The phytohormone auxin triggers transcriptional reprogramming through a well-characterized perception machinery in the nucleus. By contrast, mechanisms that underlie fast effects of auxin, such as the regulation of ion fluxes, rapid phosphorylation of proteins or auxin feedback on its transport, remain unclear1-3. Whether auxin-binding protein 1 (ABP1) is an auxin receptor has been a source of debate for decades1,4. Here we show that a fraction of Arabidopsis thaliana ABP1 is secreted and binds auxin specifically at an acidic pH that is typical of the apoplast. ABP1 and its plasma-membrane-localized partner, transmembrane kinase 1 (TMK1), are required for the auxin-induced ultrafast global phospho-response and for downstream processes that include the activation of H+-ATPase and accelerated cytoplasmic streaming. abp1 and tmk mutants cannot establish auxin-transporting channels and show defective auxin-induced vasculature formation and regeneration. An ABP1(M2X) variant that lacks the capacity to bind auxin is unable to complement these defects in abp1 mutants. These data indicate that ABP1 is the auxin receptor for TMK1-based cell-surface signalling, which mediates the global phospho-response and auxin canalization.

• MeSH
• Arabidopsis * genetika   metabolismus   MeSH
• fosforylace MeSH
• koncentrace vodíkových iontů MeSH
• kyseliny indoloctové * metabolismus   MeSH
• mutace MeSH
• protein-serin-threoninkinasy * genetika   metabolismus   MeSH
• proteiny huseníčku * genetika   metabolismus   MeSH
• protonové ATPasy metabolismus   MeSH
• proudění cytoplazmy MeSH
• regulátory růstu rostlin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• AT1G66150 protein, Arabidopsis MeSH Prohlížeč
• auxin-binding protein 1 MeSH Prohlížeč
• kyseliny indoloctové * MeSH
• protein-serin-threoninkinasy * MeSH
• proteiny huseníčku * MeSH
• protonové ATPasy MeSH
• regulátory růstu rostlin MeSH

Auxin regulates the transcription of auxin-responsive genes by the TIR1/AFBs-Aux/IAA-ARF signaling pathway, and in this way facilitates plant growth and development. However, rapid, nontranscriptional responses to auxin that cannot be explained by this pathway have been reported. In this review, we focus on several examples of rapid auxin responses: (1) the triggering of changes in plasma membrane potential in various plant species and tissues, (2) inhibition of root growth, which also correlates with membrane potential changes, cytosolic Ca2+ spikes, and a rise of apoplastic pH, (3) the influence on endomembrane trafficking of PIN proteins and other membrane cargoes, and (4) activation of ROPs (Rho of plants) and their downstream effectors such as the cytoskeleton or vesicle trafficking. In most cases, the signaling pathway triggering the response is poorly understood. A role for the TIR1/AFBs in rapid root growth regulation is emerging, as well as the involvement of transmembrane kinases (TMKs) in the activation of ROPs. We discuss similarities and differences among these rapid responses and focus on their physiological significance, which remains an enigma in most cases.

• MeSH
• endocytóza MeSH
• kořeny rostlin růst a vývoj   MeSH
• kyseliny indoloctové metabolismus   MeSH
• membránové potenciály MeSH
• proteiny vázající GTP metabolismus   MeSH
• receptory buněčného povrchu metabolismus   MeSH
• rostlinné proteiny metabolismus   MeSH
• rostliny metabolismus   MeSH
• vápník metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• auxin receptor, plant MeSH Prohlížeč
• kyseliny indoloctové MeSH
• proteiny vázající GTP MeSH
• receptory buněčného povrchu MeSH
• rostlinné proteiny MeSH
• vápník MeSH

Eukaryotic cells rely on the accuracy and efficiency of vesicular traffic. In plants, disturbances in vesicular trafficking are well studied in quickly dividing root meristem cells or polar growing root hairs and pollen tubes. The development of the female gametophyte, a unique haploid reproductive structure located in the ovule, has received far less attention in studies of vesicular transport. Key molecules providing the specificity of vesicle formation and its subsequent recognition and fusion with the acceptor membrane are Rab proteins. Rabs are anchored to membranes by covalently linked geranylgeranyl group(s) that are added by the Rab geranylgeranyl transferase (RGT) enzyme. Here we show that Arabidopsis plants carrying mutations in the gene encoding the β-subunit of RGT (rgtb1) exhibit severely disrupted female gametogenesis and this effect is of sporophytic origin. Mutations in rgtb1 lead to internalization of the PIN1 and PIN3 proteins from the basal membranes to vesicles in provascular cells of the funiculus. Decreased transport of auxin out of the ovule is accompanied by auxin accumulation in tissue surrounding the growing gametophyte. In addition, female gametophyte development arrests at the uni- or binuclear stage in a significant portion of the rgtb1 ovules. These observations suggest that communication between the sporophyte and the developing female gametophyte relies on Rab-dependent vesicular traffic of the PIN1 and PIN3 transporters and auxin efflux out of the ovule.

• Klíčová slova
• Arabidopsis, PIN1, PIN3, Rab, auxin transport, female gametophyte, funiculus, ovule, rab geranylgeranyl transferase,
• MeSH
• Arabidopsis * genetika   MeSH
• kyseliny indoloctové MeSH
• proteiny huseníčku * genetika   MeSH
• pylová láčka MeSH
• vajíčko rostlin genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyseliny indoloctové MeSH
• proteiny huseníčku * MeSH

Directional transport of the phytohormone auxin is a versatile, plant-specific mechanism regulating many aspects of plant development. The recently identified plant hormones, strigolactones (SLs), are implicated in many plant traits; among others, they modify the phenotypic output of PIN-FORMED (PIN) auxin transporters for fine-tuning of growth and developmental responses. Here, we show in pea and Arabidopsis that SLs target processes dependent on the canalization of auxin flow, which involves auxin feedback on PIN subcellular distribution. D14 receptor- and MAX2 F-box-mediated SL signaling inhibits the formation of auxin-conducting channels after wounding or from artificial auxin sources, during vasculature de novo formation and regeneration. At the cellular level, SLs interfere with auxin effects on PIN polar targeting, constitutive PIN trafficking as well as clathrin-mediated endocytosis. Our results identify a non-transcriptional mechanism of SL action, uncoupling auxin feedback on PIN polarity and trafficking, thereby regulating vascular tissue formation and regeneration.

• MeSH
• Arabidopsis genetika   metabolismus   MeSH
• heterocyklické sloučeniny tricyklické metabolismus   MeSH
• hrách setý genetika   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• laktony metabolismus   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• regulace genové exprese u rostlin genetika   fyziologie   MeSH
• regulátory růstu rostlin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• GR24 strigolactone MeSH Prohlížeč
• heterocyklické sloučeniny tricyklické MeSH
• kyseliny indoloctové MeSH
• laktony MeSH
• proteiny huseníčku MeSH
• regulátory růstu rostlin MeSH

Polar auxin transport plays a pivotal role in plant growth and development. PIN-FORMED (PIN) auxin efflux carriers regulate directional auxin movement by establishing local auxin maxima, minima, and gradients that drive multiple developmental processes and responses to environmental signals. Auxin has been proposed to modulate its own transport by regulating subcellular PIN trafficking via processes such as clathrin-mediated PIN endocytosis and constitutive recycling. Here, we further investigated the mechanisms by which auxin affects PIN trafficking by screening auxin analogs and identified pinstatic acid (PISA) as a positive modulator of polar auxin transport in Arabidopsis (Arabidopsis thaliana). PISA had an auxin-like effect on hypocotyl elongation and adventitious root formation via positive regulation of auxin transport. PISA did not activate SCFTIR1/AFB signaling and yet induced PIN accumulation at the cell surface by inhibiting PIN internalization from the plasma membrane. This work demonstrates PISA to be a promising chemical tool to dissect the regulatory mechanisms behind subcellular PIN trafficking and auxin transport.

• MeSH
• Arabidopsis účinky léků   metabolismus   MeSH
• biologický transport účinky léků   MeSH
• buněčná membrána účinky léků   metabolismus   MeSH
• endocytóza * účinky léků   MeSH
• fenotyp MeSH
• fenylacetáty farmakologie   MeSH
• gravitropismus účinky léků   MeSH
• hypokotyl účinky léků   růst a vývoj   MeSH
• kořeny rostlin účinky léků   růst a vývoj   MeSH
• kyseliny indoloctové metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• signální transdukce MeSH
• výhonky rostlin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fenylacetáty MeSH
• kyseliny indoloctové MeSH
• phenylacetic acid MeSH Prohlížeč
• pinstatic acid MeSH Prohlížeč
• proteiny huseníčku MeSH

Auxin is unique among plant hormones due to its directional transport that is mediated by the polarly distributed PIN auxin transporters at the plasma membrane. The canalization hypothesis proposes that the auxin feedback on its polar flow is a crucial, plant-specific mechanism mediating multiple self-organizing developmental processes. Here, we used the auxin effect on the PIN polar localization in Arabidopsis thaliana roots as a proxy for the auxin feedback on the PIN polarity during canalization. We performed microarray experiments to find regulators of this process that act downstream of auxin. We identified genes that were transcriptionally regulated by auxin in an AXR3/IAA17- and ARF7/ARF19-dependent manner. Besides the known components of the PIN polarity, such as PID and PIP5K kinases, a number of potential new regulators were detected, among which the WRKY23 transcription factor, which was characterized in more detail. Gain- and loss-of-function mutants confirmed a role for WRKY23 in mediating the auxin effect on the PIN polarity. Accordingly, processes requiring auxin-mediated PIN polarity rearrangements, such as vascular tissue development during leaf venation, showed a higher WRKY23 expression and required the WRKY23 activity. Our results provide initial insights into the auxin transcriptional network acting upstream of PIN polarization and, potentially, canalization-mediated plant development.

• MeSH
• Arabidopsis genetika   růst a vývoj   MeSH
• geneticky modifikované rostliny MeSH
• genové regulační sítě * účinky léků   MeSH
• kořeny rostlin účinky léků   genetika   růst a vývoj   metabolismus   MeSH
• kyseliny indoloctové metabolismus   farmakologie   MeSH
• membránové transportní proteiny genetika   metabolismus   MeSH
• mikročipová analýza MeSH
• polarita buněk * genetika   MeSH
• proteiny huseníčku genetika   metabolismus   fyziologie   MeSH
• regulace genové exprese u rostlin účinky léků   MeSH
• stanovení celkové genové exprese MeSH
• transkripční faktory fyziologie   MeSH
• zpětná vazba fyziologická účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyseliny indoloctové MeSH
• membránové transportní proteiny MeSH
• PIN1 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku MeSH
• transkripční faktory MeSH
• WRKY23 protein, Arabidopsis MeSH Prohlížeč

Auxin is a key plant regulatory molecule, which acts upon a plethora of cellular processes, including those related to cell differentiation and elongation. Despite the stunning progress in all disciplines of auxin research, the mechanisms of auxin-mediated rapid promotion of cell expansion and underlying rearrangement of cell wall components are poorly understood. This is partly due to the limitations of current methodologies for probing auxin. Here we describe a click chemistry-based approach, using an azido derivative of indole-3-propionic acid. This compound is as an active auxin analogue, which can be tagged in situ. Using this new tool, we demonstrate the existence of putative auxin binding sites in the cell walls of expanding/elongating cells. These binding sites are of protein nature but are distinct from those provided by the extensively studied AUXIN BINDING PROTEIN 1 (ABP1). Using immunohistochemistry, we have shown the apoplastic presence of endogenous auxin epitopes recognised by an anti-IAA antibody. Our results are intriguingly in line with previous observations suggesting some transcription-independent (non-genomic) activity of auxin in cell elongation.

• MeSH
• buněčná stěna metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• rostlinné proteiny metabolismus   MeSH
• syntetická chemie okamžité shody metody   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyseliny indoloctové MeSH
• rostlinné proteiny MeSH

Here we present an overview of what is known about endogenous plant compounds that act as inhibitors of hormonal transport processes in plants, about their identity and mechanism of action. We have also summarized commonly and less commonly used compounds of non-plant origin and synthetic drugs that show at least partial 'specificity' to transport or transporters of particular phytohormones. Our main attention is focused on the inhibitors of auxin transport. The urgent need to understand precisely the molecular mechanism of action of these inhibitors is highlighted.

• Klíčová slova
• Abscisic acid, Auxin, Cell biology, Cytokinins, Inhibitors, Plant hormones, Strigolactones, Transport,
• MeSH
• biologické modely MeSH
• biologický transport MeSH
• regulátory růstu rostlin metabolismus   MeSH
• rostlinné proteiny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• regulátory růstu rostlin MeSH
• rostlinné proteiny MeSH

Synchronized tissue polarization during regeneration or de novo vascular tissue formation is a plant-specific example of intercellular communication and coordinated development. According to the canalization hypothesis, the plant hormone auxin serves as polarizing signal that mediates directional channel formation underlying the spatio-temporal vasculature patterning. A necessary part of canalization is a positive feedback between auxin signaling and polarity of the intercellular auxin flow. The cellular and molecular mechanisms of this process are still poorly understood, not the least, because of a lack of a suitable model system. We show that the main genetic model plant, Arabidopsis (Arabidopsis thaliana) can be used to study the canalization during vascular cambium regeneration and new vasculature formation. We monitored localized auxin responses, directional auxin-transport channels formation, and establishment of new vascular cambium polarity during regenerative processes after stem wounding. The increased auxin response above and around the wound preceded the formation of PIN1 auxin transporter-marked channels from the primarily homogenous tissue and the transient, gradual changes in PIN1 localization preceded the polarity of newly formed vascular tissue. Thus, Arabidopsis is a useful model for studies of coordinated tissue polarization and vasculature formation after wounding allowing for genetic and mechanistic dissection of the canalization hypothesis.

• MeSH
• Arabidopsis fyziologie   MeSH
• kambium fyziologie   MeSH
• kyseliny indoloctové metabolismus   MeSH
• regenerace MeSH
• stonky rostlin fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyseliny indoloctové MeSH

The Auxin Binding Protein 1 (ABP1) is one of the most studied proteins in plants. Since decades ago, it has been the prime receptor candidate for the plant hormone auxin with a plethora of described functions in auxin signaling and development. The developmental importance of ABP1 has recently been questioned by identification of Arabidopsis thaliana abp1 knock-out alleles that show no obvious phenotypes under normal growth conditions. In this study, we examined the contradiction between the normal growth and development of the abp1 knock-outs and the strong morphological defects observed in three different ethanol-inducible abp1 knock-down mutants ( abp1-AS, SS12K, SS12S). By analyzing segregating populations of abp1 knock-out vs. abp1 knock-down crosses we show that the strong morphological defects that were believed to be the result of conditional down-regulation of ABP1 can be reproduced also in the absence of the functional ABP1 protein. This data suggests that the phenotypes in abp1 knock-down lines are due to the off-target effects and asks for further reflections on the biological function of ABP1 or alternative explanations for the missing phenotypic defects in the abp1 loss-of-function alleles.

• Klíčová slova
• AUXIN BINDING PROTEIN 1 (ABP1), Arabidopsis, auxin, knock-down mutant, off-target,
• Publikační typ
• časopisecké články MeSH