@inproceedings{2976, abstract = {Side channel attacks on cryptographic systems exploit information gained from physical implementations rather than theoretical weaknesses of a scheme. In recent years, major achievements were made for the class of so called access-driven cache attacks. Such attacks exploit the leakage of the memory locations accessed by a victim process. In this paper we consider the AES block cipher and present an attack which is capable of recovering the full secret key in almost realtime for AES-128, requiring only a very limited number of observed encryptions. Unlike previous attacks, we do not require any information about the plaintext (such as its distribution, etc.). Moreover, for the first time, we also show how the plaintext can be recovered without having access to the ciphertext at all. It is the first working attack on AES implementations using compressed tables. There, no efficient techniques to identify the beginning of AES rounds is known, which is the fundamental assumption underlying previous attacks. We have a fully working implementation of our attack which is able to recover AES keys after observing as little as 100 encryptions. It works against the OpenSSL 0.9.8n implementation of AES on Linux systems. Our spy process does not require any special privileges beyond those of a standard Linux user. A contribution of probably independent interest is a denial of service attack on the task scheduler of current Linux systems (CFS), which allows one to observe (on average) every single memory access of a victim process.}, author = {Gullasch, David and Bangerter, Endre and Stephan Krenn}, pages = {490 -- 505}, publisher = {IEEE}, title = {{Cache Games - Bringing Access-Based Cache Attacks on AES to Practice}}, doi = {10.1109/SP.2011.22}, year = {2011}, } @inproceedings{2977, abstract = {Cryptographic two-party protocols are used ubiquitously in everyday life. While some of these protocols are easy to understand and implement (e.g., key exchange or transmission of encrypted data), many of them are much more complex (e.g., e-banking and e-voting applications, or anonymous authentication and credential systems). For a software engineer without appropriate cryptographic skills the implementation of such protocols is often difficult, time consuming and error-prone. For this reason, a number of compilers supporting programmers have been published in recent years. However, they are either designed for very specific cryptographic primitives (e.g., zero-knowledge proofs of knowledge), or they only offer a very low level of abstraction and thus again demand substantial mathematical and cryptographic skills from the programmer. Finally, some of the existing compilers do not produce executable code, but only metacode which has to be instantiated with mathematical libraries, encryption routines, etc. before it can actually be used. In this paper we present a cryptographically aware compiler which is equally useful to cryptographers who want to benchmark protocols designed on paper, and to programmers who want to implement complex security sensitive protocols without having to understand all subtleties. Our tool offers a high level of abstraction and outputs well-structured and documented Java code. We believe that our compiler can contribute to shortening the development cycles of cryptographic applications and to reducing their error-proneness.}, author = {Bangerter, Endre and Stephan Krenn and Seifriz, Martial and Ultes-Nitsche, Ulrich}, editor = {Venter, Hein S. and Coetzee, Marijke and Loock, Marianne}, publisher = {IEEE}, title = {{cPLC - A Cryptographic Programming Language and Compiler}}, doi = {10.1109/ISSA.2011.6027533}, year = {2011}, } @article{3082, abstract = {Shoot branching is one of the major determinants of plant architecture. Polar auxin transport in stems is necessary for the control of bud outgrowth by a dominant apex. Here, we show that following decapitation in pea (Pisum sativum L.), the axillary buds establish directional auxin export by subcellular polarization of PIN auxin transporters. Apical auxin application on the decapitated stem prevents this PIN polarization and canalization of laterally applied auxin. These results support a model in which the apical and lateral auxin sources compete for primary channels of auxin transport in the stem to control the outgrowth of axillary buds.}, author = {Balla, Jozef and Kalousek, Petr and Reinöhl, Vilém and Jirí Friml and Procházka, Stanislav}, journal = {Plant Journal}, number = {4}, pages = {571 -- 577}, publisher = {Wiley-Blackwell}, title = {{Competitive canalization of PIN dependent auxin flow from axillary buds controls pea bud outgrowth}}, doi = {10.1111/j.1365-313X.2010.04443.x}, volume = {65}, year = {2011}, } @article{3083, author = {Robinson, David G and Scheuring, David and Naramoto, Satoshi and Jirí Friml}, journal = {Plant Cell}, number = {3}, pages = {846 -- 849}, publisher = {American Society of Plant Biologists}, title = {{ARF1 localizes to the golgi and the trans Golgi network}}, doi = {10.1105/tpc.110.082099}, volume = {23}, year = {2011}, } @article{3084, abstract = { A central question in developmental biology concerns the mechanism of generation and maintenance of cell polarity, because these processes are essential for many cellular functions and multicellular development [1]. In plants, cell polarity has an additional role in mediating directional transport of the plant hormone auxin that is crucial for multiple developmental processes [2-4]. In addition, plant cells have a complex extracellular matrix, the cell wall [5, 6], whose role in regulating cellular processes, including cell polarity, is unexplored. We have found that polar distribution of PIN auxin transporters [7] in plant cells is maintained by connections between polar domains at the plasma membrane and the cell wall. Genetic and pharmacological interference with cellulose, the major component of the cell wall, or mechanical interference with the cell wall disrupts these connections and leads to increased lateral diffusion and loss of polar distribution of PIN transporters for the phytohormone auxin. Our results reveal a plant-specific mechanism for cell polarity maintenance and provide a conceptual framework for modulating cell polarity and plant development via endogenous and environmental manipulations of the cellulose-based extracellular matrix.}, author = {Feraru, Elena and Feraru, Mugurel I and Kleine-Vehn, Jürgen and Martinière, Alexandre and Mouille, Grégory and Vanneste, Steffen and Vernhettes, Samantha and Runions, John and Jirí Friml}, journal = {Current Biology}, number = {4}, pages = {338 -- 343}, publisher = {Cell Press}, title = {{PIN polarity maintenance by the cell wall in Arabidopsis}}, doi = {10.1016/j.cub.2011.01.036}, volume = {21}, year = {2011}, } @article{3085, abstract = {Phototropism is an adaptation response, through which plants grow towards the light. It involves light perception and asymmetric distribution of the plant hormone auxin. Here we identify a crucial part of the mechanism for phototropism, revealing how light perception initiates auxin redistribution that leads to directional growth. We show that light polarizes the cellular localization of the auxin efflux carrier PIN3 in hypocotyl endodermis cells, resulting in changes in auxin distribution and differential growth. In the dark, high expression and activity of the PINOID (PID) kinase correlates with apolar targeting of PIN3 to all cell sides. Following illumination, light represses PINOID transcription and PIN3 is polarized specifically to the inner cell sides by GNOM ARF GTPase GEF (guanine nucleotide exchange factor)-dependent trafficking. Thus, differential trafficking at the shaded and illuminated hypocotyl side aligns PIN3 polarity with the light direction, and presumably redirects auxin flow towards the shaded side, where auxin promotes growth, causing hypocotyls to bend towards the light. Our results imply that PID phosphorylation-dependent recruitment of PIN proteins into distinct trafficking pathways is a mechanism to polarize auxin fluxes in response to different environmental and endogenous cues.}, author = {Ding, Zhaojun and Galván-Ampudia, Carlos S and Demarsy, Emilie and Łangowski, Łukasz and Kleine-Vehn, Jürgen and Fan, Yuanwei and Morita, Miyo T and Tasaka, Masao and Fankhauser, Christian and Offringa, Remko and Jirí Friml}, journal = {Nature Cell Biology}, number = {4}, pages = {447 -- 453}, publisher = {Nature Publishing Group}, title = {{Light-mediated polarization of the PIN3 auxin transporter for the phototropic response in Arabidopsis}}, doi = {10.1038/ncb2208}, volume = {13}, year = {2011}, } @article{3086, abstract = {PIN-FORMED (PIN)-dependent auxin transport is essential for plant development and its modulation in response to the environment or endogenous signals. A NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3)-like protein, MACCHI-BOU 4 (MAB4), has been shown to control PIN1 localization during organ formation, but its contribution is limited. The Arabidopsis genome contains four genes, MAB4/ENP/NPY1-LIKE1 (MEL1), MEL2, MEL3 and MEL4, highly homologous to MAB4. Genetic analysis disclosed functional redundancy between MAB4 and MEL genes in regulation of not only organ formation but also of root gravitropism, revealing that NPH3 family proteins have a wider range of functions than previously suspected. Multiple mutants showed severe reduction in PIN abundance and PIN polar localization, leading to defective expression of an auxin responsive marker DR5rev::GFP. Pharmacological analyses and fluorescence recovery after photo-bleaching experiments showed that mel mutations increase PIN2 internalization from the plasma membrane, but affect neither intracellular PIN2 trafficking nor PIN2 lateral diffusion at the plasma membrane. Notably, all MAB4 subfamily proteins show polar localization at the cell periphery in plants. The MAB4 polarity was almost identical to PIN polarity. Our results suggest that the MAB4 subfamily proteins specifically retain PIN proteins in a polarized manner at the plasma membrane, thus controlling directional auxin transport and plant development.}, author = {Furutani, Masahiko and Sakamoto, Norihito and Yoshida, Shuhei and Kajiwara, Takahito and Robert, Hélène S and Jirí Friml and Tasaka, Masao}, journal = {Development}, number = {10}, pages = {2069 -- 2078}, publisher = {Company of Biologists}, title = {{Polar localized NPH3-like proteins regulate polarity and endocytosis of PIN-FORMED auxin efflux carriers}}, doi = {10.1242/dev.057745}, volume = {138}, year = {2011}, } @article{3087, abstract = {Endocytosis is a crucial mechanism by which eukaryotic cells internalize extracellular and plasma membrane material, and it is required for a multitude of cellular and developmental processes in unicellular and multicellular organisms. In animals and yeast, the best characterized pathway for endocytosis depends on the function of the vesicle coat protein clathrin. Clathrinmediated endocytosis has recently been demonstrated also in plant cells, but its physiological and developmental roles remain unclear. Here, we assessed the roles of the clathrin-mediated mechanism of endocytosis in plants by genetic means. We interfered with clathrin heavy chain (CHC) function through mutants and dominant-negative approaches in Arabidopsis thaliana and established tools to manipulate clathrin function in a cell type-specific manner. The chc2 single mutants and dominant-negative CHC1 (HUB) transgenic lines were defective in bulk endocytosis as well as in internalization of prominent plasma membrane proteins. Interference with clathrin-mediated endocytosis led to defects in constitutive endocytic recycling of PIN auxin transporters and their polar distribution in embryos and roots. Consistent with this, these lines had altered auxin distribution patterns and associated auxin transport-related phenotypes, such as aberrant embryo patterning, imperfect cotyledon specification, agravitropic growth, and impaired lateral root organogenesis. Together, these data demonstrate a fundamental role for clathrin function in cell polarity, growth, patterning, and organogenesis in plants.}, author = {Kitakura, Saeko and Vanneste, Steffen and Robert, Stéphanie and Löfke, Christian and Teichmann, Thomas and Tanaka, Hirokazu and Jirí Friml}, journal = {Plant Cell}, number = {5}, pages = {1920 -- 1931}, publisher = {American Society of Plant Biologists}, title = {{Clathrin mediates endocytosis and polar distribution of PIN auxin transporters in Arabidopsis}}, doi = {10.1105/tpc.111.083030}, volume = {23}, year = {2011}, } @article{3088, abstract = {Background: Whereas the majority of animals develop toward a predetermined body plan, plants show iterative growth and continually produce new organs and structures from actively dividing meristems. This raises an intriguing question: How are these newly developed organs patterned? In Arabidopsis embryos, radial symmetry is broken by the bisymmetric specification of the cotyledons in the apical domain. Subsequently, this bisymmetry is propagated to the root promeristem. Results: Here we present a mutually inhibitory feedback loop between auxin and cytokinin that sets distinct boundaries of hormonal output. Cytokinins promote the bisymmetric distribution of the PIN-FORMED (PIN) auxin efflux proteins, which channel auxin toward a central domain. High auxin promotes transcription of the cytokinin signaling inhibitor AHP6, which closes the interaction loop. This bisymmetric auxin response domain specifies the differentiation of protoxylem in a bisymmetric pattern. In embryonic roots, cytokinin is required to translate a bisymmetric auxin response in the cotyledons to a bisymmetric vascular pattern in the root promeristem. Conclusions: Our results present an interactive feedback loop between hormonal signaling and transport by which small biases in hormonal input are propagated into distinct signaling domains to specify the vascular pattern in the root meristem. It is an intriguing possibility that such a mechanism could transform radial patterns and allow continuous vascular connections between other newly emerging organs.}, author = {Bishopp, Anthony and Help, Hanna and El-Showk, Sedeer and Weijers, Dolf and Scheres, Ben and Jirí Friml and Eva Benková and Mähönen, Ari Pekka and Helariutta, Ykä}, journal = {Current Biology}, number = {11}, pages = {917 -- 926}, publisher = {Cell Press}, title = {{A mutually inhibitory interaction between auxin and cytokinin specifies vascular pattern in roots}}, doi = {10.1016/j.cub.2011.04.017}, volume = {21}, year = {2011}, } @article{3089, abstract = {The phytohormone auxin is an important determinant of plant development. Directional auxin flow within tissues depends on polar localization of PIN auxin transporters. To explore regulation of PIN-mediated auxin transport, we screened for suppressors of PIN1 overexpression (supo) and identified an inositol polyphosphate 1-phosphatase mutant (supo1), with elevated inositol trisphosphate (InsP 3) and cytosolic Ca 2+ levels. Pharmacological and genetic increases in InsP 3 or Ca 2+ levels also suppressed the PIN1 gain-of-function phenotypes and caused defects in basal PIN localization, auxin transport and auxin-mediated development. In contrast, the reductions in InsP 3 levels and Ca 2+ signaling antagonized the effects of the supo1 mutation and disrupted preferentially apical PIN localization. InsP 3 and Ca 2+ are evolutionarily conserved second messengers involved in various cellular functions, particularly stress responses. Our findings implicate them as modifiers of cell polarity and polar auxin transport, and highlight a potential integration point through which Ca 2+ signaling-related stimuli could influence auxin-mediated development.}, author = {Zhang, Jing and Vanneste, Steffen and Brewer, Philip B and Michniewicz, Marta and Peter Grones and Kleine-Vehn, Jürgen and Löfke, Christian and Teichmann, Thomas and Bielach, Agnieszka and Cannoot, Bernard and Hoyerová, Klára and Xu Chen and Xue, Hong-Wei and Eva Benková and Zažímalová, Eva and Jirí Friml}, journal = {Developmental Cell}, number = {6}, pages = {855 -- 866}, publisher = {Cell Press}, title = {{Inositol trisphosphate-induced ca^2+ signaling modulates auxin transport and pin polarity}}, doi = {10.1016/j.devcel.2011.05.013}, volume = {20}, year = {2011}, } @article{3090, abstract = {The polarized transport of the phytohormone auxin [1], which is crucial for the regulation of different stages of plant development [2, 3], depends on the asymmetric plasma membrane distribution of the PIN-FORMED (PIN) auxin efflux carriers [4, 5]. The PIN polar localization results from clathrin-mediated endocytosis (CME) from the plasma membrane and subsequent polar recycling [6]. The Arabidopsis genome encodes two groups of dynamin-related proteins (DRPs) that show homology to mammalian dynamin - a protein required for fission of endocytic vesicles during CME [7, 8]. Here we show by coimmunoprecipitation (coIP), bimolecular fluorescence complementation (BiFC), and Förster resonance energy transfer (FRET) that members of the DRP1 group closely associate with PIN proteins at the cell plate. Localization and phenotypic analysis of novel drp1 mutants revealed a requirement for DRP1 function in correct PIN distribution and in auxin-mediated development. We propose that rapid and specific internalization of PIN proteins mediated by the DRP1 proteins and the associated CME machinery from the cell plate membranes during cytokinesis is an important mechanism for proper polar PIN positioning in interphase cells.}, author = {Mravec, Jozef and Petrášek, Jan and Li, Na and Boeren, Sjef and Karlova, Rumyana and Kitakura, Saeko and Pařezová, Markéta and Naramoto, Satoshi and Nodzyński, Thomasz and Dhonukshe, Pankaj and Bednarek, Sebastian Y and Zažímalová, Eva and De Vries, Sacco and Jirí Friml}, journal = {Current Biology}, number = {12}, pages = {1055 -- 1060}, publisher = {Cell Press}, title = {{Cell plate restricted association of DRP1A and PIN proteins is required for cell polarity establishment in arabidopsis}}, doi = {10.1016/j.cub.2011.05.018}, volume = {21}, year = {2011}, } @article{3091, author = {Sauer, Michael and Friml, Jirí}, journal = {Molecular Systems Biology}, publisher = {Nature Publishing Group}, title = {{Fleeting hormone cues get stabilized for plant organogenesis}}, doi = {10.1038/msb.2011.45}, volume = {7}, year = {2011}, } @article{3092, abstract = {The phytohormone auxin is vital to plant growth and development. A unique property of auxin among all other plant hormones is its cell-to-cell polar transport that requires activity of polarly localized PIN-FORMED (PIN) auxin efflux transporters. Despite the substantial molecular insight into the cellular PIN polarization, the mechanistic understanding for developmentally and environmentally regulated PIN polarization is scarce. The long-standing belief that auxin modulates its own transport by means of a positive feedback mechanism has inspired both experimentalists and theoreticians for more than two decades. Recently, theoretical models for auxin-dependent patterning in plants include the feedback between auxin transport and the PIN protein localization. These computer models aid to assess the complexity of plant development by testing and predicting plausible scenarios for various developmental processes that occur in planta. Although the majority of these models rely on purely heuristic principles, the most recent mechanistic models tentatively integrate biologically testable components into known cellular processes that underlie the PIN polarity regulation. The existing and emerging computational approaches to describe PIN polarization are presented and discussed in the light of recent experimental data on the PIN polar targeting.}, author = {Wabnik, Krzysztof T and Govaerts, Willy and Friml, Jirí and Kleine Vehn, Jürgen}, journal = {Molecular BioSystems}, number = {8}, pages = {2352 -- 2359}, publisher = {Royal Society of Chemistry}, title = {{Feedback models for polarized auxin transport: An emerging trend}}, doi = {10.1039/c1mb05109a}, volume = {7}, year = {2011}, } @article{3093, abstract = { Plants take up iron from the soil using the IRON-REGULATED TRANSPORTER 1 (IRT1) high-affinity iron transporter at the root surface. Sophisticated regulatory mechanisms allow plants to tightly control the levels of IRT1, ensuring optimal absorption of essential but toxic iron. Here, we demonstrate that overexpression of Arabidopsis thaliana IRT1 leads to constitutive IRT1 protein accumulation, metal overload, and oxidative stress. IRT1 is unexpectedly found in trans-Golgi network/early endosomes of root hair cells, and its levels and localization are unaffected by iron nutrition. Using pharmacological approaches, we show that IRT1 cycles to the plasma membrane to perform iron and metal uptake at the cell surface and is sent to the vacuole for proper turnover. We also prove that IRT1 is monoubiquitinated on several cytosol-exposed residues in vivo and that mutation of two putative monoubiquitination target residues in IRT1 triggers stabilization at the plasma membrane and leads to extreme lethality. Together, these data suggest a model in which monoubiquitin-dependent internalization/sorting and turnover keep the plasma membrane pool of IRT1 low to ensure proper iron uptake and to prevent metal toxicity. More generally, our work demonstrates the existence of monoubiquitin-dependent trafficking to lytic vacuoles in plants and points to proteasome-independent turnover of plasma membrane proteins.}, author = {Barberon, Marie and Zelazny, Enric and Robert, Stéphanie and Conéjéro, Geneviève and Curie, Cathy and Jirí Friml and Vert, Grégory}, journal = {PNAS}, number = {32}, pages = {E450 -- E458}, publisher = {National Academy of Sciences}, title = {{Monoubiquitin dependent endocytosis of the Iron Regulated Transporter 1 IRT1 transporter controls iron uptake in plants}}, doi = {10.1073/pnas.1100659108}, volume = {108}, year = {2011}, } @article{3094, abstract = {Summary Gravitropism aligns plant growth with gravity. It involves gravity perception and the asymmetric distribution of the phytohormone auxin. Here we provide insights into the mechanism for hypocotyl gravitropic growth. We show that the Arabidopsis thaliana PIN3 auxin transporter is required for the asymmetric auxin distribution for the gravitropic response. Gravistimulation polarizes PIN3 to the bottom side of hypocotyl endodermal cells, which correlates with an increased auxin response at the lower hypocotyl side. Both PIN3 polarization and hypocotyl bending require the activity of the trafficking regulator GNOM and the protein kinase PINOID. Our data suggest that gravity-induced PIN3 polarization diverts the auxin flow to mediate the asymmetric distribution of auxin for gravitropic shoot bending.}, author = {Rakusová, Hana and Gallego-Bartolomé, Javier and Vanstraelen, Marleen and Robert, Hélène S and Alabadí, David and Blázquez, Miguel A and Eva Benková and Jirí Friml}, journal = {Plant Journal}, number = {5}, pages = {817 -- 826}, publisher = {Wiley-Blackwell}, title = {{Polarization of PIN3 dependent auxin transport for hypocotyl gravitropic response in Arabidopsis thaliana}}, doi = {10.1111/j.1365-313X.2011.04636.x}, volume = {67}, year = {2011}, } @article{3095, abstract = {Root system architecture depends on lateral root (LR) initiation that takes place in a relatively narrow developmental window (DW). Here, we analyzed the role of auxin gradients established along the parent root in defining this DW for LR initiation. Correlations between auxin distribution and response, and spatiotemporal control of LR initiation were analyzed in Arabidopsis thaliana and tomato (Solanum lycopersicum). In both Arabidopsis and tomato roots, a well defined zone, where auxin content and response are minimal, demarcates the position of a DW for founder cell specification and LR initiation. We show that in the zone of auxin minimum pericycle cells have highest probability to become founder cells and that auxin perception via the TIR1/AFB pathway, and polar auxin transport, are essential for the establishment of this zone. Altogether, this study reveals that the same morphogen-like molecule, auxin, can act simultaneously as a morphogenetic trigger of LR founder cell identity and as a gradient-dependent signal defining positioning of the founder cell specification. This auxin minimum zone might represent an important control mechanism ensuring the LR initiation steadiness and the acropetal LR initiation pattern. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.}, author = {Dubrovsky, Joseph G and Napsucialy-Mendivil, Selene and Duclercq, Jérôme and Cheng, Yan and Shishkova, Svetlana O and Ivanchenko, Maria G and Jirí Friml and Murphy, Angus S and Eva Benková}, journal = {New Phytologist}, number = {4}, pages = {970 -- 983}, publisher = {Wiley-Blackwell}, title = {{Auxin minimum defines a developmental window for lateral root initiation}}, doi = { 10.1111/j.1469-8137.2011.03757.x}, volume = {191}, year = {2011}, } @article{3096, abstract = {Carrier-dependent, intercellular auxin transport is central to the developmental patterning of higher plants (tracheophytes). The evolution of this polar auxin transport might be linked to the translocation of some PIN auxin efflux carriers from their presumably ancestral localization at the endoplasmic reticulum (ER) to the polar domains at the plasma membrane. Here we propose an eventually ancient mechanism of intercellular auxin distribution by ER-localized auxin transporters involving intracellular auxin retention and switch-like release from the ER. The proposed model integrates feedback circuits utilizing the conserved nuclear auxin signaling for the regulation of PIN transcription and a hypothetical ER-based signaling for the regulation of PIN-dependent transport activity at the ER. Computer simulations of the model revealed its plausibility for generating auxin channels and localized auxin maxima highlighting the possibility of this alternative mechanism for polar auxin transport.}, author = {Wabnik, Krzysztof T and Kleine Vehn, Jürgen and Govaerts, Willy and Friml, Jirí}, journal = {Trends in Plant Science}, number = {9}, pages = {468 -- 475}, publisher = {Cell Press}, title = {{Prototype cell-to-cell auxin transport mechanism by intracellular auxin compartmentalization}}, doi = {10.1016/j.tplants.2011.05.002}, volume = {16}, year = {2011}, } @article{3097, abstract = {Cytokinin is an important regulator of plant growth and development. In Arabidopsis thaliana, the two-component phosphorelay mediated through a family of histidine kinases and response regulators is recognized as the principal cytokinin signal transduction mechanism activating the complex transcriptional response to control various developmental processes. Here, we identified an alternative mode of cytokinin action that uses endocytic trafficking as a means to direct plant organogenesis. This activity occurs downstream of known cytokinin receptors but through a branch of the cytokinin signaling pathway that does not involve transcriptional regulation. We show that cytokinin regulates endocytic recycling of the auxin efflux carrier PINFORMED1 (PIN1) by redirecting it for lytic degradation in vacuoles. Stimulation of the lytic PIN1 degradation is not a default effect for general downregulation of proteins from plasma membranes, but a specific mechanism to rapidly modulate the auxin distribution in cytokinin-mediated developmental processes.}, author = {Peter Marhavy and Bielach, Agnieszka and Abas, Lindy and Abuzeineh, Anas and Duclercq, Jérôme and Tanaka, Hirokazu and Pařezová, Markéta and Petrášek, Jan and Jirí Friml and Kleine-Vehn, Jürgen and Eva Benková}, journal = {Developmental Cell}, number = {4}, pages = {796 -- 804}, publisher = {Cell Press}, title = {{Cytokinin modulates endocytic trafficking of PIN1 auxin efflux carrier to control plant organogenesis}}, doi = {10.1016/j.devcel.2011.08.014}, volume = {21}, year = {2011}, } @article{3098, abstract = {Cell polarity reflected by asymmetric distribution of proteins at the plasma membrane is a fundamental feature of unicellular and multicellular organisms. It remains conceptually unclear how cell polarity is kept in cell wall-encapsulated plant cells. We have used super-resolution and semi-quantitative live-cell imaging in combination with pharmacological, genetic, and computational approaches to reveal insights into the mechanism of cell polarity maintenance in Arabidopsis thaliana. We show that polar-competent PIN transporters for the phytohormone auxin are delivered to the center of polar domains by super-polar recycling. Within the plasma membrane, PINs are recruited into non-mobile membrane clusters and their lateral diffusion is dramatically reduced, which ensures longer polar retention. At the circumventing edges of the polar domain, spatially defined internalization of escaped cargos occurs by clathrin-dependent endocytosis. Computer simulations confirm that the combination of these processes provides a robust mechanism for polarity maintenance in plant cells. Moreover, our study suggests that the regulation of lateral diffusion and spatially defined endocytosis, but not super-polar exocytosis have primary importance for PIN polarity maintenance.}, author = {Kleine-Vehn, Jürgen and Krzysztof Wabnik and Martinière, Alexandre and Łangowski, Łukasz and Willig, Katrin and Naramoto, Satoshi and Leitner, Johannes and Tanaka, Hirokazu and Jakobs, Stefan and Robert, Stéphanie and Luschnig, Christian and Govaerts, Willy J and Hell, Stefan W and Runions, John and Jirí Friml}, journal = {Molecular Systems Biology}, publisher = {Nature Publishing Group}, title = {{Recycling, clustering and endocytosis jointly maintain PIN auxin carrier polarity at the plasma membrane}}, doi = {10.1038/msb.2011.72}, volume = {7}, year = {2011}, } @article{3099, abstract = {Endomembrane trafficking relies on the coordination of a highly complex, dynamic network of intracellular vesicles. Understanding the network will require a dissection of cargo and vesicle dynamics at the cellular level in vivo. This is also a key to establishing a link between vesicular networks and their functional roles in development. We used a high-content intracellular screen to discover small molecules targeting endomembrane trafficking in vivo in a complex eukaryote, Arabidopsis thaliana. Tens of thousands of molecules were prescreened and a selected subset was interrogated against a panel of plasma membrane (PM) and other endomembrane compartment markers to identify molecules that altered vesicle trafficking. The extensive image dataset was transformed by a flexible algorithm into a marker-by-phenotype-by-treatment time matrix and revealed groups of molecules that induced similar subcellular fingerprints (clusters). This matrix provides a platform for a systems view of trafficking. Molecules from distinct clusters presented avenues and enabled an entry point to dissect recycling at the PM, vacuolar sorting, and cell-plate maturation. Bioactivity in human cells indicated the value of the approach to identifying small molecules that are active in diverse organisms for biology and drug discovery.}, author = {Drakakaki, Georgia and Robert, Stéphanie and Szatmári, Anna-Maria and Brown, Michelle Q and Nagawa, Shingo and Van Damme, Daniël and Leonard, Marylin and Yang, Zhenbiao and Girke, Thomas and Schmid, Sandra L and Russinova, Eugenia and Jirí Friml and Raikhel, Natasha V and Hicks, Glen R}, journal = {PNAS}, number = {43}, pages = {17850 -- 17855}, publisher = {National Academy of Sciences}, title = {{Clusters of bioactive compounds target dynamic endomembrane networks in vivo}}, doi = {10.1073/pnas.1108581108}, volume = {108}, year = {2011}, }