Formation of the apical hook in etiolated dicot seedlings results from differential growth in the hypocotyl apex and is tightly controlled by environmental cues and hormones, among which auxin and gibberellins (GAs) play an important role. Cell expansion is tightly regulated by the cell wall, but whether and how feedback from this structure contributes to hook development are still unclear. Here, we show that etiolated seedlings of the Arabidopsis (Arabidopsis thaliana) quasimodo2-1 (qua2) mutant, defective in pectin biosynthesis, display severe defects in apical hook formation and maintenance, accompanied by loss of asymmetric auxin maxima and differential cell expansion. Moreover, qua2 seedlings show reduced expression of HOOKLESS1 (HLS1) and PHYTOCHROME INTERACTING FACTOR4 (PIF4), which are positive regulators of hook formation. Treatment of wild-type seedlings with the cellulose inhibitor isoxaben (isx) also prevents hook development and represses HLS1 and PIF4 expression. Exogenous GAs, loss of DELLA proteins, or HLS1 overexpression partially restore hook development in qua2 and isx-treated seedlings. Interestingly, increased agar concentration in the medium restores, both in qua2 and isx-treated seedlings, hook formation, asymmetric auxin maxima, and PIF4 and HLS1 expression. Analyses of plants expressing a Förster resonance energy transfer-based GA sensor indicate that isx reduces accumulation of GAs in the apical hook region in a turgor-dependent manner. Lack of the cell wall integrity sensor THESEUS 1, which modulates turgor loss point, restores hook formation in qua2 and isx-treated seedlings. We propose that turgor-dependent signals link changes in cell wall integrity to the PIF4-HLS1 signaling module to control differential cell elongation during hook formation.

• MeSH
• Arabidopsis * genetika   růst a vývoj   metabolismus   MeSH
• benzamidy MeSH
• buněčná stěna * metabolismus   MeSH
• gibereliny metabolismus   MeSH
• hypokotyl růst a vývoj   genetika   metabolismus   MeSH
• kyseliny indoloctové * metabolismus   MeSH
• mutace genetika   MeSH
• pektiny metabolismus   MeSH
• proteiny huseníčku * metabolismus   genetika   MeSH
• regulace genové exprese u rostlin * MeSH
• semenáček * genetika   růst a vývoj   metabolismus   MeSH
• transkripční faktory bHLH * metabolismus   genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• benzamidy MeSH
• gibereliny MeSH
• isoxaben MeSH Prohlížeč
• kyseliny indoloctové * MeSH
• pektiny MeSH
• PIF4 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku * MeSH
• transkripční faktory bHLH * MeSH

The plant-specific receptor-like cytoplasmic kinases (RLCKs) form a large, poorly characterized family. Members of the RLCK VI_A class of dicots have a unique characteristic: their activity is regulated by Rho-of-plants (ROP) GTPases. The biological function of one of these kinases was investigated using a T-DNA insertion mutant and RNA interference. Loss of RLCK VI_A2 function resulted in restricted cell expansion and seedling growth. Although these phenotypes could be rescued by exogenous gibberellin, the mutant did not exhibit lower levels of active gibberellins nor decreased gibberellin sensitivity. Transcriptome analysis confirmed that gibberellin is not the direct target of the kinase; its absence rather affected the metabolism and signalling of other hormones such as auxin. It is hypothesized that gibberellins and the RLCK VI_A2 kinase act in parallel to regulate cell expansion and plant growth. Gene expression studies also indicated that the kinase might have an overlapping role with the transcription factor circuit (PIF4-BZR1-ARF6) controlling skotomorphogenesis-related hypocotyl/cotyledon elongation. Furthermore, the transcriptomic changes revealed that the loss of RLCK VI_A2 function alters cellular processes that are associated with cell membranes, take place at the cell periphery or in the apoplast, and are related to cellular transport and/or cell wall reorganisation.

• Klíčová slova
• Arabidopsis thaliana, cell expansion, gibberellins, hypocotyl growth, plant hormones, plant size, receptor-like cytoplasmic kinase, skotomorphogenesis, transcriptomic analysis,
• MeSH
• Arabidopsis účinky léků   enzymologie   genetika   růst a vývoj   MeSH
• DNA bakterií genetika   metabolismus   MeSH
• DNA vazebné proteiny genetika   metabolismus   MeSH
• geneticky modifikované rostliny MeSH
• gibereliny metabolismus   farmakologie   MeSH
• hypokotyl účinky léků   enzymologie   genetika   růst a vývoj   MeSH
• inzerční mutageneze MeSH
• kotyledon účinky léků   enzymologie   genetika   růst a vývoj   MeSH
• kyseliny indoloctové metabolismus   farmakologie   MeSH
• protein-serin-threoninkinasy genetika   metabolismus   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• regulace genové exprese u rostlin * MeSH
• regulátory růstu rostlin farmakologie   MeSH
• semenáček účinky léků   enzymologie   genetika   růst a vývoj   MeSH
• stanovení celkové genové exprese MeSH
• transkripční faktory bHLH genetika   metabolismus   MeSH
• transkripční faktory genetika   metabolismus   MeSH
• transkriptom MeSH
• vývojová regulace genové exprese MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• auxin response factor 6, Arabidopsis MeSH Prohlížeč
• BZR1 protein, Arabidopsis MeSH Prohlížeč
• DNA bakterií MeSH
• DNA vazebné proteiny MeSH
• gibereliny MeSH
• kyseliny indoloctové MeSH
• PIF4 protein, Arabidopsis MeSH Prohlížeč
• protein-serin-threoninkinasy MeSH
• proteiny huseníčku MeSH
• regulátory růstu rostlin MeSH
• T-DNA MeSH Prohlížeč
• transkripční faktory bHLH MeSH
• transkripční faktory MeSH

Peptides derived from non-functional precursors play important roles in various developmental processes, but also in (a)biotic stress signaling. Our (phospho)proteome-wide analyses of C-TERMINALLY ENCODED PEPTIDE 5 (CEP5)-mediated changes revealed an impact on abiotic stress-related processes. Drought has a dramatic impact on plant growth, development and reproduction, and the plant hormone auxin plays a role in drought responses. Our genetic, physiological, biochemical, and pharmacological results demonstrated that CEP5-mediated signaling is relevant for osmotic and drought stress tolerance in Arabidopsis, and that CEP5 specifically counteracts auxin effects. Specifically, we found that CEP5 signaling stabilizes AUX/IAA transcriptional repressors, suggesting the existence of a novel peptide-dependent control mechanism that tunes auxin signaling. These observations align with the recently described role of AUX/IAAs in stress tolerance and provide a novel role for CEP5 in osmotic and drought stress tolerance.

• Klíčová slova
• Arabidopsis, Plant biology, developmental biology, hormones, label-free quantification, mass spectrometry, phosphoproteome, protein degradation, signal transduction, stress response,
• MeSH
• Arabidopsis genetika   metabolismus   fyziologie   MeSH
• biologický transport genetika   MeSH
• fosfoproteiny metabolismus   MeSH
• fyziologická adaptace * genetika   MeSH
• fyziologický stres * genetika   MeSH
• genetická transkripce MeSH
• kyseliny indoloctové metabolismus   MeSH
• období sucha MeSH
• osmóza MeSH
• peptidy metabolismus   MeSH
• proteasomový endopeptidasový komplex metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• proteom metabolismus   MeSH
• proteomika * MeSH
• regulace genové exprese u rostlin MeSH
• semenáček růst a vývoj   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• CEP5 protein, Arabidopsis MeSH Prohlížeč
• fosfoproteiny MeSH
• kyseliny indoloctové MeSH
• peptidy MeSH
• proteasomový endopeptidasový komplex MeSH
• proteiny huseníčku MeSH
• proteom MeSH

The apical hook is a transiently formed structure that plays a protective role when the germinating seedling penetrates through the soil towards the surface. Crucial for proper bending is the local auxin maxima, which defines the concave (inner) side of the hook curvature. As no sign of asymmetric auxin distribution has been reported in embryonic hypocotyls prior to hook formation, the question of how auxin asymmetry is established in the early phases of seedling germination remains largely unanswered. Here, we analyzed the auxin distribution and expression of PIN auxin efflux carriers from early phases of germination, and show that bending of the root in response to gravity is the crucial initial cue that governs the hypocotyl bending required for apical hook formation. Importantly, polar auxin transport machinery is established gradually after germination starts as a result of tight root-hypocotyl interaction and a proper balance between abscisic acid and gibberellins.This article has an associated 'The people behind the papers' interview.

• Klíčová slova
• Apical hook, Arabidopsis, Auxin maxima, Formation stage, Green embryos, Root gravitropism,
• MeSH
• Arabidopsis MeSH
• geneticky modifikované rostliny MeSH
• gibereliny metabolismus   MeSH
• hypokotyl růst a vývoj   MeSH
• klíčení fyziologie   MeSH
• kořeny rostlin růst a vývoj   MeSH
• kyselina abscisová metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• meristém růst a vývoj   MeSH
• percepce tíhy fyziologie   MeSH
• proteiny huseníčku metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin metabolismus   MeSH
• semenáček růst a vývoj   MeSH
• vývojová regulace genové exprese MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• gibereliny MeSH
• kyselina abscisová MeSH
• kyseliny indoloctové MeSH
• proteiny huseníčku MeSH
• regulátory růstu rostlin MeSH

Developmental responses to auxin are regulated by facilitated uptake and efflux, but detailed molecular understanding of the carrier proteins is incomplete. We have used pharmacological tools to explore the chemical space that defines substrate preferences for the auxin uptake carrier AUX1. Total and partial loss-of-function aux1 mutants were assessed against wild-type for dose-dependent resistance to a range of auxins and analogues. We then developed an auxin accumulation assay with associated mathematical modelling to enumerate accurate IC50 values for a small library of auxin analogues. The structure activity relationship data were analysed using molecular field analyses to create a pharmacophoric atlas of AUX1 substrates. The uptake carrier exhibits a very high level of selectivity towards small substrates including the natural indole-3-acetic acid, and the synthetic auxin 2,4-dichlorophenoxyacetic acid. No AUX1 activity was observed for herbicides based on benzoic acid (dicamba), pyridinyloxyacetic acid (triclopyr) or the 6-arylpicolinates (halauxifen), and very low affinity was found for picolinic acid-based auxins (picloram) and quinolinecarboxylic acids (quinclorac). The atlas demonstrates why some widely used auxin herbicides are not, or are very poor substrates. We list molecular descriptors for AUX1 substrates and discuss our findings in terms of herbicide resistance management.

• Klíčová slova
• auxin transport, cheminformatics, herbicide, herbicide resistance, molecular field maps, pharmacophore, structure-activity relationship, uptake carrier,
• MeSH
• Arabidopsis metabolismus   MeSH
• biologické modely MeSH
• biotest MeSH
• herbicidy metabolismus   MeSH
• indoly metabolismus   MeSH
• inhibiční koncentrace 50 MeSH
• kořeny rostlin růst a vývoj   MeSH
• kyselina 2,4-dichlorfenoxyoctová metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• mutace genetika   MeSH
• proteiny huseníčku metabolismus   MeSH
• semenáček růst a vývoj   MeSH
• substrátová specifita MeSH
• tabák cytologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• AUX1 protein, Arabidopsis MeSH Prohlížeč
• herbicidy MeSH
• indoly MeSH
• kyselina 2,4-dichlorfenoxyoctová MeSH
• kyseliny indoloctové MeSH
• proteiny huseníčku MeSH

Membrane traffic at the trans-Golgi network (TGN) is crucial for correctly distributing various membrane proteins to their destination. Polarly localized auxin efflux proteins, including PIN-FORMED1 (PIN1), are dynamically transported between the endosomes and the plasma membrane (PM) in the plant cells. The intracellular trafficking of PIN1 protein is sensitive to the fungal toxin brefeldin A (BFA), which is known to inhibit guanine nucleotide exchange factors for ADP ribosylation factors (ARF GEFs) such as GNOM. However, the molecular details of the BFA-sensitive trafficking pathway have not been fully revealed. In a previous study, we identified an Arabidopsis mutant BFA-visualized endocytic trafficking defective 3 (ben3) which exhibited reduced sensitivity to BFA in terms of BFA-induced intracellular PIN1 agglomeration. Here, we show that BEN3 encodes a member of BIG family ARF GEFs, BIG2. BEN3/BIG2 tagged with fluorescent proteins co-localized with markers for the TGN/early endosome (EE). Inspection of conditionally induced de novo synthesized PIN1 confirmed that its secretion to the PM is BFA sensitive, and established BEN3/BIG2 as a crucial component of this BFA action at the level of the TGN/EE. Furthermore, ben3 mutation alleviated BFA-induced agglomeration of another TGN-localized ARF GEF, BEN1/MIN7. Taken together, our results suggest that BEN3/BIG2 is an ARF GEF component, which confers BFA sensitivity to the TGN/EE in Arabidopsis.

• Klíčová slova
• ARF GEF, Arabidopsis, Auxin, Brefeldin A, PIN-FORMED1, trans-Golgi network,
• MeSH
• ADP-ribosylační faktory genetika   metabolismus   MeSH
• alely MeSH
• Arabidopsis účinky léků   metabolismus   MeSH
• brefeldin A farmakologie   MeSH
• buněčná membrána účinky léků   metabolismus   MeSH
• endozomy účinky léků   metabolismus   MeSH
• fenotyp MeSH
• klonování DNA MeSH
• kompartmentace buňky MeSH
• nesmyslný kodon genetika   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• semenáček účinky léků   růst a vývoj   MeSH
• trans-Golgiho síť účinky léků   metabolismus   MeSH
• transport proteinů účinky léků   MeSH
• výměnné faktory guaninnukleotidů metabolismus   MeSH
• zelené fluorescenční proteiny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• ADP-ribosylační faktory MeSH
• big2 protein Arabidopsis MeSH Prohlížeč
• brefeldin A MeSH
• nesmyslný kodon MeSH
• proteiny huseníčku MeSH
• výměnné faktory guaninnukleotidů MeSH
• zelené fluorescenční proteiny MeSH

BACKGROUND: In seeds, the transition from dormancy to germination is regulated by abscisic acid (ABA) and gibberellins (GAs), and involves chromatin remodelling. Particularly, the repressive mark H3K27 trimethylation (H3K27me3) has been shown to target many master regulators of this transition. DAG1 (DOF AFFECTING GERMINATION1), is a negative regulator of seed germination in Arabidopsis, and directly represses the GA biosynthetic gene GA3ox1 (gibberellin 3-β-dioxygenase 1). We set to investigate the role of DAG1 in seed dormancy and maturation with respect to epigenetic and hormonal control. RESULTS: We show that DAG1 expression is controlled at the epigenetic level through the H3K27me3 mark during the seed-to-seedling transition, and that DAG1 directly represses also the ABA catabolic gene CYP707A2; consistently, the ABA level is lower while the GA level is higher in dag1 mutant seeds. Furthermore, both DAG1 expression and protein stability are controlled by GAs. CONCLUSIONS: Our results point to DAG1 as a key player in the control of the developmental switch between seed dormancy and germination.

• Klíčová slova
• ABA, Arabidopsis thaliana, Chromatin remodelling, DAG1, DOF proteins, GA, Seed development,
• MeSH
• Arabidopsis růst a vývoj   metabolismus   MeSH
• DNA vazebné proteiny genetika   metabolismus   MeSH
• gibereliny metabolismus   MeSH
• kyselina abscisová metabolismus   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• semena rostlinná genetika   růst a vývoj   metabolismus   MeSH
• semenáček genetika   růst a vývoj   metabolismus   MeSH
• transkripční faktory genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DAG1 protein, Arabidopsis MeSH Prohlížeč
• DNA vazebné proteiny MeSH
• gibereliny MeSH
• kyselina abscisová MeSH
• proteiny huseníčku MeSH
• transkripční faktory MeSH

The herbicide 2,4-D exhibits an auxinic activity and therefore can be used as a synthetic and traceable analog to study auxin-related responses. Here we identified that not only exogenous 2,4-D but also its amide-linked metabolite 2,4-D-Glu displayed an inhibitory effect on plant growth via the TIR1/AFB auxin-mediated signaling pathway. To further investigate 2,4-D metabolite conversion, identity and activity, we have developed a novel purification procedure based on the combination of ion exchange and immuno-specific sorbents combined with a sensitive liquid chromatography-mass spectrometry method. In 2,4-D treated samples, 2,4-D-Glu and 2,4-D-Asp were detected at 100-fold lower concentrations compared to 2,4-D levels, showing that 2,4-D can be metabolized in the plant. Moreover, 2,4-D-Asp and 2,4-D-Glu were identified as reversible forms of 2,4-D homeostasis that can be converted to free 2,4-D. This work paves the way to new studies of auxin action in plant development.

• MeSH
• Arabidopsis účinky léků   růst a vývoj   metabolismus   MeSH
• F-box proteiny genetika   metabolismus   MeSH
• herbicidy farmakologie   MeSH
• homeostáza MeSH
• kořeny rostlin účinky léků   růst a vývoj   metabolismus   MeSH
• kyselina 2,4-dichlorfenoxyoctová farmakologie   MeSH
• kyseliny indoloctové metabolismus   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• receptory buněčného povrchu genetika   metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin farmakologie   MeSH
• semenáček účinky léků   růst a vývoj   metabolismus   MeSH
• signální transdukce účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• F-box proteiny MeSH
• herbicidy MeSH
• kyselina 2,4-dichlorfenoxyoctová MeSH
• kyseliny indoloctové MeSH
• proteiny huseníčku MeSH
• receptory buněčného povrchu MeSH
• regulátory růstu rostlin MeSH
• TIR1 protein, Arabidopsis MeSH Prohlížeč

Plant cell morphogenesis involves concerted rearrangements of microtubules and actin microfilaments. We previously reported that FH1, the main Arabidopsis thaliana housekeeping Class I membrane-anchored formin, contributes to actin dynamics and microtubule stability in rhizodermis cells. Here we examine the effects of mutations affecting FH1 (At3g25500) on cell morphogenesis and above-ground organ development in seedlings, as well as on cytoskeletal organization and dynamics, using a combination of confocal and variable angle epifluorescence microscopy with a pharmacological approach. Homozygous fh1 mutants exhibited cotyledon epinasty and had larger cotyledon pavement cells with more pronounced lobes than the wild type. The pavement cell shape alterations were enhanced by expression of the fluorescent microtubule marker GFP-microtubule-associated protein 4 (MAP4). Mutant cotyledon pavement cells exhibited reduced density and increased stability of microfilament bundles, as well as enhanced dynamics of microtubules. Analogous results were also obtained upon treatments with the formin inhibitor SMIFH2 (small molecule inhibitor of formin homology 2 domains). Pavement cell shape in wild-type (wt) and fh1 plants in some situations exhibited a differential response towards anti-cytoskeletal drugs, especially the microtubule disruptor oryzalin. Our observations indicate that FH1 participates in the control of microtubule dynamics, possibly via its effects on actin, subsequently influencing cell morphogenesis and macroscopic organ development.

• Klíčová slova
• Arabidopsis thaliana, Confocal microscopy, Cotyledon pavement cells, Cytoskeleton, Formin, Variable angle epifluorescence microscopy,
• MeSH
• aktiny metabolismus   MeSH
• Arabidopsis cytologie   účinky léků   metabolismus   MeSH
• biologické markery metabolismus   MeSH
• biologické modely MeSH
• cytoskelet účinky léků   metabolismus   MeSH
• fluorescence MeSH
• forminy MeSH
• klathrin metabolismus   MeSH
• kotyledon účinky léků   metabolismus   MeSH
• membránové proteiny metabolismus   MeSH
• mikrofilamenta účinky léků   metabolismus   MeSH
• mikrotubuly účinky léků   metabolismus   MeSH
• mutace genetika   MeSH
• proteiny huseníčku metabolismus   MeSH
• semenáček účinky léků   růst a vývoj   metabolismus   MeSH
• thioketony farmakologie   MeSH
• tvar buňky * účinky léků   MeSH
• uracil analogy a deriváty   farmakologie   MeSH
• zelené fluorescenční proteiny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• AFH1 protein, Arabidopsis MeSH Prohlížeč
• aktiny MeSH
• biologické markery MeSH
• forminy MeSH
• klathrin MeSH
• membránové proteiny MeSH
• proteiny huseníčku MeSH
• SMIFH2 compound MeSH Prohlížeč
• thioketony MeSH
• uracil MeSH
• zelené fluorescenční proteiny MeSH

The cytokinin response factors (CRFs) are a group of related AP2/ERF transcription factors that are transcriptionally induced by cytokinin. Here we explore the role of the CRFs in Arabidopsis thaliana growth and development by analyzing lines with decreased and increased CRF function. While single crf mutations have no appreciable phenotypes, disruption of multiple CRFs results in larger rosettes, delayed leaf senescence, a smaller root apical meristem (RAM), reduced primary and lateral root growth, and, in etiolated seedlings, shorter hypocotyls. In contrast, overexpression of CRFs generally results in the opposite phenotypes. The crf1,2,5,6 quadruple mutant is embryo lethal, indicating that CRF function is essential for embryo development. Disruption of the CRFs results in partially insensitivity to cytokinin in a root elongation assay and affects the basal expression of a significant number of cytokinin-regulated genes, including the type-A ARRs, although it does not impair the cytokinin induction of the type-A ARRs. Genes encoding homeobox transcription factors are mis-expressed in the crf1,3,5,6 mutant, including STIMPY/WOX9 that is required for root and shoot apical meristem maintenance roots and which has previously been linked to cytokinin. These results indicate that the CRF transcription factors play important roles in multiple aspects of plant growth and development, in part through a complex interaction with cytokinin signaling.

• Klíčová slova
• cell division, cytokinin, plant development, root meristem, senescence, transcription factors, two-component signaling,
• MeSH
• Arabidopsis genetika   růst a vývoj   fyziologie   MeSH
• cytokininy metabolismus   MeSH
• exprese genu MeSH
• fenotyp MeSH
• homeodoménové proteiny genetika   metabolismus   MeSH
• kořeny rostlin genetika   růst a vývoj   fyziologie   MeSH
• meristém genetika   růst a vývoj   fyziologie   MeSH
• mutace MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin metabolismus   MeSH
• semenáček genetika   růst a vývoj   fyziologie   MeSH
• signální transdukce * MeSH
• transkripční faktory genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cytokininy MeSH
• homeodoménové proteiny MeSH
• proteiny huseníčku MeSH
• regulátory růstu rostlin MeSH
• transkripční faktory MeSH