The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Jiři Friml - One of the best experts on this subject based on the ideXlab platform.
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subcellular trafficking of pin Auxin efflux carriers in Auxin Transport
European Journal of Cell Biology, 2010Co-Authors: Jiři FrimlAbstract:The directional Transport of the plant hormone Auxin is a unique process mediating a wide variety of developmental processes. Auxin movement between cells depends on AUX1/LAX, PGP and PIN protein families that mediate Auxin Transport across the plasma membrane. The directionality of Auxin flow within tissues is largely determined by polar, subcellular localization of PIN Auxin efflux carriers. PIN proteins undergo rapid subcellular dynamics that is important for the process of Auxin Transport and its directionality. Furthermore, various environmental and endogenous signals can modulate trafficking and polarity of PIN proteins and by this mechanism change Auxin distribution. Thus, the subcellular dynamics of Auxin Transport proteins represents an important interface between cellular processes and development of the whole plant. This review summarizes our recent contributions to the field of PIN trafficking and Auxin Transport regulation.
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Auxin Transport — shaping the plant
Current Opinion in Plant Biology, 2003Co-Authors: Jiři FrimlAbstract:Plant growth is marked by its adaptability to continuous changes in environment. A regulated, differential distribution of Auxin underlies many adaptation processes including organogenesis, meristem patterning and tropisms. In executing its multiple roles, Auxin displays some characteristics of both a hormone and a morphogen. Studies on Auxin Transport, as well as tracing the intracellular movement of its molecular components, have suggested a possible scenario to explain how growth plasticity is conferred at the cellular and molecular level. The plant perceives stimuli and changes the subcellular position of Auxin-Transport components accordingly. These changes modulate Auxin fluxes, and the newly established Auxin distribution triggers the corresponding developmental response.
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Auxin Transport - Shaping the plant
Current Opinion in Plant Biology, 2003Co-Authors: Jiři FrimlAbstract:Plant growth is marked by its adaptability to continuous changes in environment. A regulated, differential distribution of Auxin underlies many adaptation processes including organogenesis, meristem patterning and tropisms. In executing its multiple roles, Auxin displays some characteristics of both a hormone and a morphogen. Studies on Auxin Transport, as well as tracing the intracellular movement of its molecular components, have suggested a possible scenario to explain how growth plasticity is conferred at the cellular and molecular level. The plant perceives stimuli and changes the subcellular position of Auxin-Transport components accordingly. These changes modulate Auxin fluxes, and the newly established Auxin distribution triggers the corresponding developmental response.
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Polar Auxin Transport – old questions and new concepts?
Plant Molecular Biology, 2002Co-Authors: Jiři Friml, Klaus PalmeAbstract:Polar Auxin Transport controls multiple aspects of plant development including differential growth, embryo and root patterning and vascular tissue differentiation. Identification of proteins involved in this process and availability of new tools enabling `visualization' of Auxin and Auxin routes in planta largely contributed to the significant progress that has recently been made. New data support classical concepts, but several recent findings are likely to challenge our view on the mechanism of Auxin Transport. The aim of this review is to provide a comprehensive overview of the polar Auxin Transport field. It starts with classical models resulting from physiological studies, describes the genetic contributions and discusses the molecular basis of Auxin influx and efflux. Finally, selected questions are presented in the context of developmental biology, integrating available data from different fields.
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polar Auxin Transport old questions and new concepts
Plant Molecular Biology, 2002Co-Authors: Jiři Friml, Klaus PalmeAbstract:Polar Auxin Transport controls multiple aspects of plant development including differential growth, embryo and root patterning and vascular tissue differentiation. Identification of proteins involved in this process and availability of new tools enabling `visualization' of Auxin and Auxin routes in planta largely contributed to the significant progress that has recently been made. New data support classical concepts, but several recent findings are likely to challenge our view on the mechanism of Auxin Transport. The aim of this review is to provide a comprehensive overview of the polar Auxin Transport field. It starts with classical models resulting from physiological studies, describes the genetic contributions and discusses the molecular basis of Auxin influx and efflux. Finally, selected questions are presented in the context of developmental biology, integrating available data from different fields.
Gloria K Muday - One of the best experts on this subject based on the ideXlab platform.
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Interactions Between the Actin Cytoskeleton and an Auxin Transport Protein
Actin: A Dynamic Framework for Multiple Plant Cell Functions, 2020Co-Authors: Gloria K MudayAbstract:In shoots, polar Auxin Transport is basipetal (i.e., from the shoot apex toward the base), and is driven by the basal localization of the Auxin efflux carrier complex. One mechanism by which this efflux carrier complex could be localized to the basal membrane is through attachment to the actin cytoskeleton. The efflux carrier protein complex is believed to consist of several polypeptides, including a regulatory subunit that binds Auxin Transport inhibitors such as naphthylphthalamic acid (NPA). Several lines of experimentation have been used to determine whether the NPA-binding protein interacts with actin filaments. The NPA-binding protein has been shown to partition with the actin cytoskeleton during detergent extraction. Agents that specifically alter the polymerization state of the actin cytoskeleton also change the amount of NPA-binding protein and actin recovered in these cytoskeletal pellets. Actin affinity columns were prepared with polymers of actin purified from zucchini hypocotyl tissue. NPA-binding activity was eluted in a single peak from the actin filament column. Cytochalasin D, which fragments the actin cytoskeleton, was shown to reduce polar Auxin Transport in zucchini hypocotyls. The interaction of the NPA-binding protein with the actin cytoskeleton may localize it in one plane of the plasma membrane, and thereby control the polarity of Auxin Transport.
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Control of Auxin Transport by Reactive Oxygen and Nitrogen Species
Polar Auxin Transport, 2013Co-Authors: María Fernández-marcos, Gloria K Muday, Luis Sanz, Daniel R. Lewis, Oscar LorenzoAbstract:Auxin Transport is a central process in plant growth and development and as a result is highly regulated. The amount and direction of Auxin Transport is defined by a set of Auxin influx and efflux carriers with precise localization that lead to long-distance polar Auxin Transport. These Auxin Transport proteins are regulated by transcriptional and posttranslational mechanisms and through protein-targeting machinery that directs them to the appropriate plasma membrane location. A variety of signals initiate regulatory changes in the abundance, activity, or localization of these proteins, with plant hormones, light, and other environmental signaling implicated in this process. Recent evidence indicates that changing levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) may also fine-tune the activity or synthesis of these proteins. This insight has been obtained by using mutants or treatments that alter the levels of ROS or RNS and demonstration of changing Auxin Transport and abundance of Transport proteins. The molecular mechanisms by which ROS and RNS lead to changes in Auxin Transport are not yet clear but likely include changes in protein synthesis and abundance. This chapter briefly introduces the key proteins and antioxidant molecules that control the levels of ROS and RNS and focuses on the evidence linking these changes to altered Auxin Transport.
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Role for apyrases in polar Auxin Transport in Arabidopsis.
Plant Physiology, 2012Co-Authors: Jian Wu, Gloria K Muday, Greg Clark, Stacey R. Lundy, David Arnold, Jing Chan, Wenqiang Tang, Gary GardnerAbstract:Recent evidence indicates that extracellular nucleotides regulate plant growth. Exogenous ATP has been shown to block Auxin Transport and gravitropic growth in primary roots of Arabidopsis (Arabidopsis thaliana). Cells limit the concentration of extracellular ATP in part through the activity of ectoapyrases (ectonucleoside triphosphate diphosphohydrolases), and two nearly identical Arabidopsis apyrases, APY1 and APY2, appear to share this function. These findings, plus the fact that suppression of APY1 and APY2 blocks growth in Arabidopsis, suggested that the expression of these apyrases could influence Auxin Transport. This report tests that hypothesis. The polar movement of [3H]indole-3-acetic acid in both hypocotyl sections and primary roots of Arabidopsis seedlings was measured. In both tissues, polar Auxin Transport was significantly reduced in apy2 null mutants when they were induced by estradiol to suppress the expression of APY1 by RNA interference. In the hypocotyl assays, the basal halves of APY-suppressed hypocotyls contained considerably lower free indole-3-acetic acid levels when compared with wild-type plants, and disrupted Auxin Transport in the APY-suppressed roots was reflected by their significant morphological abnormalities. When a green fluorescent protein fluorescence signal encoded by a DR5:green fluorescent protein construct was measured in primary roots whose apyrase expression was suppressed either genetically or chemically, the roots showed no signal asymmetry following gravistimulation, and both their growth and gravitropic curvature were inhibited. Chemicals that suppress apyrase activity also inhibit gravitropic curvature and, to a lesser extent, growth. Taken together, these results indicate that a critical step connecting apyrase suppression to growth suppression is the inhibition of polar Auxin Transport.
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Measurement of Auxin Transport in Arabidopsis thaliana
Nature Protocols, 2009Co-Authors: Daniel R. Lewis, Gloria K MudayAbstract:This protocol allows the measurement of Auxin Transport in roots, hypocotyls and inflorescences of Arabidopsis thaliana plants by examining Transport of radiolabeled Auxin or movement of an Auxin-induced gene expression signal. The protocol contains four stages: seedling growth, Auxin application, a Transport period of variable length, and quantification of Auxin movement or reporter expression. Beyond the time for plant growth, the Transport assay can be completed within 4–18 h. Auxin is applied to seedlings in agar cylinders or droplets, which does not require specialized liquid-handling equipment or micromanipulators, in contrast with methods that apply Auxin in liquid droplets. Spatial control of Auxin application is reduced, but this method has the advantages of being technically more feasible for most laboratories and allowing agar containing radioactive Auxin to be removed for pulse chase assays that determine Transport rates. These methods allow investigation of genetic and environmental factors that control Auxin Transport.
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Vesicular cycling mechanisms that control Auxin Transport polarity.
Trends in Plant Science, 2003Co-Authors: Gloria K Muday, Wendy Ann Peer, Angus S MurphyAbstract:The polar Transport of Auxin controls many important plant growth and developmental processes. The polarity of Auxin movement has long been suggested to be mediated by asymmetric distribution of Auxin Transport proteins, yet, until recently, little was known about the mechanisms that establish protein asymmetry in Auxin-Transporting cells. Now, a recent paper provides significant insight into the mechanism by which the GNOM protein controls the cycling of an Auxin efflux carrier protein, PIN1, between the endosome and the plasma membrane. The dynamic movement of Auxin Transport proteins between internal compartments and the plasma membrane suggests mechanisms for alterations in Auxin Transport polarity in response to changing developmental or environmental regulation.
Enrico Scarpella - One of the best experts on this subject based on the ideXlab platform.
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Vein patterning by tissue-specific Auxin Transport
Development, 2020Co-Authors: Priyanka Govindaraju, Carla Verna, Enrico ScarpellaAbstract:Unlike in animals, in plants vein patterning does not rely on direct cell-cell interaction and cell migration; instead, it depends on the Transport of the plant hormone Auxin, which in turn depends on the activity of the PIN-FORMED1 (PIN1) Auxin Transporter. The current hypotheses of vein patterning by Auxin Transport propose that in the epidermis of the developing leaf PIN1-mediated Auxin Transport converges to peaks of Auxin level. From those convergence points of epidermal PIN1 polarity, Auxin would be Transported in the inner tissues where it would give rise to major veins. Here we tested predictions of this hypothesis and found them unsupported: epidermal PIN1 expression is neither required nor sufficient for Auxin-Transport-dependent vein patterning, whereas inner-tissue PIN1 expression turns out to be both required and sufficient for Auxin-Transport-dependent vein patterning. Our results refute all vein patterning hypotheses based on Auxin Transport from the epidermis and suggest alternatives for future tests.
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Vein Patterning by Tissue-Specific Auxin Transport
bioRxiv, 2019Co-Authors: Priyanka Govindaraju, Carla Verna, Enrico ScarpellaAbstract:Unlike in animals, in plants vein patterning does not rely on direct cell-cell interaction and cell migration; instead, it depends on the Transport of the plant signal Auxin, which in turn depends on the activity of the PIN-FORMED1 (PIN1) Auxin Transporter. The current hypotheses of vein patterning by Auxin Transport propose that in the epidermis of the developing leaf PIN1-mediated Auxin Transport converges to peaks of Auxin level. From those convergence points of epidermal PIN1 polarity, Auxin would be Transported in the inner tissues where it would give rise to major veins. Here we tested predictions of this hypothesis and found them unsupported: epidermal PIN1 expression is neither required nor sufficient for Auxin-Transport-dependent vein patterning, whereas inner-tissue PIN1 expression turns out to be both required and sufficient for Auxin-Transport-dependent vein patterning. Our results refute all vein patterning hypotheses based on Auxin Transport from the epidermis and suggest alternatives for future tests.
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coordination of tissue cell polarity by Auxin Transport and signaling
eLife, 2019Co-Authors: Carla Verna, Megan G. Sawchuk, Sree Janani Ravichandran, Nguyen Manh Linh, Enrico ScarpellaAbstract:Plants coordinate the polarity of hundreds of cells during vein formation, but how they do so is unclear. The prevailing hypothesis proposes that GNOM, a regulator of membrane trafficking, positions PIN-FORMED Auxin Transporters to the correct side of the plasma membrane; the resulting cell-to-cell, polar Transport of Auxin would coordinate tissue cell polarity and induce vein formation. Contrary to predictions of the hypothesis, we find that vein formation occurs in the absence of PIN-FORMED or any other intercellular Auxin-Transporter; that the residual Auxin-Transport-independent vein-patterning activity relies on Auxin signaling; and that a GNOM-dependent signal acts upstream of both Auxin Transport and signaling to coordinate tissue cell polarity and induce vein formation. Our results reveal synergism between Auxin Transport and signaling, and their unsuspected control by GNOM in the coordination of tissue cell polarity during vein patterning, one of the most informative expressions of tissue cell polarization in plants.
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connective Auxin Transport in the shoot facilitates communication between shoot apices
PLOS Biology, 2016Co-Authors: Tom Bennett, Enrico Scarpella, Megan G. Sawchuk, Genevieve Hines, Martin Van Rongen, Tanya Waldie, Karin Ljung, Ottoline LeyserAbstract:The bulk polar movement of the plant signaling molecule Auxin through the stem is a long-recognized but poorly understood phenomenon. Here we show that the highly polar, high conductance polar Auxin Transport stream (PATS) is only part of a multimodal Auxin Transport network in the stem. The dynamics of Auxin movement through stems are inconsistent with a single polar Transport regime and instead suggest widespread low conductance, less polar Auxin Transport in the stem, which we term connective Auxin Transport (CAT). The bidirectional movement of Auxin between the PATS and the surrounding tissues, mediated by CAT, can explain the complex Auxin Transport kinetics we observe. We show that the Auxin efflux carriers PIN3, PIN4, and PIN7 are major contributors to this Auxin Transport connectivity and that their activity is important for communication between shoot apices in the regulation of shoot branching. We propose that the PATS provides a long-range, consolidated stream of information throughout the plant, while CAT acts locally, allowing tissues to modulate and be modulated by information in the PATS.
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Control of vein patterning by intracellular Auxin Transport.
Plant Signaling & Behavior, 2013Co-Authors: Megan G. Sawchuk, Enrico ScarpellaAbstract:The vein networks of plant leaves are among the most spectacular expressions of biological pattern, and the principles controlling their formation have continually inspired artists and scientists. Control of vein patterning by the polar, cell-to-cell Transport of the plant signaling molecule Auxin—mediated in Arabidopsis primarily by the plasma-membrane-localized PIN1—has long been known. By contrast, the existence of intracellular Auxin Transport and its contribution to vein patterning are recent discoveries. The endoplasmic-reticulum-localized PIN5, PIN6, and PIN8 of Arabidopsis define an intracellular Auxin-Transport pathway whose functions in vein patterning overlap with those of PIN1-mediated intercellular Auxin Transport. The genetic interaction between the components of the intracellular Auxin-Transport pathway is far from having been resolved. The study of vein patterning provides experimental access to gain such a resolution—a resolution that in turn holds the promise to improve our understanding of one of the most fascinating examples of biological pattern formation.
Klaus Palme - One of the best experts on this subject based on the ideXlab platform.
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Intracellular Auxin Transport in pollen: PIN8, PIN5 and PILS5.
Plant Signaling & Behavior, 2012Co-Authors: Cristina Dal Bosco, Alexander Dovzhenko, Klaus PalmeAbstract:Cellular Auxin homeostasis is controlled at many levels that include Auxin biosynthesis, Auxin metabolism, and Auxin Transport. In addition to intercellular Auxin Transport, Auxin homeostasis is modulated by Auxin flow through the endoplasmic reticulum (ER). PIN5, a member of the Auxin efflux facilitators PIN protein family, was the first protein to be characterized as an intracellular Auxin Transporter. We demonstrated that PIN8, the closest member of the PIN family to PIN5, represents another ER-residing Auxin Transporter. PIN8 is specifically expressed in the male gametophyte and is located in the ER. By combining genetic, physiological, cellular and biochemical data we demonstrated a role for PIN8 in intracellular Auxin homeostasis. Although our investigation shed light on intracellular Auxin Transport in pollen, the physiological function of PIN8 still remains to be elucidated. Here we discuss our data taking in consideration other recent findings.
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Polar Auxin Transport – old questions and new concepts?
Plant Molecular Biology, 2002Co-Authors: Jiři Friml, Klaus PalmeAbstract:Polar Auxin Transport controls multiple aspects of plant development including differential growth, embryo and root patterning and vascular tissue differentiation. Identification of proteins involved in this process and availability of new tools enabling `visualization' of Auxin and Auxin routes in planta largely contributed to the significant progress that has recently been made. New data support classical concepts, but several recent findings are likely to challenge our view on the mechanism of Auxin Transport. The aim of this review is to provide a comprehensive overview of the polar Auxin Transport field. It starts with classical models resulting from physiological studies, describes the genetic contributions and discusses the molecular basis of Auxin influx and efflux. Finally, selected questions are presented in the context of developmental biology, integrating available data from different fields.
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polar Auxin Transport old questions and new concepts
Plant Molecular Biology, 2002Co-Authors: Jiři Friml, Klaus PalmeAbstract:Polar Auxin Transport controls multiple aspects of plant development including differential growth, embryo and root patterning and vascular tissue differentiation. Identification of proteins involved in this process and availability of new tools enabling `visualization' of Auxin and Auxin routes in planta largely contributed to the significant progress that has recently been made. New data support classical concepts, but several recent findings are likely to challenge our view on the mechanism of Auxin Transport. The aim of this review is to provide a comprehensive overview of the polar Auxin Transport field. It starts with classical models resulting from physiological studies, describes the genetic contributions and discusses the molecular basis of Auxin influx and efflux. Finally, selected questions are presented in the context of developmental biology, integrating available data from different fields.
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Auxin Transport inhibitors block pin1 cycling and vesicle trafficking
Nature, 2001Co-Authors: Niko Geldner, Jiři Friml, Yorkdieter Stierhof, Gerd Jurgens, Klaus PalmeAbstract:Polar Transport of the phytohormone Auxin mediates various processes in plant growth and development, such as apical dominance, tropisms, vascular patterning and axis formation1,2. This view is based largely on the effects of polar Auxin Transport inhibitors. These compounds disrupt Auxin efflux from the cell but their mode of action is unknown3. It is thought that polar Auxin flux is caused by the asymmetric distribution of efflux carriers acting at the plasma membrane4. The polar localization of efflux carrier candidate PIN1 supports this model4. Here we show that the seemingly static localization of PIN1 results from rapid actin-dependent cycling between the plasma membrane and endosomal compartments. Auxin Transport inhibitors block PIN1 cycling and inhibit trafficking of membrane proteins that are unrelated to Auxin Transport. Our data suggest that PIN1 cycling is of central importance for Auxin Transport and that Auxin Transport inhibitors affect efflux by generally interfering with membrane-trafficking processes. In support of our conclusion, the vesicle-trafficking inhibitor brefeldin A mimics physiological effects of Auxin Transport inhibitors.
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pin pointing the molecular basis of Auxin Transport
Current Opinion in Plant Biology, 1999Co-Authors: Klaus Palme, Leo GalweilerAbstract:Significant advances in the genetic dissection of the Auxin Transport pathway have recently been made. Particularly relevant is the molecular analysis of mutants impaired in Auxin Transport and the subsequent cloning of genes encoding candidate proteins for the elusive Auxin efflux carrier. These studies are thought to pave the way to the detailed understanding of the molecular basis of several important facets of Auxin action.
Ulrike Mathesius - One of the best experts on this subject based on the ideXlab platform.
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The Medicago truncatula PIN2 Auxin Transporter mediates basipetal Auxin Transport but is not necessary for nodulation
Journal of Experimental Botany, 2019Co-Authors: Jason Liang Pin Ng, Rujin Chen, Astrid Welvaert, Ulrike MathesiusAbstract:: The development of root nodules leads to an increased Auxin response in early nodule primordia, which is mediated by changes in acropetal Auxin Transport in some legumes. Here, we investigated the role of root basipetal Auxin Transport during nodulation. Rhizobia inoculation significantly increased basipetal Auxin Transport in both Medicago truncatula and Lotus japonicus. In M. truncatula, this increase was dependent on functional Nod factor signalling through NFP, NIN and NSP2, as well as ethylene signalling through SKL. To test whether increased basipetal Auxin Transport is required for nodulation, we examined a loss-of-function mutant of the M. truncatula PIN2 gene. The Mtpin2 mutant exhibited a reduction in basipetal Auxin Transport and an agravitropic phenotype. Inoculation of Mtpin2 roots with rhizobia still led to a moderate increase in basipetal Auxin Transport, but the mutant nodulated normally. No clear differences in Auxin response were observed during nodule development. Interestingly, inoculation of wild type roots increased lateral root numbers, whereas inoculation of Mtpin2 mutants resulted in reduced lateral root numbers compared to uninoculated roots. We conclude that the MtPIN2 Auxin Transporter is involved in basipetal Auxin Transport, that its function is not essential for nodulation, but that it plays an important role in the control of lateral root development.
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Acropetal Auxin Transport Inhibition Is Involved in Indeterminate But Not Determinate Nodule Formation.
Frontiers in Plant Science, 2018Co-Authors: Jason Liang Pin Ng, Ulrike MathesiusAbstract:Legumes enter into a symbiotic relationship with nitrogen-fixing rhizobia, leading to nodule development. Two main types of nodules have been widely studied, indeterminate and determinate, which differ in the location of the first cell division in the root cortex, and persistency of the nodule meristem. Here we compared the control of Auxin Transport, content and response during the early stages of indeterminate and determinate nodule development in the model legumes Medicago truncatula and Lotus japonicus, respectively, to investigate whether differences in Auxin Transport control could explain the differences in the location of cortical cell divisions. While Auxin responses were activated in dividing cortical cells during nodulation of both nodule types, Auxin (indole-3-acetic acid) content at the nodule initiation site was transiently increased in M. truncatula, but transiently reduced in L. japonicus. Root acropetal Auxin Transport was reduced in M. truncatula at the very start of nodule initiation, in contrast to a prolonged increase in acropetal Auxin Transport in L. japonicus. The Auxin Transport inhibitors 2,3,5-triiodobenzoic acid (TIBA) and 1-N-naphtylphthalamic acid (NPA) only induced pseudonodules in legume species forming indeterminate nodules, but failed to elicit such structures in a range of species forming determinate nodules. The development of these pseudonodules in M. truncatula exhibited increased Auxin responses in a small primordium formed from the pericycle, endodermis and inner cortex, similar to rhizobia-induced nodule primordia. In contrast, a diffuse cortical Auxin response and no associated cortical cell divisions were found in L. japonicus. Collectively, we hypothesise that a step of acropetal Auxin Transport inhibition is unique to the process of indeterminate nodule development, leading to Auxin responses in pericycle, endodermis and inner cortex cells, while increased Auxin responses in outer cortex cells likely require a different mechanism during the formation of determinate nodules.
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The Control of Auxin Transport in Parasitic and Symbiotic Root-Microbe Interactions
Plants (Basel Switzerland), 2015Co-Authors: Jason Liang Pin Ng, Francine Perrine-walker, Anton Wasson, Ulrike MathesiusAbstract:Most field-grown plants are surrounded by microbes, especially from the soil. Some of these, including bacteria, fungi and nematodes, specifically manipulate the growth and development of their plant hosts, primarily for the formation of structures housing the microbes in roots. These developmental processes require the correct localization of the phytohormone Auxin, which is involved in the control of cell division, cell enlargement, organ development and defense, and is thus a likely target for microbes that infect and invade plants. Some microbes have the ability to directly synthesize Auxin. Others produce specific signals that indirectly alter the accumulation of Auxin in the plant by altering Auxin Transport. This review highlights root–microbe interactions in which Auxin Transport is known to be targeted by symbionts and parasites to manipulate the development of their host root system. We include case studies for parasitic root–nematode interactions, mycorrhizal symbioses as well as nitrogen fixing symbioses in actinorhizal and legume hosts. The mechanisms to achieve Auxin Transport control that have been studied in model organisms include the induction of plant flavonoids that indirectly alter Auxin Transport and the direct targeting of Auxin Transporters by nematode effectors. In most cases, detailed mechanisms of Auxin Transport control remain unknown.
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Polar Auxin Transport Regulation in Plant-Microbe Interactions
Polar Auxin Transport, 2013Co-Authors: Liang Pin Jason Ng, Giel E. Van Noorden, Ulrike MathesiusAbstract:Both symbiotic and pathogenic microorganisms can alter the growth and development of plant hosts. The phytohormone Auxin controls cell division, cell enlargement, and organogenesis and is thus a likely target for microorganisms that manipulate plants. Some microorganisms can synthesize Auxin in the rhizosphere. Others synthesize specific signals that indirectly alter the plant Auxin accumulation by altering Auxin Transport. This chapter highlights those plant–microorganism interactions in which Auxin Transport is targeted by symbionts and pathogens to manipulate the development of their plant host. The mechanism of Auxin Transport regulation by microorganisms is largely unknown, but possible mechanisms that have been studied in model organisms include the induction of plant flavonoids that indirectly alter Auxin Transport during nodulation and the direct targeting of Auxin Transporters by nematode effectors.
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The Ethylene-Insensitive sickle Mutant of Medicago truncatula Shows Altered Auxin Transport Regulation during Nodulation
Plant Physiology, 2006Co-Authors: Joko Prayitno, Barry G. Rolfe, Ulrike MathesiusAbstract:We studied the ethylene-insensitive, hypernodulating mutant, sickle (skl), to investigate the interaction of ethylene with Auxin Transport during root nodulation in Medicago truncatula. Grafting experiments demonstrated that hypernodulation in skl is root controlled. Long distance Transport of Auxin from shoot to root was reduced by rhizobia after 24 h in wild type but not in skl. Similarly, the ethylene precursor 1-amino cyclopropane-1-carboxylic acid inhibited Auxin Transport in wild type but not in skl. Auxin Transport at the nodule initiation zone was significantly reduced by rhizobia after 4 h in both wild type and skl. After 24 h, Auxin Transport significantly increased at the nodule initiation zone in skl compared to wild type, accompanied by an increase in the expression of the MtPIN1 and MtPIN2 (pin formed) Auxin efflux Transporters. Response assays to different Auxins did not show any phenotype that would suggest a defect of Auxin uptake in skl. The Auxin Transport inhibitor N-1-naphthylphtalamic acid inhibited nodulation in wild type but not skl, even though N-1-naphthylphtalamic acid still inhibited Auxin Transport in skl. Our results suggest that ethylene signaling modulates Auxin Transport regulation at certain stages of nodule development, partially through PIN gene expression, and that an increase in Auxin Transport relative to the wild type is correlated with higher nodule numbers. We also discuss the regulation of Auxin Transport in skl in comparison to previously published data on the autoregulation mutant, super numerary nodules (van Noorden et al., 2006).
