, Hélène Lacaille, Ellen E. Ladenheim, Ali Ladram, Marlyn D. Laksitorini, David G. Lambert, Angela B. Lange, Wolfgang Langhans, Muriel Larauche, Dan Larhammar, Ignacio M. Larráyoz, Roberta Lattanzi, Ronald M. Lechan, Benjamin Lefranc, Sarah F. Leibowitz, Vincent Lelièvre, Jérôme Leprince, Allen S. Levine, Qun Li, Veronica Lifshitz, Isabelle Lihrmann, James Chi-Jen Lin, Iris Lindberg, Keith Lindsey, Andrzej W. Lipkowski, T. Liron, Junli Liu, Ying Liu, Min Liu, Catherine Llorens-Cortes, Marilena Loizidou, C. Lopez, David A. Lovejoy, Vincenzo Luca, Thomas A. Lutz, Sherie Ma, Richard E. Mains, Maria M. Malagon, Ludwik K. Malendowicz, Jennifer Man-Fan Wan, Maria Luisa Mangoni, Michaele B Manigrasso, Mohamed A. Marahiel, Heather G. Marco, Christine Maric-Bilkan, Nikki J. Marks, Roland Martin, Vicente Martinez, Alfredo Martínez, Antonio J. Martinez-Fuentes, Edward P. Masler, Yoshikatsu Matsubayashi, Harman S. Mattu, Aaron G. Maule, Patricia J. McLaughlin, Ivan F. McMurtry, Ellen Meelkop, Saher Mehdi, Pietro Melchiorri, R.P. Millar, Laurence J. Miller, Miles Miller, Mulugeta Million, Naoto Minamino, M. Mittelman, Takashi Miyauchi, Mikiya Miyazato, Hirokazu Mizoguchi, Malte Mohme, Maité Montero-Hadjadje, Terry W. Moody, Neeloffer Mookherjee, Timothy H. Moran, Irene Morganstern, Masatomo Mori, Fabrice Morin, John F. Morris, Daniel S. Moura, Anna J. Mudge, Joram D. Mul, Karnam S. Murthy, Martin G. Myers, Ronald J. Nachman, Jean-Louis Nahon, Sushma Naithani, Tomoaki Nakada, Tomoya Nakamachi, Yuki Nakamura, Natalia N. Nalivaeva, June B. Nasrallah, Dick R. Nässel, L. Gabriel Navar, Pratap Neelakantan, Lucia Negri, Ingolf F. Nes, D. Neumann, Cindy Neveu, Tzi Bun Ng, Stephanie Y.L. Ng, Graham M. Nicholson, Pierre Nicolas, Toshio Nishikimi, Mariko Nishiyama, Rubén Nogueiras, Raymond S. Norton, Laura A. Novotny, Krzysztof W. Nowak, Fred Nyberg, Laura Ochoa-Callejero, Sven Ove Ögren, Hideko Ohgusu, Shinsuke Oh-I, Opeolu O. Ojo, Baldomero M. Olivera, Francisco E. Olucha-Bordonau, Joost J. Oppenheim, Ian Orchard, André J. Ouellette, Gustavo Pacheco-López, Nigel M. Page, Mario Sergio Palma, Weihong Pan, Yoonseong Park, Marc Parmentier, Sandrine Passemard, Michael Patterson, Brankica Paunovic, Gregory Pearce, Jens Pedersen, Theo L. Peeters, A. Eugene Pekary, Georges Pelletier, Simona Perboni, Diego Pérez-Tilve, Ábel Perjés, M. Perretti, Erika Pétervári, Clemencia Pinilla, Jacek Pinskim, Joseph R. Pisegna, Kristof Plankensteiner, Sonia Podvin, Pierre Poitras, Gianluca Polese, David M. Pollock, William Farias Porto, Lourival D. Possani, Charalabos Pothoulakis, Françoise Presse, Minolfa C. Prieto, S. Prutchi-Sagiv, Anthony W. Purcell, Louise Purtell, Rémi Quirion, Catalina Abad Rabat, Miriam Rademaker, Gautam Rajpal, Harpal S. Randeva, Sylvie Rebuffat, Joseph R. Reeve, Jens F. Rehfeld, Dirk Reinhold, Rainer K. Reinscheid, Jean Claude Reubi, Katayoun Rezvani, Suzana Meira Ribeiro, D. Richard, Mark Richards, Michael A. Riehle, Andrea C. Rinaldi, Bernd M. Rode, Ricardo C. Rodríguez de la Vega, Susan Rotzinger, Marcin Rucinski, Heikki Ruskoaho, Philip J. Ryan, Jean-Marc Sabatier, Hans-Georg Sahl, Sami I. Said, Tsukasa Sakurada, Shinobu Sakurada, David S. Salomon, Willis K. Samson, Zsuzsanna Sandor, H. Uri Saragovi, Kazuki Sasaki, Takahiro Sato, Ryousuke Satou, Shinichiro Sawa, Ayman I. Sayegh, Andrew V. Schally, Stephan Schilling, Liliane Schoofs, David A. Schooley, Mitchell L. Schubert, Isabelle Segalas-Milazzo, Nabil G. Seidah, Michael E. Selsted, Kim B. Seroogy, Cinzia Severini, Patrick M. Sexton, Yechiel Shai, O. Sharma, Masayoshi Shichiri, Tomoo Shimada, Hiroyuki Shimizu, Seiji Shioda, Arthur Shulkes, Teruna J. Siahaan, Ignacy Z. Siemion, Osmar Nascimento Silva, Marcio C. Silva-Filho, Mariusz Skwarczynski, Caroline. J. Small, Craig M. Smith, David E. Smith, A. Ian Smith, Beka Solomon, Travis E. Solomon, Mireia Sospedra, M.C. Souroujon, Santi Spampinato, Eliot R. Spindel, A. Steiger, Andreas Stengel, Catia Sternini, Frederik J. Steyn, Edward Stopa, Mathias Z. Strowski, Shigeo S. Sugano, Görel Sundström, J. Gregor Sutcliffe, Norbert Suttorp, Jonathan V. Sweedler, Sandor Szabo, Miklós Székely, István Szokodi, Yvette Taché, Kazuhiro Takahashi, Yoshio Takei, Fumiko Takenoya, Sébastien Talbot, E. Ann Tallant, Tricia M. Tan, Liesbet Temmerman, Bettina Temmesfeld-Wollbrück, Manuel Tena-Sempere, Annika Thorsell, Nanda Tilakaratne, Stephen S. Tobe, Takeshi Tokudome, Ganna Tolstanova, Marie-Christine Tonon, Jennifer F. Topping, Alessandro Tossi, Hervé Tostivint, Istvan Toth, Kazuhito Totsune, Fumiyo Toyoda, Rachel Troke, Matthias H. Tschöp, Patrick Tso, Hirokazu Tsukaya, Kazuyoshi Tsutsui, Hong Tu, Anthony J. Turner, Takayoshi Ubuka, Elene R. Valdivia, Hans Peter Vandersmissen, David Vaudry, Hubert Vaudry, Rafael Vazquez-Martinez, Joseph G. Verbalis, Daniele Vicari, Nicolas Vidal, Marzia Vignoni, Cécile Viollet, K.S. Vishwanatha, Mirella Vivoli, Thierry Voisin, John P. Vu, John C. Walker, B.A. Wallace, Ji Ming Wang, Lixin Wang, Jonathan H. Wardman, Takuya Watanabe, Hazel Welch, Haim Werner, L. Whitmore, Imke Wiedemann, Raphaelle Winsky-Sommerer, Ken A. Witt, Tatiana Wojciechowicz, Jack Ho Wong, Stephen C. Woods, Denise Wootten, Vincent Wu, Olivier Wurtz, Ximing Xiong, Zhi-Qing David Xu, Yube Yamaguchi, Takahiro Yamaguchi, Kazutoshi Yamamoto, E. Yamashita, Hiroyuki Yamazaki, De Yang, Masaaki Yoshikawa, Pu-Qing Yuan, Sunny C. Yung, Ian S. Zagon, S.D. Zakharov, Mehfuz Zaman, M.V. Zhalnina, Ning Zhang, Lixin Zhang-Auberson, Chun-Mei Zhao, Agnieszka Ziolkowska, and Dusan Zitnan

Published
2013
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11. Modelling and experimental analysis of hormonal crosstalk in Arabidopsis

Author

Jennifer F. Topping, Petr Tarkowski, Junli Liu, Saher Mehdi, and Keith Lindsey

Subjects
Cytokinins, root development, Transcription, Genetic, POLARIS gene, Mutant, Arabidopsis, Biology, Gene mutation, Models, Biological, Plant Roots, General Biochemistry, Genetics and Molecular Biology, Article, chemistry.chemical_compound, Plant Growth Regulators, Auxin, heterocyclic compounds, Gene, chemistry.chemical_classification, General Immunology and Microbiology, Indoleacetic Acids, Arabidopsis Proteins, Applied Mathematics, fungi, food and beverages, Ethylenes, biology.organism_classification, Cell biology, Crosstalk (biology), hormonal crosstalk, Computational Theory and Mathematics, Biochemistry, chemistry, Cytokinin, Mutation, Signal transduction, General Agricultural and Biological Sciences, mathematical model, Information Systems, Signal Transduction
Abstract

An important question in plant biology is how genes influence the crosstalk between hormones to regulate growth. We have developed the first hormonal crosstalk network in Arabidopsis by iteratively combining modelling with experimental analysis. We have revealed that the POLARIS gene interacts with the ethylene receptor and regulates both auxin transport and biosynthesis. Our modelling analysis has reproduced all known mutants. With new experimental data, it has provided new insights into how the POLARIS gene regulates auxin concentration for root development in Arabidopsis, by controlling the relative contribution of auxin transport and biosynthesis and by integrating auxin, ethylene and cytokinin signalling. Modelling and experimental analysis have revealed that a bell-shaped dose–response relationship between endogenous auxin and root length is established via POLARIS., Hormone signalling systems coordinate plant growth and development through a range of complex interactions. The activities of plant hormones, such as auxin, ethylene and cytokinin, depend on cellular context and exhibit interactions that can be either synergistic or antagonistic. An important question regarding the understanding of those interactions is how genes act on the crosstalk between hormones to regulate plant growth. Previously, we identified the POLARIS (PLS) gene of Arabidopsis, which transcribes a short mRNA encoding a 36-amino acid peptide that is required for correct root growth and vascular development (Casson et al, 2002). Experimental evidence shows that there is a link between PLS, ethylene signalling, auxin homeostasis and microtubule cytoskeleton dynamics (Chilley et al, 2006). Specifically, mutation of PLS results in an enhanced ethylene-response phenotype, defective auxin transport and homeostasis, and altered sensitivity to microtubule inhibitors. These defects, along with the short-root phenotype, are suppressed by genetic and pharmacological inhibition of ethylene action. The expression of PLS is itself repressed by ethylene and induced by auxin. It was also shown that pls mutant roots are hyper-responsive to exogenous cytokinins and show increased expression of the cytokinin inducible gene ARR5/IBC6 compared with the wild type (Casson et al, 2002). Therefore, PLS may also be required for correct auxin–cytokinin homeostasis to modulate root growth. In this study, we model PLS gene function and crosstalk between auxin, ethylene and cytokinin in Arabidopsis. Experimental evidence suggests that PLS acts on or close to the ethylene receptor ETR1, and a mathematical model describing possible PLS–ethylene pathway interactions is developed, and used to make quantitative predictions about PLS–hormone interactions. Modelling correctly predicts experimental results for the effect of the pls gene mutation on endogenous cytokinin concentration. Modelling also reveals a role for PLS in auxin biosynthesis in addition to a role in auxin transport (Figures 1 and 4). The model reproduces available mutants, and with new experimental data provides new insights into how PLS regulates auxin concentration, by controlling the relative contribution of auxin transport and biosynthesis and by integrating auxin, ethylene and cytokinin signalling. Modelling further reveals that a bell-shaped dose–response relationship between endogenous auxin and root length is established via PLS. In summary, we developed the first hormonal crosstalk model in Arabidopsis and revealed a hormonal crosstalk circuit through PLS and the downstream of ethylene signalling. Our study provides a platform to further integrate hormonal crosstalk in space and time in Arabidopsis., An important question in plant biology is how genes influence the crosstalk between hormones to regulate growth. In this study, we model POLARIS (PLS) gene function and crosstalk between auxin, ethylene and cytokinin in Arabidopsis. Experimental evidence suggests that PLS acts on or close to the ethylene receptor ETR1, and a mathematical model describing possible PLS–ethylene pathway interactions is developed, and used to make quantitative predictions about PLS–hormone interactions. Modelling correctly predicts experimental results for the effect of the pls gene mutation on endogenous cytokinin concentration. Modelling also reveals a role for PLS in auxin biosynthesis in addition to a role in auxin transport. The model reproduces available mutants, and with new experimental data provides new insights into how PLS regulates auxin concentration, by controlling the relative contribution of auxin transport and biosynthesis and by integrating auxin, ethylene and cytokinin signalling. Modelling further reveals that a bell-shaped dose–response relationship between endogenous auxin and root length is established via PLS. This combined modelling and experimental analysis provides new insights into the integration of hormonal signals in plants.

Published
2010

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