RESUMO
Production of reactive oxygen species (ROS) by NADPH oxidases (NOXs) impacts many processes in animals and plants, and many plant receptor pathways involve rapid, NOX-dependent increases of ROS. Yet, their general reactivity has made it challenging to pinpoint the precise role and immediate molecular action of ROS. A well-understood ROS action in plants is to provide the co-substrate for lignin peroxidases in the cell wall. Lignin can be deposited with exquisite spatial control, but the underlying mechanisms have remained elusive. Here, we establish a kinase signaling relay that exerts direct, spatial control over ROS production and lignification within the cell wall. We show that polar localization of a single kinase component is crucial for pathway function. Our data indicate that an intersection of more broadly localized components allows for micrometer-scale precision of lignification and that this system is triggered through initiation of ROS production as a critical peroxidase co-substrate.
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Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Lignina/metabolismo , Proteínas Quinases/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Regulação da Expressão Gênica de Plantas , NADPH Oxidases/metabolismo , Peroxidases/metabolismo , Raízes de Plantas/metabolismoRESUMO
The plant cell wall is a plastic structure of variable composition that constitutes the first line of defence against environmental challenges. Lodging and drought are two stressful conditions that severely impact maize yield. In a previous work, we characterised the cell walls of two maize inbreds, EA2024 (susceptible) and B73 (resistant) to stalk lodging. Here, we show that drought induces distinct phenotypical, physiological, cell wall, and transcriptional changes in the two inbreds, with B73 exhibiting lower tolerance to this stress than EA2024. In control conditions, EA2024 stalks had higher levels of cellulose, uronic acids and p-coumarate than B73. However, upon drought EA2024 displayed increased levels of arabinose-enriched polymers, such as pectin-arabinans and arabinogalactan proteins, and a decreased lignin content. By contrast, B73 displayed a deeper rearrangement of cell walls upon drought, including modifications in lignin composition (increased S subunits and S/G ratio; decreased H subunits) and an increase of uronic acids. Drought induced more substantial changes in gene expression in B73 compared to EA2024, particularly in cell wall-related genes, that were modulated in an inbred-specific manner. Transcription factor enrichment assays unveiled inbred-specific regulatory networks coordinating cell wall genes expression. Altogether, these findings reveal that B73 and EA2024 inbreds, with opposite stalk-lodging phenotypes, undertake different cell wall modification strategies in response to drought. We propose that the specific cell wall composition conferring lodging resistance to B73, compromises its cell wall plasticity, and renders this inbred more susceptible to drought.
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Lignina , Zea mays , Lignina/metabolismo , Zea mays/fisiologia , Secas , Parede Celular/metabolismo , Ácidos Urônicos/metabolismoRESUMO
Plants continuously face various environmental stressors throughout their lifetime. To be able to grow and adapt in different environments, they developed specialized tissues that allowed them to maintain a protected yet interconnected body. These tissues undergo specific primary and secondary cell wall modifications that are essential to ensure normal plant growth, adaptation and successful land colonization. The composition of cell walls can vary among different plant species, organs and tissues. The ability to remodel their cell walls is fundamental for plants to be able to cope with multiple biotic and abiotic stressors. A better understanding of the changes taking place in plant cell walls may help identify and develop new strategies as well as tools to enhance plants' survival under environmental stresses or prevent pathogen attack. Since the invention of microscopy, numerous imaging techniques have been developed to determine the composition and dynamics of plant cell walls during normal growth and in response to environmental stimuli. In this review, we discuss the main advances in imaging plant cell walls, with a particular focus on fluorescent stains for different cell wall components and their compatibility with tissue clearing techniques. Lay Description: Plants are continuously subjected to various environmental stresses during their lifespan. They evolved specialized tissues that thrive in different environments, enabling them to maintain a protected yet interconnected body. Such tissues undergo distinct primary and secondary cell wall alterations essential to normal plant growth, their adaptability and successful land colonization. Cell wall composition may differ among various plant species, organs and even tissues. To deal with various biotic and abiotic stresses, plants must have the capacity to remodel their cell walls. Gaining insight into changes that take place in plant cell walls will help identify and create novel tools and strategies to improve plants' ability to withstand environmental challenges. Multiple imaging techniques have been developed since the introduction of microscopy to analyse the composition and dynamics of plant cell walls during growth and in response to environmental changes. Advancements in plant tissue cleaning procedures and their compatibility with cell wall stains have significantly enhanced our ability to perform high-resolution cell wall imaging. At the same time, several factors influence the effectiveness of cleaning and staining plant specimens, as well as the time necessary for the process, including the specimen's size, thickness, tissue complexity and the presence of autofluorescence. In this review, we will discuss the major advances in imaging plant cell walls, with a particular emphasis on fluorescent stains for diverse cell wall components and their compatibility with tissue clearing techniques. We hope that this review will assist readers in selecting the most appropriate stain or combination of stains to highlight specific cell wall components of interest.
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Parede Celular , Corantes Fluorescentes , Plantas , Células Vegetais/fisiologia , Coloração e Rotulagem/métodosRESUMO
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.
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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
Gene targeting can be used to make modifications at a specific region in a plant's genome and create high-precision tools for plant biotechnology and breeding. However, its low efficiency is a major barrier to its use in plants. The discovery of CRISPR (clustered regularly interspaced short palindromic repeats)-Cas-based site-specific nucleases capable of inducing double-strand breaks in desired loci resulted in the development of novel approaches for plant gene targeting. Several studies have recently demonstrated improvements in gene targeting efficiency through cell-type-specific expression of Cas nucleases, the use of self-amplified gene-targeting-vector DNA, or manipulation of RNA silencing and DNA repair pathways. In this review, we summarize recent advances in CRISPR/Cas-mediated gene targeting in plants and discuss potential efficiency improvements. Increasing the efficiency of gene targeting technology will help pave the way for increased crop yields and food safety in environmentally friendly agriculture.
Assuntos
Sistemas CRISPR-Cas , Genoma de Planta , Melhoramento Vegetal/métodos , Marcação de Genes/métodos , Plantas/genética , Endonucleases/genéticaRESUMO
Lignin has enabled plants to colonize land, grow tall, transport water within their bodies, and protect themselves against various stresses. Consequently, this polyphenolic polymer, impregnating cellulosic plant cell walls, is the second most abundant polymer on Earth. Yet, despite its great physiological, ecological, and economical importance, our knowledge of lignin biosynthesis in vivo, especially the polymerization steps within the cell wall, remains vague-specifically, the respective roles of the two polymerizing enzymes classes, laccases and peroxidases. One reason for this lies in the very high numbers of laccases and peroxidases encoded by 17 and 73 homologous genes, respectively, in Arabidopsis Here, we have focused on a specific lignin structure, the ring-like Casparian strips (CSs) within the root endodermis. By reducing candidate numbers using cellular resolution expression and localization data and by boosting stacking of mutants using CRISPR-Cas9, we mutated the majority of laccases in Arabidopsis in a nonuple mutant-essentially abolishing laccases with detectable endodermal expression. Yet, we were unable to detect even slight defects in CS formation. By contrast, we were able to induce a complete absence of CS formation in a quintuple peroxidase mutant. Our findings are in stark contrast to the strong requirement of xylem vessels for laccase action and indicate that lignin in different cell types can be polymerized in very distinct ways. We speculate that cells lignify differently depending on whether lignin is localized or ubiquitous and whether cells stay alive during and after lignification, as well as the composition of the cell wall.
Assuntos
Lacase/genética , Lacase/metabolismo , Peroxidases/genética , Peroxidases/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Membrana Celular/metabolismo , Parede Celular/metabolismo , Regulação da Expressão Gênica de Plantas , Lignina/metabolismo , Mutação , Fenótipo , Raízes de Plantas , Polimerização , Xilema/metabolismoRESUMO
Higher plant function is contingent upon the complex three-dimensional (3D) architecture of plant tissues, yet severe light scattering renders deep, 3D tissue imaging very problematic. Although efforts to 'clear' tissues have been ongoing for over a century, many innovations have been made in recent years. Among them, a protocol called ClearSee efficiently clears tissues and diminishes chlorophyll autofluorescence while maintaining fluorescent proteins - thereby allowing analysis of gene expression and protein localisation in cleared samples. To further increase the usefulness of this protocol, we have developed a ClearSee-based toolbox in which a number of classical histological stains for lignin, suberin and other cell wall components can be used in conjunction with fluorescent reporter lines. We found that a number of classical dyes are highly soluble in ClearSee solution, allowing the old staining protocols to be enormously simplified; these additionally have been unsuitable for co-visualisation with fluorescent markers due to harsh fixation and clearing. Consecutive staining with several dyes allows 3D co-visualisation of distinct cell wall modifications with fluorescent proteins - used as transcriptional reporters or protein localisation tools - deep within tissues. Moreover, the protocol is easily applied on hand sections of different organs. In combination with confocal microscopy, this improves image quality while decreasing the time and cost of embedding/sectioning. It thus provides a low-cost, efficient method for studying thick plant tissues which are usually cumbersome to visualise. Our ClearSee-adapted protocols significantly improve and speed up anatomical and developmental investigations in numerous plant species, and we hope they will contribute to new discoveries in many areas of plant research.
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Arabidopsis/citologia , Microscopia Confocal/métodos , Ureia , Xilitol , Arabidopsis/metabolismo , Parede Celular/metabolismo , Celulose/metabolismo , Clorofila/metabolismo , Imunofluorescência , Corantes Fluorescentes/química , Indicadores e Reagentes/química , Lignina/metabolismo , Lipídeos de Membrana/metabolismo , Raízes de Plantas/citologia , Raízes de Plantas/metabolismo , Coloração e RotulagemRESUMO
The development and growth of higher plants is highly dependent on the conduction of water and minerals throughout the plant by xylem vessels. In Arabidopsis roots the xylem is organized as an axis of cell files with two distinct cell fates: the central metaxylem and the peripheral protoxylem. During vascular development, high and low expression levels of the class III HD-ZIP transcription factors promote metaxylem and protoxylem identities, respectively. Protoxylem specification is determined by both mobile, ground tissue-emanating miRNA165/6 species, which downregulate, and auxin concentrated by polar transport, which promotes HD-ZIP III expression. However, the factors promoting high HD-ZIP III expression for metaxylem identity have remained elusive. We show here that auxin biosynthesis promotes HD-ZIP III expression and metaxylem specification. Several auxin biosynthesis genes are expressed in the outer layers surrounding the vascular tissue in Arabidopsis root and downregulation of HD-ZIP III expression accompanied by specific defects in metaxylem development is seen in auxin biosynthesis mutants, such as trp2-12, wei8 tar2 or a quintuple yucca mutant, and in plants treated with L-kynurenine, a pharmacological inhibitor of auxin biosynthesis. Some of the patterning defects can be suppressed by synthetically elevated HD-ZIP III expression. Taken together, our results indicate that polar auxin transport, which was earlier shown to be required for protoxylem formation, is not sufficient to establish a proper xylem axis but that root-based auxin biosynthesis is additionally required.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Proteínas de Homeodomínio/metabolismo , Ácidos Indolacéticos/metabolismo , Triptofano/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Padronização Corporal , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Proteínas de Homeodomínio/genética , Mutação , Oxigenases/genética , Oxigenases/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Plantas Geneticamente Modificadas , Transdução de Sinais , Xilema/crescimento & desenvolvimento , Xilema/metabolismoRESUMO
A powerful method to study gene function is expression or overexpression in an inducible, cell type-specific system followed by observation of consequent phenotypic changes and visualization of linked reporters in the target tissue. Multiple inducible gene overexpression systems have been developed for plants, but very few of these combine plant selection markers, control of expression domains, access to multiple promoters and protein fusion reporters, chemical induction, and high-throughput cloning capabilities. Here, we introduce a MultiSite Gateway-compatible inducible system for Arabidopsis (Arabidopsis thaliana) plants that provides the capability to generate such constructs in a single cloning step. The system is based on the tightly controlled, estrogen-inducible XVE system. We demonstrate that the transformants generated with this system exhibit the expected cell type-specific expression, similar to what is observed with constitutively expressed native promoters. With this new system, cloning of inducible constructs is no longer limited to a few special cases but can be used as a standard approach when gene function is studied. In addition, we present a set of entry clones consisting of histochemical and fluorescent reporter variants designed for gene and promoter expression studies.
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Arabidopsis/genética , Vetores Genéticos , Arabidopsis/citologia , Clonagem Molecular , Regulação da Expressão Gênica de Plantas , Genes Reporter , Especificidade de Órgãos , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas/genética , Proteínas Recombinantes de FusãoRESUMO
The development and growth of plants, as well as their successful adaptation to a variety of environments, is highly dependent on the conduction of water, nutrients and other important molecules throughout the plant body. Xylem is a specialized vascular tissue that serves as a conduit of water and minerals and provides mechanical support for upright growth. Wood, also known as secondary xylem, constitutes the major part of mature woody stems and roots. In the past two decades, a number of key factors including hormones, signal transducers and (post)transcriptional regulators have been shown to control xylem formation. We outline the main mechanisms shown to be essential for xylem development in various plant species, with an emphasis on Arabidopsis thaliana, as well as several tree species where xylem has a long history of investigation. We also summarize the processes which have been shown to be instrumental during xylem maturation. This includes mechanisms of cell wall formation and cell death which collectively complete xylem cell fate.
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Xilema/crescimento & desenvolvimento , Morte Celular , Parede Celular/fisiologia , Folhas de Planta/fisiologia , Xilema/anatomia & histologia , Xilema/citologiaRESUMO
About 200 researchers from around the world attended the Third International Conference on Plant Vascular Biology (PVB 2013) held in July 2013 at the Rantapuisto Conference Center, in Helsinki, Finland (http://www.pvb2013.org). The plant vascular system, which connects every organ in the mature plant, continues to attract the interest of researchers representing a wide range of disciplines, including development, physiology, systems biology, and computational biology. At the meeting, participants discussed the latest research advances in vascular development, long- and short-distance vascular transport and long-distance signalling in plant defence, in addition to providing a context for how these studies intersect with each other. The meeting provided an opportunity for researchers working across a broad range of fields to share ideas and to discuss future directions in the expanding field of vascular biology. In this report, the latest advances in understanding the mechanism of vascular trafficking presented at the meeting have been summarized.
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Plantas/imunologia , Plantas/metabolismo , Transporte Biológico , Finlândia , Desenvolvimento Vegetal , Imunidade VegetalRESUMO
Plant roots integrate environmental signals with development using exquisite spatiotemporal control. This is apparent in the deposition of suberin, an apoplastic diffusion barrier, which regulates flow of water, solutes and gases, and is environmentally plastic. Suberin is considered a hallmark of endodermal differentiation but is absent in the tomato endodermis. Instead, suberin is present in the exodermis, a cell type that is absent in the model organism Arabidopsis thaliana. Here we demonstrate that the suberin regulatory network has the same parts driving suberin production in the tomato exodermis and the Arabidopsis endodermis. Despite this co-option of network components, the network has undergone rewiring to drive distinct spatial expression and with distinct contributions of specific genes. Functional genetic analyses of the tomato MYB92 transcription factor and ASFT enzyme demonstrate the importance of exodermal suberin for a plant water-deficit response and that the exodermal barrier serves an equivalent function to that of the endodermis and can act in its place.
Assuntos
Arabidopsis , Solanum lycopersicum , Solanum lycopersicum/genética , Resistência à Seca , Raízes de Plantas/metabolismo , Parede Celular/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Água/metabolismoRESUMO
The stems and roots of most dicot plants increase in diameter by radial growth, due to the activity of secondary meristems. Two types of meristems function in secondary plant body formation: the vascular cambium, which gives rise to secondary xylem and phloem, and the cork cambium, which produces a bark layer that replaces the epidermis and protects the plant stem from mechanical damage and pathogens. Cambial development, the initiation and activity of the vascular cambium, leads to an accumulation of wood, the secondary xylem tissue. The thick, cellulose-rich cell walls of wood provide a source of cellulose and have the potential to be used as a raw material for sustainable and renewable energy production. In this review, we will discuss what is known about the mechanisms regulating the cambium and secondary tissue development.
Assuntos
Câmbio/crescimento & desenvolvimento , Câmbio/genética , Magnoliopsida/crescimento & desenvolvimento , Magnoliopsida/genética , Reguladores de Crescimento de Plantas/metabolismo , Árvores/crescimento & desenvolvimento , Parede Celular , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Floema/genética , Floema/crescimento & desenvolvimento , Casca de Planta/crescimento & desenvolvimento , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Caules de Planta/genética , Caules de Planta/crescimento & desenvolvimento , Transcrição Gênica , Árvores/imunologia , Madeira/genética , Madeira/crescimento & desenvolvimentoRESUMO
Precise coordination between cells and tissues is essential for differential growth in plants. During lateral root formation in Arabidopsis thaliana, the endodermis is actively remodeled to allow outgrowth of the new organ. Here, we show that microtubule arrays facing lateral root founder cells display a higher order compared to arrays on the opposite side of the same cell, and this asymmetry is required for endodermal remodeling and lateral root initiation. We identify that MICROTUBULE ASSOCIATED PROTEIN 70-5 (MAP70-5) is necessary for the establishment of this spatially defined microtubule organization and endodermis remodeling and thus contributes to lateral root morphogenesis. We propose that MAP70-5 and cortical microtubule arrays in the endodermis integrate the mechanical signals generated by lateral root outgrowth, facilitating the channeling of organogenesis.
RESUMO
BACKGROUND: Multiplex CRISPR-Cas9-based genome editing is an efficient method for targeted disruption of gene function in plants. Use of CRISPR-Cas9 has increased rapidly in recent years and is becoming a routine method for generating single and higher order Arabidopsis thaliana mutants. Low entry, reliable assembly of CRISPR/Cas9 vectors and efficient mutagenesis is necessary to enable a maximum of researchers to break through the genetic redundancy within plant multi-gene families and allow for a plethora of gene function studies that have been previously unachievable. It will also allow routine de novo generation of mutations in ever more complex genetic backgrounds that make introgression of pre-existing alleles highly cumbersome. RESULTS: To facilitate rapid and efficient use of CRISPR/Cas9 for Arabidopsis research, we developed a CRISPR/Cas9-based toolbox for generating mutations at multiple genomic loci, using two-color fluorescent seed selection. In our system, up-to eight gRNAs can be routinely introduced into a binary vector carrying either a FastRed, FastGreen or FastCyan fluorescent seed selection cassette. FastRed and FastGreen binary vectors can be co-transformed as a cocktail via floral dip to introduce sixteen gRNAs at the same time. The seeds can be screened either for red or green fluorescence, or for the presence of both colors. Importantly, in the second generation after transformation, Cas9 free plants are identified simply by screening the non-fluorescent seeds. Our collection of binary vectors allows to choose between two widely-used promoters to drive Cas enzymes, either the egg cell-specific (pEC1.2) from A. thaliana or the constitutive promoter from Petroselinum crispum (PcUBi4-2). Available enzymes are "classical" Cas9 codon-optimized for A. thaliana and a recently reported, intron-containing version of Cas9 codon-optimized for Zea mays, zCas9i. We observed the highest efficiency in producing knockout phenotypes by using intron-containing zCas9i driven under egg-cell specific pEC1.2 promoter. Finally, we introduced convenient restriction sites flanking promoter, Cas9 and fluorescent selection cassette in some of the T-DNA vectors, thus allowing straightforward swapping of all three elements for further adaptation and improvement of the system. CONCLUSION: A rapid, simple and flexible CISPR/Cas9 cloning system was established that allows assembly of multi-guide RNA constructs in a robust and reproducible fashion, by avoiding generation of very big constructs. The system enables a flexible, fast and efficient screening of single or higher order A. thaliana mutants.
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Stress granules (SGs) are ribonucleoprotein functional condensates that form under stress conditions in all eukaryotic cells. Although their stress-survival function is far from clear, SGs have been implicated in the regulation of many vital cellular pathways. Consequently, SG dysfunction is thought to be a mechanistic point of origin for many neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS). Additionally, SGs are thought to play a role in pathogenic pathways as diverse as viral infection and chemotherapy resistance. There is a growing consensus on the hypothesis that understanding the mechanistic regulation of SG physical properties is essential to understanding their function. Although the internal dynamics and condensation mechanisms of SGs have been broadly investigated, there have been fewer investigations into the timing of SG formation and clearance in live cells. Because the lifetime of SG persistence can be a key factor in their function and tendency toward pathological dysregulation, SG clearance mechanisms deserve particular attention. Here we show that resveratrol and its analogues piceatannol, pterostilbene, and 3,4,5,4'-tetramethoxystilbene induce G3BP-dependent SG formation with atypically rapid clearance kinetics. Resveratrol binds to G3BP, thereby reducing its protein-protein association valency. We suggest that altering G3BP valency is a pathway for the formation of uniquely transient SGs.
Assuntos
DNA Helicases/metabolismo , Proteínas de Ligação a Poli-ADP-Ribose/metabolismo , RNA Helicases/metabolismo , Proteínas com Motivo de Reconhecimento de RNA/metabolismo , Resveratrol/farmacologia , Grânulos de Estresse/metabolismo , Proteínas de Transporte/metabolismo , Linhagem Celular Tumoral , Grânulos Citoplasmáticos/efeitos dos fármacos , Grânulos Citoplasmáticos/metabolismo , DNA Helicases/efeitos dos fármacos , Células HEK293 , Células HeLa , Humanos , Cinética , Proteínas de Ligação a Poli-ADP-Ribose/efeitos dos fármacos , RNA Helicases/efeitos dos fármacos , Proteínas com Motivo de Reconhecimento de RNA/efeitos dos fármacos , Ribonucleoproteínas/metabolismo , Grânulos de Estresse/efeitos dos fármacosRESUMO
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.
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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
In the plant meristem, tissue-wide maturation gradients are coordinated with specialized cell networks to establish various developmental phases required for indeterminate growth. Here, we used single-cell transcriptomics to reconstruct the protophloem developmental trajectory from the birth of cell progenitors to terminal differentiation in the Arabidopsis thaliana root. PHLOEM EARLY DNA-BINDING-WITH-ONE-FINGER (PEAR) transcription factors mediate lineage bifurcation by activating guanosine triphosphatase signaling and prime a transcriptional differentiation program. This program is initially repressed by a meristem-wide gradient of PLETHORA transcription factors. Only the dissipation of PLETHORA gradient permits activation of the differentiation program that involves mutual inhibition of early versus late meristem regulators. Thus, for phloem development, broad maturation gradients interface with cell-type-specific transcriptional regulators to stage cellular differentiation.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/citologia , Floema/citologia , Floema/crescimento & desenvolvimento , Raízes de Plantas/citologia , Fatores de Transcrição/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Diferenciação Celular , Proteínas de Ligação ao GTP/genética , Proteínas de Ligação ao GTP/metabolismo , Meristema/citologia , Floema/genética , Floema/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , RNA-Seq , Transdução de Sinais , Análise de Célula Única , Fatores de Transcrição/genética , TranscriptomaRESUMO
The soil surface is a major natural system that accumulates pollutants and allows researchers to disclose the history and the present state of contamination of an area with toxic pollutants. This conclusion is based on the comparison of genotoxicity of aqueous extracts and DMSO extracts of topsoil from military territories in various locations left behind after the retreat of the Soviet Army from Lithuania, and several sites in the city of Vilnius, characterized by different history and current traffic intensity. The specific character of the soil-surface contamination was shown in a series of Tradescantia micronucleus (Trad-MN) and stamen-hair mutation (Trad-SHM) bioassays and tests. The most effective ones were the Trad-MN and, unexpectedly, the branched-hair tests. A preliminary result of the study is the somaclonal variation of individual Tradescantia plants revealed by the RAPD method of DNA analysis. A comparison of aqueous extracts and DMSO extracts of the soil showed the permanent character of the mobile forms of genotoxic pollutants in the soil surface, despite the fact that several military territories were already closed 20 years ago.