B-Box-containing zinc finger transcription factors (BBX) are involved in light-mediated growth, affecting processes such as hypocotyl elongation in Arabidopsis thaliana. However, the molecular and hormonal framework that regulates plant growth through BBX proteins is incomplete. Here, we demonstrate that BBX21 inhibits the hypocotyl elongation through the brassinosteroid (BR) pathway. BBX21 reduces the sensitivity to 24-epiBL, a synthetic active BR, principally at very low concentrations in simulated shade. The biosynthesis profile of BRs showed that two active BR-brassinolide and 28-homobrassinolide-and 8 of 11 intermediates can be repressed by BBX21 under white light (WL) or simulated shade. Furthermore, BBX21 represses the expression of CYTOCHROME P450 90B1 (DWF4/CYP90B1), BRASSINOSTEROID-6-OXIDASE 1 (BR6OX1, CYP85A1) and BR6OX2 (CYP85A2) genes involved in the BR biosynthesis in WL while specifically promoting DWF4 and PHYB ACTIVATION TAGGED SUPPRESSOR 1 (CYP2B1/BAS1) expression in WL supplemented with far-red (WL + FR), a treatment that simulates shade. In addition, BBX21 represses BR signaling genes, such as PACLOBUTRAZOL RESISTANCE1 (PRE1), PRE3 and ARABIDOPSIS MYB-LIKE 2 (MYBL2), and auxin-related and expansin genes, such as INDOLE-3-ACETIC ACID INDUCIBLE 1 (IAA1), IAA4 and EXPANSIN 11 in short-term shade. By a genetic approach, we found that BBX21 acts genetically upstream of BRASSINAZOLE-RESISTANT 1 (BZR1) for the promotion of DWF4 and BAS1 gene expression in shade. We propose that BBX21 integrates the BR homeostasis and shade-light signaling, allowing the fine-tuning of hypocotyl elongation in Arabidopsis.
- Klíčová slova
- Arabidopsis, BBX21, BZR1, Brassinosteroids (BRs), Shade light,
- MeSH
- Arabidopsis * genetika růst a vývoj metabolismus účinky záření MeSH
- brassinosteroidy * metabolismus biosyntéza MeSH
- hypokotyl * růst a vývoj genetika metabolismus MeSH
- proteiny huseníčku * metabolismus genetika MeSH
- regulace genové exprese u rostlin * MeSH
- regulátory růstu rostlin metabolismus MeSH
- signální transdukce * MeSH
- světlo * MeSH
- systém (enzymů) cytochromů P-450 metabolismus genetika MeSH
- transkripční faktory * metabolismus genetika MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- brassinosteroidy * MeSH
- proteiny huseníčku * MeSH
- regulátory růstu rostlin MeSH
- systém (enzymů) cytochromů P-450 MeSH
- transkripční faktory * MeSH
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
Plant growth is continuously modulated by endogenous and exogenous stimuli. By no means the only, but well described, signaling molecules produced in plants and distributed through the plant body to orchestrate efficient growth are photosynthates. Light is a potent exogenous stimulus that determines, first, the rate of photosynthesis, but also the rate of plant growth. Root meristem activity is reduced with direct illumination but enhanced with increased sugar levels. With reduced cotyledon illumination, the seedling increases hypocotyl elongation until adequate light exposure is again provided. If endogenous carbon sources are limited, this leads to a temporary inhibition of root growth. Experimental growth conditions include exogenous supplementation of sucrose or glucose in addition to culturing seedlings under light exposure in Petri dishes. We compared total root length and hypocotyl elongation of Arabidopsis thaliana wild type Col-0 in response to illumination status and carbon source in the growth medium. Overall, sucrose supplementation promoted hypocotyl and root length to a greater extent than glucose supplementation. Glucose promoted root length compared to non-supplemented seedlings especially when cotyledon illumination was greatly reduced.
- Klíčová slova
- Arabidopsis thaliana, carbon source, dark grown root, drootsystem, etiolated, hypocotyl growth, illumination, root growth, shaded cotyledons,
- MeSH
- adaptace oční fyziologie MeSH
- Arabidopsis růst a vývoj metabolismus MeSH
- glukosa metabolismus MeSH
- hypokotyl růst a vývoj metabolismus MeSH
- kořeny rostlin růst a vývoj metabolismus MeSH
- kotyledon růst a vývoj metabolismus MeSH
- sacharosa metabolismus MeSH
- uhlík metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- glukosa MeSH
- sacharosa MeSH
- uhlík MeSH
Temperature passively affects biological processes involved in plant growth. Therefore, it is challenging to study the dedicated temperature signalling pathways that orchestrate thermomorphogenesis, a suite of elongation growth-based adaptations that enhance leaf-cooling capacity. We screened a chemical library for compounds that restored hypocotyl elongation in the pif4-2-deficient mutant background at warm temperature conditions in Arabidopsis thaliana to identify modulators of thermomorphogenesis. The small aromatic compound 'Heatin', containing 1-iminomethyl-2-naphthol as a pharmacophore, was selected as an enhancer of elongation growth. We show that ARABIDOPSIS ALDEHYDE OXIDASES redundantly contribute to Heatin-mediated hypocotyl elongation. Following a chemical proteomics approach, the members of the NITRILASE1-subfamily of auxin biosynthesis enzymes were identified among the molecular targets of Heatin. Our data reveal that nitrilases are involved in promotion of hypocotyl elongation in response to high temperature and Heatin-mediated hypocotyl elongation requires the NITRILASE1-subfamily members, NIT1 and NIT2. Heatin inhibits NIT1-subfamily enzymatic activity in vitro and the application of Heatin accordingly results in the accumulation of NIT1-subfamily substrate indole-3-acetonitrile in vivo. However, levels of the NIT1-subfamily product, bioactive auxin (indole-3-acetic acid), were also significantly increased. It is likely that the stimulation of hypocotyl elongation by Heatin might be independent of its observed interaction with NITRILASE1-subfamily members. However, nitrilases may contribute to the Heatin response by stimulating indole-3-acetic acid biosynthesis in an indirect way. Heatin and its functional analogues present novel chemical entities for studying auxin biology.
- Klíčová slova
- 1-iminomethyl-2-naphthol, Arabidopsis, Heatin, IAN, NIT1-subfamily, PIF4, aldehyde oxidase, chemical genetics, indole-3-acetonitrile, nitrilases, thermomorphogenesis,
- MeSH
- aldehydoxidasa genetika metabolismus MeSH
- aminohydrolasy genetika metabolismus MeSH
- apomorfin analogy a deriváty farmakologie MeSH
- Arabidopsis účinky léků růst a vývoj MeSH
- herbicidy farmakologie MeSH
- hypokotyl účinky léků růst a vývoj MeSH
- inhibitory enzymů aplikace a dávkování chemie farmakologie MeSH
- kyseliny indoloctové MeSH
- molekulární struktura MeSH
- pikloram farmakologie MeSH
- proteiny huseníčku genetika metabolismus MeSH
- regulace genové exprese u rostlin účinky léků MeSH
- transkriptom účinky léků MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- 10,11-dihydroxy-N-n-propylnorapomorphine MeSH Prohlížeč
- AAO1 protein, Arabidopsis MeSH Prohlížeč
- aldehydoxidasa MeSH
- aminohydrolasy MeSH
- apomorfin MeSH
- herbicidy MeSH
- inhibitory enzymů MeSH
- kyseliny indoloctové MeSH
- nitrilase MeSH Prohlížeč
- pikloram MeSH
- proteiny huseníčku MeSH
Auxin is a major plant growth regulator, but current models on auxin perception and signaling cannot explain the whole plethora of auxin effects, in particular those associated with rapid responses. A possible candidate for a component of additional auxin perception mechanisms is the AUXIN BINDING PROTEIN 1 (ABP1), whose function in planta remains unclear. Here we combined expression analysis with gain- and loss-of-function approaches to analyze the role of ABP1 in plant development. ABP1 shows a broad expression largely overlapping with, but not regulated by, transcriptional auxin response activity. Furthermore, ABP1 activity is not essential for the transcriptional auxin signaling. Genetic in planta analysis revealed that abp1 loss-of-function mutants show largely normal development with minor defects in bolting. On the other hand, ABP1 gain-of-function alleles show a broad range of growth and developmental defects, including root and hypocotyl growth and bending, lateral root and leaf development, bolting, as well as response to heat stress. At the cellular level, ABP1 gain-of-function leads to impaired auxin effect on PIN polar distribution and affects BFA-sensitive PIN intracellular aggregation. The gain-of-function analysis suggests a broad, but still mechanistically unclear involvement of ABP1 in plant development, possibly masked in abp1 loss-of-function mutants by a functional redundancy.
- Klíčová slova
- AUXIN BINDING PROTEIN 1 (ABP1), Auxin, Auxin signaling, Plant development,
- MeSH
- Arabidopsis růst a vývoj metabolismus MeSH
- hypokotyl růst a vývoj metabolismus MeSH
- konfokální mikroskopie MeSH
- kořeny rostlin růst a vývoj metabolismus MeSH
- kvantitativní polymerázová řetězová reakce MeSH
- kyseliny indoloctové metabolismus MeSH
- proteiny huseníčku metabolismus fyziologie MeSH
- protoplasty metabolismus MeSH
- receptory buněčného povrchu metabolismus fyziologie MeSH
- regulace genové exprese u rostlin MeSH
- regulátory růstu rostlin metabolismus fyziologie MeSH
- rostlinné proteiny metabolismus fyziologie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- auxin-binding protein 1 MeSH Prohlížeč
- kyseliny indoloctové MeSH
- proteiny huseníčku MeSH
- receptory buněčného povrchu MeSH
- regulátory růstu rostlin MeSH
- rostlinné proteiny 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
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
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
Phytohormones are crucial molecules regulating plant development and responses to environmental challenges, including abiotic stresses, microbial and insect attacks. Most notably, phytohormones play important roles in the biosynthesis of lignocellulosics. Jasmonates are involved in secondary growth and secondary metabolism, such as phenylpropanoids and lignin biosyntheses. At the physiological and molecular levels, the actions of phytohormones depend on subtle concentration changes, as well as antagonistic equilibria between two or more of these molecules. In this article, we investigate the consequences of jasmonic acid (JA) spraying on young hemp hypocotyls. First, we show that JA application results in changes in the monomeric composition of lignin. Second, we highlight that, five days after application, JA leads to an increase in salicylic acid (SA) content in hemp hypocotyls. These results are discussed in the light of the known antagonism between JA and SA at both the physiological and molecular levels.
- Klíčová slova
- Hemp, jasmonic acid, lignin composition, salicylic acid,
- MeSH
- Cannabis účinky léků metabolismus MeSH
- cyklopentany farmakologie MeSH
- hypokotyl účinky léků růst a vývoj metabolismus MeSH
- kyselina salicylová farmakologie MeSH
- lignin metabolismus MeSH
- oxylipiny farmakologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- cyklopentany MeSH
- jasmonic acid MeSH Prohlížeč
- kyselina salicylová MeSH
- lignin MeSH
- oxylipiny MeSH
The collet (root-hypocotyl junction) region is an important plant transition zone between soil and atmospheric environments. Despite its crucial importance for plant development, little is known about how this transition zone is specified. Here we document the involvement of the exocyst complex in this process. The exocyst, an octameric tethering complex, participates in secretion and membrane recycling and is central to numerous cellular and developmental processes, such as growth of root hairs, cell expansion, recycling of PIN auxin efflux carriers and many others. We show that dark-grown Arabidopsis mutants deficient in exocyst subunits can form a hair-bearing ectopic collet-like structure above the true collet, morphologically resembling the true collet but also retaining some characteristics of the hypocotyl. The penetrance of this phenotypic defect is significantly influenced by cultivation temperature and carbon source, and is related to a defect in auxin regulation. These observations provide new insights into the regulation of collet region formation and developmental plasticity of the hypocotyl.
- Klíčová slova
- Arabidopsis thaliana, auxin, collet, etiolated hypocotyl, exocyst, root–hypocotyl junction, starch accumulation,
- MeSH
- Arabidopsis genetika růst a vývoj MeSH
- hypokotyl genetika růst a vývoj metabolismus MeSH
- proteiny huseníčku genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- proteiny huseníčku MeSH
