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1.
EMBO J ; 43(9): 1822-1842, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38565947

RESUMO

A key question in plant biology is how oriented cell divisions are integrated with patterning mechanisms to generate organs with adequate cell type allocation. In the root vasculature, a gradient of miRNA165/6 controls the abundance of HD-ZIP III transcription factors, which in turn control cell fate and spatially restrict vascular cell proliferation to specific cells. Here, we show that vascular development requires the presence of ARGONAUTE10, which is thought to sequester miRNA165/6 and protect HD-ZIP III transcripts from degradation. Our results suggest that the miR165/6-AGO10-HDZIP III module acts by buffering cytokinin responses and restricting xylem differentiation. Mutants of AGO10 show faster growth rates and strongly enhanced survival under severe drought conditions. However, this superior performance is offset by markedly increased variation and phenotypic plasticity in sub-optimal carbon supply conditions. Thus, AGO10 is required for the control of formative cell division and coordination of robust cell fate specification of the vasculature, while altering its expression provides a means to adjust phenotypic plasticity.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Proteínas Argonautas , Divisão Celular , Regulação da Expressão Gênica de Plantas , MicroRNAs , Raízes de Plantas , Arabidopsis/genética , Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/citologia , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas Argonautas/metabolismo , Proteínas Argonautas/genética , Divisão Celular/genética , Raízes de Plantas/citologia , Raízes de Plantas/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/genética , MicroRNAs/genética , MicroRNAs/metabolismo , Diferenciação Celular , Xilema/citologia , Xilema/metabolismo , Xilema/crescimento & desenvolvimento , Xilema/genética
2.
Nat Rev Mol Cell Biol ; 17(1): 30-40, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26580717

RESUMO

Vascular tissues in plants are crucial to provide physical support and to transport water, sugars and hormones and other small signalling molecules throughout the plant. Recent genetic and molecular studies have identified interconnections among some of the major signalling networks that regulate plant vascular development. Using Arabidopsis thaliana as a model system, these studies enable the description of vascular development from the earliest tissue specification events during embryogenesis to the differentiation of phloem and xylem tissues. Moreover, we propose a model for how oriented cell divisions give rise to a three-dimensional vascular bundle within the root meristem.


Assuntos
Padronização Corporal , Diferenciação Celular , Feixe Vascular de Plantas/citologia , Feixe Vascular de Plantas/embriologia , Floema/citologia , Raízes de Plantas/embriologia , Xilema/citologia
3.
Plant Cell ; 36(10): 4309-4322, 2024 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-39163271

RESUMO

Xylem tracheary elements (TEs) synthesize patterned secondary cell walls (SCWs) to reinforce against the negative pressure of water transport. VASCULAR-RELATED NAC-DOMAIN 7 (VND7) induces differentiation, accompanied by cellulose, xylan, and lignin deposition into banded domains. To investigate the effect of polymer biosynthesis mutations on SCW patterning, we developed a method to induce tracheary element transdifferentiation of isolated protoplasts, by transient transformation with VND7. Our data showed that proper xylan elongation is necessary for distinct cellulose bands, cellulose-xylan interactions are essential for coincident polymer patterns, and cellulose deposition is needed to override the intracellular organization that yields unique xylan patterns. These data indicate that a properly assembled cell wall network acts as a scaffold to direct polymer deposition into distinctly banded domains. We describe the transdifferentiation of protoplasts into TEs, providing an avenue to study patterned SCW biosynthesis in a tissue-free environment and in various mutant backgrounds.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Parede Celular , Celulose , Lignina , Protoplastos , Xilanos , Xilema , Arabidopsis/genética , Arabidopsis/metabolismo , Parede Celular/metabolismo , Xilema/metabolismo , Xilema/genética , Xilema/citologia , Xilanos/metabolismo , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Protoplastos/metabolismo , Celulose/metabolismo , Lignina/metabolismo , Transdiferenciação Celular , Mutação , Regulação da Expressão Gênica de Plantas , Fatores de Transcrição
4.
Proc Natl Acad Sci U S A ; 121(28): e2402514121, 2024 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-38959034

RESUMO

Leaves of flowering plants are characterized by diverse venation patterns. Patterning begins with the selection of vein-forming procambial initial cells from within the ground meristem of a developing leaf, a process which is considered to be auxin-dependent, and continues until veins are anatomically differentiated with functional xylem and phloem. At present, the mechanisms responsible for leaf venation patterning are primarily characterized in the model eudicot Arabidopsis thaliana which displays a reticulate venation network. However, evidence suggests that vein development may proceed via a different mechanism in monocot leaves where venation patterning is parallel. Here, we employed Molecular Cartography, a multiplexed in situ hybridization technique, to analyze the spatiotemporal localization of a subset of auxin-related genes and candidate regulators of vein patterning in maize leaves. We show how different combinations of auxin influx and efflux transporters are recruited during leaf and vein specification and how major and minor vein ranks develop with distinct identities. The localization of the procambial marker PIN1a and the spatial arrangement of procambial initial cells that give rise to major and minor vein ranks further suggests that vein spacing is prepatterned across the medio-lateral leaf axis prior to accumulation of the PIN1a auxin transporter. In contrast, patterning in the adaxial-abaxial axis occurs progressively, with markers of xylem and phloem gradually becoming polarized as differentiation proceeds. Collectively, our data suggest that both lineage- and position-based mechanisms may underpin vein patterning in maize leaves.


Assuntos
Hibridização In Situ , Ácidos Indolacéticos , Folhas de Planta , Zea mays , Zea mays/genética , Zea mays/crescimento & desenvolvimento , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Folhas de Planta/genética , Ácidos Indolacéticos/metabolismo , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/metabolismo , Proteínas de Plantas/genética , Xilema/metabolismo , Xilema/crescimento & desenvolvimento , Xilema/citologia , Xilema/genética
5.
EMBO J ; 40(15): e107455, 2021 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-34152631

RESUMO

Plant microRNAs (miRNAs) guide cytosolic post-transcriptional gene silencing of sequence-complementary transcripts within the producing cells, as well as in distant cells and tissues. Here, we used an artificial miRNA-based system (amiRSUL) in Arabidopsis thaliana to explore the still elusive mechanisms of inter-cellular miRNA movement via forward genetics. This screen identified many mutant alleles of HASTY (HST), the ortholog of mammalian EXPORTIN5 (XPO5) with a recently reported role in miRNA biogenesis in Arabidopsis. In both epidermis-peeling and grafting assays, amiRSUL levels were reduced much more substantially in miRNA-recipient tissues than in silencing-emitting tissues. We ascribe this effect to HST controlling cell-to-cell and phloem-mediated movement of the processed amiRSUL, in addition to regulating its biogenesis. While HST is not required for the movement of free GFP or siRNAs, its cell-autonomous expression in amiRSUL-emitting tissues suffices to restore amiRSUL movement independently of its nucleo-cytosolic shuttling activity. By contrast, HST is dispensable for the movement and activity of amiRSUL within recipient tissues. Finally, HST enables movement of endogenous miRNAs that display mostly unaltered steady-state levels in hst mutant tissues. We discuss a role for HST as a hitherto unrecognized regulator of miRNA movement in relation to its recently assigned nuclear function at the nexus of MIRNA transcription and miRNA processing.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Carioferinas/metabolismo , MicroRNAs/metabolismo , Arabidopsis/citologia , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Transporte Biológico/genética , Regulação da Expressão Gênica de Plantas , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Carioferinas/genética , Mutação , Floema/citologia , Floema/genética , Células Vegetais , Raízes de Plantas/citologia , Raízes de Plantas/genética , Plantas Geneticamente Modificadas , Interferência de RNA , RNA de Plantas , Xilema/citologia , Xilema/genética
6.
Nature ; 565(7740): 485-489, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30626967

RESUMO

Wood, a type of xylem tissue, originates from cell proliferation of the vascular cambium. Xylem is produced inside, and phloem outside, of the cambium1. Morphogenesis in plants is typically coordinated by organizer cells that direct the adjacent stem cells to undergo programmed cell division and differentiation. The location of the vascular cambium stem cells and whether the organizer concept applies to the cambium are currently unknown2. Here, using lineage-tracing and molecular genetic studies in the roots of Arabidopsis thaliana, we show that cells with a xylem identity direct adjacent vascular cambial cells to divide and function as stem cells. Thus, these xylem-identity cells constitute an organizer. A local maximum of the phytohormone auxin, and consequent expression of CLASS III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIP III) transcription factors, promotes xylem identity and cellular quiescence of the organizer cells. Additionally, the organizer maintains phloem identity in a non-cell-autonomous fashion. Consistent with this dual function of the organizer cells, xylem and phloem originate from a single, bifacial stem cell in each radial cell file, which confirms the classical theory of a uniseriate vascular cambium3. Clones that display high levels of ectopically activated auxin signalling differentiate as xylem vessels; these clones induce cell divisions and the expression of cambial and phloem markers in the adjacent cells, which suggests that a local auxin-signalling maximum is sufficient to specify a stem-cell organizer. Although vascular cambium has a unique function among plant meristems, the stem-cell organizer of this tissue shares features with the organizers of root and shoot meristems.


Assuntos
Arabidopsis/citologia , Arabidopsis/metabolismo , Câmbio/citologia , Câmbio/metabolismo , Ácidos Indolacéticos/metabolismo , Transdução de Sinais , Células-Tronco/citologia , Células-Tronco/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Diferenciação Celular , Divisão Celular , Linhagem da Célula , Meristema/citologia , Meristema/metabolismo , Floema/citologia , Floema/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Raízes de Plantas/citologia , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Brotos de Planta/citologia , Brotos de Planta/metabolismo , Fatores de Transcrição/metabolismo , Xilema/citologia , Xilema/metabolismo
7.
New Phytol ; 243(3): 851-865, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38890801

RESUMO

Secondary xylem and phloem originate from a lateral meristem called the vascular cambium that consists of one to several layers of meristematic cells. Recent lineage tracing studies have shown that only one of the cambial cells in each radial cell file functions as the stem cell, capable of producing both secondary xylem and phloem. Here, we first review how phytohormones and signalling peptides regulate vascular cambium formation and activity. We then propose how the stem cell concept, familiar from apical meristems, could be applied to cambium studies. Finally, we discuss how this concept could set the basis for future research.


Assuntos
Câmbio , Células-Tronco , Xilema , Câmbio/citologia , Câmbio/crescimento & desenvolvimento , Câmbio/fisiologia , Células-Tronco/citologia , Xilema/citologia , Floema/citologia , Reguladores de Crescimento de Plantas/metabolismo , Transdução de Sinais , Feixe Vascular de Plantas/crescimento & desenvolvimento , Feixe Vascular de Plantas/citologia , Meristema/citologia , Meristema/crescimento & desenvolvimento
8.
Annu Rev Cell Dev Biol ; 26: 605-37, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20590454

RESUMO

Plant vascular tissues, the conduits of water, nutrients, and small molecules, play important roles in plant growth and development. Vascular tissues have allowed plants to successfully adapt to various environmental conditions since they evolved 450 Mya. The majority of plant biomass, an important source of renewable energy, comes from the xylem of the vascular tissues. Efforts have been made to identify the underlying mechanisms of cell specification and patterning of plant vascular tissues and their proliferation. The formation of the plant vascular system is a complex process that integrates signaling and gene regulation at transcriptional and posttranscriptional levels. Recently, a wealth of molecular genetic studies and the advent of cell biology and genomic tools have enabled important progress toward understanding its underlying mechanisms. Here, we provide a comprehensive review of the cell and developmental processes of plant vascular tissue and resources recently available for studying them that will enable the discovery of new ways to develop sustainable energy using plant biomass.


Assuntos
Regulação da Expressão Gênica de Plantas , Plantas/embriologia , Transdução de Sinais , Xilema/crescimento & desenvolvimento , Diferenciação Celular , Floema/citologia , Floema/crescimento & desenvolvimento , Células Vegetais , Desenvolvimento Vegetal , Sementes/citologia , Sementes/crescimento & desenvolvimento , Xilema/citologia
9.
Proc Natl Acad Sci U S A ; 118(12)2021 03 23.
Artigo em Inglês | MEDLINE | ID: mdl-33723062

RESUMO

Xylem patterning in the root is established through the creation of opposing gradients of miRNAs and their targets, transcripts of the HD-ZIP III family of transcriptions factors, enabled by the cell-to-cell spread of the former. The miRNAs regulating xylem patterning, miR165/6, move through plasmodesmata, but how their trafficking is regulated remains elusive. Here, we describe that simultaneous mutation of the plasma membrane- and plasmodesmata-localized receptor-like kinases (RLKs) BARELY ANY MERISTEM (BAM) 1 and 2 or expression of the geminivirus-encoded BAM1/2-interactor C4 results in higher accumulation and broader distribution of the HD-ZIP III transcripts despite normal total accumulation of miR165/6, and ultimately causes defects in xylem patterning, which depend on the function of the aforementioned miRNA targets. Taken together, our results show that BAM1 and BAM2 are redundantly required for proper xylem patterning in the Arabidopsis root, by ensuring the proper distribution and accumulation of miR165/6-targeted transcripts.


Assuntos
Genes de Plantas , Desenvolvimento Vegetal/genética , Raízes de Plantas/citologia , Raízes de Plantas/genética , Proteínas Serina-Treonina Quinases/genética , Xilema/citologia , Xilema/genética , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , MicroRNAs/genética , Proteínas Serina-Treonina Quinases/metabolismo
11.
Proc Natl Acad Sci U S A ; 117(9): 5059-5066, 2020 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-32041869

RESUMO

The radiation of angiosperms led to the emergence of the vast majority of today's plant species and all our major food crops. Their extraordinary diversification occurred in conjunction with the evolution of a more efficient vascular system for the transport of water, composed of vessel elements. The physical dimensions of these water-conducting specialized cells have played a critical role in angiosperm evolution; they determine resistance to water flow, influence photosynthesis rate, and contribute to plant stature. However, the genetic factors that determine their dimensions are unclear. Here we show that a previously uncharacterized gene, ENLARGED VESSEL ELEMENT (EVE), contributes to the dimensions of vessel elements in Populus, impacting hydraulic conductivity. Our data suggest that EVE is localized in the plasma membrane and is involved in potassium uptake of differentiating xylem cells during vessel development. In plants, EVE first emerged in streptophyte algae, but expanded dramatically among vessel-containing angiosperms. The phylogeny, structure and composition of EVE indicates that it may have been involved in an ancient horizontal gene-transfer event.


Assuntos
Magnoliopsida/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Populus/genética , Populus/metabolismo , Evolução Biológica , Membrana Celular , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Fotossíntese , Phycodnaviridae , Plantas Geneticamente Modificadas , Potássio/metabolismo , Água/metabolismo , Xilema/citologia , Xilema/metabolismo
12.
Proc Natl Acad Sci U S A ; 117(1): 733-740, 2020 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-31874927

RESUMO

Vascular plants provide most of the biomass, food, and feed on earth, yet the molecular innovations that led to the evolution of their conductive tissues are unknown. Here, we reveal the evolutionary trajectory for the heterodimeric TMO5/LHW transcription factor complex, which is rate-limiting for vascular cell proliferation in Arabidopsis thaliana Both regulators have origins predating vascular tissue emergence, and even terrestrialization. We further show that TMO5 evolved its modern function, including dimerization with LHW, at the origin of land plants. A second innovation in LHW, coinciding with vascular plant emergence, conditioned obligate heterodimerization and generated the critical function in vascular development in Arabidopsis In summary, our results suggest that the division potential of vascular cells may have been an important factor contributing to the evolution of vascular plants.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Evolução Molecular , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Transativadores/genética , Proteínas de Arabidopsis/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Proliferação de Células/genética , Floema/citologia , Floema/crescimento & desenvolvimento , Floema/metabolismo , Filogenia , Plantas Geneticamente Modificadas , Multimerização Proteica/genética , Transativadores/metabolismo , Xilema/citologia , Xilema/crescimento & desenvolvimento , Xilema/metabolismo
13.
Development ; 146(1)2019 01 09.
Artigo em Inglês | MEDLINE | ID: mdl-30626594

RESUMO

A reduced rate of stem cell division is considered a widespread feature which ensures the integrity of genetic information during somatic development of plants and animals. Radial growth of plant shoots and roots is a stem cell-driven process that is fundamental for the mechanical and physiological support of enlarging plant bodies. In most dicotyledonous species, the underlying stem cell niche, the cambium, generates xylem inwards and phloem outwards. Despite the importance and intriguing dynamics of the cambium, the functional characterization of its stem cells is hampered by the lack of experimental tools for accessing distinct cambium sub-domains. Here, we use the hypocotyl of Arabidopsis thaliana to map stem cell activity in the proliferating cambium. Through pulse labeling and genetically encoded lineage tracing, we find that a single bifacial stem cell generates both xylem and phloem cell lineages. This cell is characterized by a specific combination of PXY (TDR), SMXL5 and WOX4 gene activity and a high division rate in comparison with tissue-specific progenitors. Our analysis provides a cellular fate map of radial plant growth, and suggests that stem cell quiescence is not a general prerequisite for life-long tissue production.This article has an associated 'The people behind the papers' interview.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Câmbio/fisiologia , Floema/fisiologia , Células Vegetais/metabolismo , Desenvolvimento Vegetal/fisiologia , Células-Tronco/metabolismo , Xilema/fisiologia , Arabidopsis/citologia , Proteínas de Arabidopsis/biossíntese , Câmbio/citologia , Regulação da Expressão Gênica de Plantas/fisiologia , Hipocótilo/citologia , Hipocótilo/fisiologia , Floema/citologia , Raízes de Plantas/citologia , Raízes de Plantas/fisiologia , Células-Tronco/citologia , Xilema/citologia
14.
Plant Cell Environ ; 45(1): 55-68, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34783044

RESUMO

Xylem conductive capacity is a key determinant of plant hydraulic function and intimately linked to photosynthesis and productivity, but can be impeded by temporary or permanent conduit dysfunctions. Here we show that persistent xylem dysfunctions in unstressed plants are frequent in Alpine dwarf shrubs and occur in various but species-specific cross-sectional patterns. Combined synchrotron micro-computed tomography (micro-CT) imaging, xylem staining, and flow measurements in saturated samples of six widespread Ericaceae species evidence a high proportion (19%-50%) of hydraulically nonfunctional xylem areas in the absence of drought stress, with regular distribution of dysfunctions between or within growth rings. Dysfunctions were only partly reversible and reduced the specific hydraulic conductivity to 1.38 to 3.57 ×10-4 m2 s-1 MPa-1 . Decommission of inner growth rings was clearly related to stem age and a higher vulnerability to cavitation of older rings, while the high proportion of nonfunctional conduits in each annual ring needs further investigations. The lower the xylem fraction contributing to the transport function, the higher was the hydraulic efficiency of conducting xylem areas. Improved understanding of the functional lifespan of xylem elements and the prevalence and nature of dysfunctions is critical to correctly assess structure-function relationships and whole-plant hydraulic strategies.


Assuntos
Ericaceae/fisiologia , Xilema/fisiologia , Áustria , Ericaceae/anatomia & histologia , Ericaceae/citologia , Região dos Alpes Europeus , Caules de Planta/anatomia & histologia , Caules de Planta/citologia , Especificidade da Espécie , Síncrotrons , Fatores de Tempo , Microtomografia por Raio-X , Xilema/anatomia & histologia , Xilema/citologia
15.
Plant J ; 101(2): 293-309, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31587430

RESUMO

The transcription factor KNOTTED ARABIDOPSIS THALIANA7 (KNAT7) is a Class II KNOTTED1-like homeobox (KNOX2) gene that, in interfascicular fibres, acts as a negative regulator of secondary cell wall biosynthesis. In addition, knat7 loss-of-function mutants display an irregular xylem (irx) phenotype, suggesting a potential positive regulatory role in xylem vessel secondary cell wall deposition. Although our understanding of the role of KNAT7 is evolving, the function(s) of the closely related KNOX2 genes, KNAT3, KNAT4, and KNAT5, in secondary wall formation still remain unclear. We found that all four Arabidopsis KNOX2 genes were expressed in the inflorescence stems. However, only the knat3 knat7 double mutants showed a phenotype, displaying an enhanced irx phenotypes relative to the single mutants, as well as decreased interfascicular fibre cell wall thickness. Moreover, knat3 knat7 double mutants had reduced stem tensile and flexural strength compared with wild-type and single mutants. In contrast, KNAT3 overexpression resulted in thicker interfascicular fibre secondary cell walls in inflorescence stems, suggesting a potential positive regulation in interfascicular fibre secondary wall development. This work identifies KNAT3 as a potential transcriptional activator working together with KNAT7 to promote secondary cell wall biosynthesis in xylem vessels, while concurrently acting antagonistically with KNAT7 to influence secondary wall formation in interfascicular fibres.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Parede Celular/metabolismo , Proteínas de Homeodomínio/metabolismo , Proteínas Repressoras/metabolismo , Transcriptoma , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Parede Celular/genética , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Técnicas de Inativação de Genes , Proteínas de Homeodomínio/genética , Mutação , Proteínas Nucleares , Fenótipo , Caules de Planta/citologia , Caules de Planta/genética , Caules de Planta/metabolismo , Proteínas Repressoras/genética , Fatores de Transcrição/genética , Xilema/citologia , Xilema/metabolismo
16.
Development ; 145(14)2018 07 23.
Artigo em Inglês | MEDLINE | ID: mdl-29950390

RESUMO

The haustorium in parasitic plants is an organ specialized for invasion and nutrient uptake from host plant tissues. Despite its importance, the developmental processes of haustoria are mostly unknown. To understand the dynamics of cell fate change and cellular lineage during haustorium development, we performed live imaging-based marker expression analysis and cell-lineage tracing during haustorium formation in the model facultative root parasite Phtheirospermum japonicum Our live-imaging analysis revealed that haustorium formation was associated with induction of simultaneous cell division in multiple cellular layers, such as epidermis, cortex and endodermis. In addition, we found that procambium-like cells, monitored by cell type-specific markers, emerged within the central region of the haustorium before xylem connection to the host plant. Our clonal analysis of cell lineages showed that cells in multiple cellular layers differentiated into procambium-like cells, whereas epidermal cells eventually transitioned into specialized cells interfacing with the host plant. Thus, our data provide a cell fate transition map during de novo haustorium organogenesis in parasitic plants.


Assuntos
Câmbio , Modelos Biológicos , Orobanchaceae , Epiderme Vegetal , Xilema , Câmbio/citologia , Câmbio/embriologia , Orobanchaceae/citologia , Orobanchaceae/embriologia , Epiderme Vegetal/citologia , Epiderme Vegetal/embriologia , Xilema/citologia , Xilema/embriologia
17.
Development ; 145(21)2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30355726

RESUMO

Division of the cambial cells and their subsequent differentiation into xylem and phloem drives radial expansion of the hypocotyl. Following the transition to reproductive growth, a phase change occurs in the Arabidopsis hypocotyl. During this second phase, the relative rate of xylem production is dramatically increased compared with that of phloem, and xylem fibres that contain thick secondary cell walls also form. Using two different genetic backgrounds and different environmental conditions, we identified a set of core transcriptional changes that is associated with the switch to the second phase of growth in the hypocotyl. Abscisic acid (ABA) signalling pathways are significantly over-represented in this set of core genes. Reverse genetic analysis demonstrated that mutants that are defective in ABA-biosynthesis enzymes exhibited significantly delayed fibre production without affecting the xylem:phloem ratio, and that these effects can be reversed by the application of ABA. The altered morphology is also reflected at the transcript level, with a reduced expression of marker genes that are associated with fibre formation in aba1 mutants. Taken together, the data reveal an essential role for ABA in the regulation of fibre formation.


Assuntos
Ácido Abscísico/farmacologia , Arabidopsis/citologia , Diferenciação Celular/efeitos dos fármacos , Xilema/citologia , Ácido Abscísico/biossíntese , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Flores/efeitos dos fármacos , Flores/fisiologia , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Genes de Plantas , Hipocótilo/efeitos dos fármacos , Hipocótilo/crescimento & desenvolvimento , Mutação/genética , Fenótipo , Reguladores de Crescimento de Plantas/farmacologia , Transcriptoma/efeitos dos fármacos , Transcriptoma/genética , Xilema/efeitos dos fármacos , Xilema/genética
18.
Development ; 145(23)2018 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-30389856

RESUMO

The thickening of plant organs is supported by secondary growth, a process by which new vascular tissues (xylem and phloem) are produced. Xylem is composed of several cell types, including xylary fibers, parenchyma and vessel elements. In Arabidopsis, it has been shown that fibers are promoted by the class-I KNOX gene KNAT1 and the plant hormones gibberellins, and are repressed by a small set of receptor-like kinases; however, we lack a mechanistic framework to integrate their relative contributions. Here, we show that DELLAs, negative elements of the gibberellin signaling pathway, physically interact with KNAT1 and impair its binding to KNAT1-binding sites. Our analysis also indicates that at least 37% of the transcriptome mobilized by KNAT1 is potentially dependent on this interaction, and includes genes involved in secondary cell wall modifications and phenylpropanoid biosynthesis. Moreover, the promotion by constitutive overexpression of KNAT1 of fiber formation and the expression of genes required for fiber differentiation were still reverted by DELLA accumulation, in agreement with post-translational regulation of KNAT1 by DELLA proteins. These results suggest that gibberellins enhance fiber development by promoting KNAT1 activity.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/citologia , Arabidopsis/metabolismo , Diferenciação Celular , Giberelinas/farmacologia , Proteínas de Homeodomínio/metabolismo , Xilema/citologia , Xilema/metabolismo , Arabidopsis/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Mutação com Ganho de Função/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Fenótipo , Feixe Vascular de Plantas/efeitos dos fármacos , Feixe Vascular de Plantas/metabolismo , Regiões Promotoras Genéticas/genética , Ligação Proteica/efeitos dos fármacos , Transcriptoma/efeitos dos fármacos , Transcriptoma/genética , Xilema/efeitos dos fármacos
19.
Plant Cell Rep ; 40(1): 127-142, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33068174

RESUMO

KEY MESSAGE: The HbCAld5H1 gene cloned from Hevea brasiliensis regulates the cambial activity, xylem differentiation, syringyl-guaiacyl ratio, secondary wall structure, lignification pattern and xylan distribution in xylem fibres of transgenic tobacco plants. Molecular characterization of lignin biosynthesis gene coniferaldehyde-5-hydroxylase (CAld5H) from Hevea brasiliensis and its functional validation was performed. Both sense and antisense constructs of HbCAld5H1 gene were introduced into tobacco through Agrobacterium-mediated genetic transformation for over expression and down-regulation of this key enzyme to understand its role affecting structural and cell wall chemistry. The anatomical studies of transgenic tobacco plants revealed the increase of cambial activity leading to xylogenesis in sense lines and considerable reduction in antisense lines. The ultra-structural studies showed that the thickness of secondary wall (S2 layer) of fibre had been decreased with non-homogenous lignin distribution in antisense lines, while sense lines showed an increase in S2 layer thickness. Maule color reaction revealed that syringyl lignin distribution in the xylem elements was increased in sense and decreased in antisense lines. The immunoelectron microscopy revealed a reduction in LM 10 and LM 11 labelling in the secondary wall of antisense tobacco lines. Biochemical studies showed a radical increase in syringyl lignin in sense lines without any significant change in total lignin content, while S/G ratio decreased considerably in antisense lines. Our results suggest that CAld5H gene plays an important role in xylogenesis stages such as cambial cell division, secondary wall thickness, xylan and syringyl lignin distribution in tobacco. Therefore, CAld5H gene could be considered as a promising target for lignin modification essential for timber quality improvement in rubber.


Assuntos
Parede Celular/química , Oxigenases de Função Mista/genética , Nicotiana/genética , Proteínas de Plantas/genética , Xilema/citologia , Acroleína/análogos & derivados , Acroleína/metabolismo , Parede Celular/genética , Parede Celular/metabolismo , Regulação da Expressão Gênica de Plantas , Lignina/genética , Lignina/metabolismo , Oxigenases de Função Mista/metabolismo , Fenótipo , Células Vegetais/metabolismo , Folhas de Planta/anatomia & histologia , Folhas de Planta/genética , Proteínas de Plantas/metabolismo , Caules de Planta/anatomia & histologia , Caules de Planta/genética , Caules de Planta/metabolismo , Plantas Geneticamente Modificadas , Nicotiana/citologia , Nicotiana/metabolismo , Xilanos/genética , Xilanos/metabolismo , Xilema/metabolismo
20.
J Integr Plant Biol ; 63(11): 1906-1921, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34347368

RESUMO

High-throughput single-cell RNA sequencing (scRNA-seq) has advantages over traditional RNA-seq to explore spatiotemporal information on gene dynamic expressions in heterogenous tissues. We performed Drop-seq, a method for the dropwise sequestration of single cells for sequencing, on protoplasts from the differentiating xylem of Populus alba × Populus glandulosa. The scRNA-seq profiled 9,798 cells, which were grouped into 12 clusters. Through characterization of differentially expressed genes in each cluster and RNA in situ hybridizations, we identified vessel cells, fiber cells, ray parenchyma cells and xylem precursor cells. Diffusion pseudotime analyses revealed the differentiating trajectory of vessels, fiber cells and ray parenchyma cells and indicated a different differentiation process between vessels and fiber cells, and a similar differentiation process between fiber cells and ray parenchyma cells. We identified marker genes for each cell type (cluster) and key candidate regulators during developmental stages of xylem cell differentiation. Our study generates a high-resolution expression atlas of wood formation at the single cell level and provides valuable information on wood formation.


Assuntos
Populus/citologia , Xilema/citologia , Diferenciação Celular , Parede Celular/metabolismo , Perfilação da Expressão Gênica , Genoma de Planta , Populus/genética , Populus/metabolismo , Análise de Sequência de RNA , Análise de Célula Única
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