-
[show abstract]
[hide abstract]
ABSTRACT: PIN-FORMED (PIN) proteins localize asymmetrically at the plasma membrane and mediate intercellular polar transport of the plant hormone auxin that is crucial for a multitude of developmental processes in plants. PIN localization is under extensive control by environmental or developmental cues, but mechanisms regulating PIN localization are not fully understood. Here we show that early endosomal components ARF GEF BEN1 and newly identified Sec1/Munc18 family protein BEN2 are involved in distinct steps of early endosomal trafficking. BEN1 and BEN2 are collectively required for polar PIN localization, for their dynamic repolarization, and consequently for auxin activity gradient formation and auxin-related developmental processes including embryonic patterning, organogenesis, and vasculature venation patterning. These results show that early endosomal trafficking is crucial for cell polarity and auxin-dependent regulation of plant architecture.
PLoS Genetics 05/2013; 9(5):e1003540. · 8.69 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Cell surface proteins play critical roles in the perception of environmental stimuli at the plasma membrane (PM) and ensuing signal transduction. Intracellular localization of such proteins must be strictly regulated, which requires elaborate integration of exocytic and endocytic trafficking pathways. Subcellular localization of Arabidopsis thaliana FLAGELLIN SENSING2 (FLS2), a receptor that recognizes bacterial flagellin, also depends on membrane trafficking. However, our understanding about the mechanisms involved is still limited. In this study, we visualized ligand-induced endocytosis of FLS2 using green fluorescent protein (GFP)-tagged FLS2 expressed in Nicotiana benthamiana. Upon treatment with the flg22 peptide, internalized FLS2-GFP from the PM was transported to a compartment with properties intermediate between the trans-Golgi network (TGN) and the multivesicular endosome. This compartment gradually discarded the TGN characteristics as it continued along the trafficking pathway. We further found that FLS2 endocytosis involves distinct RABA/RAB11 subgroups at different steps. Moreover, we demonstrated that transport of de novo-synthesized FLS2 to the PM also involves a distinct RABA/RAB11 subgroup. Our results demonstrate the complex regulatory system for properly localizing FLS2 and functional differentiation in RABA members in endo- and exocytosis.
The Plant Cell 03/2013; · 8.99 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: RAB GTPases are key regulators of membrane traffic. Among them, RAB11, a widely conserved subgroup, has evolved in a unique way in plants; plant RAB11 has notable diversity, whereas yeast and animals possess only a few RAB11 members. In Arabidopsis thaliana, 57 RAB GTPases are encoded in its genome, 26 of which are classified in the RAB11 group (further divided into RABA1-RABA6 subgroups). Although several plant RAB11 members have been shown to play pivotal roles in plant-unique developmental processes, including cytokinesis and tip growth, molecular and physiological functions of the majority of RAB11 members remain unknown. To reveal precise functions of plant RAB11, we investigated subcellular localization and dynamics of the largest subgroup of Arabidopsis RAB11, RABA1, which consists of 9 members. RABA1 members resided on mobile punctate structures beside the trans-Golgi network (TGN) and colocalized with VAMP721/722, R-SNARE proteins operating in the secretory pathway. In addition, the constitutive-active mutant of the RABA1 representative, RABA1b(Q72L) , was observed on the plasma membrane. The RABA1b compartment showed actin-dependent dynamic motion. Vesicles labeled by GFP-RABA1b moved dynamically forming queues along actin filaments. Interestingly, the Arabidopsis plants whose four major RABA1 members were knocked out and those expressing the dominant-negative mutant of RABA1B exhibited hypersensitivity to salinity stress. Altogether, these results indicate that RABA1 members mediate transport between the TGN and the plasma membrane and are required for salinity stress tolerance. © 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.
The Plant Journal 09/2012; · 6.16 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The trans-Golgi network (TGN) contains multiple sorting domains and acts as the compartment for cargo sorting. Recent evidence indicates that the TGN also functions as an early endosome, the first compartment in the endocytic pathway in plants. The SYP4 group, plant Qa-SNAREs localized on the TGN, regulates both secretory and vacuolar transport pathways. Consistent with a secretory role, SYP4 proteins are required for extracellular resistance to fungal pathogens. However, the physiological role of SYP4 in abiotic stress remains unknown. Here, we report the phenotypes of a syp4-mutant in regard to salinity and osmotic response, and describe the physiological roles of the SYP4 group in the abiotic stress response.
Plant signaling & behavior 09/2012; 7(9).
-
[show abstract]
[hide abstract]
ABSTRACT: The Golgi apparatus forms stacks of cisternae in many eukaryotic cells. However, little is known about how such a stacked structure is formed and maintained. To address this question, plant cells provide a system suitable for live-imaging approaches because individual Golgi stacks are well separated in the cytoplasm. We established tobacco BY-2 cell lines expressing multiple Golgi markers tagged by different fluorescent proteins and observed their responses to brefeldin A (BFA) treatment and BFA removal. BFA treatment disrupted cis, medial, and trans cisternae but caused distinct relocalization patterns depending on the proteins examined. Medial- and trans-Golgi proteins, as well as one cis-Golgi protein, were absorbed into the endoplasmic reticulum (ER), but two other cis-Golgi proteins formed small punctate structures. After BFA removal, these puncta coalesced first, and then the Golgi stacks regenerated from them in the cis-to-trans order. We suggest that these structures have a property similar to the ER-Golgi intermediate compartment and function as the scaffold of Golgi regeneration.
Molecular biology of the cell 06/2012; 23(16):3203-14. · 5.98 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In all eukaryotic cells, a membrane-trafficking system connects the post-Golgi organelles, such as the trans-Golgi network (TGN), endosomes, vacuoles, and the plasma membrane. This complex network plays critical roles in several higher-order functions in multicellular organisms. The TGN, one of the important organelles for protein transport in the post-Golgi network, functions as a sorting station, where cargo proteins are directed to the appropriate post-Golgi compartments. Unlike its roles in animal and yeast cells, the TGN has also been reported to function like early endosomal compartments in plant cells. However, the physiological roles of the TGN functions in plants are not understood. Here, we report a study of the SYP4 group (SYP41, SYP42, and SYP43), which represents the plant orthologs of the Tlg2/syntaxin16 Qa-SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptor) that localizes on the TGN in yeast and animal cells. The SYP4 group regulates the secretory and vacuolar transport pathways in the post-Golgi network and maintains the morphology of the Golgi apparatus and TGN. Consistent with a secretory role, SYP4 proteins are required for extracellular resistance responses to a fungal pathogen. We also reveal a plant cell-specific higher-order role of the SYP4 group in the protection of chloroplasts from salicylic acid-dependent biotic stress.
Proceedings of the National Academy of Sciences 01/2012; 109(5):1784-9. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Lineage-specific expansion, followed by functional diversification of key components that act in membrane trafficking, is thought to contribute to lineage-specific diversification of organelles and membrane trafficking pathways. Indeed, recent comparative genomic studies have indicated that specific expansion of RAB and SNARE molecules occurred independently in various eukaryotic lineages over evolutionary history. However, experimental verification of this notion is difficult, because detailed functional analyses of RAB and SNARE proteins uniquely acquired by specific lineages are essential to understanding how new membrane trafficking pathways may have evolved. Recently, we found that a plant-specific RAB GTPase, ARA6, and a plant-unique R-SNARE, VAMP727, mediate a trafficking pathway from endosomes to the plasma membrane in Arabidopsis thaliana. Although a similar endosomal trafficking pathway was also reported in animals, the molecular machineries acting in these trafficking systems differ between animals and plants. Thus, trafficking pathways from endosomes to the plasma membrane appear to have been acquired independently in animal and plant systems. We further demonstrated that the ARA6-mediated trafficking pathway is required for the proper salt-stress response of A. thaliana. These results indicate that acquisition of a new membrane trafficking pathway may be associated with maximization of the fitness of each organism in a lineage-specific manner.
Small GTPases 01/2012; 3(1):23-7.
-
[show abstract]
[hide abstract]
ABSTRACT: The transition of plant growth from vegetative to reproductive phases is one of the most important and dramatic events during the plant life cycle. In Arabidopsis thaliana, flowering promotion involves at least four genetically defined regulatory pathways, including the photoperiod-dependent, vernalization-dependent, gibberellin-dependent, and autonomous promotion pathways. Among these regulatory pathways, the vernalization-dependent and autonomous pathways are integrated by the expression of FLOWERING LOCUS C (FLC), a negative regulator of flowering; however, the upstream regulation of this locus has not been fully understood. The SYP22 gene encodes a vacuolar SNARE protein that acts in vacuolar and endocytic trafficking pathways. Loss of SYP22 function was reported to lead to late flowering in A. thaliana plants, but the mechanism has remained completely unknown. In this study, we demonstrated that the late flowering phenotype of syp22 was due to elevated expression of FLC caused by impairment of the autonomous pathway. In addition, we investigated the DOC1/BIG pathway, which is also suggested to regulate vacuolar/endosomal trafficking. We found that elevated levels of FLC transcripts accumulated in the doc1-1 mutant, and that syp22 phenotypes were exaggerated with a double syp22 doc1-1 mutation. We further demonstrated that the elevated expression of FLC was suppressed by ara6-1, a mutation in the gene encoding plant-unique Rab GTPase involved in endosomal trafficking. Our results indicated that vacuolar and/or endocytic trafficking is involved in the FLC regulation of flowering time in A. thaliana.
PLoS ONE 01/2012; 7(7):e42239. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: "Bulb" is a mobile and complex structure appearing in vacuolar membrane of plant cell. We recently reported new fluorescent marker lines for bulbs and bulb-less mutants. We tried multicolor visualization of vacuolar membrane to show distinct segregation of bulb-positive protein (γTIP or AtVAM3) and bulb-negative protein (AtRab75). Unexpectedly, GFP-AtRab75 resulted to localize in bulb under the condition of co-expression with TagRFP-AtVAM3. The signal intensities of GFP-AtRab75 and TagRFP-AtVAM3 were quantified and compared. The result indicates that TagRFP-AtVAM3 is concentrated in bulb than GFP-AtRab75.
Plant signaling & behavior 12/2011; 6(12):1914-7.
-
[show abstract]
[hide abstract]
ABSTRACT: Clathrin-coated vesicles (CCV) are necessary for selective transport events, including receptor-mediated endocytosis on the plasma membrane and cargo molecule sorting in the trans-Golgi network (TGN). Components involved in CCV formation include clathrin heavy and light chains and several adaptor proteins that are conserved among plants. Clathrin-dependent endocytosis has been shown to play an integral part in plant endocytosis. However, little information is known about clathrin dynamics in living plant cells. In this study, we have visualized clathrin in Arabidopsis thaliana by tagging clathrin light chain with green fluorescent protein (CLC-GFP). Quantitative evaluations of colocalization demonstrate that the majority of CLC-GFP is localized to the TGN, and a minor population is associated with multivesicular endosomes and the Golgi trans-cisternae. Live imaging further demonstrated the presence of highly dynamic clathrin-positive tubules and vesicles, which appeared to mediate interactions between the TGNs. CLC-GFP is also targeted to cell plates and the plasma membrane. Although CLC-GFP colocalizes with a dynamin isoform at the plasma membrane, these proteins exhibit distinct distributions at newly forming cell plates. This finding indicates independent functions of CLC (clathrin light chains) and dynamin during the formation of cell plates. We have also found that brefeldin A and wortmannin treatment causes distinctly different alterations in the dynamics and distribution of clathrin-coated domains at the plasma membrane. This could account for the different effects of these drugs on plant endocytosis.
The Plant Journal 09/2011; 69(2):204-16. · 6.16 Impact Factor
-
Chieko Saito, Tomohiro Uemura,
Chie Awai,
Motoki Tominaga,
Kazuo Ebine,
Jun Ito,
Takashi Ueda,
Hiroshi Abe,
Miyo Terao Morita,
Masao Tasaka,
Akihiko Nakano
[show abstract]
[hide abstract]
ABSTRACT: The plant vacuole fulfills a variety of functions, and is essential for plant growth and development. We previously identified complex and mobile structures on the continuous vacuolar membrane, which we refer to as ‘bulbs’. To ascertain their biological significance and function, we searched for markers associated with bulbs, and mutants that show abnormalities with respect to bulbs. We observed bulb-like structures after expression of non-membranous proteins as well as the functional soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) molecules VAM3 and VTI11. Bulbs are formed in more tissues than previously reported, including flowering organs, suspension culture cells, endodermal cells in the flowering stem, and at very early stages of seed germination. Using existing and newly developed marker lines, we found that the frequency of bulb occurrence is significantly decreased in multiple shoot gravitropism (sgr) mutants, which are known to have a defect in vacuolar membrane properties in endodermal cells. Based on results with new marker lines, which enabled us to observe the process of bulb biogenesis, and analysis of the phenotypes of these mutants, we propose multiple mechanisms for bulb formation, one of which may be that used for formation of transvacuolar strands.
The Plant Journal 07/2011; 68(1):64 - 73. · 6.16 Impact Factor
-
Kazuo Ebine,
Masaru Fujimoto,
Yusuke Okatani,
Tomoaki Nishiyama,
Tatsuaki Goh,
Emi Ito,
Tomoko Dainobu,
Aiko Nishitani, Tomohiro Uemura,
Masa H Sato,
Hans Thordal-Christensen,
Nobuhiro Tsutsumi,
Akihiko Nakano,
Takashi Ueda
[show abstract]
[hide abstract]
ABSTRACT: Endosomal trafficking plays an integral role in various eukaryotic cell activities and serves as a basis for higher-order functions in multicellular organisms. An understanding of the importance of endosomal trafficking in plants is rapidly developing, but its molecular mechanism is mostly unknown. Several key regulators of endosomal trafficking, including RAB5, which regulates diverse endocytic events in animal cells, are highly conserved. However, the identification of lineage-specific regulators in eukaryotes indicates that endosomal trafficking is diversified according to distinct body plans and lifestyles. In addition to orthologues of metazoan RAB5, land plants possess a unique RAB5 molecule, which is one of the most prominent features of plant RAB GTPase organization. Plants have also evolved a unique repertoire of SNAREs, the most distinctive of which are diverse VAMP7-related longins, including plant-unique VAMP72 derivatives. Here, we demonstrate that a plant-unique RAB5 protein, ARA6, acts in an endosomal trafficking pathway in Arabidopsis thaliana. ARA6 modulates the assembly of a distinct SNARE complex from conventional RAB5, and has a functional role in the salinity stress response. Our results indicate that plants possess a unique endosomal trafficking network and provide the first indication of a functional link between a specific RAB and a specific SNARE complex in plants.
Nature Cell Biology 06/2011; 13(7):853-9. · 19.49 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: SNAREs (soluble N-ethylmaleimide sensitive factor attachment protein receptors) mediate specific membrane fusion between transport vesicles or organelles and target membranes. VAM3/SYP22 and PEP12/SYP21 are Qa-SNAREs that act in the vacuolar transport pathway of Arabidopsis thaliana, and are localized predominantly on the vacuolar membrane and the pre-vacuolar compartment (PVC), respectively. Previous studies have shown that loss-of-function mutants of VAM3/SYP22 or PEP12/SYP21 showed male gametophytic lethality, suggesting that VAM3/SYP22 and PEP12/SYP21 possess different, non-redundant functions. We have re-evaluated the effects of mutations in these genes using T-DNA insertion mutants in the Columbia accession. We found that a mutation in VAM3/SYP22 (vam3-1) caused pleiotropic abnormalities, including semi-dwarfism and wavy leaves. In contrast, a loss-of-function mutant of PEP12/SYP21 (pep12) showed no apparent abnormal phenotype. We also found that the double vam3-1 pep12 mutant had severely reduced fertilization competence, although male and female gametophytes (vam3-1(-) pep12(-) ) maintained the ability to fertilize. Moreover, promoter swapping analysis revealed that expression of a GFP-PEP12/SYP21 fusion under the control of the VAM3/SYP22 promoter suppressed all phenotypes of the vam3-1 mutant. These results indicate that the functions of VAM3/SYP22 and PEP12/SYP21 were redundant and interchangeable.
The Plant Journal 12/2010; 64(5):864-73. · 6.16 Impact Factor
-
Kohei Hamaji,
Megumi Nagira,
Katsuhisa Yoshida,
Miwa Ohnishi,
Yoshihisa Oda, Tomohiro Uemura,
Tatsuaki Goh,
Masa H Sato,
Miyo T Morita,
Masao Tasaka,
Sei-ichiro Hasezawa,
Akihiko Nakano,
Ikuko Hara-Nishimura,
Masayoshi Maeshima,
Hidehiro Fukaki,
Tetsuro Mimura
[show abstract]
[hide abstract]
ABSTRACT: The intracellular membrane dynamics of Arabidopsis cells under high salt treatment were investigated. When Arabidopsis was treated with high levels of NaCl in hydroponic culture, root tip cells showed rapid changes in the vacuolar volume, a decrease in the number of small acid compartments, active movement of vesicles and accumulation of Na(+) both in the central vacuole and in the vesicles around the main vacuole observed with the Na(+)-dependent fluorescence of Sodium Green. Detailed observation of Arabidopsis suspension-cultured cells under high salt treatment showed a similar pattern of response to that observed in root tip cells. Immunostaining of suspension-cultured cells with antibodies against AtNHX1 clearly showed the occurrence of dotted fluorescence in the cytoplasm only under salt treatment. We also confirmed the existence of AtNHX1 in the vacuolar membrane isolated from suspension-cultured cells with immunofluorescence. Knockout of the vacuolar Q(a)-SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein VAM3/SYP22 caused an increase in salt tolerance. In mutant plants, the distribution of Na(+) between roots and shoots differed from that of wild-type plants, with Na(+) accumulating more in roots and less in the shoots of the mutant plants. The role of vesicle traffic under salt stress is discussed.
Plant and Cell Physiology 10/2009; 50(12):2023-33. · 4.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: ACAP-type ARF GTPase activating proteins (ARF-GAPs) regulate multiple cellular processes, including endocytosis, secretion, phagocytosis, cell adhesion and cell migration. However, the regulation of ACAP functions by other cellular proteins is poorly understood. We have reported previously that a plant ACAP, VAN3, plays a pivotal role in plant venation continuity. Here, we report on newly identified VAN3 regulators: the CVP2 (cotyledon vascular pattern 2) 5 PTase, which is considered to degrade IP(3) and also to produce PtdIns(4)P from PtdIns(4,5)P(2); and a PH domain-containing protein, VAB (VAN3 binding protein). Combinational mutations of both CVP2 and its closest homologue CVL1 (CVP2 like 1) phenocopied the strong allele of van3 mutants, showing severe vascular continuity. The phenotype of double mutants between van3, cvp2 and vab suggested that VAN3, CVP2 and VAB function in vascular pattern formation in the same pathway. Localization analysis revealed that both CVP2 and VAB colocalize with VAN3 in the trans-Golgi network (TGN), supporting their functions in the same pathway. The subcellular localization of VAN3 was dependent on its PH domain, and mislocalization of VAN3 was induced in cvp2 or vab mutants. These results suggest that CVP2 and VAB cooperatively regulate the subcellular localization of VAN3 through the interaction between its PH domain and phosphoinositides and/or inositol phosphates. In addition, PtdIns(4)P, to which VAN3 binds preferentially, enhanced the ARF-GAP activity of VAN3, whereas IP(3) inhibited it. These results suggest the existence of PtdIns(4)P and/or IP(3)-dependent subcellular targeting and regulation of VAN3 ACAP activity that governs plant vascular tissue continuity.
Development 06/2009; 136(9):1529-38. · 6.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Membrane trafficking to the plasma membrane (PM) is a highly organized process which enables plant cells to build up their bodies. SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) genes, which encode the proteins involved in membrane trafficking, are much more abundant in the Arabidopsis genome than in that of any other eukaryote. We have previously shown that a large number of SNARE molecules in the Arabidopsis cell are localized predominantly on the PM. In the present study, in order to elucidate the physiological function of each PM-localized SNARE, we analyzed the spatiotemporal expression profiling of nine SYP1s that are resident in the PM of Arabidopsis, and used the information thus acquired to generate transgenic Arabidopsis plants expressing green fluorescent protein-fused Qa-SNAREs under control of their authentic promoters. Among the nine SYP1s, only SYP132 is expressed ubiquitously in all tissues throughout plant development. The expression patterns of the other SYP1s, in contrast, are tissue specific, and all different from one another. A particularly noteworthy example is SYP123, which is predominantly expressed in root hair cells during root development, and shows a focal accumulation pattern at the tip region of root hairs. These results suggest that SYP132 is involved in constitutive membrane trafficking to the PM throughout plant development, while the other SYP1s are involved in membrane trafficking events such as root formation or tip growth of root hair, with some redundancy.
Plant and Cell Physiology 01/2009; 50(2):280-9. · 4.70 Impact Factor
-
Kazuo Ebine,
Yusuke Okatani, Tomohiro Uemura,
Tatsuaki Goh,
Keiko Shoda,
Mitsuru Niihama,
Miyo Terao Morita,
Christoph Spitzer,
Marisa S Otegui,
Akihiko Nakano,
Takashi Ueda
[show abstract]
[hide abstract]
ABSTRACT: The SNARE complex is a key regulator of vesicular traffic, executing membrane fusion between transport vesicles or organelles and target membranes. A functional SNARE complex consists of four coiled-coil helical bundles, three of which are supplied by Q-SNAREs and another from an R-SNARE. Arabidopsis thaliana VAMP727 is an R-SNARE, with homologs only in seed plants. We have found that VAMP727 colocalizes with SYP22/ VAM3, a Q-SNARE, on a subpopulation of prevacuolar compartments/endosomes closely associated with the vacuolar membrane. Genetic and biochemical analyses, including examination of a synergistic interaction of vamp727 and syp22 mutations, histological examination of protein localization, and coimmunoprecipitation from Arabidopsis lysates indicate that VAMP727 forms a complex with SYP22, VTI11, and SYP51 and that this complex plays a crucial role in vacuolar transport, seed maturation, and vacuole biogenesis. We suggest that the VAMP727 complex mediates the membrane fusion between the prevacuolar compartment and the vacuole and that this process has evolved as an essential step for seed development.
The Plant Cell 12/2008; 20(11):3006-21. · 8.99 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: SNAREs ('Soluble N-ethyl-maleimide sensitive factor attachment protein receptors') play a critical role in the membrane fusion step of the vesicular transport system in eukaryotes. The number of the genes encoding SNARE proteins is estimated to be 64 in Arabidopsis thaliana. This number is much larger than those in other eukaryotes, suggesting a complex membrane trafficking in plants. The Arabidopsis SNAREs, the SYP7 group proteins, SYP71, SYP72, and SYP73, form a plant-specific SNARE subfamily with not-yet-identified functions. We have previously reported that the SYP7 subfamily proteins are predominantly localized to the endoplasmic reticulum in the Arabidopsis suspension cultured cells under transient expression condition. However, several proteomic analyzes indicated the plasma membrane localizations of one of SYP7 subfamily proteins, SYP71. In order to confirm the expression patterns and subcellular localization of SYP7, we performed combination analyses including promoter GUS analysis, a sucrose density gradient centrifugation analysis, as well as an observation on transgenic Arabidopsis plants expressing GFP-fused SYP71 under control of its native promoter. From these analyses, we concluded that one of the SYP7 subfamily proteins, SYP71, is predominantly expressed in all vegetative tissues and mainly localized to the plasma membrane. We also found that SYP71 is localized to the endoplasmic reticulum in the dividing cells of various types of tissues.
Cell Structure and Function 11/2008; 33(2):185-92. · 2.29 Impact Factor
-
Pankaj Dhonukshe,
Hirokazu Tanaka,
Tatsuaki Goh,
Kazuo Ebine,
Ari Pekka Mähönen,
Kalika Prasad,
Ikram Blilou,
Niko Geldner,
Jian Xu, Tomohiro Uemura,
Joanne Chory,
Takashi Ueda,
Akihiko Nakano,
Ben Scheres,
Jirí Friml
[show abstract]
[hide abstract]
ABSTRACT: Dynamically polarized membrane proteins define different cell boundaries and have an important role in intercellular communication-a vital feature of multicellular development. Efflux carriers for the signalling molecule auxin from the PIN family are landmarks of cell polarity in plants and have a crucial involvement in auxin distribution-dependent development including embryo patterning, organogenesis and tropisms. Polar PIN localization determines the direction of intercellular auxin flow, yet the mechanisms generating PIN polarity remain unclear. Here we identify an endocytosis-dependent mechanism of PIN polarity generation and analyse its developmental implications. Real-time PIN tracking showed that after synthesis, PINs are initially delivered to the plasma membrane in a non-polar manner and their polarity is established by subsequent endocytic recycling. Interference with PIN endocytosis either by auxin or by manipulation of the Arabidopsis Rab5 GTPase pathway prevents PIN polarization. Failure of PIN polarization transiently alters asymmetric auxin distribution during embryogenesis and increases the local auxin response in apical embryo regions. This results in ectopic expression of auxin pathway-associated root-forming master regulators in embryonic leaves and promotes homeotic transformation of leaves to roots. Our results indicate a two-step mechanism for the generation of PIN polar localization and the essential role of endocytosis in this process. It also highlights the link between endocytosis-dependent polarity of individual cells and auxin distribution-dependent cell fate establishment for multicellular patterning.
Nature 11/2008; 456(7224):962-6. · 36.28 Impact Factor
-
Pankaj Dhonukshe,
Hirokazu Tanaka,
Tatsuaki Goh,
Kazuo Ebine,
Ari Pekka M|[auml]|h|[ouml]|nen,
Kalika Prasad,
Ikram Blilou,
Niko Geldner,
Jian Xu, Tomohiro Uemura,
Joanne Chory,
Takashi Ueda,
Akihiko Nakano,
Ben Scheres,
Ji|[rcaron]||[iacute]| Friml
[show abstract]
[hide abstract]
ABSTRACT: Dynamically polarized membrane proteins define different cell boundaries and have an important role in intercellular communication—a vital feature of multicellular development. Efflux carriers for the signalling molecule auxin from the PIN family
Nature 10/2008; 456(7224):962-966. · 36.28 Impact Factor
