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1.
Genes Dev ; 31(6): 617-627, 2017 03 15.
Artículo en Inglés | MEDLINE | ID: mdl-28404632

RESUMEN

In many plants, the asymmetric division of the zygote sets up the apical-basal axis of the embryo. Unlike animals, plant zygotes are transcriptionally active, implying that plants have evolved specific mechanisms to control transcriptional activation of patterning genes in the zygote. In Arabidopsis, two pathways have been found to regulate zygote asymmetry: YODA (YDA) mitogen-activated protein kinase (MAPK) signaling, which is potentiated by sperm-delivered mRNA of the SHORT SUSPENSOR (SSP) membrane protein, and up-regulation of the patterning gene WOX8 by the WRKY2 transcription factor. How SSP/YDA signaling is transduced into the nucleus and how these pathways are integrated have remained elusive. Here we show that paternal SSP/YDA signaling directly phosphorylates WRKY2, which in turn leads to the up-regulation of WOX8 transcription in the zygote. We further discovered the transcription factors HOMEODOMAIN GLABROUS11/12 (HDG11/12) as maternal regulators of zygote asymmetry that also directly regulate WOX8 transcription. Our results reveal a framework of how maternal and paternal factors are integrated in the zygote to regulate embryo patterning.


Asunto(s)
Arabidopsis/genética , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Transcripción Genética , Cigoto/metabolismo , Arabidopsis/enzimología , Arabidopsis/metabolismo , Proteínas de Arabidopsis/biosíntesis , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Quinasas Asociadas a Receptores de Interleucina-1/metabolismo , Sistema de Señalización de MAP Quinasas , Herencia Materna , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Herencia Paterna , Factores de Transcripción/biosíntesis , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Cigoto/enzimología
2.
Plant Cell ; 24(2): 589-607, 2012 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-22327741

RESUMEN

Plant cells are encased by a cellulose-containing wall that is essential for plant morphogenesis. Cellulose consists of ß-1,4-linked glucan chains assembled into paracrystalline microfibrils that are synthesized by plasma membrane-located cellulose synthase (CESA) complexes. Associations with hemicelluloses are important for microfibril spacing and for maintaining cell wall tensile strength. Several components associated with cellulose synthesis have been identified; however, the biological functions for many of them remain elusive. We show that the chitinase-like (CTL) proteins, CTL1/POM1 and CTL2, are functionally equivalent, affect cellulose biosynthesis, and are likely to play a key role in establishing interactions between cellulose microfibrils and hemicelluloses. CTL1/POM1 coincided with CESAs in the endomembrane system and was secreted to the apoplast. The movement of CESAs was compromised in ctl1/pom1 mutant seedlings, and the cellulose content and xyloglucan structures were altered. X-ray analysis revealed reduced crystalline cellulose content in ctl1 ctl2 double mutants, suggesting that the CTLs cooperatively affect assembly of the glucan chains, which may affect interactions between hemicelluloses and cellulose. Consistent with this hypothesis, both CTLs bound glucan-based polymers in vitro. We propose that the apoplastic CTLs regulate cellulose assembly and interaction with hemicelluloses via binding to emerging cellulose microfibrils.


Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Celulosa/biosíntesis , Quitinasas/metabolismo , Glucanos/metabolismo , Glicósido Hidrolasas/metabolismo , Arabidopsis/enzimología , Proteínas de Arabidopsis/genética , Pared Celular/metabolismo , Quitinasas/genética , Glicósido Hidrolasas/genética , Microfibrillas/metabolismo , Plantas Modificadas Genéticamente/enzimología , Plantas Modificadas Genéticamente/genética , Polisacáridos/metabolismo
3.
Plant Cell ; 23(3): 1047-60, 2011 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-21441433

RESUMEN

The chromatin modifying Polycomb group (PcG) and trithorax group (trxG) proteins are central regulators of cell identity that maintain a tightly controlled balance between cell proliferation and cell differentiation. The opposing activities of PcG and trxG proteins ensure the correct expression of specific transcriptional programs at defined developmental stages. Here, we report that the chromatin remodeling factor PICKLE (PKL) and the PcG protein CURLY LEAF (CLF) antagonistically determine root meristem activity. Whereas loss of PKL function caused a decrease in meristematic activity, loss of CLF function increased meristematic activity. Alterations of meristematic activity in pkl and clf mutants were not connected with changes in auxin concentration but correlated with decreased or increased expression of root stem cell and meristem marker genes, respectively. Root stem cell and meristem marker genes are modified by the PcG-mediated trimethylation of histone H3 on lysine 27 (H3K27me3). Decreased expression levels of root stem cell and meristem marker genes in pkl correlated with increased levels of H3K27me3, indicating that root meristem activity is largely controlled by the antagonistic activity of PcG proteins and PKL.


Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Proteínas de Homeodominio/metabolismo , Meristema/crecimiento & desarrollo , Raíces de Plantas/crecimiento & desarrollo , Proteínas Represoras/metabolismo , Arabidopsis/citología , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Diferenciación Celular , División Celular , Ensamble y Desensamble de Cromatina , ADN Helicasas , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Histonas/metabolismo , Meristema/citología , Meristema/metabolismo , Metilación , Mutación , Raíces de Plantas/citología , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Proteínas del Grupo Polycomb
4.
PLoS Genet ; 5(8): e1000605, 2009 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-19680533

RESUMEN

Dynamic regulation of chromatin structure is of fundamental importance for modulating genomic activities in higher eukaryotes. The opposing activities of Polycomb group (PcG) and trithorax group (trxG) proteins are part of a chromatin-based cellular memory system ensuring the correct expression of specific transcriptional programs at defined developmental stages. The default silencing activity of PcG proteins is counteracted by trxG proteins that activate PcG target genes and prevent PcG mediated silencing activities. Therefore, the timely expression and regulation of PcG proteins and counteracting trxG proteins is likely to be of fundamental importance for establishing cell identity. Here, we report that the chromodomain/helicase/DNA-binding domain CHD3 proteins PICKLE (PKL) and PICKLE RELATED2 (PKR2) have trxG-like functions in plants and are required for the expression of many genes that are repressed by PcG proteins. The pkl mutant could partly suppress the leaf and flower phenotype of the PcG mutant curly leaf, supporting the idea that CHD3 proteins and PcG proteins antagonistically determine cell identity in plants. The direct targets of PKL in roots include the PcG genes SWINGER and EMBRYONIC FLOWER2 that encode subunits of Polycomb repressive complexes responsible for trimethylating histone H3 at lysine 27 (H3K27me3). Similar to mutants lacking PcG proteins, lack of PKL and PKR2 caused reduced H3K27me3 levels and, therefore, increased expression of a set of PcG protein target genes in roots. Thus, PKL and PKR2 are directly required for activation of PcG protein target genes and in roots are also indirectly required for repression of PcG protein target genes. Reduced PcG protein activity can lead to cell de-differentiation and callus-like tissue formation in pkl pkr2 mutants. Thus, in contrast to mammals, where PcG proteins are required to maintain pluripotency and to prevent cell differentiation, in plants PcG proteins are required to promote cell differentiation by suppressing embryonic development.


Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/citología , Arabidopsis/metabolismo , Diferenciación Celular , Regulación de la Expresión Génica de las Plantas , Proteínas Represoras/metabolismo , Transactivadores/metabolismo , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Proteínas de Arabidopsis/genética , Linaje de la Célula , ADN Helicasas , Regulación del Desarrollo de la Expresión Génica , Histonas/metabolismo , Raíces de Plantas/citología , Raíces de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Proteínas del Grupo Polycomb , Unión Proteica , Proteínas Represoras/genética , Transactivadores/genética
5.
Dev Cell ; 33(5): 576-88, 2015 Jun 08.
Artículo en Inglés | MEDLINE | ID: mdl-26028217

RESUMEN

Stem cells in plants and animals are maintained pluripotent by signals from adjacent niche cells. In plants, WUSCHEL HOMEOBOX (WOX) transcription factors are central regulators of stem cell maintenance in different meristem types, yet their molecular mode of action has remained elusive. Here we show that in the Arabidopsis root meristem, the WOX5 protein moves from the root niche organizer, the quiescent center, into the columella stem cells, where it directly represses the transcription factor gene CDF4. This creates a gradient of CDF4 transcription, which promotes differentiation opposite to the WOX5 gradient, allowing stem cell daughter cells to exit the stem cell state. We further show that WOX5 represses CDF4 transcription by recruiting TPL/TPR co-repressors and the histone deacetylase HDA19, which consequently induces histone deacetylation at the CDF4 regulatory region. Our results show that chromatin-mediated repression of differentiation programs is a common strategy in plant and animal stem cell niches.


Asunto(s)
Proteínas de Arabidopsis/genética , Arabidopsis/metabolismo , Diferenciación Celular , Cromatina/genética , Proteínas de Homeodominio/metabolismo , Meristema/citología , Raíces de Plantas/citología , Células Madre/citología , Acetilación , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Proteínas de Arabidopsis/metabolismo , Inmunoprecipitación de Cromatina , Proteínas Co-Represoras/genética , Proteínas Co-Represoras/metabolismo , Ensayo de Cambio de Movilidad Electroforética , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Histona Desacetilasas/genética , Histona Desacetilasas/metabolismo , Histonas/metabolismo , Proteínas de Homeodominio/genética , Hibridación in Situ , Meristema/metabolismo , Análisis por Micromatrices , Microscopía Confocal , Proteínas de Complejo Poro Nuclear/genética , Proteínas de Complejo Poro Nuclear/metabolismo , Raíces de Plantas/metabolismo , Regiones Promotoras Genéticas/genética , Transducción de Señal , Nicho de Células Madre , Células Madre/metabolismo
6.
Curr Biol ; 24(16): 1939-44, 2014 Aug 18.
Artículo en Inglés | MEDLINE | ID: mdl-25127220

RESUMEN

In Arabidopsis, stem cells maintain the provision of new cells for root growth. They surround a group of slowly dividing cells named the quiescent center (QC), and, together, they form the stem cell niche (SCN). The QC acts as the signaling center of the SCN, repressing differentiation of the surrounding stem cells and providing a pool of cells able to replace damaged stem cells. Maintenance of the stem cells depends on the transcription factor WUSCHEL-RELATED HOMEOBOX 5 (WOX5), which is specifically expressed in the QC. However, the molecular mechanisms by which WOX5 promotes stem cell fate and whether WOX5 regulates proliferation of the QC are unknown. Here, we reveal a new role for WOX5 in restraining cell division in the cells of the QC, thereby establishing quiescence. In contrast, WOX5 and CYCD3;3/CYCD1;1 both promote cell proliferation in the nascent columella. The additional QC divisions occurring in wox5 mutants are suppressed in mutant combinations with the D type cyclins CYCD3;3 and CYCD1;1. Moreover, ectopic expression of CYCD3;3 in the QC is sufficient to induce cell division in the QC. WOX5 thus suppresses QC divisions that are otherwise promoted by CYCD3;3 and CYCD1;1, in part by interacting with the CYCD3;3 promoter to repress CYCD3;3 expression in the QC. Therefore, we propose a specific role for WOX5 in initiating and maintaining quiescence of the QC by excluding CYCD activity from the QC.


Asunto(s)
Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/fisiología , Arabidopsis/genética , Ciclina D3/genética , Regulación de la Expresión Génica de las Plantas , Proteínas de Homeodominio/fisiología , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Diferenciación Celular , División Celular , Ciclina D3/metabolismo , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Raíces de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Nicho de Células Madre , Células Madre/citología
7.
Annu Rev Plant Biol ; 63: 615-36, 2012.
Artículo en Inglés | MEDLINE | ID: mdl-22404469

RESUMEN

Multicellular organisms possess pluripotent stem cells to form new organs, replenish the daily loss of cells, or regenerate organs after injury. Stem cells are maintained in specific environments, the stem cell niches, that provide signals to block differentiation. In plants, stem cell niches are situated in the shoot, root, and vascular meristems-self-perpetuating units of organ formation. Plants' lifelong activity-which, as in the case of trees, can extend over more than a thousand years-requires that a robust regulatory network keep the balance between pluripotent stem cells and differentiating descendants. In this review, we focus on current models in plant stem cell research elaborated during the past two decades, mainly in the model plant Arabidopsis thaliana. We address the roles of mobile signals on transcriptional modules involved in balancing cell fates. In addition, we discuss shared features of and differences between the distinct stem cell niches of Arabidopsis.


Asunto(s)
Arabidopsis/citología , Arabidopsis/crecimiento & desarrollo , Raíces de Plantas/citología , Raíces de Plantas/metabolismo , Haz Vascular de Plantas/citología , Haz Vascular de Plantas/fisiología , Nicho de Células Madre/fisiología , Animales , Proteínas de Arabidopsis/metabolismo , Comunicación Celular , Diferenciación Celular , Genes de Plantas/fisiología , Meristema/citología , Meristema/metabolismo , Modelos Biológicos , Tallos de la Planta/citología , Tallos de la Planta/metabolismo , Células Madre Pluripotentes/metabolismo , Regeneración , Transducción de Señal , Transcripción Genética
8.
Methods Mol Biol ; 655: 433-43, 2010.
Artículo en Inglés | MEDLINE | ID: mdl-20734278

RESUMEN

DNA methylation is a prominent epigenetic mark and extensively found within plant genomes. It has two major roles- first, defending the genome against invasive DNA and second, regulation of gene expression. Since the first report of 5-methylcytosine found in wheat germ, many improvements in detection of methylated cytosine residues have been made and genome-wide methylation maps for Arabidopsis thaliana are now available. The development of fast, reproducible, and single-base pair resolving detection methods for DNA methylation at defined loci advanced our understanding of the establishment and maintenance of DNA methylation patterns. Bisulphite conversion of unmethylated cytosine residues followed by detection methods such as sequencing of distinct loci has become accepted as the gold standard for detecting 5-methylcytosines. Treatment of single-stranded DNA with bisulphite under acidic conditions leads to the conversion of cytosine residues to uracil whereas 5-methylcytosine is less sensitive and remains unchanged. Here, a detailed protocol for bisulphite conversion, primer design, and optimization of PCR conditions is given. Specific requirements for plant DNA are discussed.


Asunto(s)
Metilación de ADN , ADN de Plantas/metabolismo , Plantas/genética , Reacción en Cadena de la Polimerasa/métodos , Análisis de Secuencia de ADN/métodos , Sulfitos/metabolismo , 5-Metilcitosina/metabolismo , Secuencia de Bases , Citosina/metabolismo , ADN de Plantas/genética , ADN de Plantas/aislamiento & purificación , ADN de Cadena Simple/genética , ADN de Cadena Simple/aislamiento & purificación , ADN de Cadena Simple/metabolismo , Epigenómica/métodos , Genoma de Planta , Plantas/metabolismo , Uracilo/metabolismo
9.
Epigenetics ; 5(1): 20-3, 2010 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-20083900

RESUMEN

Cellular identity is maintained by epigenetic processes that prevent changes of cell-type specific transcriptional programs. Polycomb group (PcG) proteins are evolutionary conserved key players of cellular identity that repress central developmental regulators by modifying chromatin structure. PcG-mediated repression is antagonized by trithorax group (trxG) proteins that prevent inappropriate repression by PcG proteins. The molecular basis for this antagonistic activity is unclear. So far, only few chromatin regulatory proteins have been associated with trxG function in Arabidopsis. Recent work revealed that ATP-dependent chromatin remodeling factors of the Chromodomain-Helicase-DNA-binding (CHD) subfamily have trxG-like functions in Arabidopsis. Here we will discuss the implications of these findings that point towards an evolutionary conservation of PcG/trxG mediated gene regulation in higher eukaryotes.


Asunto(s)
Cromatina/química , Epigénesis Genética , Regulación de la Expresión Génica de las Plantas , Regulación de la Expresión Génica , Proteínas Represoras/genética , Adenosina Trifosfato/metabolismo , Animales , Arabidopsis/metabolismo , Ensamble y Desensamble de Cromatina , Humanos , Modelos Biológicos , Mutación , Proteína de la Leucemia Mieloide-Linfoide/metabolismo , Proteínas de Plantas/metabolismo , Proteínas del Grupo Polycomb , Estructura Terciaria de Proteína , Proteínas Represoras/metabolismo
10.
PLoS One ; 4(4): e5335, 2009.
Artículo en Inglés | MEDLINE | ID: mdl-19399177

RESUMEN

Polycomb group (PcG) proteins are essential to maintain gene expression patterns during development. Transcriptional repression by PcG proteins involves trimethylation of H3K27 (H3K27me3) by Polycomb Repressive Complex 2 (PRC2) in animals and plants. PRC1 binds to H3K27me3 and is required for transcriptional repression in animals, but in plants PRC1-like activities have remained elusive. One candidate protein that could be involved in PRC1-like functions in plants is LIKE HETEROCHROMATIN PROTEIN 1 (LHP1), because LHP1 associates with genes marked by H3K27me3 in vivo and has a chromodomain that binds H3K27me3 in vitro. Here, we show that disruption of the chromodomain of Arabidopsis thaliana LHP1 abolishes H3K27me3 recognition, releases gene silencing and causes similar phenotypic alterations as transcriptional lhp1 null mutants. Therefore, binding to H3K27me3 is essential for LHP1 protein function.


Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Proteínas Cromosómicas no Histona/metabolismo , Histonas/metabolismo , Alelos , Secuencia de Aminoácidos , Arabidopsis/genética , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Secuencia de Bases , Proteínas Cromosómicas no Histona/química , Proteínas Cromosómicas no Histona/genética , ADN de Plantas/genética , Silenciador del Gen , Genes de Plantas , Modelos Moleculares , Datos de Secuencia Molecular , Mutación , Filogenia , Plantas Modificadas Genéticamente , Unión Proteica , Estructura Terciaria de Proteína , Homología de Secuencia de Aminoácido
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