Plants as non-mobile organisms constantly integrate varying environmental signals to flexibly adapt their growth and development. Local fluctuations in water and nutrient availability, sudden changes in temperature or other abiotic and biotic stresses can trigger changes in the growth of plant organs. Multiple mutually interconnected hormonal signaling cascades act as essential endogenous translators of these exogenous signals in the adaptive responses of plants. Although the molecular backbones of hormone transduction pathways have been identified, the mechanisms underlying their interactions are largely unknown. Here, using genome wide transcriptome profiling we identify an auxin and cytokinin cross-talk component; SYNERGISTIC ON AUXIN AND CYTOKININ 1 (SYAC1), whose expression in roots is strictly dependent on both of these hormonal pathways. We show that SYAC1 is a regulator of secretory pathway, whose enhanced activity interferes with deposition of cell wall components and can fine-tune organ growth and sensitivity to soil pathogens.

• MeSH
• Arabidopsis genetika   růst a vývoj   metabolismus   MeSH
• buněčná stěna chemie   metabolismus   MeSH
• cytokininy metabolismus   MeSH
• endozomy metabolismus   MeSH
• geneticky modifikované rostliny metabolismus   MeSH
• Golgiho aparát metabolismus   MeSH
• kořeny rostlin metabolismus   mikrobiologie   MeSH
• kyseliny indoloctové metabolismus   MeSH
• membránové proteiny genetika   metabolismus   MeSH
• odolnost vůči nemocem genetika   MeSH
• Plasmodiophorida patogenita   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• půda MeSH
• regulace genové exprese u rostlin genetika   MeSH
• regulátory růstu rostlin metabolismus   MeSH
• sekreční dráha genetika   MeSH
• stanovení celkové genové exprese MeSH
• transkriptom genetika   MeSH
• vezikulární transportní proteiny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• AT2G18840 protein, Arabidopsis MeSH Prohlížeč
• AT4G30260 protein, Arabidopsis MeSH Prohlížeč
• cytokininy MeSH
• ECHIDNA protein, Arabidopsis MeSH Prohlížeč
• kyseliny indoloctové MeSH
• membránové proteiny MeSH
• proteiny huseníčku MeSH
• půda MeSH
• regulátory růstu rostlin MeSH
• SYAC1 protein, Arabidopsis MeSH Prohlížeč
• vezikulární transportní proteiny MeSH

Seedling establishment following germination requires the fine tuning of plant hormone levels including that of auxin. Directional movement of auxin has a central role in the associated processes, among others, in hypocotyl hook development. Regulated auxin transport is ensured by several transporters (PINs, AUX1, ABCB) and their tight cooperation. Here we describe the regulatory role of the Arabidopsis thaliana CRK5 protein kinase during hypocotyl hook formation/opening influencing auxin transport and the auxin-ethylene-GA hormonal crosstalk. It was found that the Atcrk5-1 mutant exhibits an impaired hypocotyl hook establishment phenotype resulting only in limited bending in the dark. The Atcrk5-1 mutant proved to be deficient in the maintenance of local auxin accumulation at the concave side of the hypocotyl hook as demonstrated by decreased fluorescence of the auxin sensor DR5::GFP. Abundance of the polar auxin transport (PAT) proteins PIN3, PIN7, and AUX1 were also decreased in the Atcrk5-1 hypocotyl hook. The AtCRK5 protein kinase was reported to regulate PIN2 protein activity by phosphorylation during the root gravitropic response. Here it is shown that AtCRK5 can also phosphorylate in vitro the hydrophilic loops of PIN3. We propose that AtCRK5 may regulate hypocotyl hook formation in Arabidopsis thaliana through the phosphorylation of polar auxin transport (PAT) proteins, the fine tuning of auxin transport, and consequently the coordination of auxin-ethylene-GA levels.

• Klíčová slova
• Arabidopsis thaliana, Ca2+/calmodulin-dependent kinase-related kinases (CRKs), polar auxin transport (PAT) proteins, GA3, auxin gradient, ethylene, skotomorphogenesis,
• MeSH
• Arabidopsis účinky léků   fyziologie   MeSH
• biologické markery MeSH
• fenotyp MeSH
• fosforylace MeSH
• hypokotyl fyziologie   MeSH
• klíčení MeSH
• morfogeneze * účinky léků   genetika   MeSH
• protein-serin-threoninkinasy metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• receptory buněčného povrchu metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• reportérové geny MeSH
• signální transdukce MeSH
• vývoj rostlin * účinky léků   genetika   MeSH
• xantony farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• biologické markery MeSH
• CRK5 protein, Arabidopsis MeSH Prohlížeč
• GA3 compound MeSH Prohlížeč
• protein-serin-threoninkinasy MeSH
• proteiny huseníčku MeSH
• receptory buněčného povrchu MeSH
• xantony MeSH

Auxin phytohormones control most aspects of plant development through a complex and interconnected signaling network. In the presence of auxin, AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) transcriptional repressors are targeted for degradation by the SKP1-CULLIN1-F-BOX (SCF) ubiquitin-protein ligases containing TRANSPORT INHIBITOR RESISTANT 1/AUXIN SIGNALING F-BOX (TIR1/AFB). CULLIN1-neddylation is required for SCFTIR1/AFB functionality, as exemplified by mutants deficient in the NEDD8-activating enzyme subunit AUXIN-RESISTANT 1 (AXR1). Here, we report a chemical biology screen that identifies small molecules requiring AXR1 to modulate plant development. We selected four molecules of interest, RubNeddin 1 to 4 (RN1 to -4), among which RN3 and RN4 trigger selective auxin responses at transcriptional, biochemical, and morphological levels. This selective activity is explained by their ability to consistently promote the interaction between TIR1 and a specific subset of AUX/IAA proteins, stimulating the degradation of particular AUX/IAA combinations. Finally, we performed a genetic screen using RN4, the RN with the greatest potential for dissecting auxin perception, which revealed that the chromatin remodeling ATPase BRAHMA is implicated in auxin-mediated apical hook development. These results demonstrate the power of selective auxin agonists to dissect auxin perception for plant developmental functions, as well as offering opportunities to discover new molecular players involved in auxin responses.

• Klíčová slova
• auxin, chemical biology, hormone perception, prohormone, selective agonist,
• MeSH
• Arabidopsis genetika   metabolismus   MeSH
• F-box proteiny metabolismus   MeSH
• genetická transkripce účinky léků   MeSH
• geneticky modifikované rostliny genetika   MeSH
• kyseliny indoloctové metabolismus   MeSH
• protein NEDD8 genetika   MeSH
• proteinligasy komplexu SCF metabolismus   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• proteolýza * MeSH
• receptory buněčného povrchu metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin genetika   metabolismus   MeSH
• semenáček metabolismus   MeSH
• signální transdukce MeSH
• transkripční faktory metabolismus   MeSH
• vývoj rostlin genetika   fyziologie   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
• F-box proteiny MeSH
• indoleacetic acid MeSH Prohlížeč
• kyseliny indoloctové MeSH
• protein NEDD8 MeSH
• proteinligasy komplexu SCF MeSH
• proteiny huseníčku MeSH
• receptory buněčného povrchu MeSH
• regulátory růstu rostlin MeSH
• transkripční faktory MeSH

The volatile two-carbon hormone ethylene acts in concert with an array of signals to affect etiolated seedling development. From a chemical screen, we isolated a quinoline carboxamide designated ACCERBATIN (AEX) that exacerbates the 1-aminocyclopropane-1-carboxylic acid-induced triple response, typical for ethylene-treated seedlings in darkness. Phenotypic analyses revealed distinct AEX effects including inhibition of root hair development and shortening of the root meristem. Mutant analysis and reporter studies further suggested that AEX most probably acts in parallel to ethylene signaling. We demonstrated that AEX functions at the intersection of auxin metabolism and reactive oxygen species (ROS) homeostasis. AEX inhibited auxin efflux in BY-2 cells and promoted indole-3-acetic acid (IAA) oxidation in the shoot apical meristem and cotyledons of etiolated seedlings. Gene expression studies and superoxide/hydrogen peroxide staining further revealed that the disrupted auxin homeostasis was accompanied by oxidative stress. Interestingly, in light conditions, AEX exhibited properties reminiscent of the quinoline carboxylate-type auxin-like herbicides. We propose that AEX interferes with auxin transport from its major biosynthesis sites, either as a direct consequence of poor basipetal transport from the shoot meristematic region, or indirectly, through excessive IAA oxidation and ROS accumulation. Further investigation of AEX can provide new insights into the mechanisms connecting auxin and ROS homeostasis in plant development and provide useful tools to study auxin-type herbicides.

• Klíčová slova
• Arabidopsis, auxin homeostasis, chemical genetics, ethylene signaling, herbicide, quinoline carboxamide, reactive oxygen species, triple response,
• MeSH
• aminokyseliny cyklické metabolismus   MeSH
• Arabidopsis genetika   metabolismus   MeSH
• chinolony metabolismus   MeSH
• ethyleny metabolismus   MeSH
• exprese genu MeSH
• herbicidy chemie   MeSH
• homeostáza MeSH
• kyseliny indoloctové metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• semenáček metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 1-aminocyclopropane-1-carboxylic acid MeSH Prohlížeč
• aminokyseliny cyklické MeSH
• chinolony MeSH
• ethylene MeSH Prohlížeč
• ethyleny MeSH
• herbicidy MeSH
• kyseliny indoloctové MeSH
• proteiny huseníčku MeSH
• reaktivní formy kyslíku MeSH

In plants, the multistep phosphorelay (MSP) pathway mediates a range of regulatory processes, including those activated by cytokinins. The cross talk between cytokinin response and light has been known for a long time. However, the molecular mechanism underlying the interaction between light and cytokinin signaling remains elusive. In the screen for upstream regulators we identified a LONG PALE HYPOCOTYL (LPH) gene whose activity is indispensable for spatiotemporally correct expression of CYTOKININ INDEPENDENT1 (CKI1), encoding the constitutively active sensor His kinase that activates MSP signaling. lph is a new allele of HEME OXYGENASE1 (HY1) that encodes the key protein in the biosynthesis of phytochromobilin, a cofactor of photoconvertible phytochromes. Our analysis confirmed the light-dependent regulation of the CKI1 expression pattern. We show that CKI1 expression is under the control of phytochrome A (phyA), functioning as a dual (both positive and negative) regulator of CKI1 expression, presumably via the phyA-regulated transcription factors (TF) PHYTOCHROME INTERACTING FACTOR3 and CIRCADIAN CLOCK ASSOCIATED1. Changes in CKI1 expression observed in lph/hy1-7 and phy mutants correlate with misregulation of MSP signaling, changed cytokinin sensitivity, and developmental aberrations that were previously shown to be associated with cytokinin and/or CKI1 action. Besides that, we demonstrate a novel role of phyA-dependent CKI1 expression in the hypocotyl elongation and hook development during skotomorphogenesis. Based on these results, we propose that the light-dependent regulation of CKI1 provides a plausible mechanistic link underlying the well-known interaction between light- and cytokinin-controlled plant development.

• MeSH
• Arabidopsis genetika   metabolismus   účinky záření   MeSH
• cytokininy metabolismus   MeSH
• fytochrom A genetika   metabolismus   MeSH
• geneticky modifikované rostliny MeSH
• hemová oxygenasa (decyklizující) genetika   metabolismus   MeSH
• hypokotyl genetika   metabolismus   účinky záření   MeSH
• modely genetické MeSH
• mutace MeSH
• proteinkinasy genetika   metabolismus   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• regulace genové exprese u rostlin genetika   účinky záření   MeSH
• signální transdukce genetika   účinky záření   MeSH
• světlo * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• CKI1 protein, Arabidopsis MeSH Prohlížeč
• cytokininy MeSH
• fytochrom A MeSH
• hemová oxygenasa (decyklizující) MeSH
• HY1 protein, Arabidopsis MeSH Prohlížeč
• proteinkinasy MeSH
• proteiny huseníčku MeSH