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2.
Development ; 146(5)2019 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-30770391

RESUMO

Root hairs are protrusions from root epidermal cells with crucial roles in plant soil interactions. Although much is known about patterning, polarity and tip growth of root hairs, contributions of membrane trafficking to hair initiation remain poorly understood. Here, we demonstrate that the trans-Golgi network-localized YPT-INTERACTING PROTEIN 4a and YPT-INTERACTING PROTEIN 4b (YIP4a/b) contribute to activation and plasma membrane accumulation of Rho-of-plant (ROP) small GTPases during hair initiation, identifying YIP4a/b as central trafficking components in ROP-dependent root hair formation.


Assuntos
Proteínas de Arabidopsis/fisiologia , Arabidopsis/enzimologia , Genes de Plantas , Proteínas de Membrana/farmacologia , Raízes de Plantas/fisiologia , Proteínas rho de Ligação ao GTP/fisiologia , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/farmacologia , Membrana Celular/fisiologia , Genótipo , Proteínas de Membrana/genética , Proteínas Monoméricas de Ligação ao GTP/fisiologia , Mutação , Fenótipo , Transporte Proteico , Sementes , Rede trans-Golgi/fisiologia
3.
Development ; 145(21)2018 11 07.
Artigo em Inglês | MEDLINE | ID: mdl-30404777

RESUMO

The trans-Golgi-network (TGN) has essential housekeeping functions in secretion, endocytosis and protein sorting, but also more specialized functions in plant development. How the robustness of basal TGN function is ensured while specialized functions are differentially regulated is poorly understood. Here, we investigate two key regulators of TGN structure and function, ECHIDNA and the Transport Protein Particle II (TRAPPII) tethering complex. An analysis of physical, network and genetic interactions suggests that two network communities are implicated in TGN function and that ECHIDNA and TRAPPII belong to distinct yet overlapping pathways. Whereas ECHIDNA and TRAPPII colocalized at the TGN in interphase cells, their localization diverged in dividing cells. Moreover, ECHIDNA and TRAPPII localization patterns were mutually independent. TGN structure, endocytosis and sorting decisions were differentially impacted in echidna and trappii mutants. Our analyses point to a partitioning of specialized TGN functions, with ECHIDNA being required for cell elongation and TRAPPII for cytokinesis. Two independent pathways able to compensate for each other might contribute to the robustness of TGN housekeeping functions and to the responsiveness and fine tuning of its specialized functions.


Assuntos
Arabidopsis/metabolismo , Transdução de Sinais , Rede trans-Golgi/metabolismo , Arabidopsis/citologia , Arabidopsis/embriologia , Arabidopsis/ultraestrutura , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Biomarcadores/metabolismo , Membrana Celular/metabolismo , Citocinese , Endocitose , Epistasia Genética , Proteínas de Fluorescência Verde/metabolismo , Hipocótilo/metabolismo , Hipocótilo/ultraestrutura , Mutação/genética , Raízes de Plantas/metabolismo , Transporte Proteico , Rede trans-Golgi/ultraestrutura
4.
Plant Cell ; 29(5): 1039-1052, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28442598

RESUMO

During early seedling development, the shoot apical meristem is protected from damage as the seedling emerges from soil by the formation of apical hook. Hook formation requires differential growth across the epidermis below the meristem in the hypocotyl. The plant hormones ethylene and auxin play key roles during apical hook development by controlling differential growth. We provide genetic and cell biological evidence for the role of ADP-ribosylation factor 1 (ARF1)-GTPase and its effector ARF-guanine-exchange factors (GEFs) of the Brefeldin A-inhibited GEF (BIG) family and GNOM in ethylene- and auxin-mediated control of hook development. We show that ARF-GEF GNOM acts early, whereas BIG ARF-GEFs act at a later stage of apical hook development. We show that the localization of ARF1 and BIG4 at the trans-Golgi network (TGN) depends on ECHIDNA (ECH), a plant homolog of yeast Triacylglycerol lipase (TLG2/SYP4) interacting protein Tgl2-Vesicle Protein 23 (TVP23). BIGs together with ECH and ARF1 mediate the secretion of AUX1 influx carrier to the plasma membrane from the TGN during hook development and defects in BIG or ARF1 result in insensitivity to ethylene. Thus, our data indicate a division of labor within the ARF-GEF family in mediating differential growth with GNOM acting during the formation phase whereas BIGs act during the hook maintenance phase downstream of plant hormone ethylene.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Etilenos/metabolismo , Complexo de Golgi/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
5.
Protoplasma ; 252(2): 385-98, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25187082

RESUMO

The secretion of proteins, lipids, and carbohydrates to the cell surface is essential for plant development and adaptation. Secreted substances synthesized at the endoplasmic reticulum pass through the Golgi apparatus and trans-Golgi network (TGN) en route to the plasma membrane via the conventional secretion pathway. The TGN is morphologically and functionally distinct from the Golgi apparatus. The TGN is located at the crossroads of many trafficking pathways and regulates a range of crucial processes including secretion to the cell surface, transport to the vacuole, and the reception of endocytic cargo. This review outlines the TGN's central role in cargo secretion, showing that its behavior is more complex and controlled than the bulk-flow hypothesis suggests. Its formation, structure, and maintenance are discussed along with the formation and release of secretory vesicles.


Assuntos
Proteínas de Plantas/metabolismo , Plantas/metabolismo , Rede trans-Golgi/fisiologia , Membrana Celular/metabolismo , Metabolismo dos Lipídeos , Fusão de Membrana , Plantas/ultraestrutura , Transporte Proteico , Via Secretória , Vesículas Secretórias
6.
Proc Natl Acad Sci U S A ; 110(40): 16259-64, 2013 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-24043780

RESUMO

The plant hormone indole-acetic acid (auxin) is essential for many aspects of plant development. Auxin-mediated growth regulation typically involves the establishment of an auxin concentration gradient mediated by polarly localized auxin transporters. The localization of auxin carriers and their amount at the plasma membrane are controlled by membrane trafficking processes such as secretion, endocytosis, and recycling. In contrast to endocytosis or recycling, how the secretory pathway mediates the localization of auxin carriers is not well understood. In this study we have used the differential cell elongation process during apical hook development to elucidate the mechanisms underlying the post-Golgi trafficking of auxin carriers in Arabidopsis. We show that differential cell elongation during apical hook development is defective in Arabidopsis mutant echidna (ech). ECH protein is required for the trans-Golgi network (TGN)-mediated trafficking of the auxin influx carrier AUX1 to the plasma membrane. In contrast, ech mutation only marginally perturbs the trafficking of the highly related auxin influx carrier LIKE-AUX1-3 or the auxin efflux carrier PIN-FORMED-3, both also involved in hook development. Electron tomography reveals that the trafficking defects in ech mutant are associated with the perturbation of secretory vesicle genesis from the TGN. Our results identify differential mechanisms for the post-Golgi trafficking of de novo-synthesized auxin carriers to plasma membrane from the TGN and reveal how trafficking of auxin influx carriers mediates the control of differential cell elongation in apical hook development.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Crescimento Celular , Ácidos Indolacéticos/metabolismo , Caules de Planta/citologia , Proteínas de Transporte Vesicular/metabolismo , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Membrana Celular/metabolismo , Tomografia com Microscopia Eletrônica , Complexo de Golgi/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Caules de Planta/crescimento & desenvolvimento , Transporte Proteico/fisiologia , Proteínas de Transporte Vesicular/genética
7.
Plant Cell Physiol ; 54(11): 1867-80, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24058145

RESUMO

During cell wall biosynthesis, the Golgi apparatus is the platform for cell wall matrix biosynthesis and the site of packaging, of both matrix polysaccharides and proteins, into secretory vesicles with the correct targeting information. The objective of this study was to dissect the post-Golgi trafficking of cell wall polysaccharides using echidna as a vesicle traffic mutant of Arabidopsis thaliana and the pectin-secreting cells of the seed coat as a model system. ECHIDNA encodes a trans-Golgi network (TGN)-localized protein, which was previously shown to be required for proper structure and function of the secretory pathway. In echidna mutants, some cell wall matrix polysaccharides accumulate inside cells, rather than being secreted to the apoplast. In this study, live cell imaging of fluorescent protein markers as well as transmission electron microscopy (TEM)/immunoTEM of cryofixed seed coat cells were used to examine the consequences of TGN disorganization in echidna mutants under conditions of high polysaccharide production and secretion. While in wild-type seed coat cells, pectin is secreted to the apical surface, in echidna, polysaccharides accumulate in post-Golgi vesicles, the central lytic vacuole and endoplasmic reticulum-derived bodies. In contrast, proteins were partially mistargeted to internal multilamellar membranes in echidna. These results suggest that while secretion of both cell wall polysaccharides and proteins at the TGN requires ECHIDNA, different vesicle trafficking components may mediate downstream events in their secretion from the TGN.


Assuntos
Arabidopsis/metabolismo , Pectinas/metabolismo , Polissacarídeos/metabolismo , Vesículas Transportadoras/metabolismo , Vacúolos/metabolismo , Rede trans-Golgi/metabolismo , Arabidopsis/genética , Arabidopsis/ultraestrutura , Transporte Biológico , Membrana Celular/metabolismo , Parede Celular/metabolismo , Retículo Endoplasmático/metabolismo , Complexo de Golgi/metabolismo , Mutação , Fenótipo , Mucilagem Vegetal/metabolismo , Sementes/genética , Sementes/metabolismo , Sementes/ultraestrutura
8.
Plant Cell ; 25(7): 2633-46, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23832588

RESUMO

The secretion of cell wall polysaccharides through the trans-Golgi network (TGN) is required for plant cell elongation. However, the components mediating the post-Golgi secretion of pectin and hemicellulose, the two major cell wall polysaccharides, are largely unknown. We identified evolutionarily conserved YPT/RAB GTPase Interacting Protein 4a (YIP4a) and YIP4b (formerly YIP2), which form a TGN-localized complex with ECHIDNA (ECH) in Arabidopsis thaliana. The localization of YIP4 and ECH proteins at the TGN is interdependent and influences the localization of VHA-a1 and SYP61, which are key components of the TGN. YIP4a and YIP4b act redundantly, and the yip4a yip4b double mutants have a cell elongation defect. Genetic, biochemical, and cell biological analyses demonstrate that the ECH/YIP4 complex plays a key role in TGN-mediated secretion of pectin and hemicellulose to the cell wall in dark-grown hypocotyls and in secretory cells of the seed coat. In keeping with these observations, Fourier transform infrared microspectroscopy analysis revealed that the ech and yip4a yip4b mutants exhibit changes in their cell wall composition. Overall, our results reveal a TGN subdomain defined by ECH/YIP4 that is required for the secretion of pectin and hemicellulose and distinguishes the role of the TGN in secretion from its roles in endocytic and vacuolar trafficking.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Parede Celular/metabolismo , Polissacarídeos/metabolismo , Rede trans-Golgi/metabolismo , Sequência de Aminoácidos , Arabidopsis/genética , Proteínas de Arabidopsis/classificação , Proteínas de Arabidopsis/genética , Parede Celular/genética , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Microscopia Confocal , Dados de Sequência Molecular , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Mutação , Filogenia , Plantas Geneticamente Modificadas , Ligação Proteica , Homologia de Sequência de Aminoácidos , Técnicas do Sistema de Duplo-Híbrido
9.
Plant Physiol ; 161(1): 440-54, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23104861

RESUMO

The molecular basis of primary wall extension endures as one of the central enigmas in plant cell morphogenesis. Classical cell wall models suggest that xyloglucan endo-transglycosylase activity is the primary catalyst (together with expansins) of controlled cell wall loosening through the transient cleavage and religation of xyloglucan-cellulose cross links. The genome of Arabidopsis (Arabidopsis thaliana) contains 33 phylogenetically diverse XYLOGLUCAN ENDO-TRANSGLYCOSYLASE/HYDROLASE (XTH) gene products, two of which were predicted to be predominant xyloglucan endohydrolases due to clustering into group III-A. Enzyme kinetic analysis of recombinant AtXTH31 confirmed this prediction and indicated that this enzyme had similar catalytic properties to the nasturtium (Tropaeolum majus) xyloglucanase1 responsible for storage xyloglucan hydrolysis during germination. Global analysis of Genevestigator data indicated that AtXTH31 and the paralogous AtXTH32 were abundantly expressed in expanding tissues. Microscopy analysis, utilizing the resorufin ß-glycoside of the xyloglucan oligosaccharide XXXG as an in situ probe, indicated significant xyloglucan endohydrolase activity in specific regions of both roots and hypocotyls, in good correlation with transcriptomic data. Moreover, this hydrolytic activity was essentially completely eliminated in AtXTH31/AtXTH32 double knockout lines. However, single and double knockout lines, as well as individual overexpressing lines, of AtXTH31 and AtXTH32 did not demonstrate significant growth or developmental phenotypes. These results suggest that although xyloglucan polysaccharide hydrolysis occurs in parallel with primary wall expansion, morphological effects are subtle or may be compensated by other mechanisms. We hypothesize that there is likely to be an interplay between these xyloglucan endohydrolases and recently discovered apoplastic exo-glycosidases in the hydrolytic modification of matrix xyloglucans.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Arabidopsis/crescimento & desenvolvimento , Genes de Plantas , Glicosiltransferases/metabolismo , Sequência de Aminoácidos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Parede Celular/enzimologia , Ativação Enzimática , Ensaios Enzimáticos , Técnicas de Inativação de Genes , Germinação , Glucanos/metabolismo , Glicosiltransferases/genética , Hidrólise , Hipocótilo/enzimologia , Hipocótilo/genética , Hipocótilo/metabolismo , Dados de Sequência Molecular , Pectinas/metabolismo , Filogenia , Pichia/genética , Pichia/metabolismo , Raízes de Plantas/enzimologia , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Sementes/enzimologia , Sementes/genética , Sementes/metabolismo , Alinhamento de Sequência , Transcriptoma , Xilanos/metabolismo
10.
Proc Natl Acad Sci U S A ; 108(19): 8048-53, 2011 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-21512130

RESUMO

Multiple steps of plant growth and development rely on rapid cell elongation during which secretory and endocytic trafficking via the trans-Golgi network (TGN) plays a central role. Here, we identify the ECHIDNA (ECH) protein from Arabidopsis thaliana as a TGN-localized component crucial for TGN function. ECH partially complements loss of budding yeast TVP23 function and a Populus ECH complements the Arabidopsis ech mutant, suggesting functional conservation of the genes. Compared with wild-type, the Arabidopsis ech mutant exhibits severely perturbed cell elongation as well as defects in TGN structure and function, manifested by the reduced association between Golgi bodies and TGN as well as mislocalization of several TGN-localized proteins including vacuolar H(+)-ATPase subunit a1 (VHA-a1). Strikingly, ech is defective in secretory trafficking, whereas endocytosis appears unaffected in the mutant. Some aspects of the ech mutant phenotype can be phenocopied by treatment with a specific inhibitor of vacuolar H(+)-ATPases, concanamycin A, indicating that mislocalization of VHA-a1 may account for part of the defects in ech. Hence, ECH is an evolutionarily conserved component of the TGN with a central role in TGN structure and function.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Sequência de Aminoácidos , Arabidopsis/citologia , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Sequência de Bases , Compartimento Celular/efeitos dos fármacos , Compartimento Celular/genética , Compartimento Celular/fisiologia , Forma Celular/genética , Forma Celular/fisiologia , DNA de Plantas/genética , Evolução Molecular , Genes de Plantas , Teste de Complementação Genética , Macrolídeos/farmacologia , Dados de Sequência Molecular , Mutação , Fenótipo , Filogenia , Plantas Geneticamente Modificadas , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Homologia de Sequência de Aminoácidos , Proteínas de Transporte Vesicular/genética , Rede trans-Golgi/metabolismo , Rede trans-Golgi/ultraestrutura
11.
Plant J ; 49(1): 1-15, 2007 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17144893

RESUMO

The two main features of plant hyper-accumulator species are the massive translocation of heavy metal ions to the aerial parts and their tolerance to such high metal concentrations. Recently, several lines of evidence have indicated a role for nicotianamine (NA) in metal homeostasis, through the chelation and transport of NA-metal complexes. The function of transport of NA-metal chelates, required for the loading and unloading of vessels, has been assigned to the Yellow Stripe 1 (YSL)-Like family of proteins. We have characterized three YSL genes in Thlaspi caerulescens in the context of hyper-accumulation. The three YSL genes are expressed at high rates compared with their Arabidopsis thaliana homologs but with distinct patterns. While TcYSL7 was highly expressed in the flowers, TcYSL5 was more highly expressed in the shoots, and the expression of TcYSL3 was equivalent in all the organs tested. In situ hybridizations have shown that TcYSL7 and TcYSL5 are expressed around the vasculature of the shoots and in the central cylinder in the roots. The exposure to heavy metals (Zn, Cd, Ni) does not affect the high and constitutive expression of the TcYSL genes. Finally, we have demonstrated by mutant yeast complementation and uptake measurements that TcYSL3 is an Fe/Ni-NA influx transporter. This work provides therefore molecular, histological and biochemical evidence supporting a role for YSL transporters in the overall scheme of NA and NA-metal, particularly NA-Ni, circulation in a metal hyper-accumulator plant.


Assuntos
Ácido Azetidinocarboxílico/análogos & derivados , Ferro/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Níquel/metabolismo , Proteínas de Plantas/metabolismo , Thlaspi/genética , Thlaspi/metabolismo , Sequência de Aminoácidos , Ácido Azetidinocarboxílico/metabolismo , Clonagem Molecular , Regulação da Expressão Gênica de Plantas , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/genética , Dados de Sequência Molecular , Família Multigênica/genética , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/genética , Raízes de Plantas/metabolismo , Caules de Planta/metabolismo
12.
J Exp Bot ; 57(15): 4111-22, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-17079698

RESUMO

Plant metal hyperaccumulator species are widely used as models to unravel the heavy metal tolerance and hyperaccumulation mechanisms. Thlaspi caerulescens is capable of tolerating and hyperaccumulating Zn, Cd, and Ni. A search for factors involved in the cellular tolerance to Ni, based on yeast screens, led to isolation of a cDNA encoding a functional nicotianamine (NA) synthase (NAS). The T. caerulescens genome appears to contain a single copy of the NAS gene named TcNAS whose expression is restricted to the leaves. The analysis of dose-response and time-course Ni treatments have revealed that the exposure to Ni triggers the accumulation of NA in the roots. Because neither TcNAS expression nor NAS activity were detected in the roots, the NA accumulation in roots is most probably the result of its translocation from the leaves. Once in the roots, NA, together with Ni, is subsequently found in the xylem, for redirection to the aerial parts. Using liquid chromatography coupled to inductively coupled plasma or electrospray ionization mass spectrometry, it has been shown that part of the Ni is translocated as a stable Ni-NA complex in the xylem sap. This circulation of NA, Ni, and NA-Ni chelates is absent in the non-tolerant non-hyperaccumulator related species T. arvense. Taken together, the results provide direct physiological and chemical evidence for NA and NA-heavy metal complex translocation in a hyperaccumulator species.


Assuntos
Ácido Azetidinocarboxílico/análogos & derivados , Quelantes/metabolismo , Níquel/metabolismo , Thlaspi/metabolismo , Alquil e Aril Transferases/química , Alquil e Aril Transferases/genética , Alquil e Aril Transferases/metabolismo , Sequência de Aminoácidos , Ácido Azetidinocarboxílico/metabolismo , Transporte Biológico , Cromatografia Líquida , Genoma de Planta , Dados de Sequência Molecular , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raízes de Plantas/metabolismo , Brotos de Planta/metabolismo , RNA Mensageiro/metabolismo , Alinhamento de Sequência , Espectrometria de Massas por Ionização por Electrospray , Xilema/metabolismo
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