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The strigolactones, a class of plant hormones, regulate many aspects of plant physiology. In the inhibition of shoot branching, the [alpha]/[beta] hydrolase D14--which metabolizes strigolactone--interacts with the F-box protein D3 to ubiquitinate and degrade the transcription repressor D53. Despite the fact that multiple modes of interaction between D14 and strigolactone have recently been determined, how the hydrolase functions with D3 to mediate hormone-dependent D53 ubiquitination remains unknown. Here we show that D3 has a C-terminal [alpha]-helix that can switch between two conformational states. The engaged form of this [alpha]-helix facilitates the binding of D3 and D14 with a hydrolysed strigolactone intermediate, whereas the dislodged form can recognize unmodified D14 in an open conformation and inhibits its enzymatic activity. The D3 C-terminal [alpha]-helix enables D14 to recruit D53 in a strigolactone-dependent manner, which in turn activates the hydrolase. By revealing the structural plasticity of the SCF.sup.D3-D14 ubiquitin ligase, our results suggest a mechanism by which the E3 coordinates strigolactone signalling and metabolism.The plant F-box protein D3 has a C-terminal [alpha]-helix that switches between two conformational states, allowing the [alpha]/[beta] hydrolase D14 to recruit the transcription repressor D53 for strigolactone-dependent degradation., Author(s): Nitzan Shabek [sup.1] [sup.2] [sup.4] , Fabrizio Ticchiarelli [sup.3] , Haibin Mao [sup.1] [sup.2] , Thomas R. Hinds [sup.1] , Ottoline Leyser [sup.3] , Ning Zheng [sup.1] [sup.2] Author [...]

Background/Objectives: Evidence on the role of diet in relation to prostate cancer progression is sparse. Foods rich in lignans have shown beneficial effects on prostate cancer progression in both animal studies and small human intervention studies, including beneficial effects on prostate-specific antigen levels and tumour growth. The lignan metabolite, enterolactone, has further shown to slow prostate cancer cell growth in vitro. The aim was to investigate the association between prediagnostic enterolactone concentrations and mortality among men with prostate cancer. Subljects/Methods: Prediagnostic plasma concentrations of enterolactone from 1390 men diagnosed with prostate cancer from the Danish Diet, Cancer and Health cohort were related to all-cause or prostate cancer-specific death, using Cox proportional hazards models with follow-up time (from the date of diagnose until the date of death, emigration or end of follow-up by December 2013) as the underlying time axis. Results: The hazard ratios for enterolactone concentrations assessed linearly by 20 nmol/l increments was 0.95 (0.90, 1.02) for all-cause mortality and 0.98 (0.92, 1.05) for prostate cancer-specific mortality. Categorisation of enterolactone concentrations into quartiles did not reveal a different pattern. No effect modifications by smoking, body mass index or sport were observed, and the associations did not differ by prostate cancer aggressiveness. Conclusions: We found no association between enterolactone concentrations and mortality among men diagnosed with prostate cancer., Author(s): A K Eriksen [sup.1] , C Kyrø [sup.1] , N Nørskov [sup.2] , A K Bolvig [sup.2] , J Christensen [sup.1] , A Tjønneland [sup.1] , K Overvad [sup.3] [...]

Conjugative transfer of the Ti plasmids of Agrobacterium tumefaciens is controlled by a quorum-sensing system composed of TraR and its signal N-(3-oxo-octanoyl)-L-homoserine lactone. This system is, in turn, controlled by the conjugative opines produced by crown gall tumors induced on plants by the bacteria. Using nonpolar traI mutants, we examined the kinetics of induction of conjugative transfer in response to exogenous acyl-homoserine lactone. In the absence of the antiactivator TraM, onset of induction of transfer requires about 30 min, 15 to 20 min of which is needed for expression and construction of the conjugative apparatus. TraM delays the onset of conjugation by 30 min. While the rate of development of conjugative competence was not significantly affected by levels of TraR, maximum efficiencies of transfer were correlated with amounts of the activator in the donors. Donors harboring Ti plasmids lacking TraM were fully induced by the quormone at concentrations as low as 100 pM. TraM raised the concentration of signal required for maximum activity to 1 nM. Donors grown in batch culture retained conjugative competence following signal removal, even when in stationary phase. However, donors kept in balanced growth rapidly lost transfer ability following signal removal. Loss of transfer was mirrored by a decrease in levers of active TraR. Decreases in TraR activity and conjugative competence could be accounted for by dilution associated with cell division, suggesting that while induction of Ti plasmid conjugation is an active process, the cells lack a mechanism for disassembling the conjugative apparatus when signals become limiting.

The RhlR transcriptional regulator of Pseudomonas aeruginosa, along with its cognate autoinducer, N-butyryl homoserine lactone ([C.sub.4]-HSL), regulates gene expression in response to cell density. With an Escherichia coli LexA-based protein interaction system, we demonstrated that RhlR multimerized and that the degree of multimerization was dependent on the [C.sub.4]-HSL concentration. Studies with an E. coli lasB::lacZ lysogen demonstrated that RhlR multimerization was necessary for it to function as a transcriptional activator. Deletion analysis of RhlR indicated that the N-terminal domain of the protein is necessary for [C.sub.4]-HSL binding. Single amino acid substitutions in the C-terminal domain of RhlR generated mutant RhlR proteins that had the ability to bind [C.sub.4]-HSL and multimerize but were unable to activate lasB expression, demonstrating that the C-terminal domain is important for target gene activation. Single amino acid substitutions in both the N-terminal and C-terminal domains of RhlR demonstrated that both domains possess residues involved in multimerization. RhlR with a C-terminal deletion and an RhlR site-specific mutant form that possessed multimerization but not transcriptional activation capabilities were able to inhibit the ability of wild-type RhlR to activate rhlA expression in P. aeruginosa. We conclude that C4-HSL binding is necessary for RhlR multimerization and that RhlR functions as a multimer in P. aeruginosa.

The ceplR genes encode an N-acyl homoserine lactone (AHL)-dependent quorum-sensing system consisting of an AHL synthase that directs the synthesis of N-octanoyI-L-homoserine lactone (OHL) and N-hexanoyI-L-homoserine lactone and a transcriptional regulator. The virulence of cepIR mutants was examined in two animal models. Rats were infected with agar beads containing Burkholderia cenocepacia K56-2, K56-12 (cepl: :[Tp.sup.r]) or K56-R2 (cepR'' Tn5-OT182). At 10 days post-infection, the extent of lung histopathological changes was significantly lower in lungs infected with K56-12 or K56-R2 compared to the parent strain. Intranasal infections were performed in [Cftr.sup.(-/-)] mice and their wild-type siblings. K56-2 was more virulent in both groups of mice. K56-12 was the least virulent strain and was not invasive in the [Cftr.sup.(-/-)] mice. OHL was readily detected in lung homogenates from [Cftr.sup.(-/-)] mice infected with K56-2 but was only detected at levels slightly above background in a few mice infected with K56-12. Lung homogenates from mice infected with K56-2 had significantly higher levels of the inflammatory mediators murine macrophage inflammatory protein-2, KC/N51, interleukin-1 [beta] and interleukin-6 than those from K56-12-infected animals. These studies indicate that a functional CepIR quorum-sensing system contributes to the severity of B. cenocepacia infections. A zinc metalloprotease gene (zmpA) was shown to be regulated by CepR and may be one of the factors that accounts for the difference in virulence between the cepl mutant and the parent strain.

Most LuxR homologues function as activators of transcription during the process of quorum sensing, but a few, including EsaR and Exp[R.sub.ECC], negatively impact gene expression. The LuxR-activated luxI promoter and LuxR binding site, the lux box, were used in artificial contexts to assess the potential for transcriptional activation and DNA binding by EsaR and Exp[R.sub.ECC]. Although the acyl-homoserine lactone responsiveness of both proteins is the opposite of that shown by most LuxR family members, EsaR and Exp[R.sub.ECC] have preserved the ability to interact with RNA polymerase and activate transcription despite their low affinity for the lux box DNA.

Bacteria degrading the quorum-sensing (QS) signal molecule N-hexanoylhomoserine lactone were isolated from a tobacco rhizosphere. Twenty-five isolates degrading this homoserine lactone fell into six groups according to their genomic REP-PCR and rrs PCR-RFLP profiles. Representative strains from each group were identified as members of the genera Pseudomonas, Comamonas, Variovorax and Rhodococcus. All these isolates degraded N-acylhomoserine lactones other than the hexanoic acid derivative, albeit with different specificity and kinetics. One of these isolates, Rhodococcus erythropolis strain W2, was used to quench QS-regulated functions of other microbes. In vitro, W2 strongly interfered with violacein production by Chromobacterium violaceum, and transfer of pathogenicity in Agrobacterium tumefaciens. In planta, R. erythropolis W2 markedly reduced the pathogenicity of Pectobacterium carotovorum subsp, carotovorum in potato tubers. These series of results reveal the diversity of the QS-interfering bacteria in the rhizosphere and demonstrate the validity of targeting QS signal molecules to control pathogens with natural bacterial isolates.

Quorum sensing systems serve as a means of 'census taking' of conspecific and non-conspecific bacteria in the near vicinity. The acylated homoserine lactone (AHL) quorum sensing system has been proposed to be primarily an intra-specific communication system, while the AI-2 autoinducer signalling system is proposed to be an interspecific communication system. Here it is shown that AI-2-like signalling in two marine Vibrio species, Vibrio vulnificus and 'Vibrio angustum' S14, induces the core response phenotypes of starvation adaptation and stress resistance, and that a signal antagonist can competitively inhibit these phenotypes. Furthermore, the signals produced by a range of Vibrio species have the ability to induce these phenotypes in V. vulnificus and 'V. angustum' S14, indicating that, at least in Vibrio species, AI-2-1ike signalling systems function as interspecies communication systems capable of 'cross-talk' and of regulating environmentally relevant phenotypes.

Many bacteria use N-acyl homoserine lactone (AHL) signals to coordinate the behavior of individual cells in a local population. The successful infection of eukaryotic hosts by bacteria seems to depend particularly on such AHL-mediated 'quorum-sensing' regulation. We have used proteome analysis to show that a eukaryotic host, the model legume Medicago truncatula, is able to detect nanomolar to micromolar concentrations of bacterial AHLs from both symbiotic (Sinorhizobium meliloti) and pathogenic (Pseudomonas aeruginosa) bacteria, and that it responds in a global manner by significant changes in the accumulation of over 150 proteins, 99 of which have been identified by peptide mass fingerprinting. The accumulation of specific proteins and isoforms depended on AHL structure, concentration, and time of exposure. AHLs were also found to induce tissue-specific activation of [beta]-glucuronidase (GUS) reporter fusions to an auxin-responsive and three chalcone synthase promoters, consistent with AHL-induced changes in the accumulation of auxin-responsive and flavonoid synthesis proteins. In addition, exposure to AHLs was found to induce changes in the secretion of compounds by the plants that mimic quorum-sensing signals and thus have the potential to disrupt quorum sensing in associated bacteria. Our results indicate that eukaryotes have an extensive range of functional responses to AHLs that may play important roles in the beneficial or pathogenic outcomes of eukaryote-prokaryote interactions.

Research demonstrates that sinR/sinI locus generates many unique N-acyl homoserine lactones with acyl side chains ranging from 12 to 18 carbons. Data indicate that the synthesis of these long-chain lactones is dependent on sinI gene, whereas short-chain lactones are not affected. Disruption of the sin system delays the appearance of nitrogen-fixing nodules sugesting a role in quorum sensing.

Research has been conducted on the Neu5Ac methyl ether. The route to this ester with sugar D-glucono-delta-lactone used as a starting material has been developed and is described.

Research has been conducted on the methyl 4-aryl-5-tosyloxypentanoate and 4-aryl-5-tosylxyhexanoate concomitant. The lactonization of these compounds with a phenyl rearrangement has been investigated and the results are reported.

Research has been conducted on the allene chemistry. The results of the palladium(0)-catalyzed coupling-cyclization of 2,3-allenamides and organic iodides are presented.

Research has been conducted on the delta-lactone (+)-boronolide. The synthesis of this compound in the enantiopure form with L-erythrulose as a chiral starting material has been carried out and the results are reported.

Research has been conducted on the organosulfur compounds. The use of reagents in preparing thioamides, thioketones and thiolactams and the utility of P (sub)4 S (sub)10/hexamethyldisiloxane as a thionating agent are discussed.

Research has been conducted on the antiobiotic (+)-negamycin. The synthesis of this antibiotic carried out via stabilized Wittig olefination of the lactone carbonyl group and asymmetric hydrogenation is described.

Research has been conducted on Streptomyces virginiae. The cloning and characterization of the hormone biosynthetic gene in Escherichia coli via heterologous expression and in S. virginiae via gene disruption have been carried out and the results indicate that this gene is essential in the autoregulator virginiae butanolide biosynthesis in S. virginiae.

Research has been conducted on palladium(II)-catalyzed lactonization reaction. Results indicate that regioconvergent lactone synthesis from the olefin equimolar mixture has been achieved via palladium(II) chemistry.

Research has been conducted on the chiral pilocarpine analogue. The synthesis of this analogue where the lactone ring is replaced by oxazolidinone and the bridging methylene group is in the ketone oxidation state has been carried out and the results are reported.

Research has been conducted on the (eta (super)3 -allyl)molybdenum complexes. Results indicate that oxidative demetalation of these complexes carried out via the use of pyridinium dichromate leads to the carbonyl group introduction at the allylic terminus of the pi-system.

Research has been conducted on the farnesol's alpha-phosphono lactone derivative. The preparation of this derivative in racemic and nonracemic forms has been carried out in producing farnesyl pyrophosphate analogue and the details are presented.

Results reveal that two luxR-type regulatory genes control plasmid transfer, growth inhibition by N-(3-hydroxy-7-cis tetra-decenoyl)-L-homoserine lactone and its repression in Rhizobium leguminosarum bv. viciae.

Research has been conducted on the bacteria associated with marine snow. Results indicate that this bacteria isolated from marine snow and marine diatoms can produce acylated homoserine lactones.

Research has been conducted on the bacteria from the Gotland Deep in the central Baltic Sea. The cultivation efficiency of these bacteria has been investigated via the most-probable-number technique used to determine the cultivated cell numbers and the details are reported.

Research has been conducted on the insecticidal Bacillus thuringiensis. The distribution of the aiiA-homologous genes in this bacterium and the possible plant-pathogenic bacteria control by B. thuringiensis are discussed.

Research has been conducted on 1,2-dioxines. The use of these dioxines as masked cis gamma-hydroxy enones and dioxines' conversion to the substituted gamma-lactones in enantiomeric and racemic forms are described.

Research has been conducted on (+/-)-momilactone A. The synthesis of this compound carried out via the use of trans-trans-cis macrocyclic triene's diastereoselective transannular Diels-Alder reaction is described.

Research has been conducted on the sphingomyelin carbon analogues. The stereocontrolled synthesis of these analogues has been carried out via Hoffmann rearrangement of beta-hydroxyamide which has been prepared by asymmetric hydrogenation of alpha-acyl-gamma-butyrolactone and ring opening with NH (sub)3.

Research has been conducted on the catalytic asymmetric acyl halide-aldehyde cyclocondensation reaction. The implementation of the reaction design is described and the results indicate that the reaction strategy allows to employ differentially substituted organocuprates in the 4-substituted 2-oxetanone ring opening.

Research has been conducted on the ginkgolide C. Selective acetylation of ginkgolide C hydroxyl groups has been carried out and the results are reported.

Research has been conducted on the 8-epi-griseoviridine's lactone core. The synthesis of this lactone core from D-(R)-cysteine methyl ester has been carried out and the details are reported.

Research has been conducted on the terpenoid lactones isolated from a marine sponge. The results of the Diels-Alder cyclization reaction which has produced tricyclic lactones are reported.

Research has been conducted on the pentose sugar gamma-lactone. The conversion strategy of these sugars into 3,4-dihydroxyprolines has been developed and is presented.

Research has been conducted on the alpha-D-Galp-(1(approaches)3)-D-Man. The synthesis of this compound which is present in type-2 glycoinositolphospholipids and in the lipophosphoglycan core of Leishmania has been carried out and is described.

Research has been conducted on the samarium(II) iodide. The use of this compound in the presence of nickel(II) iodide in promoting intramolecular conjugate alkyl halide additions onto alpha,beta-unsaturated lactones is described.

Research has been conducted on the fragrant target molecules, cis-3-methyl-4-decanolide and aerangis lactone. The route to these molecules which does not require air-sensitive reagents has been developed and the details are presented.

Research has been conducted on the gamma-lactone-fused cyclopentanoids. The effect of the tetrahalonorborene derivatives' structural flexibility and stereochemical control on these cyclopentannulated gamma-lactones has been investigated and the details are described.

Research has been conducted on the exo-glycans. Different methods used for the stereoselective synthesis of these compounds have been investigated and the details are reported.

Research has been conducted on the lactones' gas-phase acidities. The use of the Fourier transform ion cyclotron resonance mass spectrometer in measuring these acidities is discussed and the differential electronic effects and differential strength between the reactant and the product species have been investigated.

Research has been conducted on the tarchonanthuslactone. The synthesis of this compound has been carried out from ethyl sorbate and the details are reported.

Research has been conducted on the fungicide oidiolactone C. The synthesis of this compound carried out starting from the diterpenic trans-communic acid and the study of the podolactones' structure and biological activity are described.

Research has been conducted on the intramolecular Diels-Alder reaction. The thermolysis of dienals prepared in the presence of zinc metal with ethyl 2-bromo-methylacrylate has produced tricyclic cycloadducts in the intramolecular Diels-Alder reaction.