@article{2616, abstract = {Neurons in the rat cerebral cortex are enriched in group I metabotropic glutamate receptor (mGluR) subtypes and respond to their activation during development. To understand better the mechanisms by which mGluR1 and mGluR5 mediate these effects, the goal of this study was to elucidate the expression pattern and to determine the cellular and the precise subcellular localization of these two receptor subtypes in the rat neocortex and hippocampus during late prenatal and postnatal development. At the light microscopic level, mGluR1 α and mGluR5 were first detected in the cerebral cortex with different expression levels at embryonic day E18. Thus, mGluR5 had a moderate expression, whereas mGluR1 α was detected as a diffuse and weak labeling. mGluR5 was localized in some Cajal-Retzius cells as well as in other cell types, such as pioneer neurons of the marginal zone. During postnatal development, the distribution of the receptors dramatically changed. From P0 to around P10, mGluR1α was localized in identified, transient Cajal-Retzius cells of neocortex and hippocampus, until these cells disappear. In addition, a population of interneurons localized the receptor from the second/third postnatal week. In contrast, mGluR5 was localized mainly in pyramidal cells and in some interneurons, with a neuropilar staining throughout the cerebral cortex. At the electron microscopic level, the immunoreactivity for both group I mGluR subtypes was expressed postsynaptically. Using immunogold methods, mGluR1α and mGluR5 immunoreactivities were found throughout postnatal development at the edge of postsynaptic specialization of asymmetrical synapses. These results show that the two group I mGluRs have a differential expression pattern in neocortex and hippocampus that may suggest roles for the receptors in the early processing of cortical information and in the control of cortical developmental events.}, author = {López Bendito, Guillermina and Shigemoto, Ryuichi and Fairén, Alfonso and Luján, Rafael}, issn = {1047-3211}, journal = {Cerebral Cortex}, number = {6}, pages = {625 -- 638}, publisher = {Oxford University Press}, title = {{Differential distribution of group I metabotropic glutamate receptors during rat cortical development}}, doi = {10.1093/cercor/12.6.625}, volume = {12}, year = {2002}, } @article{2617, abstract = {Synapses exhibit different short-term plasticity patterns and this behaviour influences information processing in neuronal networks. We tested how the short-term plasticity of excitatory postsynaptic currents (EPSCs) depends on the postsynaptic cell type, identified by axonal arborizations and molecular markers in the hippocampal CA1 area. Three distinct types of short-term synaptic behaviour (facilitating, depressing and combined facilitating-depressing) were defined by fitting a dynamic neurotransmission model to the data. Approximately 75 % of the oriens-lacunosum-moleculare (O-LM) interneurones received facilitating EPSCs, but in three of 12 O-LM cells EPSCs also showed significant depression. Over 90 % of the O-LM cells were immunopositive for somatostatin and mGluR1α and all tested cells were decorated by strongly mGluR7a positive axon terminals. Responses in eight of 12 basket cells were described well with a model involving only depression, but the other cells displayed combined facilitating-depressing EPSCs. No apparent difference was found between the plasticity of EPSCs in cholecystokinin- or parvalbumin-containing basket cells. In oriens-bistratified cells (O-Bi), two of nine cells showed facilitating EPSCs, another two depressing, and the remaining five cells combined facilitating-depressing EPSCs. Seven of 10 cells tested for somatostatin were immunopositive, but mGluR1α was detectable only in two of 11 tested cells. Furthermore, most O-Bi cells projected to the CA3 area and the subiculum, as well as outside the hippocampal formation. Postsynaptic responses to action potentials recorded in vivo from a CA1 place cell were modelled, and revealed great differences between and within cell types. Our results demonstrate that the short-term plasticity of EPSCs is cell type dependent, but with significant heterogeneity within all three interneurone populations.}, author = {Losonczy, Attila and Zhang, Limei and Ryuichi Shigemoto and Somogyi, Péter and Nusser, Zoltán}, journal = {Journal of Physiology}, number = {1}, pages = {193 -- 210}, publisher = {Wiley-Blackwell}, title = {{Cell type dependence and variability in the short-term plasticity of EPSCs in identified mouse hippocampal interneurones}}, doi = {10.1113/jphysiol.2002.020024}, volume = {542}, year = {2002}, } @article{2618, abstract = {The unipolar brush cell (UBC) is a type of glutamatergic interneuron in the granular layer of the cerebellum. The UBC brush and a single mossy fiber (MF) terminal contact each other within a cerebellar glomerulus, forming a giant synapse. Many UBCs receive input from extrinsic MFs, whereas others are innervated by intrinsic mossy terminals formed by the axons of other UBCs. In all mammalian species so far examined, the vestibulocerebellum is enriched of UBCs that are strongly immunoreactive for the calcium binding protein calretinin (CR) in both the somatodendritic and axonal compartment. UBCs have postsynaptic ionotropic glutamate receptors and extrasynaptic metabotropic glutamate receptors that immunocytochemically highlight their somatodendritic compartment and brush, respectively. In this study on the mouse cerebellum, we present evidence that immunoreactivities to CR and mGluR1α define two distinct UBC subsets with partly overlapping distributions in lobule X (the nodulus). In sections double-labeled for CR and mGluR1α, the patterns of distributions of CR+/mGluR1α- UBCs and CR-/mGluR1α+ UBCs differed along the mediolateral and dorsoventral axes of the folium. Moreover, mGluR1α+ UBCs outnumbered CR+ UBCs. Both UBC subsets were mGluR2/3, GluR2/3, and NMDAR1 immunoreactive. The different distribution patterns of the two UBC subsets within lobule X suggest that expression of CR or mGluR1α by UBCs may be afferent-specific and related to the terminal fields of different vestibular MF afferents.}, author = {Nunzi, Maria and Shigemoto, Ryuichi and Mugnaini, Enrico}, issn = {0021-9967}, journal = {Journal of Comparative Neurology}, number = {2}, pages = {189 -- 199}, publisher = {Wiley-Blackwell}, title = {{Differential expression of calretinin and metabotropic glutamate receptor mGluR1α defines subsets of unipolar brush cells in mouse cerebellum}}, doi = {10.1002/cne.10344}, volume = {451}, year = {2002}, } @article{2619, abstract = {The release of glutamate and GABA is modulated by presynaptic metabotropic glutamate receptors (mGluRs). We used immunocytochemical methods to define the location of the group III receptor mGluR7a in glutamatergic and GABAergic terminals innervating GABAergic interneurons and pyramidal cells. Immunoreactivity for mGluR7a was localized in the presynaptic active zone of both identified GABAergic and presumed glutamatergic terminals. Terminals innervating dendritic spines showed a variable level of receptor immunoreactivity, ranging from immunonegative to strongly immunopositive. The frequency of strongly mGluR7a positive terminals innervating the soma and dendrites of mGluR1α/somatostatin-expressing interneurons was very high relative to other neurons. On dendrites that received mGluR7a-enriched glutamatergic innervation, at least 80% of GABAergic terminals were immunopositive for mGluR7a. On such dendrites virtually all (95%) vasoactive intestinal polypeptide (VIP) positive (GABAergic) terminals were enriched in mGluR7a. The targets of VIP/mGluR7a-expressing terminals were mainly (88%) mGluR1α-expressing interneurons, which were mostly somatostatin immunopositive. Parvalbumin positive terminals were immunonegative for mGluR7a. Some parvalbumin immunoreactive dendrites received strongly mGluR7a positive terminals. The subcellular location, as well as the cell type and synapse-specific distribution of mGluR7a in isocortical neuronal circuits, is homologous to its distribution in the hippocampus. The specific location of mGluR7a in the presynaptic active zone of both glutamatergic and GABAergic synapses may be related to the proximity of calcium channels and the vesicle fusion machinery. The enrichment of mGluR7a in the main GABAergic, as well as in the glutamatergic, innervation of mGluR1α/somatostatin-expressing interneurons suggests that their activation is under unique regulation by extracellular glutamate.}, author = {Dalezios, Yannis and Luján, Rafael and Shigemoto, Ryuichi and Roberts, John and Somogyi, Péter}, issn = {1047-3211}, journal = {Cerebral Cortex}, number = {9}, pages = {961 -- 974}, publisher = {Oxford University Press}, title = {{Enrichment of mGluR7a in the Presynaptic active zones of GABAergic and Non-GABAergic terminals on interneurons in the rat somatosensory cortex}}, doi = {10.1093/cercor/12.9.961}, volume = {12}, year = {2002}, } @article{2620, abstract = {An ion channel's function depends largely on its location and density on neurons. Here we used high-resolution immunolocalization to determine the subcellular distribution of the hyperpolarization-activated and cyclic-nucleotide-gated channel subunit 1 (HCN1) in rat brain. Light microscopy revealed graded HCN1 immunoreactivity in apical dendrites of hippocampal, subicular and neocortical layer-5 pyramidal cells. Quantitative comparison of immunogold densities showed a 60-fold increase from somatic to distal apical dendritic membranes. Distal dendritic shafts had 16 times more HCN1 labeling than proximal dendrites of similar diameters. At the same distance from the soma, the density of HCN1 was significantly higher in dendritic shafts than in spines. Our results reveal the complex cell surface distribution of voltage-gated ion-channels, and predict its role in increasing the computational power of single neurons via subcellular domain and input-specific mechanisms.}, author = {Lörincz, Andrea and Notomi, Takuya and Tamás, Gábor and Shigemoto, Ryuichi and Nusser, Zoltán}, issn = {1097-6256}, journal = {Nature Neuroscience}, number = {11}, pages = {1185 -- 1193}, publisher = {Nature Publishing Group}, title = {{Polarized and compartment-dependent distribution of HCN1 in pyramidal cell dendrites}}, doi = {10.1038/nn962}, volume = {5}, year = {2002}, } @article{2621, abstract = {The release properties of glutamatergic nerve terminals are influenced by a number of factors, including the subtype of voltage-dependent calcium channel and the presence of presynaptic autoreceptors. Group III metabotropic glutamate receptors (mGluRs) mediate feedback inhibition of glutamate release by inhibiting Ca2+ channel activity. By imaging Ca2+ in preparations of cerebrocortical nerve terminals, we show that voltage-dependent Ca2+ channels are distributed in a heterogeneous manner in individual nerve terminals. Presynaptic terminals contained only N-type (47.5%; conotoxin GVIA-sensitive), P/Q-type (3.9%; agatoxin IVA-sensitive), or both N- and P/Q-type (42.6%) Ca2+ channels, although the remainder of the terminals (6.1%) were insensitive to these two toxins. In this preparation, two mGluRs with high and low affinity for L(+)-2-amino-4-phosphonobutyrate were identified by immunocytochemistry as mGluR4 and mGluR7, respectively. These receptors were responsible for 22.2 and 24.1% reduction of glutamate release, and they reduced the Ca2+ response in 24.4 and 30.3% of the nerve terminals, respectively. Interestingly, mGluR4 was largely (73.7%) located in nerve terminals expressing both N- and P/Q-type Ca2+ channels, whereas mGluR7 was predominantly (69.9%) located in N-type Ca2+ channel-expressing terminals. This specific coexpression of different group III mGluRs and Ca2+ channels may endow synaptic terminals with distinct release properties and reveals the existence of a high degree of presynaptic heterogeneity.}, author = {Millán, Carmelo and Luján, Rafael and Shigemoto, Ryuichi and Sánchez Prieto, José}, issn = {0021-9258}, journal = {Journal of Biological Chemistry}, number = {49}, pages = {47796 -- 47803}, publisher = {American Society for Biochemistry and Molecular Biology}, title = {{Subtype-specific expression of Group III metabotropic glutamate receptors and Ca2+ channels in single nerve terminals}}, doi = {10.1074/jbc.M207531200}, volume = {277}, year = {2002}, } @article{2622, abstract = {To understand the possible contribution of metabotropic γ-aminobutyric acid receptors (GABABR) in cortical development, we investigated the expression pattern and the cellular and subcellular localization of the GABABR1 and GABABR2 subtypes in the rat neocortex from embryonic day 14 (E14) to adulthood. At the light microscopic level, both GABABR1 and GABABR2 were detected as early as E14. During prenatal development, both subtypes were expressed highly in the cortical plate. Using double immunofluorescence, GABABR1 colocalized with GABABR2 in neurons of the marginal zone and subplate, indicating that these proteins are coexpressed and could be forming functional GABABRs during prenatal development in vivo. In contrast, only GABABR1 but not GABABR2 was detected in the tangentially migratory cells in the lower intermediate zone. During postnatal development, immunoreactivity for GABABR1 and GABABR2 was distributed mainly in pyramidal cells. Discrete GABABR1-immunopositive cell bodies of interneurons were present throughout the neocortex. In addition, GABABR1 but not GABABR2 was found in identified Cajal-Retzius cells in layer I. At the electron microscopic level, immunoreactivity for GABABR1 and GABABR2 was found in dendritic spines and dendritic shafts at extrasynaptic and perisynaptic sites throughout postnatal development. We further demonstrated the presynaptic localization of GABABR1 and GABABR2, as well as the association of the receptors with asymmetrical synaptic junctions. These results indicate potentially important roles for the GABABRs in the regulation of migratory processes during corticogenesis and in the modulation of synaptic transmission during early development of cortical circuitry.}, author = {López Bendito, Guillermina and Shigemoto, Ryuichi and Kulik, Ákos and Paulsen, Ole and Fairén, Alfonso and Luján, Rafael}, issn = {0953-816X}, journal = {European Journal of Neuroscience}, number = {11}, pages = {1766 -- 1778}, publisher = {Wiley-Blackwell}, title = {{Expression and distribution of metabotropic GABA receptor subtypes GABABR1 and GABABR2 during rat neocortical development}}, doi = {10.1046/j.1460-9568.2002.02032.x}, volume = {15}, year = {2002}, } @article{2624, abstract = {Metabotropic γ-aminobutyric acid receptors (GABABRs) are involved in modulation of synaptic transmission and activity of cerebellar and thalamic neurons. We used subtype-specific antibodies in pre- and postembedding immunohistochemistry combined with three-dimensional reconstruction of labelled profiles and quantification of immunoparticles to reveal the subcellular distribution of pre- and postsynaptic GABABR1a/b and GABABR2 in the rat cerebellum and ventrobasal thalamus. GABABR1a/b and R2 were extensively colocalized in most brain regions including the cerebellum and thalamus. In the cerebellum, immunoreactivity for both subtypes was prevalent in the molecular layer. The most intense immunoreactivity was found in Purkinje cell spines with a high density of immunoparticles at extrasynaptic sites peaking at around 240 nm from glutamatergic synapses between spines and parallel fibre varicosities. This is in contrast to dendrites at sites around GABAergic synapses where sparse and random distribution was found for both subtypes. In addition, more than one-tenth of the synaptic membrane specialization of spine-parallel fibre synapses were labelled at pre- or postsynaptic sites. Weak immunolabelling for both subtypes was also seen in parallel fibres but only rarely in GABAergic axons. In the ventrobasal thalamus, immunolabelling for both receptor subtypes was intense over the dendritic field of thalamocortical cells. Electron microscopy demonstrated an extrasynaptic localization of GABABR1a/b and R2 exclusively in postsynaptic elements. Quantitative analysis further revealed the density of GABABR1a/b around GABAergic synapses was higher than glutamatergic synapses on thalamocortical cell dendrites. The distinct localization of GABABRs relative to synaptic sites in the cerebellum and ventrobasal thalamus suggests that GABABRs differentially regulate activity of different neuronal populations.}, author = {Kulik, Ákos and Nakadate, Kazuhiko and Nyíri, Gábor and Notomi, Takuya and Malitschek, Barbara and Bettler, Bernhard and Shigemoto, Ryuichi}, issn = {0953-816X}, journal = {European Journal of Neuroscience}, number = {2}, pages = {291 -- 307}, publisher = {Wiley-Blackwell}, title = {{Distinct localization of GABAB receptors relative to synaptic sites in the rat cerebellum and ventrobasal thalamus}}, doi = {10.1046/j.0953-816x.2001.01855.x}, volume = {15}, year = {2002}, } @inbook{2694, abstract = {We outline the status of rigorous derivations of certain classical evolution equations as limits of Schrödinger dynamics. We explain two recent results jointly with H.T. Yau in more details. The first one is the derivation of the linear Boltzmann equation as the long time limit of the one-body Schrödinger equation with a random potential. The second one is the mean field limit of high density bosons with Coulomb interaction that leads to the nonlinear Hartree equation.}, author = {Erdös, László}, booktitle = {Dynamics of Dissipation}, isbn = {9783540441113}, pages = {487 -- 506}, publisher = {Springer}, title = {{Scaling limits of Schrödinger quantum mechanics}}, doi = {10.1007/3-540-46122-1_19}, year = {2002}, } @inproceedings{2708, author = {László Erdös}, pages = {129 -- 133}, publisher = {World Scientific Publishing}, title = {{Two dimensional Pauli operator via scalar potential}}, doi = {10.1090/conm/307}, volume = {307}, year = {2002}, } @article{2737, abstract = {We derive the time-dependent Schrödinger–Poisson equation as the weak coupling limit of the N-body linear Schrödinger equation with Coulomb potential.}, author = {Bardos, Claude and Erdös, László and Golse, François and Mauser, Norbert and Yau, Horng}, issn = {1631-073X}, journal = {Comptes Rendus Mathematique}, number = {6}, pages = {515 -- 520}, publisher = {Elsevier}, title = {{Derivation of the Schrödinger-Poisson equation from the quantum N-body problem}}, doi = {10.1016/S1631-073X(02)02253-7}, volume = {334}, year = {2002}, } @article{2738, abstract = {We consider the long time evolution of a quantum particle weakly interacting with a phonon field. We show that in the weak coupling limit the Wigner distribution of the electron density matrix converges to the solution of the linear Boltzmann equation globally in time. The collision kernel is identified as the sum of an emission and an absorption term that depend on the equilibrium distribution of the free phonon modes.}, author = {Erdös, László}, issn = {0022-4715}, journal = {Journal of Statistical Physics}, number = {5-6}, pages = {1043 -- 1127}, publisher = {Springer}, title = {{Linear Boltzmann equation as the long time dynamics of an electron weakly coupled to a phonon field}}, doi = {10.1023/A:1015157624384}, volume = {107}, year = {2002}, } @article{2739, abstract = {We define the two dimensional Pauli operator and identify its core for magnetic fields that are regular Borel measures. The magnetic field is generated by a scalar potential hence we bypass the usual A L 2loc condition on the vector potential, which does not allow to consider such singular fields. We extend the Aharonov-Casher theorem for magnetic fields that are measures with finite total variation and we present a counterexample in case of infinite total variation. One of the key technical tools is a weighted L 2 estimate on a singular integral operator.}, author = {Erdös, László and Vougalter, Vitali}, issn = {0010-3616}, journal = {Communications in Mathematical Physics}, number = {2}, pages = {399 -- 421}, publisher = {Springer}, title = {{Pauli operator and Aharonov–Casher theorem¶ for measure valued magnetic fields}}, doi = {10.1007/s002200100585}, volume = {225}, year = {2002}, } @article{2740, abstract = {We show that the lowest eigenvalue of the magnetic Schrödinger operator on a line bundle over a compact Riemann surface M is bounded by the L1-norm of the magnetic field B. This implies a similar bound on the multiplicity of the ground state. An example shows that this degeneracy can indeed be comparable with ∫M |B| even in case of the trivial bundle.}, author = {Erdös, László}, issn = {0373-0956}, journal = {Annales de l'Institut Fourier}, number = {6}, pages = {1833--1874}, publisher = {Association des Annales de l'Institut Fourier}, title = {{Spectral shift and multiplicity of the first eigenvalue of the magnetic Schrödinger operator in two dimensions}}, doi = {10.5802/aif.1936}, volume = {52}, year = {2002}, } @article{2866, abstract = {Developmental responses to the plant hormone auxin are thought to be mediated by interacting pairs from two protein families: short-lived inhibitory IAA proteins and ARF transcription factors binding to auxin-response elements. Monopteros mutants lacking activating ARF5 and the auxin-insensitive mutant bodenlos fail to initiate the root meristem during early embryogenesis. Here we show that the bodenlos phenotype results from an amino-acid exchange in the conserved degradation domain of IAA12. BODENLOS and MONOPTEROS interact in the yeast two-hybrid assay and the two genes are coexpressed in early embryogenesis, suggesting that BODENLOS inhibits MONOPTEROS action in root meristem initiation.}, author = {Hamann, Thorsten and Benková, Eva and Bäurle, Isabel and Kientz, Marika and Jürgens, Gerd}, issn = {0890-9369}, journal = {Genes and Development}, number = {13}, pages = {1610 -- 1615}, publisher = {Cold Spring Harbor Laboratory Press}, title = {{The Arabidopsis BODENLOS gene encodes an auxin response protein inhibiting MONOPTEROS-mediated embryo patterning}}, doi = {10.1101/gad.229402}, volume = {16}, year = {2002}, } @inproceedings{2927, abstract = {In the last few years, several new algorithms based on graph cuts have been developed to solve energy minimization problems in computer vision. Each of these techniques constructs a graph such that the minimum cut on the graph also minimizes the energy. Yet because these graph constructions are complex and highly specific to a particular energy function, graph cuts have seen limited application to date. In this paper we characterize the energy functions that can be minimized by graph cuts. Our results are restricted to energy functions with binary variables. However, our work generalizes many previous constructions, and is easily applicable to vision problems that involve large numbers of labels, such as stereo, motion, image restoration and scene reconstruction. We present three main results: a necessary condition for any energy function that can be minimized by graph cuts; a sufficient condition for energy functions that can be written as a sum of functions of up to three variables at a time; and a general-purpose construction to minimize such an energy function. Researchers who are considering the use of graph cuts to optimize a particular energy function can use our results to determine if this is possible, and then follow our construction to create the appropriate graph.}, author = {Kolmogorov, Vladimir and Zabih, Ramin}, booktitle = {Proceedings of the 7th European Conference on Computer Vision}, isbn = {9783540437468}, location = {Copenhagen, Denmark}, pages = {65 -- 81}, publisher = {Springer}, title = {{Multi-camera scene reconstruction via graph cuts}}, doi = {10.1007/3-540-47977-5_5}, year = {2002}, } @article{2986, abstract = {Long-standing models propose that plant growth responses to light or gravity are mediated by asymmetric distribution of the phytohormone auxin. Physiological studies implicated a specific transport system that relocates auxin laterally, thereby effecting differential growth; however, neither the molecular components of this system nor the cellular mechanism of auxin redistribution on light or gravity perception have been identified. Here, we show that auxin accumulates asymmetrically during differential growth in an efflux-dependent manner. Mutations in the Arabidopsis gene PIN3, a regulator of auxin efflux, alter differential growth. PIN3 is expressed in gravity-sensing tissues, with PIN3 protein accumulating predominantly at the lateral cell surface. PIN3 localizes to the plasma membrane and to vesicles that cycle in an actin-dependent manner. In the root columella, PIN3 is positioned symmetrically at the plasma membrane but rapidly relocalizes laterally on gravity stimulation. Our data indicate that PIN3 is a component of the lateral auxin transport system regulating tropic growth. In addition, actin-dependent relocalization of PIN3 in response to gravity provides a mechanism for redirecting auxin flux to trigger asymmetric growth.}, author = {Friml, Jirí and Wiśniewska, Justyna and Benková, Eva and Mendgen, Kurt and Palme, Klaus}, issn = {0028-0836}, journal = {Nature}, number = {6873}, pages = {806 -- 809}, publisher = {Nature Publishing Group}, title = {{Lateral relocation of auxin efflux regulator PIN3 mediates tropism in Arabidopsis}}, doi = {10.1038/415806a}, volume = {415}, year = {2002}, } @article{2987, abstract = {The hydra mutants of Arabidopsis are characterized by a pleiotropic phenotype that shows defective embryonic and seedling cell patterning, morphogenesis, and root growth. We demonstrate that the HYDRA1 gene encodes a Δ8-Δ7 sterol isomerase, whereas HYDRA2 encodes a sterol C14 reductase, previously identified as the FACKEL gene product. Seedlings mutant for each gene are similarly defective in the concentrations of the three major Arabidopsis sterols. Promoter::reporter gene analysis showed misexpression of the auxin-regulated DR5 and ACS1 promoters and of the epidermal cell file-specific GL2 promoter in the mutants. The mutants exhibit enhanced responses to auxin. The phenotypes can be rescued partially by inhibition of auxin and ethylene signaling but not by exogenous sterols or brassinosteroids. We propose a model in which correct sterol profiles are required for regulated auxin and ethylene signaling through effects on membrane function.}, author = {Souter, Martin and Topping, Jennifer and Pullen, Margaret and Friml, Jirí and Palme, Klaus and Hackett, Rachel and Grierson, Don and Lindsey, Keith}, issn = {1040-4651}, journal = {Plant Cell}, number = {5}, pages = {1017 -- 1031}, publisher = {American Society of Plant Biologists}, title = {{Hydra mutants of Arabidopsis are defective in sterol profiles and auxin and ethylene signaling}}, doi = {10.1105/tpc.001248}, volume = {14}, year = {2002}, } @article{2988, abstract = {Coordination of cell and tissue polarity commonly involves directional signaling [1]. In the Arabidopsis root epidermis, cell polarity is revealed by basal, root tip-oriented, hair outgrowth from hair-forming cells (trichoblasts) [2]. The plant hormone auxin displays polar movements [1, 3] and accumulates at maximum concentration in the root tip [4, 5]. The application of polar auxin transport inhibitors [3] evokes changes in trichoblast polarity only at high concentrations and after long-term application [2, 4]. Thus, it remains open whether components of the auxin transport machinery mediate establishment of trichoblast polarity. Here we report that the presumptive auxin influx carrier AUX1 [6, 7] contributes to apical-basal hair cell polarity. AUX1 function is required for polarity changes induced by exogenous application of the auxin 2,4-D, a preferential influx carrier substrate. Similar to aux1 mutants, the vesicle trafficking inhibitor brefeldin A (BFA) interferes with polar hair initiation, and AUX1 function is required for BFA-mediated polarity changes. Consistently, BFA inhibits membrane trafficking of AUX1, trichoblast hyperpolarization induced by 2,4-D, and alters the distal auxin maximum. Our results identify AUX1 as one component of a novel BFA-sensitive auxin transport pathway polarizing cells toward a hormone maximum.}, author = {Grebe, Markus and Friml, Jirí and Swarup, Ranjan and Ljung, Karin and Sandberg, Göran and Terlou, Maarten and Palme, Klaus and Bennett, Malcolm and Scheres, Ben}, issn = {0960-9822}, journal = {Current Biology}, number = {4}, pages = {329 -- 334}, publisher = {Cell Press}, title = {{Cell polarity signaling in Arabidopsis involves a BFA sensitive auxin influx pathway}}, doi = {10.1016/S0960-9822(02)00654-1}, volume = {12}, year = {2002}, } @article{2989, abstract = {In contrast to animals, little is known about pattern formation in plants. Physiological and genetic data suggest the involvement of the phytohormone auxin in this process. Here, we characterize a novel member of the PIN family of putative auxin efflux carriers, Arabidopsis PIN4, that is localized in developing and mature root meristems. Atpin4 mutants are defective in establishment and maintenance of endogenous auxin gradients, fail to canalize externally applied auxin, and display various patterning defects in both embryonic and seedling roots. We propose a role for AtPIN4 in generating a sink for auxin below the quiescent center of the root meristem that is essential for auxin distribution and patterning.}, author = {Friml, Jirí and Benková, Eva and Blilou, Ikram and Wiśniewska, Justyna and Hamann, Thorsten and Ljung, Karin and Woody, Scott and Sandberg, Göran and Scheres, Ben and Jürgens, Gerd and Palme, Klaus}, issn = {0092-8674}, journal = {Cell}, number = {5}, pages = {661 -- 673}, publisher = {Cell Press}, title = {{AtPIN4 mediates sink-driven auxin gradients and root patterning in Arabidopsis}}, doi = {10.1016/S0092-8674(02)00656-6}, volume = {108}, year = {2002}, }