Analysis of structure-activity relationships of auxin-like molecules

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Complementation of the embryo-lethal T-DNA insertion mutant of AUXIN-BINDING-PROTEIN 1 (ABP1) with abp1 point mutated versions reveals crosstalk of ABP1 and phytochromes

The function of the extracytoplasmic AUXIN-BINDING-PROTEIN1 (ABP1) is largely enigmatic. We complemented a homozygous T-DNA insertion null mutant of ABP1 in Arabidopsis thaliana Wassilewskia with three mutated and one wild-type (wt) ABP1 cDNA, all tagged C-terminally with a strepII–FLAG tag upstream the KDEL signal. Based on in silico modelling, the abp1 mutants were predicted to have altered geometries of the auxin binding pocket and calculated auxin binding energies lower than the wt. Phenotypes linked to auxin transport were compromised in these three complemented abp1 mutants. Red light effects, such as elongation of hypocotyls in constant red (R) and far-red (FR) light, in white light supplemented by FR light simulating shade, and inhibition of gravitropism by R or FR, were all compromised in the complemented lines. Using auxin- or light-induced expression of marker genes, we showed that auxin-induced expression was delayed already after 10min, and light-induced expression within 60min, even though TIR1/AFB or phyB are thought to act as receptors relevant for gene expression regulation. The expression of marker genes in seedlings responding to both auxin and shade showed that for both stimuli regulation of marker gene expression was altered after 10–20min in the wild type and phyB mutant. The rapidity of expression responses provides a framework for the mechanics of functional interaction of ABP1 and phyB to trigger interwoven signalling pathways

Fine-Structure Map of the Histidine Transport Genes in \u3cem\u3eSalmonella typhimurium\u3c/em\u3e

Afine-structure genetic map of the histidine transport region of the Salmonella typhimurium chromosome was constructed. Twenty-five deletion mutants were isolated and used for dividing the hisJ and hisP genes into 8 and 13 regions respectively. A total of 308 mutations, spontaneous and mutagen induced, have been placed in these regions by deletion mapping. The histidine transport operon is presumed to be constituted of genes dhuA, hisJ, and hisP, and the regulation of the hosP and hisJ genes by dhuA is discussed. The orientation of this operon relative to purF has been established by three-point crosses as being: purF duhA hisJ hisP

Complementation of the embryo-lethal T-DNA insertion mutant of AUXIN-BINDING-PROTEIN 1 (ABP1) with abp1 point mutated versions reveals crosstalk of ABP1 and phytochromes

AUXIN BINDING PROTEIN1 (ABP1) mutants have properties of auxin- and red light-signalling mutants. A novel concept for growth control by ABP1 and phytochromes is indicated by this functional lin

Ecdiesteroides II. Propiedades geométricas y electrónicas: una aproximación QSAR para determinar el potencial de actividad biológica

Se hace un análisis molecular a nivel semiempírico de los ecdiesteroides, uno de los grupos hormonales más importantes del reino animal. Actualmente, se han descrito mas de 120 compuestos naturales pertenecientes a esta familia, los cuales están involucrados en los procesos de metamorfosis, desarrollo, reproducción y activación metabólica de los procesos vitales de los invertebrados (esp. Artrópodos) y además, pueden ser antagónicos de los brasinoesteroides en plantas, donde actúan como agentes protectores contra insectos fitófagos. En esta comunicación, se describen los estudios preliminares mecanocuánticos y estructurales, de 21 ecdiesteroides naturales diferentes (a partir de la ecdisona y sus modificaciones) y la relación estructuraactividad biológica, así como los principales parámetros y descriptores que potencian la acción ecdiesteroide y las interacciones con el receptor (distancia O3-O22; O22HOMO 3; áng. 2,3,4; áng. 8,9,10; distancia C2-C3; O3 Mayor contribuyente a HOMO-3; Carga de C16) . Se detalla el proceso analítico hasta la obtención de una ecuación que describe el comportamiento de las relaciones estructura-actividad para una serie de dichos compuestos a partir de las variables determinadas a partir de cuya resolución se diferencian significativamente los grupos de moléculas con actividad biológica diferente a partir de la estructura base. Y = 15 071,3 + 66,506 (O22 HOMO 3) 10,166 (O3 HOMO-3) + 34,278 (distancia O3-O22) +172,698 3 (distancia C2-C3) 24, 306 (áng. C2,3,4) +127, 276 (áng. C8,9,10) 611,975 (qC16)

Synthesis of ternary transition metal fluorides Li 3MF 6via a sol-gel route as candidates for cathode materials in lithium-ion batteries

A sol-gel route for ternary lithium fluorides of transition metals (M) is presented allowing the synthesis of Li 3MF 6-type and Li 2MF 5-type compounds. It is based on a fluorolytic process using transition metal acetylacetonates as precursors. The domain size of the obtained powders can be controlled by modifying the conditions of synthesis. 6Li and 7Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is used to study local environments of the Li ions in orthorhombic and monoclinic Li 3VF 6 as well as Li 2MnF 5. The number of magnetically inequivalent Li sites found by MAS NMR is in agreement with the respective crystal structure of the compounds studied. Quantum chemical calculations show that all materials have high de-lithiation energies making them suitable candidates to be used as high-voltage battery cathode materials. © 2012 The Royal Society of Chemistry

Non-steroidal anti-inflammatory drugs target TWISTED DWARF1-regulated actin dynamics and auxin transport-mediated plant development

The widely used non-steroidal anti-inflammatory drugs (NSAIDs) are derivatives of the phytohormone salicylic acid (SA). SA is well known to regulate plant immunity and development, whereas there have been few reports focusing on the effects of NSAIDs in plants. Our studies here reveal that NSAIDs exhibit largely overlapping physiological activities to SA in the model plant Arabidopsis. NSAID treatments lead to shorter and agravitropic primary roots and inhibited lateral root organogenesis. Notably, in addition to the SA-like action, which in roots involves binding to the protein phosphatase 2A (PP2A), NSAIDs also exhibit PP2A-independent effects. Cell biological and biochemical analyses reveal that many NSAIDs bind directly to and inhibit the chaperone activity of TWISTED DWARF1, thereby regulating actin cytoskeleton dynamics and subsequent endosomal trafficking. Our findings uncover an unexpected bioactivity of human pharmaceuticals in plants and provide insights into the molecular mechanism underlying the cellular action of this class of anti-inflammatory compounds

Defining binding efficiency and specificity of auxins for SCF(TIR1/AFB)-Aux/IAA co-receptor complex formation.

Structure-activity profiles for the phytohormone auxin have been collected for over 70 years, and a number of synthetic auxins are used in agriculture. Auxin classification schemes and binding models followed from understanding auxin structures. However, all of the data came from whole plant bioassays, meaning the output was the integral of many different processes. The discovery of Transport Inhibitor-Response 1 (TIR1) and the Auxin F-Box (AFB) proteins as sites of auxin perception and the role of auxin as molecular glue in the assembly of co-receptor complexes has allowed the development of a definitive quantitative structure-activity relationship for TIR1 and AFB5. Factorial analysis of binding activities offered two uncorrelated factors associated with binding efficiency and binding selectivity. The six maximum-likelihood estimators of Efficiency are changes in the overlap matrixes, inferring that Efficiency is related to the volume of the electronic system. Using the subset of compounds that bound strongly, chemometric analyses based on quantum chemical calculations and similarity and self-similarity indices yielded three classes of Specificity that relate to differential binding. Specificity may not be defined by any one specific atom or position and is influenced by coulomb matrixes, suggesting that it is driven by electrostatic forces. These analyses give the first receptor-specific classification of auxins and indicate that AFB5 is the preferred site for a number of auxinic herbicides by allowing interactions with analogues having van der Waals surfaces larger than that of indole-3-acetic acid. The quality factors are also examined in terms of long-standing models for the mechanism of auxin binding

TWISTED DWARF1 mediates the action of auxin transport inhibitors on actin cytoskeleton dynamics

Plant growth and architecture is regulated by the polar distribution of the hormone auxin. Polarity and flexibility of this process is provided by constant cycling of auxin transporter vesicles along actin filaments, coordinated by a positive auxin-actin feedback loop. Both polar auxin transport and vesicle cycling are inhibited by synthetic auxin transport inhibitors, such as 1-N-naphthylphthalamic acid (NPA), counteracting the effect of auxin; however, underlying targets and mechanisms are unclear. Using NMR, we map the NPA binding surface on the Arabidopsis thaliana ABCB chaperone TWISTED DWARF1 (TWD1). We identify ACTIN7 as a relevant, although likely indirect, TWD1 interactor, and show TWD1-dependent regulation of actin filament organization and dynamics and that TWD1 is required for NPA-mediated actin cytoskeleton remodeling. The TWD1-ACTIN7 axis controls plasma membrane presence of efflux transporters, and as a consequence act7 and twd1 share developmental and physiological phenotypes indicative of defects in auxin transport. These can be phenocopied by NPA treatment or by chemical actin (de)stabilization. We provide evidence that TWD1 determines downstream locations of auxin efflux transporters by adjusting actin filament debundling and dynamizing processes and mediating NPA action on the latter. This function appears to be evolutionary conserved since TWD1 expression in budding yeast alters actin polarization and cell polarity and provides NPA sensitivity