201
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Ploense SE, Wu MF, Nagpal P, Reed JW. A gain-of-function mutation in IAA18 alters Arabidopsis embryonic apical patterning. Development 2009; 136:1509-17. [PMID: 19363152 DOI: 10.1242/dev.025932] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Lateral organ emergence in plant embryos and meristems depends on spatially coordinated auxin transport and auxin response. Here, we report the gain-of-function iaa18-1 mutation in Arabidopsis, which stabilizes the Aux/IAA protein IAA18 and causes aberrant cotyledon placement in embryos. IAA18 was expressed in the apical domain of globular stage embryos, and in the shoot apical meristem and adaxial domain of cotyledons of heart stage embryos. Mutant globular embryos had asymmetric PIN1:GFP expression in the apical domain, indicating that IAA18-1 disrupts auxin transport. Genetic interactions among iaa18-1, loss-of-function mutations in ARF (Auxin response factor) genes and ARF-overexpressing constructs suggest that IAA18-1 inhibits activity of MP/ARF5 and other ARF proteins in the apical domain. The iaa18-1 mutation also increased the frequency of rootless seedlings in mutant backgrounds in which auxin regulation of basal pole development was affected. These results indicate that apical patterning requires Aux/IAA protein turnover, and that apical domain auxin response also influences root formation.
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Affiliation(s)
- Sara E Ploense
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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202
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Wolters H, Jürgens G. Survival of the flexible: hormonal growth control and adaptation in plant development. Nat Rev Genet 2009; 10:305-17. [PMID: 19360022 DOI: 10.1038/nrg2558] [Citation(s) in RCA: 292] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Plant development is subject to hormonal growth control and adapts to environmental cues such as light or stress. Recently, significant progress has been made in elucidating hormone synthesis, signalling and degradation pathways, and in resolving spatial and temporal aspects of hormone responses. Here we review how hormones control maintenance of stem cell systems, influence developmental transitions of stem cell daughters and define developmental compartments in Arabidopsis thaliana. We also discuss how environmental cues change plant growth by modulating hormone levels and response. Future analysis of hormone crosstalk and of hormone action at both single cell and organ levels will substantially improve our understanding of how plant development adapts to changes in intrinsic and environmental conditions.
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Affiliation(s)
- Hanno Wolters
- ZMBP, Entwicklungsgenetik, Universität Tübingen, Auf der Morgenstelle 3, 72076 Tübingen, Germany
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203
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Cole M, Chandler J, Weijers D, Jacobs B, Comelli P, Werr W. DORNRÖSCHEN is a direct target of the auxin response factor MONOPTEROS in the Arabidopsis embryo. Development 2009; 136:1643-51. [DOI: 10.1242/dev.032177] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
DORNRÖSCHEN (DRN), which encodes a member of the AP2-type transcription factor family, contributes to auxin transport and perception in the Arabidopsis embryo. Live imaging performed with transcriptional or translational GFP fusions shows DRN to be activated in the apical cell after the first zygotic division, to act cell-autonomously and to be expressed in single cells extending laterally from the apical shoot stem-cell zone at the position of incipient leaf primordia. Here, we show that the Auxin response factor (ARF) MONOPTEROS (MP) directly controls DRN transcription in the tips of the embryonic cotyledons,which depends on the presence of canonical Auxin response elements (AuxREs),potential ARF-binding sites flanking the DRN transcription unit. Chromatin immunoprecipitation experiments show that MP binds in vivo to two AuxRE-spanning fragments in the DRN promoter, and that MP is required for expression of DRN in cotyledon tips. Hence, DRNrepresents a direct target of MP and functions downstream of MP in cotyledon development.
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Affiliation(s)
- Melanie Cole
- Institute of Developmental Biology, University of Cologne, Gyrhofstrasse 17,50931 Cologne, Germany
| | - John Chandler
- Institute of Developmental Biology, University of Cologne, Gyrhofstrasse 17,50931 Cologne, Germany
| | - Dolf Weijers
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
| | - Bianca Jacobs
- Institute of Developmental Biology, University of Cologne, Gyrhofstrasse 17,50931 Cologne, Germany
| | - Petra Comelli
- Institute of Developmental Biology, University of Cologne, Gyrhofstrasse 17,50931 Cologne, Germany
| | - Wolfgang Werr
- Institute of Developmental Biology, University of Cologne, Gyrhofstrasse 17,50931 Cologne, Germany
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204
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Benková E, Hejátko J. Hormone interactions at the root apical meristem. PLANT MOLECULAR BIOLOGY 2009; 69:383-96. [PMID: 18807199 DOI: 10.1007/s11103-008-9393-6] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Accepted: 08/27/2008] [Indexed: 05/18/2023]
Abstract
Plants exhibit an amazing developmental flexibility. Plant embryogenesis results in the establishment of a simple apical-basal axis represented by apical shoot and basal root meristems. Later, during postembryonic growth, shaping of the plant body continues by the formation and activation of numerous adjacent meristems that give rise to lateral shoot branches, leaves, flowers, or lateral roots. This developmental plasticity reflects an important feature of the plant's life strategy based on the rapid reaction to different environmental stimuli, such as temperature fluctuations, availability of nutrients, light or water and response resulting in modulation of developmental programs. Plant hormones are important endogenous factors for the integration of these environmental inputs and regulation of plant development. After a period of studies focused primarily on single hormonal pathways that enabled us to understand the hormone perception and signal transduction mechanisms, it became obvious that the developmental output mediated by a single hormonal pathway is largely modified through a whole network of interactions with other hormonal pathways. In this review, we will summarize recent knowledge on hormonal networks that regulate the development and growth of root with focus on the hormonal interactions that shape the root apical meristem.
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Affiliation(s)
- Eva Benková
- Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), Gent University, Technologiepark 927, 9052 Gent, Belgium.
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205
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Capron A, Chatfield S, Provart N, Berleth T. Embryogenesis: pattern formation from a single cell. THE ARABIDOPSIS BOOK 2009; 7:e0126. [PMID: 22303250 PMCID: PMC3243344 DOI: 10.1199/tab.0126] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
During embryogenesis a single cell gives rise to a functional multicellular organism. In higher plants, as in many other multicellular systems, essential architectural features, such as body axes and major tissue layers are established early in embryogenesis and serve as a positional framework for subsequent pattern elaboration. In Arabidopsis, the apicalbasal axis and the radial pattern of tissues wrapped around it are already recognizable in young embryos of only about a hundred cells in size. This early axial pattern seems to provide a coordinate system for the embryonic initiation of shoot and root. Findings from genetic studies in Arabidopsis are revealing molecular mechanisms underlying the initial establishment of the axial core pattern and its subsequent elaboration into functional shoots and roots. The genetic programs operating in the early embryo organize functional cell patterns rapidly and reproducibly from minimal cell numbers. Understanding their molecular details could therefore greatly expand our ability to generate plant body patterns de novo, with important implications for plant breeding and biotechnology.
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Affiliation(s)
- Arnaud Capron
- Dept. of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, Ontario, M5S 3G5 Canada
- Each of these authors contributed equally. Address correspondence to or
| | - Steven Chatfield
- Dept. of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, Ontario, M5S 3G5 Canada
- Each of these authors contributed equally. Address correspondence to or
| | - Nicholas Provart
- Dept. of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, Ontario, M5S 3G5 Canada
| | - Thomas Berleth
- Dept. of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, Ontario, M5S 3G5 Canada
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206
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Willemsen V, Bauch M, Bennett T, Campilho A, Wolkenfelt H, Xu J, Haseloff J, Scheres B. The NAC Domain Transcription Factors FEZ and SOMBRERO Control the Orientation of Cell Division Plane in Arabidopsis Root Stem Cells. Dev Cell 2008; 15:913-22. [DOI: 10.1016/j.devcel.2008.09.019] [Citation(s) in RCA: 185] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Revised: 09/05/2008] [Accepted: 09/29/2008] [Indexed: 12/18/2022]
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207
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Gao X, Nagawa S, Wang G, Yang Z. Cell polarity signaling: focus on polar auxin transport. MOLECULAR PLANT 2008; 1:899-909. [PMID: 19825591 PMCID: PMC2902905 DOI: 10.1093/mp/ssn069] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Polar auxin transport, which is required for the formation of auxin gradients and directional auxin flows that are critical for plant pattern formation, morphogenesis, and directional growth response to vectorial cues, is mediated by polarized sub-cellular distribution of PIN-FORMED Proteins (PINs, auxin efflux carriers), AUX1/AUX1-like proteins (auxin influx facilitators), and multidrug resistance P-glycoproteins (MDR/PGP). Polar localization of these proteins is controlled by both developmental and environmental cues. Recent studies have revealed cellular (endocytosis, transcytosis, and endosomal sorting and recycling) and molecular (PINOID kinase, protein phosphatase 2A) mechanisms underlying the polar distribution of these auxin transport proteins. Both TIR1-mediated auxin signaling and TIR1-independent auxin-mediated endocytosis have been shown to regulate polar PIN localization and auxin flow, implicating auxin as a self-organizing signal in directing polar transport and directional flows.
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Affiliation(s)
- Xiaowei Gao
- Key Laboratory of Arid and Grassland Agroeology at Lanzhou University, Ministry of Education, Lanzhou 730000, China
- CAU–UCR Joint Center for Biological Science, China Agricultural University, Beijing 100094, China
| | - Shingo Nagawa
- Center for Plant Cell Biology and Department of Botany and Plant Science, University of California, Riverside, CA 92521, USA
| | - Genxuan Wang
- College of Life Science, Zhejiang University, Hangzhou 310029, China
| | - Zhenbiao Yang
- CAU–UCR Joint Center for Biological Science, China Agricultural University, Beijing 100094, China
- Center for Plant Cell Biology and Department of Botany and Plant Science, University of California, Riverside, CA 92521, USA
- To whom correspondence should be addressed. E-mail , fax 9011-886-2-2651-6234, tel. 951-827-7351
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208
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Affiliation(s)
| | - Mark Estelle
- Department of Biology, Indiana University, Bloomington, Indiana 47405; ,
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209
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Song SK, Hofhuis H, Lee MM, Clark SE. Key divisions in the early Arabidopsis embryo require POL and PLL1 phosphatases to establish the root stem cell organizer and vascular axis. Dev Cell 2008; 15:98-109. [PMID: 18606144 DOI: 10.1016/j.devcel.2008.05.008] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Revised: 04/15/2008] [Accepted: 05/16/2008] [Indexed: 11/17/2022]
Abstract
Arabidopsis development proceeds from three stem cell populations located at the shoot, flower, and root meristems. The relationship between the highly related shoot and flower stem cells and the very divergent root stem cells has been unclear. We show that the related phosphatases POL and PLL1 are required for all three stem cell populations. pol pll1 mutant embryos lack key asymmetric divisions that give rise to the root stem cell organizer and the central vascular axis. Instead, these cells divide in a superficially symmetric fashion in pol pll1 embryos, leading to a loss of embryonic and postembryonic root stem cells and vascular specification. We present data that show that POL/PLL1 drive root stem cell specification by promoting expression of the WUS homolog WOX5. We propose that POL and PLL1 are required for the proper divisions of shoot, flower, and root stem cell organizers, WUS/WOX5 gene expression, and stem cell maintenance.
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Affiliation(s)
- Sang-Kee Song
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
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210
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Breuninger H, Rikirsch E, Hermann M, Ueda M, Laux T. Differential expression of WOX genes mediates apical-basal axis formation in the Arabidopsis embryo. Dev Cell 2008; 14:867-76. [PMID: 18539115 DOI: 10.1016/j.devcel.2008.03.008] [Citation(s) in RCA: 256] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2007] [Revised: 03/07/2008] [Accepted: 03/13/2008] [Indexed: 10/22/2022]
Abstract
Axis formation is one of the earliest patterning events in plant and animal embryogenesis. In Arabidopsis, the main axis of the embryo is evident at the asymmetric division of the zygote into a small, embryonic apical cell and a large extraembryonic basal cell. Here we show that the homeobox genes WOX2 and WOX8, which are initially coexpressed in the zygote, act as complementary cell fate regulators in the apical and basal lineage, respectively. Furthermore, WOX8 expression in the basal cell lineage is required for WOX2 expression and normal development of the proembryo, suggesting an inductive mechanism. The identified WOX cascade is required for normal expression of a reporter gene of the auxin efflux carrier PIN1 and for the formation of auxin response maxima in the proembryo. Thus, our results link the spatial separation of WOX transcription factors to localized auxin response and the formation of the main body axis in the embryo.
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Affiliation(s)
- Holger Breuninger
- Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
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211
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Uehara T, Okushima Y, Mimura T, Tasaka M, Fukaki H. Domain II mutations in CRANE/IAA18 suppress lateral root formation and affect shoot development in Arabidopsis thaliana. PLANT & CELL PHYSIOLOGY 2008; 49:1025-38. [PMID: 18505759 DOI: 10.1093/pcp/pcn079] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Lateral root formation is an important developmental component of root systems in vascular plants. Several regulatory genes for lateral root formation have been identified from recent studies mainly using Arabidopsis thaliana. In this study, we isolated two dominant mutant alleles, crane-1 and crane-2, which are defective in lateral root formation in Arabidopsis. The crane mutants have dramatically reduced lateral root and auxin-induced lateral root formation, indicating that the crane mutations reduce auxin sensitivity. In addition, the crane mutants have pleiotropic phenotypes in the aerial shoots, including long hypocotyls when grown in the light, up-curled leaves and reduced fertility. The crane mutant phenotypes are caused by a gain-of-function mutation in domain II of IAA18, a member of the Aux/IAA transcriptional repressor family which is expressed in almost all organs. In roots, IAA18 promoter::GUS was expressed in the early stages of lateral root development. In the yeast two-hybrid system, IAA18 interacts with AUXIN RESPONSE FACTOR 7 (ARF7) and ARF19, transcriptional activators that positively regulate lateral root formation. Taken together, our results indicate that CRANE/IAA18 is involved in lateral root formation in Arabidopsis, and suggest that it negatively regulates the activity of ARF7 and ARF19 for lateral root formation.
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Affiliation(s)
- Takeo Uehara
- Graduate School of Science and Technology, Kobe University, 1-1 Rokkodai, Kobe, 657-8501 Japan
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212
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Saiga S, Furumizu C, Yokoyama R, Kurata T, Sato S, Kato T, Tabata S, Suzuki M, Komeda Y. The Arabidopsis OBERON1 and OBERON2 genes encode plant homeodomain finger proteins and are required for apical meristem maintenance. Development 2008; 135:1751-9. [PMID: 18403411 DOI: 10.1242/dev.014993] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Maintenance of the stem cell population located at the apical meristems is essential for repetitive organ initiation during the development of higher plants. Here, we have characterized the roles of OBERON1 (OBE1) and its paralog OBERON2 (OBE2), which encode plant homeodomain finger proteins, in the maintenance and/or establishment of the meristems in Arabidopsis. Although the obe1 and obe2 single mutants were indistinguishable from wild-type plants, the obe1 obe2 double mutant displayed premature termination of the shoot meristem, suggesting that OBE1 and OBE2 function redundantly. Further analyses revealed that OBE1 and OBE2 allow the plant cells to acquire meristematic activity via the WUSCHEL-CLAVATA pathway, which is required for the maintenance of the stem cell population, and they function parallel to the SHOOT MERISTEMLESS gene, which is required for preventing cell differentiation in the shoot meristem. In addition, obe1 obe2 mutants failed to establish the root apical meristem, lacking both the initial cells and the quiescent center. In situ hybridization revealed that expression of PLETHORA and SCARECROW, which are required for stem cell specification and maintenance in the root meristem, was lost from obe1 obe2 mutant embryos. Taken together, these data suggest that the OBE1 and OBE2 genes are functionally redundant and crucial for the maintenance and/or establishment of both the shoot and root meristems.
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Affiliation(s)
- Shunsuke Saiga
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo, Tokyo 113-0033, Japan
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213
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Stepanova AN, Robertson-Hoyt J, Yun J, Benavente LM, Xie DY, Doležal K, Schlereth A, Jürgens G, Alonso JM. TAA1-Mediated Auxin Biosynthesis Is Essential for Hormone Crosstalk and Plant Development. Cell 2008; 133:177-91. [PMID: 18394997 DOI: 10.1016/j.cell.2008.01.047] [Citation(s) in RCA: 726] [Impact Index Per Article: 45.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2007] [Revised: 12/14/2007] [Accepted: 01/24/2008] [Indexed: 12/22/2022]
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214
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Szemenyei H, Hannon M, Long JA. TOPLESS mediates auxin-dependent transcriptional repression during Arabidopsis embryogenesis. Science 2008; 319:1384-6. [PMID: 18258861 DOI: 10.1126/science.1151461] [Citation(s) in RCA: 514] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The transcriptional response to auxin is critical for root and vascular development during Arabidopsis embryogenesis. Auxin induces the degradation of AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) transcriptional repressors, freeing their binding partners, the AUXIN RESPONSE FACTOR (ARF) proteins, which can activate transcription of auxin response genes. We show that TOPLESS (TPL) can physically interact with IAA12/BODENLOS (IAA12/BDL) through an ETHYLENE RESPONSE FACTOR (ERF)-associated amphiphilic repression (EAR) motif. TPL can repress transcription in vivo and is required for IAA12/BDL repressive activity. In addition, tpl-1 can suppress the patterning defects of the bdl-1 mutant. Direct interaction between TPL and ARF5/MONOPTEROS, which is regulated by IAA12/BDL, results in a loss-of-function arf5/mp phenotype. These observations show that TPL is a transcriptional co-repressor and further our understanding of how auxin regulates transcription during plant development.
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Affiliation(s)
- Heidi Szemenyei
- Plant Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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215
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Bureau M, Simon R. JLO regulates embryo patterning and organ initiation by controlling auxin transport. PLANT SIGNALING & BEHAVIOR 2008; 3:145-7. [PMID: 19704738 PMCID: PMC2634008 DOI: 10.4161/psb.3.2.5080] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Accepted: 09/25/2007] [Indexed: 05/21/2023]
Abstract
In Arabidopsis, lateral organ initiation correlates with the formation of an auxin maximum in a group of cells at the periphery of the shoot apical meristem (SAM). This signal establishes founder cells that build the lateral organ. Primordia initiation is closely associated with the creation of a functional boundary that separates the newly formed primordium from the remainder of the meristem. In the June issue of Plant Cell, we have characterised the JLO (for Jagged Lateral Organ) gene of Arabidopsis, a member of the Lateral Organ boundary Domain gene family. JLO is expressed in boundaries and regulates both auxin transport, via a negative regulation of PIN auxin export carriers, and meristem fate by promoting the expression of the KNOX genes SHOOTMERISTEMLESS (STM) and BP/KNAT1. In this Addendum, we discuss the regulation of PIN genes by JLO, and propose a model for JLO function during embryonic and post-embryonic development.
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Affiliation(s)
- Marina Bureau
- Institut für Genetik; Heinrich-Heine-Universität; Düsseldorf, Germany
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216
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Nawy T, Lukowitz W, Bayer M. Talk global, act local-patterning the Arabidopsis embryo. CURRENT OPINION IN PLANT BIOLOGY 2008; 11:28-33. [PMID: 18060828 DOI: 10.1016/j.pbi.2007.10.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2007] [Revised: 10/10/2007] [Accepted: 10/11/2007] [Indexed: 05/25/2023]
Abstract
The primary axis and main tissue types of Arabidopsis are laid down in the early embryo. Apical-to-basal auxin flux functions as a global organizer of the axis, and recent reports are clarifying our mechanistic understanding of how a graded auxin distribution is generated and interpreted. Polar targeting of PIN transporters in the cells of the embryo is dynamic and linked to their phosphorylation status, suggesting a flexible mechanism for regulating auxin flux in space and time. PLETHORA transcription factors then interpret the graded auxin distribution to provide positional values along the axis in a dose-dependent manner. A comparable framework for tissue patterning in the radial dimension is still lacking, although cell surface signaling probably plays a key role.
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Affiliation(s)
- Tal Nawy
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, United States.
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217
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Ten Hove CA, Heidstra R. Who begets whom? Plant cell fate determination by asymmetric cell division. CURRENT OPINION IN PLANT BIOLOGY 2008; 11:34-41. [PMID: 18162432 DOI: 10.1016/j.pbi.2007.11.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Revised: 10/31/2007] [Accepted: 11/07/2007] [Indexed: 05/25/2023]
Abstract
Asymmetric cell division generates cell types with different fates. Recent studies have improved our understanding of the molecular mechanisms involved in asymmetric cell division in Arabidopsis thaliana. Genetic approaches have identified candidate intrinsic factors and signaling components that mediate extrinsic cues. WOX genes appear to be putative intrinsic determinants acting in early embryonic asymmetric divisions. A non-canonical mechanism involving specific SHORT ROOT (SHR)-SCARECROW (SCR) nuclear complexes is implicated in ground tissue asymmetric divisions. Asymmetric stem cell division requires extrinsic organizer signaling, whereas the involvement of intrinsic stem cell segregants is unknown. Finally, new studies on stomatal development have identified several intrinsic acting factors that specify cell fate and an extrinsic signaling cascade that controls the number and plane of asymmetric divisions.
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Affiliation(s)
- Colette A Ten Hove
- Molecular Genetics Group, Department of Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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218
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Abstract
The phytohormone auxin is a key factor in plant growth and development. Forward and reverse genetic strategies have identified important molecular components in auxin perception, signaling, and transport. These advances resulted in the identification of some of the underlying regulatory mechanisms as well as the emergence of functional frameworks for auxin action. This review focuses on the feedback loops that form an integrative part of these regulatory mechanisms.
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Affiliation(s)
- René Benjamins
- Department of Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands.
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219
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Chandler JW, Cole M, Werr W. The role of DORNROESCHEN (DRN) and DRN-LIKE (DRNL) in Arabidopsis embryonic patterning. PLANT SIGNALING & BEHAVIOR 2008; 3:49-51. [PMID: 19704719 PMCID: PMC2633969 DOI: 10.4161/psb.3.1.4864] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Accepted: 08/13/2007] [Indexed: 05/08/2023]
Abstract
Appropriate embryonic patterning is amongst the most fundamental processes in plant development, necessary for the correct specification of root and shoot apical meristems which generate all post-germination organs of a plant. Many mutations have been characterized which disrupt embryonic pattern formation and many recent studies have focussed on the role of auxin in establishing apical-basal polarity. Our recent work has demonstrated the role of two redundant AP2 transcription factors, DORNROESCHEN (DRN) and DORNROESCHEN-LIKE (DRNL) in the control of embryo patterning, upstream of auxin perception and/or response and that DRN in turn, is regulated by auxin. We also suggest both genes are involved in the change from radial to bilateral symmetry in the globular embryo and are responsible for positional information of meristem-specific genes such as STM. The promiscuous interaction of DRN and DRNL proteins with the redundant family of class III HD-ZIP partners may represent a way by which embryonic cell specification can be controlled by combinations of transcription factor complexes, together with auxin.
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Affiliation(s)
- John W Chandler
- Department of Developmental Biology; University of Cologne; Cologne, Germany
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220
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Abstract
Early embryonic development in the flowering plant Arabidopsis thaliana follows a predictable sequence of cell divisions. Anatomical hallmarks and the expression of marker genes in dynamic patterns indicate that new cell fates are established with virtually every round of mitosis. Although some of the factors regulating these early patterning events have been identified, the overall process remains relatively poorly understood. Starting at the globular stage, when the embryo has approximately 100 cells, the organization of development appears to be taken over by programs that regulate postembryonic patterning throughout the life cycle.
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Affiliation(s)
- Pablo D Jenik
- Carnegie Institution, Department of Plant Biology, Stanford University, Stanford, CA 94305, USA.
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221
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Nodine MD, Tax FE. Two receptor-like kinases required together for the establishment of Arabidopsis cotyledon primordia. Dev Biol 2007; 314:161-70. [PMID: 18158146 DOI: 10.1016/j.ydbio.2007.11.021] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2007] [Revised: 10/31/2007] [Accepted: 11/19/2007] [Indexed: 11/29/2022]
Abstract
Inter-regional signaling coordinates pattern formation in Arabidopsis thaliana embryos. However, little is known regarding the cells and molecules involved in inter-regional communication. We have characterized two related leucine-rich repeat receptor-like kinases (LRR-RLKs), RECEPTOR-LIKE PROTEIN KINASE1 (RPK1) and TOADSTOOL2 (TOAD2), which are required together for patterning the apical embryonic domain cell types that generate cotyledon primordia. Central domain protoderm patterning defects were always observed subjacent to the defective cotyledon primordia cell types in mutant embryos. In addition, RPK1-GFP and TOAD2-GFP translational fusions were both localized to the central domain protodermal cells when cotyledon primordia were first recognizable. We propose that RPK1 and TOAD2 are primarily required to maintain central domain protoderm cell fate and that the loss of this key embryonic cell type in mutant embryos results in patterning defects in other regions of the embryo including the failure to initiate cotyledon primordia.
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Affiliation(s)
- Michael D Nodine
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721, USA
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222
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Leroy O, Hennig L, Breuninger H, Laux T, Köhler C. Polycomb group proteins function in the female gametophyte to determine seed development in plants. Development 2007; 134:3639-48. [PMID: 17855429 DOI: 10.1242/dev.009027] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Polycomb group (PcG) proteins are evolutionary conserved proteins that stably maintain established transcriptional patterns over cell generations. The FERTILIZATION INDEPENDENT SEED (FIS) PcG complex from plants has a similar composition to the Polycomb repressive complex 2 from animals. Mutations in FIS genes cause parent-of-origin-dependent seed abortion. Every seed inheriting a mutant fis allele from the mother is destined to abort, regardless of the presence of a wild-type paternal allele. We tested in Arabidopsis whether the parent-of-origin-dependent seed abortion caused by lack of the FIS subunit MSI1 is caused by parental imprinting of the MSI1 gene. Our data show that MSI1 is not an imprinted gene and that early paternal MSI1 expression is not sufficient to rescue msi1 mutant seeds. By contrast, expression of MSI1 in msi1 female gametophytes is necessary to restore normal seed development, strongly arguing that the female gametophytic effect of fis mutants is caused by a functional requirement for an intact FIS complex in the female gametophyte. Thus, FIS-mediated expression patterns established in the female gametophyte can impact on seed development, establishing fis mutants as true female gametophytic maternal-effect mutants.
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Affiliation(s)
- Olivier Leroy
- Institute of Plant Sciences and Zürich-Base Plant Science Center, Swiss Federal Institute of Technology, ETH Centre, CH-8092 Zürich, Switzerland
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223
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Tucker MR, Laux T. Connecting the paths in plant stem cell regulation. Trends Cell Biol 2007; 17:403-10. [PMID: 17766120 DOI: 10.1016/j.tcb.2007.06.002] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2007] [Revised: 06/04/2007] [Accepted: 06/06/2007] [Indexed: 01/11/2023]
Abstract
Stem cell niches are specialized microenvironments where pluripotent cells are maintained to provide undifferentiated cells for the formation of new tissues and organs. The balance between stem cell maintenance within the niche and differentiation of cells that exit it is regulated by local cell-cell communication, together with external cues. Recent findings have shown connections between key developmental pathways and added significant insights into the central principles of stem cell maintenance in plant meristems. These insights include the convergence of important stem cell transcriptional regulators with cytokinin signaling in the shoot meristem, the biochemical dissection of peptide signaling in the shoot niche and the identification of conserved regulators in shoot and root niches.
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Affiliation(s)
- Matthew R Tucker
- Institute of Biology III, University of Freiburg, Freiburg 79104, Germany
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224
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De Smet I, Jürgens G. Patterning the axis in plants – auxin in control. Curr Opin Genet Dev 2007; 17:337-43. [PMID: 17627808 DOI: 10.1016/j.gde.2007.04.012] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Revised: 04/26/2007] [Accepted: 04/29/2007] [Indexed: 01/23/2023]
Abstract
Axis formation and patterning are fundamental processes establishing the body organization of multicellular organisms. In plants, patterning is not confined to embryogenesis but continues to produce new structures--lateral organs--along the growing primary body axis and also initiates secondary body axes. The signalling molecule auxin has been identified as a key player in plant axial patterning. The shoot and root sections of the axis seem to produce lateral organs in different ways. However, very recent findings suggest a general mechanism of branching triggered by local accumulation of auxin in a 'zone of competence' at the margin of stem-cell systems. How the general auxin signal is converted into organ-specific developmental programs remains a major challenge for the future.
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Affiliation(s)
- Ive De Smet
- Centre for Plant Molecular Biology (ZMBP), Developmental Genetics, Tübingen University, Auf der Morgenstelle 3, D-72076 Tübingen, Germany.
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225
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Cheng Y, Dai X, Zhao Y. Auxin synthesized by the YUCCA flavin monooxygenases is essential for embryogenesis and leaf formation in Arabidopsis. THE PLANT CELL 2007; 19:2430-9. [PMID: 17704214 PMCID: PMC2002601 DOI: 10.1105/tpc.107.053009] [Citation(s) in RCA: 447] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Auxin plays a key role in embryogenesis and seedling development, but the auxin sources for the two processes are not defined. Here, we demonstrate that auxin synthesized by the YUCCA (YUC) flavin monooxygenases is essential for the establishment of the basal body region during embryogenesis and the formation of embryonic and postembryonic organs. Both YUC1 and YUC4 are expressed in discrete groups of cells throughout embryogenesis, and their expression patterns overlap with those of YUC10 and YUC11 during embryogenesis. The quadruple mutants of yuc1 yuc4 yuc10 yuc11 fail to develop a hypocotyl and a root meristem, a phenotype similar to those of mp and tir1 afb1 afb2 afb3 auxin signaling mutants. We further show that YUC genes play an essential role in the formation of rosette leaves by analyzing combinations of yuc mutants and the polar auxin transport mutants pin1 and aux1. Disruption of YUC1, YUC4, or PIN1 alone does not abolish leaf formation, but the triple mutant yuc1 yuc4 pin1 fails to form leaves and flowers. Furthermore, disruption of auxin influx carrier AUX1 in the quadruple mutant yuc1 yuc2 yuc4 yuc6, but not in wild-type background, phenocopies yuc1 yuc4 pin1, demonstrating that auxin influx is required for plant leaf and flower development. Our data demonstrate that auxin synthesized by the YUC flavin monooxygenases is an essential auxin source for Arabidopsis thaliana embryogenesis and postembryonic organ formation.
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Affiliation(s)
- Youfa Cheng
- Section of Cell and Developmental Biology, University of California San Diego, La Jolla, California 92093-0116, USA
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226
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Borghi L, Bureau M, Simon R. Arabidopsis JAGGED LATERAL ORGANS is expressed in boundaries and coordinates KNOX and PIN activity. THE PLANT CELL 2007; 19:1795-808. [PMID: 17557810 PMCID: PMC1955719 DOI: 10.1105/tpc.106.047159] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Plant lateral organs are initiated as small protrusions on the flanks of shoot apical meristems. Organ primordia are separated from the remainder of the meristem by distinct cell types that create a morphological boundary. The Arabidopsis thaliana gain-of-function mutant jagged lateral organs-D (jlo-D) develops strongly lobed leaves, indicative of KNOX gene misexpression, and the shoot apical meristem arrests organ initiation prematurely, terminating in a pin-like structure. The JLO gene, a member of the LATERAL ORGAN BOUNDARY DOMAIN gene family, is expressed in boundaries between meristems and organ primordia and during embryogenesis. Inducible JLO misexpression activates expression of the KNOX genes SHOOT MERISTEMLESS and KNAT1 in leaves and downregulates the expression of PIN auxin export facilitators. Consequently, bulk auxin transport through the inflorescence stem is drastically reduced. During embryogenesis, JLO is required for the initiation of cotyledons and development beyond the globular stage. Converting JLO into a transcriptional repressor causes organ fusions, showing that during postembryonic development, JLO function is required to maintain the integrity of boundaries between cell groups with indeterminate or determinate fates.
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Affiliation(s)
- Lorenzo Borghi
- Institut für Genetik, Heinrich-Heine-Universität, Düsseldorf, Germany
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227
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Nodine MD, Yadegari R, Tax FE. RPK1 and TOAD2 Are Two Receptor-like Kinases Redundantly Required for Arabidopsis Embryonic Pattern Formation. Dev Cell 2007; 12:943-56. [PMID: 17543866 DOI: 10.1016/j.devcel.2007.04.003] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Revised: 04/05/2007] [Accepted: 04/06/2007] [Indexed: 12/01/2022]
Abstract
Although the basic plant body plan is established during embryogenesis, the molecular basis of embryonic patterning remains to be fully understood. We have identified two receptor-like kinases, RECEPTOR-LIKE PROTEIN KINASE1 (RPK1) and TOADSTOOL2 (TOAD2), required for Arabidopsis embryonic pattern formation. Genetic analysis indicates that RPK1 and TOAD2 have overlapping embryonic functions. The zygotic gene dosage of TOAD2 in an rpk1 background is of critical importance, suggesting that signaling mediated by RPK1 and TOAD2 must be above a threshold level for proper embryo development. The localization of RPK1 and TOAD2 translational fusions to GFP coupled with the analysis of cell-type-specific markers indicate that RPK1 and TOAD2 are redundantly required for both pattern formation along the radial axis and differentiation of the basal pole during early embryogenesis. We propose that RPK1 and TOAD2 receive intercellular signals and mediate intracellular responses that are necessary for embryonic pattern formation.
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Affiliation(s)
- Michael D Nodine
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721, USA
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228
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Chandler JW, Cole M, Flier A, Grewe B, Werr W. The AP2 transcription factors DORNROSCHEN and DORNROSCHEN-LIKE redundantly control Arabidopsis embryo patterning via interaction with PHAVOLUTA. Development 2007; 75:223-36. [PMID: 21161330 DOI: 10.1007/s11103-010-9721-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 12/03/2010] [Indexed: 04/25/2023]
Abstract
DORNROSCHEN (DRN) (also known as ENHANCER OF SHOOT REGENERATION1; ESR1) and DRN-LIKE (DRNL; also known as ESR2) are two linked paralogues encoding AP2 domain-containing proteins. drn mutants show embryo cell patterning defects and, similarly to drnl mutants, disrupt cotyledon development at incomplete penetrance. drn drnl double mutants with weak or strong drnl alleles show more highly penetrant and extreme phenotypes, including a pin-like embryo without cotyledons, confirming a high degree of functional redundancy for the two genes in embryo patterning. Altered expression of PIN1::PIN1-GFP and DR5::GFP in drn mutant embryos places DRN upstream of auxin transport and response. A yeast two-hybrid screen with DRN followed by co-immunoprecipitation and bimolecular fluorescence complementation revealed PHAVOLUTA (PHV) to be a protein interaction partner in planta. drn phv double mutants show an increased penetrance of embryo cell division defects. DRNL can also interact with PHV and both DRN and DRNL can heterodimerise with additional members of the class III HD-ZIP family, PHABULOSA, REVOLUTA, CORONA and ATHB8. Interactions involve the PAS-like C-terminal regions of these proteins and the DRN/DRNL AP2 domain.
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Affiliation(s)
- John W Chandler
- Institute of Developmental Biology, University of Cologne, Gyrhofstrasse 17, Cologne, Germany.
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229
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Sarkar AK, Luijten M, Miyashima S, Lenhard M, Hashimoto T, Nakajima K, Scheres B, Heidstra R, Laux T. Conserved factors regulate signalling in Arabidopsis thaliana shoot and root stem cell organizers. Nature 2007; 446:811-4. [PMID: 17429400 DOI: 10.1038/nature05703] [Citation(s) in RCA: 713] [Impact Index Per Article: 41.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Accepted: 02/23/2007] [Indexed: 01/27/2023]
Abstract
Throughout the lifespan of a plant, which in some cases can last more than one thousand years, the stem cell niches in the root and shoot apical meristems provide cells for the formation of complete root and shoot systems, respectively. Both niches are superficially different and it has remained unclear whether common regulatory mechanisms exist. Here we address whether root and shoot meristems use related factors for stem cell maintenance. In the root niche the quiescent centre cells, surrounded by the stem cells, express the homeobox gene WOX5 (WUSCHEL-RELATED HOMEOBOX 5), a homologue of the WUSCHEL (WUS) gene that non-cell-autonomously maintains stem cells in the shoot meristem. Loss of WOX5 function in the root meristem stem cell niche causes terminal differentiation in distal stem cells and, redundantly with other regulators, also provokes differentiation of the proximal meristem. Conversely, gain of WOX5 function blocks differentiation of distal stem cell descendents that normally differentiate. Importantly, both WOX5 and WUS maintain stem cells in either a root or shoot context. Together, our data indicate that stem cell maintenance signalling in both meristems employs related regulators.
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Affiliation(s)
- Ananda K Sarkar
- Institute of Biology III, University of Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany
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230
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Perez-Perez JM. Hormone signalling and root development: an update on the latest Arabidopsis thaliana research. FUNCTIONAL PLANT BIOLOGY : FPB 2007; 34:163-171. [PMID: 32689342 DOI: 10.1071/fp06341] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2006] [Accepted: 02/23/2007] [Indexed: 06/11/2023]
Abstract
Plants are sessile organisms whose developmental programs depend mainly on environmental cues that are sensed and interpreted through hormonal signalling pathways. Roots are specialised plant organs that are instrumental during water and nutrient uptake, biotic interactions, stress responses and for mechanical support. Our knowledge about the basic molecular events shaping root patterning and growth has advanced significantly in the past few years thanks to the use of Arabidopsis thaliana (L.) Heynh. as a model system. In this review, I will discuss recent findings that indicate crosstalk between growth regulators and hormone signalling pathways during primary root development. Further comparative research using non-model species will shed light on the conserved developmental modules among distant lineages involved in root architecture.
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Affiliation(s)
- Jose Manuel Perez-Perez
- Division de Genetica and Instituto de Bioingenieria, Universidad Miguel Hernandez, Edificio Vinalopo, Avda. de la Universidad s/n, 03202 Elche (Alicante), Spain. Email
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231
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Krogan NT, Berleth T. From genes to patterns: Auxin distribution and auxin-dependent gene regulation in plant pattern formation. ACTA ACUST UNITED AC 2007. [DOI: 10.1139/b07-029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has long been recognized that the plant hormone auxin plays integral roles in a variety of plant processes. More recently, it has become clear that these processes include some of the most basic pattern formation mechanisms needed to establish a functional plant body. Considerable insight into how this regulation plays out at the molecular level has been attained in recent years. Of special note are the complementary actions of the auxin efflux carrier proteins responsible for the formation of instructive auxin concentration gradients and the transcription factor complexes required for the appropriate interpretation of such instructions. The numerous players involved and the complexity of their regulation provide insight into how a single plant hormone can operate in such a multifunctional fashion. Many new features of auxin action can now be quantified and visualized, and three-dimensional models of auxin patterning can be tested and mathematically modeled. With these new advances, the developmental biology of auxin-mediated patterning has turned into a subject of plant systems biology research.
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Affiliation(s)
- Naden T. Krogan
- Department of Cell and Systems Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada
| | - Thomas Berleth
- Department of Cell and Systems Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada
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232
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Chandler JW, Cole M, Flier A, Grewe B, Werr W. The AP2 transcription factors DORNROSCHEN and DORNROSCHEN-LIKE redundantly control Arabidopsis embryo patterning via interaction with PHAVOLUTA. Development 2007; 134:1653-62. [PMID: 17376809 DOI: 10.1242/dev.001016] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
DORNROSCHEN (DRN) (also known as ENHANCER OF SHOOT REGENERATION1; ESR1) and DRN-LIKE (DRNL; also known as ESR2) are two linked paralogues encoding AP2 domain-containing proteins. drn mutants show embryo cell patterning defects and, similarly to drnl mutants, disrupt cotyledon development at incomplete penetrance. drn drnl double mutants with weak or strong drnl alleles show more highly penetrant and extreme phenotypes, including a pin-like embryo without cotyledons, confirming a high degree of functional redundancy for the two genes in embryo patterning. Altered expression of PIN1::PIN1-GFP and DR5::GFP in drn mutant embryos places DRN upstream of auxin transport and response. A yeast two-hybrid screen with DRN followed by co-immunoprecipitation and bimolecular fluorescence complementation revealed PHAVOLUTA (PHV) to be a protein interaction partner in planta. drn phv double mutants show an increased penetrance of embryo cell division defects. DRNL can also interact with PHV and both DRN and DRNL can heterodimerise with additional members of the class III HD-ZIP family, PHABULOSA, REVOLUTA, CORONA and ATHB8. Interactions involve the PAS-like C-terminal regions of these proteins and the DRN/DRNL AP2 domain.
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Affiliation(s)
- John W Chandler
- Institute of Developmental Biology, University of Cologne, Gyrhofstrasse 17, Cologne, Germany.
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233
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Takada S, Jürgens G. Transcriptional regulation of epidermal cell fate in the Arabidopsis embryo. Development 2007; 134:1141-50. [PMID: 17301085 DOI: 10.1242/dev.02803] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
How distinct cell fates are specified at correct positions within the plant embryo is unknown. In Arabidopsis, different cell fates are generated early on, starting with the two daughter cells of the zygote. To address mechanisms of position-dependent gene activation and cell fate specification,we analyzed the regulatory region of the Arabidopsis thaliana MERISTEM LAYER 1 (ATML1) gene, which is already expressed at the one-cell stage and whose expression is later restricted to the outermost, epidermal cell layer from its inception. A sensitive, multiple GFP reporter revealed a modular organization to the ATML1 promoter. Each region contributes positively to specific spatial and temporal aspects of the overall expression pattern, including position-dependent but auxin-independent regulation along the apical-basal axis of the embryo. A 101 bp fragment that conferred all aspects of ATML1 expression contained known binding sites for homeodomain transcription factors and other regulatory sequences. Our results suggest that expression patterns associated with cell fate determination in the plant embryo result from positional signals targeting different regulatory sequences in complex promoters.
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Affiliation(s)
- Shinobu Takada
- Developmental Genetics, Center for Molecular Biology of Plants, University of Tübingen, D-72076 Tübingen, Germany
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234
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Heidstra R. Asymmetric Cell Division in Plant Development. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2007; 45:1-37. [PMID: 17585494 DOI: 10.1007/978-3-540-69161-7_1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Plant embryogenesis creates a seedling with a basic body plan. Post-embryonically the seedling elaborates with a lifelong ability to develop new tissues and organs. As a result asymmetric cell divisions serve essential roles during embryonic and postembryonic development to generate cell diversity. This review highlights selective cases of asymmetric division in the model plant Arabidopsis thaliana and describes the current knowledge on fate determinants and mechanisms involved. Common themes that emerge are: 1. role of the plant hormone auxin and its polar transport machinery; 2. a MAP kinase signaling cascade and; 3. asymmetric segregating transcription factors that are involved in several asymmetric cell divisions.
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Affiliation(s)
- Renze Heidstra
- Department of Biology, Section Molecular Genetics, Utrecht University, Padualaan 8, 3584CH Utrecht, Netherlands.
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235
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Abstract
In August 2006, plant biologists gathered at the FASEB `Mechanisms in Plant Development' meeting in Vermont, which was organized by Laurie Smith and Ueli Grossniklaus. A variety of plant developmental mechanisms were presented at this meeting and, although many talks focused on Arabidopsis thalianaas a primary model in which to study plant development, research in maize,tomato, Chlamydomonas and other plants also provided insight into various topics, such as cell-type specification, small RNA biosynthesis and action, hormone perception and transport, and cell and organ size.
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Affiliation(s)
- Jeff A Long
- Salk Institute for Biological Studies, Plant Molecular and Cellular Biology, 10010 North Torrey Pines Road, La Jolla, California 92037, USA
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236
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Long TA, Benfey PN. Transcription factors and hormones: new insights into plant cell differentiation. Curr Opin Cell Biol 2006; 18:710-4. [PMID: 17034999 DOI: 10.1016/j.ceb.2006.09.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2006] [Accepted: 09/29/2006] [Indexed: 02/05/2023]
Abstract
Plant development is a continuous process, mainly due to the presence of stem cell niches within the root and shoot. The interplay between a host of transcription factors determines whether the cells within the meristem maintain their stem cell state, differentiate into leaves or form secondary meristems, which develop into shoots and flowers. Several recent studies provide new insight into how transcription factors and phytohormones interact within meristems to control cell proliferation and differentiation.
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Affiliation(s)
- Terri A Long
- Department of Biology and Institute for Genome Sciences and Policy, Duke University, Durham, NC 27710, USA
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237
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Teale WD, Paponov IA, Palme K. Auxin in action: signalling, transport and the control of plant growth and development. Nat Rev Mol Cell Biol 2006; 7:847-59. [PMID: 16990790 DOI: 10.1038/nrm2020] [Citation(s) in RCA: 673] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Hormones have been at the centre of plant physiology research for more than a century. Research into plant hormones (phytohormones) has at times been considered as a rather vague subject, but the systematic application of genetic and molecular techniques has led to key insights that have revitalized the field. In this review, we will focus on the plant hormone auxin and its action. We will highlight recent mutagenesis and molecular studies, which have delineated the pathways of auxin transport, perception and signal transduction, and which together define the roles of auxin in controlling growth and patterning.
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Affiliation(s)
- William D Teale
- Institut für Biologie II/Botanik, Schänzlestrasse 1, 79104 Freiburg, Germany
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238
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Abstract
Recent years have seen rapid progress in our understanding of the mechanism of action of the plant hormone auxin. A major emerging theme is the central importance of the interplay between auxin signalling and the active transport of auxin through the plant to create dynamic patterns of auxin accumulation. Even in tissues where auxin distribution patterns appear stable, they are the product of standing waves, with auxin flowing through the tissue, maintaining local pockets of high and low concentration. The auxin distribution patterns result in changes in gene expression to trigger diverse, context-dependent growth and differentiation responses. Multi-level feedback loops between the signal transduction network and the auxin transport network provide self-stabilising patterns that remain sensitive to the external environment and to the developmental progression of the plant. The full biological implications of the behaviour of this system are only just beginning to be understood through a combination of experimental manipulation and mathematical modelling.
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Affiliation(s)
- Ottoline Leyser
- Department of Biology, University of York, York YO10 5YW, UK.
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239
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Muto H, Nagao I, Demura T, Fukuda H, Kinjo M, Yamamoto KT. Fluorescence cross-correlation analyses of the molecular interaction between an Aux/IAA protein, MSG2/IAA19, and protein-protein interaction domains of auxin response factors of arabidopsis expressed in HeLa cells. PLANT & CELL PHYSIOLOGY 2006; 47:1095-101. [PMID: 16854942 DOI: 10.1093/pcp/pcj080] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Since auxin may elicit numerous developmental responses by the use of a combination of auxin response factors (ARFs) and their Aux/IAA repressors, it is important to determine the interaction between the two protein families in a quantitative manner. We transiently expressed the C-terminal protein-protein interaction domains (CTDs) of Arabidopsis ARFs, MP/ARF5 and NPH4/ARF7, and MSG2/IAA19, fused to fluorescent proteins in HeLa cells, and determined their molecular interactions with fluorescence cross-correlation spectroscopy (FCCS). Almost complete association was found between MSG2 and MP-CTD and between MSG2 and NPH4-CTD. Approximately 20% association was found for MSG2 homodimers, NPH4-CTD homodimers and MP-CTD/NPH4-CTD heterodimers. Homotypic binding of MP-CTD may be weaker than that of MSG2. MSG2 was localized in cytoplasmic compartments in HeLa cells, whereas it was localized in the nuclei in plant cells. The fact that the heterotypic interaction between MSG2 and ARF-CTDs is stronger than each of the homotypic interactions appears to be the molecular basis for tight control of the transcriptional activity of ARFs by auxin. These results also show that FCCS is useful to examine protein-protein interactions especially for transcriptional regulators.
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Affiliation(s)
- Hideki Muto
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, 060-0810 Japan
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