RESUMO
The root system of plants is a vital part for successful development and adaptation to different soil types and environments. A major determinant of the shape of a plant root system is the formation of lateral roots, allowing for expansion of the root system. Arabidopsis thaliana, with its simple root anatomy, has been extensively studied to reveal the genetic program underlying root branching. However, to get a more general understanding of lateral root development, comparative studies in species with a more complex root anatomy are required. Here, by combining optimized clearing methods and histology, we describe an atlas of lateral root development in Brachypodium distachyon, a wild, temperate grass species. We show that lateral roots initiate from enlarged phloem pole pericycle cells and that the overlying endodermis reactivates its cell cycle and eventually forms the root cap. In addition, auxin signaling reported by the DR5 reporter was not detected in the phloem pole pericycle cells or young primordia. In contrast, auxin signaling was activated in the overlying cortical cell layers, including the exodermis. Thus, Brachypodium is a valuable model to investigate how signaling pathways and cellular responses have been repurposed to facilitate lateral root organogenesis.
RESUMO
The development of lateral roots starts with a round of anticlinal, asymmetric cell divisions in lateral root founder cells in the pericycle, deep within the root. The reorientation of the cell division plane occurs in parallel with changes in cell shape and needs to be coordinated with its direct neighbor, the endodermis. This accommodation response requires the integration of biochemical and mechanical signals in both cell types. Recently, it was reported that dynamic changes in the cytoskeleton and possibly the cell wall are part of the molecular mechanism required to correctly orient and position the cell division plane. Here we discuss the latest progress made towards our understanding of the regulation of cell shape and division plane orientation underlying lateral root initiation in Arabidopsis.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Divisão Celular , Raízes de Plantas/metabolismo , Forma Celular , Proteínas de Arabidopsis/metabolismo , Ácidos Indolacéticos/metabolismoRESUMO
Plant roots acquire nutrients and water while managing interactions with the soil microbiota. The root endodermis provides an extracellular diffusion barrier through a network of lignified cell walls called Casparian strips, supported by subsequent formation of suberin lamellae. Whereas lignification is thought to be irreversible, suberin lamellae display plasticity, which is crucial for root adaptative responses. Although suberin is a major plant polymer, fundamental aspects of its biosynthesis and turnover have remained obscure. Plants shape their root system via lateral root formation, an auxin-induced process requiring local breaking and re-sealing of endodermal lignin and suberin barriers. Here, we show that differentiated endodermal cells have a specific, auxin-mediated transcriptional response dominated by cell wall remodelling genes. We identified two sets of auxin-regulated GDSL lipases. One is required for suberin synthesis, while the other can drive suberin degradation. These enzymes have key roles in suberization, driving root suberin plasticity.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Hidrolases de Éster Carboxílico/metabolismo , Lipídeos , Domínios Proteicos , Arabidopsis/enzimologia , Proteínas de Arabidopsis/genética , Hidrolases de Éster Carboxílico/genética , Conjuntos de Dados como Assunto , Endoderma/metabolismo , Técnicas de Inativação de Genes , Ácidos Indolacéticos/metabolismo , Lipídeos/genética , Células Vegetais/metabolismo , Raízes de Plantas/metabolismo , Polimerização , ProteóliseRESUMO
By forming lateral roots, plants expand their root systems to improve anchorage and absorb more water and nutrients from the soil. Each phase of this developmental process in Arabidopsis is tightly regulated by dynamic and continuous signalling of the phytohormones cytokinin and auxin. While the roles of auxin in lateral root organogenesis and spatial accommodation by overlying cell layers have been well studied, insights on the importance of cytokinin is still somewhat limited. Cytokinin is a negative regulator of lateral root formation with versatile modes of action being activated at different root developmental zones. Here, we review the latest progress made towards our understanding of these spatially separated mechanisms of cytokinin-mediated signalling that shape lateral root initiation, outgrowth and emergence and highlight some of the enticing open questions.
RESUMO
During post-embryonic development, the pericycle specifies the stem cells that give rise to both lateral roots (LRs) and the periderm, a suberized barrier that protects the plant against biotic and abiotic stresses. Comparable auxin-mediated signaling hubs regulate meristem establishment in many developmental contexts; however, it is unknown how specific outputs are achieved. Using the Arabidopsis root as a model, we show that while LR formation is the main auxin-induced program after de-etiolation, plants with age become competent to form a periderm in response to auxin. The establishment of the vascular cambium acts as the developmental switch required to trigger auxin-mediated periderm initiation. Moreover, distinct auxin signaling components and targets control LR versus periderm formation. Among the periderm-specific-promoting transcription factors, WUSCHEL-RELATED HOMEOBOX 4 (WOX4) and KNAT1/BREVIPEDICELLUS (BP) stand out as their specific overexpression in the periderm results in an increased number of periderm layers, a trait of agronomical importance in breeding programs targeting stress tolerance. These findings reveal that specificity in pericycle stem cell fate is achieved by the integration of developmental cues into distinct regulatory modules.
Assuntos
Arabidopsis/crescimento & desenvolvimento , Meristema/crescimento & desenvolvimento , Raízes de Plantas/crescimento & desenvolvimento , Células-Tronco Pluripotentes/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Proteínas de Homeodomínio/metabolismo , Ácidos Indolacéticos/metabolismo , Meristema/genética , Meristema/metabolismo , Melhoramento Vegetal/métodos , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Plantas Geneticamente ModificadasRESUMO
During land colonization, plants acquired a range of body plan adaptations, of which the innovation of three-dimensional (3D) tissues increased organismal complexity and reproductivity. In the moss, Physcomitrella patens, a 3D leafy gametophore originates from filamentous cells that grow in a two-dimensional (2D) plane through a series of asymmetric cell divisions. Asymmetric cell divisions that coincide with different cell division planes and growth directions enable the developmental switch from 2D to 3D, but insights into the underlying mechanisms coordinating this switch are still incomplete. Using 2D and 3D imaging and image segmentation, we characterized two geometric cues, the width of the initial cell and the angle of the transition division plane, which sufficiently distinguished a gametophore initial cell from a branch initial cell. These identified cues were further confirmed in gametophore formation mutants. The identification of a fluorescent marker allowed us to successfully predict the gametophore initial cell with > 90% accuracy before morphological changes, supporting our hypothesis that, before the transition division, parental cells of the gametophore initials possess different properties from those of the branch initials. Our results suggest that the cell fate decision of the initial cell is determined in the parental cell, before the transition division.
Assuntos
Bryopsida , Bryopsida/genética , Diferenciação Celular , Sinais (Psicologia)RESUMO
How plant cells re-establish differential growth to initiate organs is poorly understood. Morphogenesis of lateral roots relies on the asymmetric cell division of initially symmetric founder cells. This division is preceded by the tightly controlled asymmetric radial expansion of these cells. The cellular mechanisms that license and ensure the coordination of these events are unknown. Here, we quantitatively analyze microtubule and F-actin dynamics during lateral root initiation. Using mutants and pharmacological and tissue-specific genetic perturbations, we show that dynamic reorganization of both microtubule and F-actin networks is necessary for the asymmetric expansion of the founder cells. This cytoskeleton remodeling intertwines with auxin signaling in the pericycle and endodermis in order for founder cells to acquire a basic polarity required for initiating lateral root development. Our results reveal the conservation of cell remodeling and polarization strategies between the Arabidopsis zygote and lateral root founder cells. We propose that coordinated, auxin-driven reorganization of the cytoskeleton licenses asymmetric cell growth and divisions during embryonic and post-embryonic organogenesis.
Assuntos
Actinas/metabolismo , Arabidopsis/crescimento & desenvolvimento , Microtúbulos/metabolismo , Proteínas de Plantas/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Arabidopsis/metabolismo , Citoesqueleto/metabolismo , Raízes de Plantas/metabolismoRESUMO
During plant cytokinesis a radially expanding membrane-enclosed cell plate is formed from fusing vesicles that compartmentalizes the cell in two. How fusion is spatially restricted to the site of cell plate formation is unknown. Aggregation of cell-plate membrane starts near regions of microtubule overlap within the bipolar phragmoplast apparatus of the moss Physcomitrella patens Since vesicle fusion generally requires coordination of vesicle tethering and subsequent fusion activity, we analyzed the subcellular localization of several subunits of the exocyst, a tethering complex active during plant cytokinesis. We found that the exocyst complex subunit Sec6 but not the Sec3 or Sec5 subunits localized to microtubule overlap regions in advance of cell plate construction in moss. Moreover, Sec6 exhibited a conserved physical interaction with an ortholog of the Sec1/Munc18 protein KEULE, an important regulator for cell-plate membrane vesicle fusion in Arabidopsis Recruitment of the P. patens protein KEULE and vesicles to the early cell plate was delayed upon Sec6 gene silencing. Our findings, thus, suggest that vesicle-vesicle fusion is, in part, enabled by a pool of exocyst subunits at microtubule overlaps, which is recruited independently of vesicle delivery.
Assuntos
Bryopsida/genética , Citocinese/genética , Regulação da Expressão Gênica de Plantas , Microtúbulos/metabolismo , Proteínas de Plantas/genética , Proteínas de Transporte Vesicular/genética , Citoesqueleto de Actina/metabolismo , Citoesqueleto de Actina/ultraestrutura , Arabidopsis/genética , Arabidopsis/metabolismo , Arabidopsis/ultraestrutura , Proteínas de Arabidopsis/antagonistas & inibidores , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Bryopsida/metabolismo , Bryopsida/ultraestrutura , Proteínas de Transporte/antagonistas & inibidores , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Proteínas de Ciclo Celular , Membrana Celular/metabolismo , Membrana Celular/ultraestrutura , Inativação Gênica , Genes Reporter , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Microtúbulos/ultraestrutura , Células Vegetais/metabolismo , Células Vegetais/ultraestrutura , Proteínas de Plantas/metabolismo , Subunidades Proteicas/genética , Subunidades Proteicas/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Proteína Vermelha FluorescenteRESUMO
Roots provide a means to plants for gathering belowground resources. They are plastic and can adapt to ever-changing environmental cues. The plasticity of the roots comes from their ability to branch out by developing lateral and/or adventitious roots. In this chapter, we make an attempt to document the diversity in plant root systems and understand their role in evolutionary adaptation. After a brief introduction to different root systems, such as homorhizic and allorhizic ones, the relationship of plant roots with their surroundings, i.e., the rhizosphere and its effect on adaptation, will be discussed. Despite the difficulty to conclusively construct a timeline of evolution of plant root systems, documented facts from previous publications are examined and an effort has been made to delve into how rooting structures in plants adapted to prevailing conditions by bringing about endogenous changes vis-à-vis evolutionary development and exogenous changes to their surroundings.
Assuntos
Adaptação Fisiológica , Evolução Biológica , Desenvolvimento Vegetal , Raízes de Plantas/fisiologia , Plantas , Raízes de Plantas/anatomia & histologiaRESUMO
Plants adapt to heterogeneous soil conditions by altering their root architecture. For example, roots branch when in contact with water by using the hydropatterning response. We report that hydropatterning is dependent on auxin response factor ARF7. This transcription factor induces asymmetric expression of its target gene LBD16 in lateral root founder cells. This differential expression pattern is regulated by posttranslational modification of ARF7 with the small ubiquitin-like modifier (SUMO) protein. SUMOylation negatively regulates ARF7 DNA binding activity. ARF7 SUMOylation is required to recruit the Aux/IAA (indole-3-acetic acid) repressor protein IAA3. Blocking ARF7 SUMOylation disrupts IAA3 recruitment and hydropatterning. We conclude that SUMO-dependent regulation of auxin response controls root branching pattern in response to water availability.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Raízes de Plantas/crescimento & desenvolvimento , Sumoilação , Fatores de Transcrição/metabolismo , Água/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , DNA de Plantas/metabolismo , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos/metabolismo , Proteínas Nucleares/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Ligação Proteica , Proteína SUMO-1/metabolismoRESUMO
In this Letter, owing to a copying error in Illustrator, the two centre panels in Extended Data Fig. 7a were identical. This error has been corrected online. The old, incorrect Extended Data Fig. 7 is shown in the Supplementary Information to this Amendment for transparency. Some typos ('occurence') in Figs. 1, 2 and 3 have also been corrected and the publication details for ref. 32 have been added.
RESUMO
In vascular plants, the root endodermis surrounds the central vasculature as a protective sheath that is analogous to the polarized epithelium in animals, and contains ring-shaped Casparian strips that restrict diffusion. After an initial lag phase, individual endodermal cells suberize in an apparently random fashion to produce 'patchy' suberization that eventually generates a zone of continuous suberin deposition. Casparian strips and suberin lamellae affect paracellular and transcellular transport, respectively. Most angiosperms maintain some isolated cells in an unsuberized state as so-called 'passage cells', which have previously been suggested to enable uptake across an otherwise-impermeable endodermal barrier. Here we demonstrate that these passage cells are late emanations of a meristematic patterning process that reads out the underlying non-radial symmetry of the vasculature. This process is mediated by the non-cell-autonomous repression of cytokinin signalling in the root meristem, and leads to distinct phloem- and xylem-pole-associated endodermal cells. The latter cells can resist abscisic acid-dependent suberization to produce passage cells. Our data further demonstrate that, during meristematic patterning, xylem-pole-associated endodermal cells can dynamically alter passage-cell numbers in response to nutrient status, and that passage cells express transporters and locally affect the expression of transporters in adjacent cortical cells.
Assuntos
Arabidopsis/anatomia & histologia , Arabidopsis/citologia , Padronização Corporal , Citocininas/metabolismo , Difusão , Endoderma/citologia , Endoderma/metabolismo , Transdução de Sinais , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Diferenciação Celular , Endoderma/anatomia & histologia , Ácidos Indolacéticos/metabolismo , Meristema/anatomia & histologia , Meristema/citologia , Meristema/crescimento & desenvolvimento , Meristema/metabolismo , Células Vegetais/metabolismoRESUMO
Plants exhibit an intriguing morphological and physiological plasticity that enables them to thrive in a wide range of environments. To understand the cell biological basis of this unparalleled competence, a number of methodologies have been adapted or developed over the last decades that allow minimal or non-invasive live-cell imaging in the context of tissues. Combined with the ease to generate transgenic reporter lines in specific genetic backgrounds or accessions, we are witnessing a blooming in plant cell biology. However, the imaging of plant cells entails a number of specific challenges, such as high levels of autofluorescence, light scattering that is caused by cell walls and their sensitivity to environmental conditions. Quantitative live-cell imaging in plants therefore requires adapting or developing imaging techniques, as well as mounting and incubation systems, such as micro-fluidics. Here, we discuss some of these obstacles, and review a number of selected state-of-the-art techniques, such as two-photon imaging, light sheet microscopy and variable angle epifluorescence microscopy that allow high performance and minimal invasive live-cell imaging in plants.
Assuntos
Imageamento Tridimensional/métodos , Luz , Plantas/anatomia & histologia , Microfluídica , Células Vegetais/metabolismo , Proteínas de Plantas/metabolismoRESUMO
Phospholipase C (PLC) is well known for its role in animal signaling, where it generates the second messengers, inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG), by hydrolyzing the minor phospholipid, phosphatidylinositol 4,5-bisphosphate (PIP2), upon receptor stimulation. In plants, PLC's role is still unclear, especially because the primary targets of both second messengers are lacking, i.e. the ligand-gated Ca2+ channel and protein kinase C, and because PIP2 levels are extremely low. Nonetheless, the Arabidopsis genome encodes nine PLCs. We used a reversed-genetic approach to explore PLC's function in Arabidopsis, and report here that PLC3 is required for proper root development, seed germination and stomatal opening. Two independent knock-down mutants, plc3-2 and plc3-3, were found to exhibit reduced lateral root densities by 10-20%. Mutant seeds germinated more slowly but were less sensitive to ABA to prevent germination. Guard cells of plc3 were also compromised in ABA-dependent stomatal closure. Promoter-ß-glucuronidase (GUS) analyses confirmed PLC3 expression in guard cells and germinating seeds, and revealed that the majority is expressed in vascular tissue, most probably phloem companion cells, in roots, leaves and flowers. In vivo 32Pi labeling revealed that ABA stimulated the formation of PIP2 in germinating seeds and guard cell-enriched leaf peels, which was significantly reduced in plc3 mutants. Overexpression of PLC3 had no effect on root system architecture or seed germination, but increased the plant's tolerance to drought. Our results provide genetic evidence for PLC's involvement in plant development and ABA signaling, and confirm earlier observations that overexpression increases drought tolerance. Potential molecular mechanisms for the above observations are discussed.
Assuntos
Ácido Abscísico/farmacologia , Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Arabidopsis/crescimento & desenvolvimento , Germinação/efeitos dos fármacos , Fosfoinositídeo Fosfolipase C/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Estômatos de Plantas/fisiologia , Sementes/crescimento & desenvolvimento , Adaptação Fisiológica/efeitos dos fármacos , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Secas , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Técnicas de Silenciamento de Genes , Germinação/genética , Mutação com Perda de Função , Pressão Osmótica/efeitos dos fármacos , Ácidos Fosfatídicos/metabolismo , Fosfatidilinositol 4,5-Difosfato , Fosfoinositídeo Fosfolipase C/genética , Raízes de Plantas/anatomia & histologia , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/genética , Estômatos de Plantas/citologia , Estômatos de Plantas/efeitos dos fármacos , Plantas Geneticamente Modificadas , Plântula/efeitos dos fármacos , Plântula/crescimento & desenvolvimento , Sementes/efeitos dos fármacos , Estresse Fisiológico/efeitos dos fármacosRESUMO
The plant vascular network consists of specialized phloem and xylem elements that undergo two distinct morphogenetic developmental programs to become transport-functional units. Whereas vacuolar rupture is a determinant step in protoxylem differentiation, protophloem elements never form a big central vacuole. Here, we show that a genetic disturbance of phosphatidylinositol 4,5-bis-phosphate [PtdIns(4,5)P2] homeostasis rewires cell trafficking towards the vacuole in Arabidopsis thaliana roots. Consequently, an enhanced phosphoinositide-mediated vacuolar biogenesis correlates with premature programmed cell death (PCD) and secondary cell wall elaboration in xylem cells. By contrast, vacuolar fusion events in protophloem cells trigger the abnormal formation of big vacuoles, preventing cell clearance and tissue functionality. Removal of the inositol 5' phosphatase COTYLEDON VASCULAR PATTERN 2 from the plasma membrane (PM) by brefeldin A (BFA) treatment increases PtdIns(4,5)P2 content at the PM and disrupts protophloem continuity. Conversely, BFA application abolishes vacuolar fusion events in xylem tissue without preventing PCD, suggesting the existence of additional PtdIns(4,5)P2-dependent cell death mechanisms. Overall, our data indicate that tight PM phosphoinositide homeostasis is required to modulate intracellular trafficking contributing to oppositely regulate vascular differentiation.
Assuntos
Arabidopsis/citologia , Diferenciação Celular , Homeostase , Fosfatidilinositóis/metabolismo , Raízes de Plantas/citologia , Feixe Vascular de Plantas/citologia , Apoptose/efeitos dos fármacos , Arabidopsis/efeitos dos fármacos , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Transporte Biológico/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Estradiol/farmacologia , Homeostase/efeitos dos fármacos , Espaço Intracelular/metabolismo , Floema/citologia , Floema/efeitos dos fármacos , Floema/metabolismo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Feixe Vascular de Plantas/efeitos dos fármacos , Feixe Vascular de Plantas/metabolismo , Vacúolos/efeitos dos fármacos , Vacúolos/metabolismo , Xilema/citologia , Xilema/efeitos dos fármacos , Xilema/metabolismoRESUMO
Diacylglycerol (DAG) is an important intermediate in lipid biosynthesis and plays key roles in cell signaling, either as a second messenger itself or as a precursor of phosphatidic acid. Methods to identify distinct DAG pools have proven difficult because biochemical fractionation affects the pools, and concentrations are limiting. Here, we validate the use of a genetically encoded DAG biosensor in living plant cells. The sensor is composed of a fusion between yellow fluorescent protein and the C1a domain of protein kinase C (YFP-C1aPKC) that specifically binds DAG, and was stably expressed in suspension-cultured tobacco BY-2 cells and whole Arabidopsis thaliana plants. Confocal imaging revealed that the majority of the YFP-C1aPKC fluorescence did not locate to membranes but was present in the cytosol and nucleus. Treatment with short-chain DAG or PMA (phorbol-12-myristate-13-acetate), a phorbol ester that binds the C1a domain of PKC, caused the recruitment of the biosensor to the plasma membrane. These results indicate that the biosensor works and that the basal DAG concentration in the cytoplasmic leaflet of membranes (i.e. accessible to the biosensor) is in general too low, and confirms that the known pools in plastids, the endoplasmic reticulum and mitochondria are located at the luminal face of these compartments (i.e. inaccessible to the biosensor). Nevertheless, detailed further analysis of different cells and tissues discovered four novel DAG pools, namely at: (i) the trans-Golgi network; (ii) the cell plate during cytokinesis; (iii) the plasma membrane of root epidermal cells in the transition zone, and (iv) the apex of growing root hairs. The results provide new insights into the spatiotemporal dynamics of DAG in plants and offer a new tool to monitor this in vivo.
Assuntos
Arabidopsis/metabolismo , Diglicerídeos/metabolismo , Arabidopsis/citologia , Técnicas Biossensoriais , Membrana Celular/metabolismo , Células Cultivadas , Citocinese , Citosol/metabolismo , Retículo Endoplasmático/metabolismo , Microscopia Confocal , Mitocôndrias/metabolismo , Ésteres de Forbol/metabolismo , Epiderme Vegetal/citologia , Epiderme Vegetal/metabolismo , Raízes de Plantas/citologia , Raízes de Plantas/metabolismo , Domínios Proteicos , Proteína Quinase C/metabolismo , Nicotiana/citologia , Nicotiana/metabolismo , Rede trans-Golgi/metabolismoRESUMO
Casparian strips are precisely localized and aligned ring-like cell wall modifications in the root of all higher plants. They set up an extracellular diffusion barrier analogous to animal tight junctions, and are crucial for maintaining the homeostatic capacity of plant roots. Casparian strips become localized because of the formation of a highly stable plasma membrane domain, consisting of a family of small transmembrane proteins called Casparian strip membrane domain proteins (CASPs). Here we report a large-scale forward genetic screen directly visualizing endodermal barrier function, which allowed us to identify factors required for the formation and integrity of Casparian strips. We present the identification and characterization of one of the mutants, schengen1 (sgn1), a receptor-like cytoplasmic kinase that we show localizes in a strictly polar fashion to the outer plasma membrane of endodermal cells and is required for the positioning and correct formation of the centrally located CASP domain.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Membrana Celular/metabolismo , Parede Celular/metabolismo , Proteínas de Membrana/genética , Proteínas de Arabidopsis/metabolismo , Difusão , Proteínas de Membrana/metabolismoRESUMO
To sustain a lifelong ability to initiate organs, plants retain pools of undifferentiated cells with a preserved proliferation capacity. The root pericycle represents a unique tissue with conditional meristematic activity, and its tight control determines initiation of lateral organs. Here we show that the meristematic activity of the pericycle is constrained by the interaction with the adjacent endodermis. Release of these restraints by elimination of endodermal cells by single-cell ablation triggers the pericycle to re-enter the cell cycle. We found that endodermis removal substitutes for the phytohormone auxin-dependent initiation of the pericycle meristematic activity. However, auxin is indispensable to steer the cell division plane orientation of new organ-defining divisions. We propose a dual, spatiotemporally distinct role for auxin during lateral root initiation. In the endodermis, auxin releases constraints arising from cell-to-cell interactions that compromise the pericycle meristematic activity, whereas, in the pericycle, auxin defines the orientation of the cell division plane to initiate lateral roots.