bluuebunny/crossref_metadata_2025 huggingface dataset:
RT03 Education and 3Rs: an Italian experience in veterinary toxicology
Authors: CALONI F.
Published: August 2006

Objective

After the Bologna declaration, signed by 29 European countries in 1999, a strong debate on veterinary education arose. Although at present none of the European veterinary schools have officially introduced the Bologna process to veterinary curricula, the discussion about the definition of competence and professional skill of graduates in veterinary medicine is controversial. In this context, veterinary pharmacology and toxicology are disciplines undergoing continuous development and becoming increasingly important in the different areas of veterinary profession. In this round‐table, different points of view on the challenge to teach Veterinary Pharmacology and Toxicology at a high quality level in the third millennium will be considered.
RT05 Teaching environmental toxicology for veterinary students and veterinarians: some new trends
Authors: KECK G.
Published: August 2006

Objective

After the Bologna declaration, signed by 29 European countries in 1999, a strong debate on veterinary education arose. Although at present none of the European veterinary schools have officially introduced the Bologna process to veterinary curricula, the discussion about the definition of competence and professional skill of graduates in veterinary medicine is controversial. In this context, veterinary pharmacology and toxicology are disciplines undergoing continuous development and becoming increasingly important in the different areas of veterinary profession. In this round‐table, different points of view on the challenge to teach Veterinary Pharmacology and Toxicology at a high quality level in the third millennium will be considered.
RT06 Pharmacological and other sources of variability in response to drugs including lack of compliance to prescribed medication
Authors: LEES P. , MADDISON J. E.
Published: August 2006

Objective

There are several means whereby dosage schedules for clinical use may be set, some more appropriate and scientific than others! The challenge of the 21st century must be for colleagues in the pharmaceutical industry, those serving registration bodies and academic colleagues to pool their expertise with the objective of designing dosage schedules for clinical use, which are based on the application of sound scientific principles appropriate for each drug class. In this Roundtable Session colleagues of international standing will review (a) pharmacological and other sources of variability in the responses to drugs; (b) the advantages and limitations of pre‐clinical studies for dose selection; (c) the roles of population PK and population PK/PD together with Monte Carlo simulations in dosage regimen selection; (d) Bayesian approaches to dosage selection and (e) regulatory guidelines on the type and extent of studies required for selecting dosages. There is no unanimity amongst stakeholders on either the principles or the methods underlying dosage schedule design. Dose titration studies have long been the principal means of fixing doses but PK‐PD and population PK‐PD studies are now challenging more traditional approaches. The papers and discussion in this Roundtable Session will provide a critical basis for future advances in this crucial area of therapeutic drug usage. Getting the doses right means that the patient will receive maximum benefit, in terms of optimal efficacy with minimal toxicity, and hence correct dosing will contribute enormously to animal welfare.
RT08 Population PK and PK/PD investigations and Monte Carlo simulations for a rational dosage regimen
Authors: TOUTAIN P. L.
Published: August 2006

Objective

There are several means whereby dosage schedules for clinical use may be set, some more appropriate and scientific than others! The challenge of the 21st century must be for colleagues in the pharmaceutical industry, those serving registration bodies and academic colleagues to pool their expertise with the objective of designing dosage schedules for clinical use, which are based on the application of sound scientific principles appropriate for each drug class. In this Roundtable Session colleagues of international standing will review (a) pharmacological and other sources of variability in the responses to drugs; (b) the advantages and limitations of pre‐clinical studies for dose selection; (c) the roles of population PK and population PK/PD together with Monte Carlo simulations in dosage regimen selection; (d) Bayesian approaches to dosage selection and (e) regulatory guidelines on the type and extent of studies required for selecting dosages. There is no unanimity amongst stakeholders on either the principles or the methods underlying dosage schedule design. Dose titration studies have long been the principal means of fixing doses but PK‐PD and population PK‐PD studies are now challenging more traditional approaches. The papers and discussion in this Roundtable Session will provide a critical basis for future advances in this crucial area of therapeutic drug usage. Getting the doses right means that the patient will receive maximum benefit, in terms of optimal efficacy with minimal toxicity, and hence correct dosing will contribute enormously to animal welfare.
RT09 Bayesian approaches in dosage selection
Authors: CONCORDET D.
Published: August 2006

Objective

There are several means whereby dosage schedules for clinical use may be set, some more appropriate and scientific than others! The challenge of the 21st century must be for colleagues in the pharmaceutical industry, those serving registration bodies and academic colleagues to pool their expertise with the objective of designing dosage schedules for clinical use, which are based on the application of sound scientific principles appropriate for each drug class. In this Roundtable Session colleagues of international standing will review (a) pharmacological and other sources of variability in the responses to drugs; (b) the advantages and limitations of pre‐clinical studies for dose selection; (c) the roles of population PK and population PK/PD together with Monte Carlo simulations in dosage regimen selection; (d) Bayesian approaches to dosage selection and (e) regulatory guidelines on the type and extent of studies required for selecting dosages. There is no unanimity amongst stakeholders on either the principles or the methods underlying dosage schedule design. Dose titration studies have long been the principal means of fixing doses but PK‐PD and population PK‐PD studies are now challenging more traditional approaches. The papers and discussion in this Roundtable Session will provide a critical basis for future advances in this crucial area of therapeutic drug usage. Getting the doses right means that the patient will receive maximum benefit, in terms of optimal efficacy with minimal toxicity, and hence correct dosing will contribute enormously to animal welfare.
RT10 The lost art of dosing
Authors: HOLZHAUSER‐ALBERTI M. A.
Published: August 2006

Objective

There are several means whereby dosage schedules for clinical use may be set, some more appropriate and scientific than others! The challenge of the 21st century must be for colleagues in the pharmaceutical industry, those serving registration bodies and academic colleagues to pool their expertise with the objective of designing dosage schedules for clinical use, which are based on the application of sound scientific principles appropriate for each drug class. In this Roundtable Session colleagues of international standing will review (a) pharmacological and other sources of variability in the responses to drugs; (b) the advantages and limitations of pre‐clinical studies for dose selection; (c) the roles of population PK and population PK/PD together with Monte Carlo simulations in dosage regimen selection; (d) Bayesian approaches to dosage selection and (e) regulatory guidelines on the type and extent of studies required for selecting dosages. There is no unanimity amongst stakeholders on either the principles or the methods underlying dosage schedule design. Dose titration studies have long been the principal means of fixing doses but PK‐PD and population PK‐PD studies are now challenging more traditional approaches. The papers and discussion in this Roundtable Session will provide a critical basis for future advances in this crucial area of therapeutic drug usage. Getting the doses right means that the patient will receive maximum benefit, in terms of optimal efficacy with minimal toxicity, and hence correct dosing will contribute enormously to animal welfare.
WS01 Basic mechanisms of resistance to antibiotics
Authors: STEFANI S.
Published: August 2006

Objective

Antimicrobial resistance is not only here, it is here to stay and it poses major threats to the effective use of antimicrobial drugs in humans and other animals. Nevertheless, a defeatist attitude is not acceptable. There is much that can and must be done to retard or prevent the emergence and spread of resistance. Clinicians and scientists from many disciplines have roles to play in combating resistance and we veterinary pharmacologists arguably have the most important role of all. As Schentag (1996) indicated 10 years ago, ‘‘The design of appropriate dosage regimens may be the single most important contribution of clinical pharmacology to the resistance problem’’. However, progress has not been rapid and as recently as 2003 Drusano commented, ‘‘One area in which there is little investigation is the use of proper dosing to help prevent emergence of resistance’’ and, again in 2005, Drusano et al. commented ‘‘little attention has been focussed on delineating the correct dose to suppress the amplification of less susceptible mutant bacterial sub‐populations’’. In this Workshop we address, with the help of internationally recognised authorities, antimicrobial resistance in veterinary medicine, from the perspectives of basic mechanisms, epidemiology and pre‐clinical and population PK‐PD modelling in dosage design. In addition, we review prudent use, clinical aspects and the contribution of regulatory efforts to minimise the selection of resistant microorganisms.
WS03 Minimising antimicrobial resistance through rational design of dosing schedules: a role for pre‐clinical PK‐PD modelling?
Authors: LEES P. , ALIABADI F. S. , TOUTAIN P. L.
Published: August 2006

Objective

Antimicrobial resistance is not only here, it is here to stay and it poses major threats to the effective use of antimicrobial drugs in humans and other animals. Nevertheless, a defeatist attitude is not acceptable. There is much that can and must be done to retard or prevent the emergence and spread of resistance. Clinicians and scientists from many disciplines have roles to play in combating resistance and we veterinary pharmacologists arguably have the most important role of all. As Schentag (1996) indicated 10 years ago, ‘‘The design of appropriate dosage regimens may be the single most important contribution of clinical pharmacology to the resistance problem’’. However, progress has not been rapid and as recently as 2003 Drusano commented, ‘‘One area in which there is little investigation is the use of proper dosing to help prevent emergence of resistance’’ and, again in 2005, Drusanoet al.commented ‘‘little attention has been focussed on delineating the correct dose to suppress the amplification of less susceptible mutant bacterial sub‐populations’’. In this Workshop we address, with the help of internationally recognised authorities, antimicrobial resistance in veterinary medicine, from the perspectives of basic mechanisms, epidemiology and pre‐clinical and population PK‐PD modelling in dosage design. In addition, we review prudent use, clinical aspects and the contribution of regulatory efforts to minimise the selection of resistant microorganisms.
WS05 Regulatory efforts to minimize the selection of resistant bacteria
Authors: MARTINEZ M. N.
Published: August 2006

Objective

Antimicrobial resistance is not only here, it is here to stay and it poses major threats to the effective use of antimicrobial drugs in humans and other animals. Nevertheless, a defeatist attitude is not acceptable. There is much that can and must be done to retard or prevent the emergence and spread of resistance. Clinicians and scientists from many disciplines have roles to play in combating resistance and we veterinary pharmacologists arguably have the most important role of all. As Schentag (1996) indicated 10 years ago, ‘‘The design of appropriate dosage regimens may be the single most important contribution of clinical pharmacology to the resistance problem’’. However, progress has not been rapid and as recently as 2003 Drusano commented, ‘‘One area in which there is little investigation is the use of proper dosing to help prevent emergence of resistance’’ and, again in 2005, Drusano et al. commented ‘‘little attention has been focussed on delineating the correct dose to suppress the amplification of less susceptible mutant bacterial sub‐populations’’. In this Workshop we address, with the help of internationally recognised authorities, antimicrobial resistance in veterinary medicine, from the perspectives of basic mechanisms, epidemiology and pre‐clinical and population PK‐PD modelling in dosage design. In addition, we review prudent use, clinical aspects and the contribution of regulatory efforts to minimise the selection of resistant microorganisms.
WS06 Antimicrobial resistance in veterinary medicine: clinical aspects
Authors: BROWN S. A.
Published: August 2006

Objective

Antimicrobial resistance is not only here, it is here to stay and it poses major threats to the effective use of antimicrobial drugs in humans and other animals. Nevertheless, a defeatist attitude is not acceptable. There is much that can and must be done to retard or prevent the emergence and spread of resistance. Clinicians and scientists from many disciplines have roles to play in combating resistance and we veterinary pharmacologists arguably have the most important role of all. As Schentag (1996) indicated 10 years ago, ‘‘The design of appropriate dosage regimens may be the single most important contribution of clinical pharmacology to the resistance problem’’. However, progress has not been rapid and as recently as 2003 Drusano commented, ‘‘One area in which there is little investigation is the use of proper dosing to help prevent emergence of resistance’’ and, again in 2005, Drusano et al. commented ‘‘little attention has been focussed on delineating the correct dose to suppress the amplification of less susceptible mutant bacterial sub‐populations’’. In this Workshop we address, with the help of internationally recognised authorities, antimicrobial resistance in veterinary medicine, from the perspectives of basic mechanisms, epidemiology and pre‐clinical and population PK‐PD modelling in dosage design. In addition, we review prudent use, clinical aspects and the contribution of regulatory efforts to minimise the selection of resistant microorganisms.
WS11 Comprehensive investigation of the transcriptome
Authors: PINEAU T. , LASSERRE F. , EVEILLARD A. , MSELLI‐LAKHAL L. , MARTIN P. G. P.
Published: August 2006

Objective

Tremendous progress has been made in the ability to measure particular contaminants or veterinary drugs at very low concentrations. However, rare or previously unknown compounds, metabolites and mixtures are still presenting considerable analytical challenges, while this category in particular might be relevant in terms of food safety. In addition, the need for higher throughput screening strategies at lower costs also demands for methods in addition to chemical analysis. There is considerable development in methodology based on the interaction with bio‐macromolecules or living cells or on a biological response in the exposed animal. The aim of this workshop is to provide an up‐o‐date and practical overview of the various analytical and biological strategies that are available to screen or detect (prior) exposure to drugs, contaminants and pollutants.
WS13 Antibiotic ban in the European Union: a Pyrrhic victory?
Authors: PRADELLA G.
Published: August 2006

Objective

This Workshop offers a forum to colleagues from academia and industry. It will present a critical re‐appraisal on the rational of the EU ban, and the overall economic impact of this measure as well as regulatory attempts to stimulate licensing of new products. Additional contributions are devoted to current RD activities within the industry, and new targets and strategies in product development will be presented and discussed.
WS15 EU promoted research towards zootechnical feed additives for the safe use in poultry production
Authors: KLOSE V. , PLAIL R. , MOHNL M. , SCHATZMAYR G.
Published: August 2006

Objective

This Workshop offers a forum to colleagues from academia and industry. It will present a critical re‐appraisal on the rational of the EU ban, and the overall economic impact of this measure as well as regulatory attempts to stimulate licensing of new products. Additional contributions are devoted to current RD activities within the industry, and new targets and strategies in product development will be presented and discussed.
WS16 The role of mannan oligosaccharide in maximizing intestinal health and animal performance
Authors: SPRING P.
Published: August 2006

Objective

This Workshop offers a forum to colleagues from academia and industry. It will present a critical re‐appraisal on the rational of the EU ban, and the overall economic impact of this measure as well as regulatory attempts to stimulate licensing of new products. Additional contributions are devoted to current RD activities within the industry, and new targets and strategies in product development will be presented and discussed.
Interference of Mycobacterium tuberculosis cell division by Rv2719c, a cell wall hydrolase
Authors: Chauhan Ashwini , Lofton Hava , Maloney Erin , Moore Jacob , Fol Marek , Madiraju Murty V. V. S. , Rajagopalan Malini
Published: August 2006

The genetic factors responsible for the regulation of cell division in Mycobacterium tuberculosis are largely unknown. We showed that exposure of M. tuberculosis to DNA damaging agents, or to cephalexin, or growth of M. tuberculosis in macrophages increased cell length and sharply elevated the expression of Rv2719c, a LexA‐controlled gene. Overexpression of Rv2719c in the absence of DNA damage or of antibiotic treatment also led to filamentation and reduction in viability both in broth and in macrophages indicating a correlation between Rv2719c levels and cell division. Overproduction of Rv2719c compromised midcell localization of FtsZ rings, but had no effect on the intracellular levels of FtsZ. In vitro, the Rv2719c protein did not interfere with the GTP‐dependent polymerization activity of FtsZ indicating that the effects of Rv2719c on Z‐ring assembly are indirect. Rv2719c protein exhibited mycobacterial murein hydrolase activity that was localized to the N‐terminal 110 amino acids. Visualization of nascent peptidoglycan (PG) synthesis zones by probing with fluoresceinated vancomycin (Van‐FL) and localization of green fluorescent protein‐Rv2719c fusion suggested that the Rv2719c activity is targeted to potential PG synthesis zones. We propose that Rv2719c is a potential regulator of M. tuberculosis cell division and that its levels, and possibly activities, are modulated under a variety of growth conditions including growth in vivo and during DNA damage, so that the assembly of FtsZ‐rings, and therefore the cell division, can proceed in a regulated manner.
Serum opacity factor promotes group A streptococcal epithelial cell invasion and virulence
Authors: Timmer Anjuli M. , Kristian Sascha A. , Datta Vivekanand , Jeng Arthur , Gillen Christine M. , Walker Mark J. , Beall Bernard , Nizet Victor
Published: August 2006

Serum opacity factor (SOF) is a bifunctional cell surface protein expressed by 40–50% of group A streptococcal (GAS) strains comprised of a C‐terminal domain that binds fibronectin and an N‐terminal domain that mediates opacification of mammalian sera. The sof gene was recently discovered to be cotranscribed in a two‐gene operon with a gene encoding another fibronectin‐binding protein, sfbX. We compared the ability of a SOF(+) wild‐type serotype M49 GAS strain and isogenic mutants lacking SOF or SfbX to invade cultured HEp‐2 human pharyngeal epithelial cells. Elimination of SOF led to a significant decrease in HEp‐2 intracellular invasion while loss of SfbX had minimal effect. The hypoinvasive phenotype of the SOF(–) mutant could be restored upon complementation with the sof gene on a plasmid vector, and heterologous expression of sof49 in M1 GAS or Lactococcus lactis conferred marked increases in HEp‐2 cell invasion. Studies using a mutant sof49 gene lacking the fibronectin‐binding domain indicated that the N‐terminal opacification domain of SOF contributes to HEp‐2 invasion independent of the C‐terminal fibronectin binding domain, findings corroborated by observations that a purified SOF N‐terminal peptide could promote latex bead adherence to HEp‐2 cells and inhibit GAS invasion of HEp‐2 cells in a dose‐dependent manner. Finally, the first in vivo studies to employ a single gene allelic replacement mutant of SOF demonstrate that this protein contributes to GAS virulence in a murine model of necrotizing skin infection.
Regulation of tylosin biosynthesis involving ‘SARP‐helper’ activity
Authors: Bate Neil , Bignell Dawn R. D. , Cundliffe Eric
Published: August 2006

Tylosin production in Streptomyces fradiae is regulated via interplay between a repressor, TylQ, and an activator of the SARP family, TylS, during regulation of tylR. The latter encodes the pathway‐specific activator of the tylosin‐biosynthetic (tyl) genes. Also controlled by TylS is a hitherto unassigned gene, tylU, whose product is shown here to be important for tylosin production. Thus, targeted disruption of tylU reduced tylosin yields by about 80% and bioconversion analysis with the resultant strain revealed defects in both polyketide metabolism and deoxyhexose biosynthesis. Such defects were completely eliminated by engineered overexpression of tylR (but not tylS) and Western analysis revealed significantly reduced levels of TylR in the tylU‐disrupted strain. These results are consistent with a model in which TylS and TylU act in concert to facilitate expression of tylR, for which TylU (but not TylS) is nonessential. Activator proteins of the SARP family, such as TylS, are widespread among Streptomyces spp. and are important regulators of antibiotic production. Their action has been widely studied with no prior indication of associated ‘helper’ activity, the prevalence of which now remains to be established.
The type III effector repertoire of Pseudomonas syringae pv. syringae B728a and its role in survival and disease on host and non‐host plants
Authors: Vinatzer Boris A. , Teitzel Gail M. , Lee Min‐Woo , Jelenska Joanna , Hotton Sara , Fairfax Keke , Jenrette Jenny , Greenberg Jean T.
Published: August 2006

The bacterial plant pathogen Pseudomonas syringae injects a large repertoire of effector proteins into plant cells using a type III secretion apparatus. Effectors can trigger or suppress defences in a host‐dependent fashion. Host defences are often accompanied by programmed cell death, while interference with defences is sometimes associated with cell death suppression. We previously predicted the effector repertoire of the sequenced bean pathogen P. syringae pv. syringae (Psy) B728a using bioinformatics. Here we show that PsyB728a is also pathogenic on the model plant species Nicotiana benthamiana (tobacco). We confirm our effector predictions and clone the nearly complete PsyB728a effector repertoire. We find effectors to have different cell death‐modulating activities and distinct roles during the infection of the susceptible bean and tobacco hosts. Unexpectedly, we do not find a strict correlation between cell death‐eliciting and defence‐eliciting activity and between cell death‐suppressing activity and defence‐interfering activity. Furthermore, we find several effectors with quantitative avirulence activities on their susceptible hosts, but with growth‐promoting effects on Arabidopsis thaliana, a species on which PsyB728a does not cause disease. We conclude that P. syringae strains may have evolved large effector repertoires to extend their host ranges or increase their survival on various unrelated plant species.
Succinic semialdehyde couples stress response to quorum‐sensing signal decay in Agrobacterium tumefaciens
Authors: Wang Chao , Zhang Hai‐Bao , Wang Lian‐Hui , Zhang Lian‐Hui
Published: August 2006

Quorum sensing (QS) signal decay in Agrobacterium tumefaciens occurs in response to starvation or host signals. We have demonstrated that the γ‐aminobutyric acid (GABA) shunt metabolite links stress response to QS signal decay. Mutation of the aldH gene encoding a succinic semialdehyde dehydrogenase (SSADH) that converts succinic semialdehyde (SSA) to succinic acid results in early expression of the signal degrading enzyme, AttM. Exogenous addition of SSA or its precursor GABA induces AttM expression and abolishes Ti plasmid conjugative transfer. SSA acts by binding to the repressor AttJ that regulates the attKLM operon. attK encodes another SSADH. The stress alarmone ppGpp and SSA modulates separately the expression of the two SSADH enzymes, which might control the intracellular SSA level and hence to switch on/off the QS signal decay system in response to environmental changes. These findings document for the first time a sophisticated signalling mechanism of the widely conserved GABA degradation pathway in prokaryotes.
Spatial and temporal organization of the Bacillus subtilis replication cycle
Authors: Berkmen Melanie B. , Grossman Alan D.
Published: August 2006

DNA replication occurs at discrete sites in the cell. To gain insight into the spatial and temporal organization of the Bacillus subtilis replication cycle, we simultaneously visualized replication origins and the replication machinery (replisomes) inside live cells. We found that the origin of replication is positioned near midcell prior to replication. After initiation, the replisome colocalizes with the origin, confirming that replication initiates near midcell. The replisome remains near midcell after duplicated origins separate. Artificially mispositioning the origin region leads to mislocalization of the replisome indicating that the location of the origin at the time of initiation establishes the position of the replisome. Time‐lapse microscopy revealed that a single replisome focus reversibly splits into two closely spaced foci every few seconds in many cells, including cells that recently initiated replication. Thus, sister replication forks are likely not intimately associated with each other throughout the replication cycle. Fork dynamics persisted when replication elongation was halted, and is thus independent of the relative movement of DNA through the replisome. Our results provide new insights into how the replisome is positioned in the cell and refine our current understanding of the spatial and temporal events of the B. subtilis replication cycle.
Heterozygosity and functional allelic variation in theCandida albicansefflux pump genesCDR1andCDR2
Authors: Holmes Ann R. , Tsao Sarah , Ong Soo‐Wee , Lamping Erwin , Niimi Kyoko , Monk Brian C. , Niimi Masakazu , Kaneko Aki , Holland Barbara R. , Schmid Jan , Cannon Richard D.
Published: August 2006

Elevated expression of the plasma membrane drug efflux pump proteins Cdr1p and Cdr2p was shown to accompany decreased azole susceptibility inCandida albicansclinical isolates. DNA sequence analysis revealed extensive allelic heterozygosity, particularly ofCDR2. Cdr2p alleles showed different abilities to transport azoles when individually expressed inSaccharomyces cerevisiae. Loss of heterozygosity, however, did not accompany decreased azole sensitivity in isogenic clinical isolates. Two adjacent non‐synonymous single nucleotide polymorphisms (NS‐SNPs), G1473A and I1474V in the putative transmembrane (TM) helix 12 ofCDR2,were found to be present in six strains including two isogenic pairs. Site‐directed mutagenesis showed that the TM‐12 NS‐SNPs, and principally the G1473A NS‐SNP, contributed to functional differences between the proteins encoded by the two Cdr2p alleles in a single strain. Allele‐specific PCR revealed that both alleles were equally frequent among 69 clinical isolates and that the majority of isolates (81%) were heterozygous at the G1473A/I1474V locus, a significant (P < 0.001) deviation from the Hardy–Weinberg equilibrium. Phylogenetic analysis by maximum likelihood (Paml) identified 33 codons inCDR2in which amino acid allelic changes showed a high probability of being selectively advantageous. In contrast, all codons inCDR1were under purifying selection. Collectively, these results indicate that possession of two functionally differentCDR2alleles in individual strains may confer a selective advantage, but that this is not necessarily due to azole resistance.
Evidence that Plasmodium falciparum chromosome end clusters are cross‐linked by protein and are the sites of both virulence gene silencing and activation
Authors: Marty Allison J. , Thompson Jennifer K. , Duffy Michael F. , Voss Till S. , Cowman Alan F. , Crabb Brendan S.
Published: August 2006

The malaria parasite Plasmodium falciparum undergoes antigenic variation through allelic exclusion and variant expression of surface proteins encoded by the var gene family. Regulation of var genes is under epigenetic control and involves reversible silencing and activation that requires the physical repositioning of a var locus into a transcriptionally permissive zone of the nuclear periphery. P. falciparum chromosome ends appear to aggregate into large perinuclear clusters which house both subtelomeric and chromosome central var genes. In this study we further define the composition of telomeric clusters using fluorescent in situ hybridization, and provide evidence that chromosome end clusters are formed by cross‐linking protein. In addition, we demonstrate that a subtelomeric reporter gene and a var gene remain within clusters regardless of their transcriptional status. Our findings support a model whereby a highly localized structure dedicated to the activation of a single var gene can be housed within a gene dense chromosome end cluster that is otherwise transcriptionally silent.
Al–Fe interactions and growth enhancement in Melastoma malabathricum and Miscanthus sinensis dominating acid sulphate soils
Authors: WATANABE TOSHIHIRO , JANSEN STEVEN , OSAKI MITSURU
Published: August 2006

Plants growing in acid sulphate soils are subject to high levels of Al availability, which may have effects on the growth and distribution of these species. Although Fe availability is also high in acid sulphate soils, little is known about the effect of Fe on the growth of native plants in these soils. Two species dominating this soil type in Asia, viz. Melastoma malabathricum and Miscanthus sinensis were grown hydroponically in a nutrient solution with different concentrations of Al and Fe. Melastoma malabathricum is found to be sensitive to Fe (40 and 100 µm). Application of 500 µm Al, however, completely ameliorates Fe toxicity and is associated with a decrease of Fe concentration in shoots and roots. The primary reason for the Al‐induced growth enhancement of M. malabathricum is considered to be the Al‐induced reduction of toxic Fe accumulation in roots and shoots. Therefore, Al is nearly essential for M. malabathricum when growing in acid sulphate soils. In contrast, application of both Fe and Al does not reduce the growth of M. sinensis, and Al application does not result in lower shoot concentrations of Fe, suggesting that this grass species has developed different mechanisms for adaptation to acid sulphate soils.
The impact of coral bleaching on the pigment profile of the symbiotic alga, Symbiodinium
Authors: VENN ALEXANDER A. , WILSON MICHAEL A. , TRAPIDO‐ROSENTHAL HENRY G. , KEELY BRENDAN J. , DOUGLAS ANGELA E.
Published: August 2006

Bleaching of corals by loss of symbiotic dinoflagellate algae and/or photosynthetic pigments is commonly triggered by elevated temperatures coupled with high irradiance, and is a first‐order threat to coral reef communities. In this study, a high‐resolution high‐performance liquid chromatography method integrated with mass spectrometry was applied to obtain the first definitive identification of chlorophyll and carotenoid pigments of three clades of symbiotic dinoflagellate algae (Symbiodinium) in corals, and their response to experimentally elevated temperature and irradiance. The carotenoids peridinin, dinoxanthin, diadinoxanthin (Dn), diatoxanthin (Dt) and β‐carotene were detected, together with chlorophylls a and c2, and phaeophytin a, in all three algal clades in unstressed corals. On exposure to elevated temperature and irradiance, three coral species (Montastrea franksi and Favia fragum with clade B algae, and Montastrea cavernosa with clade C) bleached by loss of 50–80% of their algal cells, with no significant impact to chlorophyll a or c2, or peridinin in retained algal cells. One species (Agaricia sp. with clade C) showed no significant reduction in algal cells at elevated temperature and irradiance, but lost substantial amounts of chlorophyll a and carotenoid pigments, presumably through photo‐oxidative processes. Two coral species (Porites astreoides and Porites porites both bearing clade A algae) did not bleach. The impact of elevated temperature and irradiance on the levels of the photoprotective xanthophylls (Dn + Dt) and β‐carotene varied among the corals, both in pool size and xanthophyll cycling, and was not correlated to coral bleaching resistance.
Drought stress response in wheat: physiological and molecular analysis of resistant and sensitive genotypes
Authors: RAMPINO PATRIZIA , PATALEO STEFANO , GERARDI CARMELA , MITA GIOVANNI , PERROTTA CARLA
Published: August 2006

Water deficit is a severe environmental stress and the major constraint on plant productivity with an evident effect on plant growth. The aim of this work was to study Triticum and Aegilops seedlings differing in their response to drought stress at the physiological and molecular levels. The identification of resistant and sensitive genotypes was firstly based on the relative water content (RWC) measurement. Further characterization of genotypes contrasting in their response to water stress was performed at the physiological level by determination of RWC, water loss rate (WLR) and free proline content after different hours of dehydration. Modification in the expression level of five dehydrin (DHN) genes was also analysed by reverse transcription–polymerase chain reaction (RT‐PCR). Five cDNAs coding for different DHNs were identified and characterized. These genes are not expressed in the well‐watered plants, but only in the stressed plants. Four of these cDNAs are related to novel DHN sequences. The results obtained clearly indicate a relation between the expression of these genes and tissue water content. In particular, in the resistant genotypes the expression of DHN genes is initiated even though tissue hydration levels are still high, indicating also in wheat the involvement of these proteins in water retention.
Phototropin involvement in the expression of genes encoding chlorophyll and carotenoid biosynthesis enzymes and LHC apoproteins in Chlamydomonas reinhardtii
Authors: Im Chung‐Soon , Eberhard Stephan , Huang Kaiyao , Beck Christoph F. , Grossman Arthur R.
Published: August 2006

Phototropin (PHOT) is a photoreceptor involved in a variety of blue‐light‐elicited physiological processes including phototropism, chloroplast movement and stomatal opening in plants. The work presented here tests whether PHOT is involved in expression of light‐regulated genes in Chlamydomonas reinhardtii. When C. reinhardtii was transferred from the dark to very low‐fluence rate white light, there was a substantial increase in the level of transcripts encoding glutamate‐1‐semialdehyde aminotransferase (GSAT), phytoene desaturase (PDS) and light‐harvesting polypeptides (e.g. LHCBM6). Increased levels of these transcripts were also elicited by low‐intensity blue light, and this blue‐light stimulation was suppressed in three different RNAi strains that synthesize low levels of PHOT. The levels of GSAT and LHCBM6 transcripts also increased following exposure of algal cells to low‐intensity red light (RL). The red‐light‐dependent increase in transcript abundance was not affected by the electron transport inhibitor 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea, implying that the influence of RL on transcript accumulation was not controlled by cytoplasmic redox conditions, and that a red‐light photoreceptor(s) may be involved in regulating the levels of transcripts from specific photosynthesis‐related genes in C. reinhardtii. Interestingly, elevated GSAT and LHCBM6 transcript levels in RL were significantly reduced in the PHOT RNAi strains, which raises the possibility of co‐action between blue and RL signaling pathways. Microarray experiments indicated that the levels of several transcripts for photosystem (PS) I and II polypeptides were also modulated by PHOT. These data suggest that, in C. reinhardtii, (i) PHOT is involved in blue‐light‐mediated changes in transcript accumulation, (ii) synchronization of the synthesis of chlorophylls (Chl), carotenoids, Chl‐binding proteins and other components of the photosynthetic apparatus is achieved, at least in part, through PHOT‐mediated signaling, and (iii) a red‐light photoreceptor can also influence levels of certain transcripts associated with photosynthetic function, although its action requires normal levels of PHOT.
Biosynthesis and secretion of mugineic acid family phytosiderophores in zinc‐deficient barley
Authors: Suzuki Motofumi , Takahashi Michiko , Tsukamoto Takashi , Watanabe Satoshi , Matsuhashi Shinpei , Yazaki Junshi , Kishimoto Naoki , Kikuchi Shoshi , Nakanishi Hiromi , Mori Satoshi , Nishizawa Naoko K.
Published: August 2006

Mugineic acid family phytosiderophores (MAs) are metal chelators that are produced in graminaceous plants in response to iron (Fe) deficiency, but current evidence regarding secretion of MAs during zinc (Zn) deficiency is contradictory. Our studies using HPLC analysis showed that Zn deficiency induces the synthesis and secretion of MAs in barley plants. The levels of the HvNAS1, HvNAAT‐A, HvNAAT‐B, HvIDS2 and HvIDS3 transcripts, which encode the enzymes involved in the synthesis of MAs, were increased in Zn‐deficient roots. Studies of the genes involved in the methionine cycle using microarray analysis showed that the transcripts of these genes were increased in both Zn‐deficient and Fe‐deficient barley roots, probably allowing the plant to meet its demand for methionine, a precursor in the synthesis of MAs. In addition, HvNAAT‐B transcripts were detected in Zn‐deficient shoots, but not in those that were deficient in Fe. Increased synthesis of MAs in Zn‐deficient barley was not due to a deficiency of Fe, because Zn‐deficient barley accumulated more Fe than did the control plants, ferritin transcripts were increased in Zn‐deficient plants, and Zn deficiency promoted Fe transport from root to shoot. Moreover, analysis using the positron‐emitting tracer imaging system (PETIS) confirmed that more 62Zn(II)‐MAs than 62Zn2+ were absorbed by the roots of Zn‐deficient barley plants. These data suggest that the increased biosynthesis and secretion of MAs arising from a shortage of Zn are not due to an induced Fe deficiency, and that secreted MAs are effective in absorbing Zn from the soil.
Multi‐site genetic modulation of monolignol biosynthesis suggests new routes for formation of syringyl lignin and wall‐bound ferulic acid in alfalfa (Medicago sativa L.)
Authors: Chen Fang , Srinivasa Reddy Marry S. , Temple Stephen , Jackson Lisa , Shadle Gail , Dixon Richard A.
Published: August 2006

Genes encoding seven enzymes of the monolignol pathway were independently downregulated in alfalfa (Medicago sativa) using antisense and/or RNA interference. In each case, total flux into lignin was reduced, with the largest effects arising from the downregulation of earlier enzymes in the pathway. The downregulation of l‐phenylalanine ammonia‐lyase, 4‐coumarate 3‐hydroxylase, hydroxycinnamoyl CoA quinate/shikimate hydroxycinnamoyl transferase, ferulate 5‐hydroxylase or caffeic acid 3‐O‐methyltransferase resulted in compositional changes in lignin and wall‐bound hydroxycinnamic acids consistent with the current models of the monolignol pathway. However, downregulating caffeoyl CoA 3‐O‐methyltransferase neither reduced syringyl (S) lignin units nor wall‐bound ferulate, inconsistent with a role for this enzyme in 3‐O‐methylation ofS monolignol precursors and hydroxycinnamic acids. Paradoxically, lignin composition differed in plants downregulated in either cinnamate 4‐hydroxylase or phenylalanine ammonia‐lyase. No changes in the levels of acylated flavonoids were observed in the various transgenic lines. The current model for monolignol and ferulate biosynthesis appears to be an over‐simplification, at least in alfalfa, and additional enzymes may be needed for the 3‐O‐methylation reactions of S lignin and ferulate biosynthesis.
DamID, a new tool for studying plant chromatin profiling in vivo, and its use to identify putative LHP1 target loci
Authors: Germann Sophie , Juul‐Jensen Trine , Letarnec Bruno , Gaudin Valérie
Published: August 2006

We show here that the in vivo methylation‐based tagging technique DamID (DNA adenine methyltransferase identification) can be used for studies of DNA–protein interactions or chromatin profiling in plants. We have demonstrated the feasibility, reproducibility and sensitivity of the method in Arabidopsis thaliana, using the well‐known yeast GAL4 transcription factor, for which DNA‐binding sites (UASG) were introduced into the plant genome. We monitored the methylation resulting from the activity of DNA adenine methyltransferase fused to the protein of interest, by combining digestion with methylation‐sensitive restriction enzymes and quantitative PCR. We then used DamID to identify genomic targets of LHP1, a protein mostly associated with euchromatin. We showed that LHP1 was targeted to the promoter and transcribed regions of four genes: AG, AP3, FT and PI. Our data also demonstrate that LHP1, like its animal homologues, has a high binding affinity for A/T‐rich regions, binding particularly strongly to the large regulatory introns of AG and PI. We identified three major characteristics of LHP1 binding, highlighting the similarities between plant LHP1 and animal HP1 proteins.
Developing fructan‐synthesizing capability in a plant invertase via mutations in the sucrose‐binding box
Authors: Ritsema Tita , Hernández Lázaro , Verhaar Auke , Altenbach Denise , Boller Thomas , Wiemken Andres , Smeekens Sjef
Published: August 2006

Fructans are fructose polymers that are synthesized from sucrose by fructosyltransferases. Fructosyltransferases are present in unrelated plant families suggesting a polyphyletic origin for their transglycosylation activity. Based on sequence comparisons and enzymatic properties, fructosyltransferases are proposed to have evolved from vacuolar invertases. Between 1% and 5% of the total activity of vacuolar invertase is transglycosylating activity. We investigated the nature of the changes that can convert a hydrolysing invertase into a transglycosylating enzyme. Remarkably, replacing 33 amino acids (amino acids 143–175) corresponding to the N‐terminus of the mature onion vacuolar invertase with the corresponding region of onion fructan:fructan 6G‐fructosyltransferase (6G‐FFT) led to a shift in activity from hydrolysis of sucrose towards transglycosylation between two sucrose molecules. The substituted N‐terminal region contains the sucrose‐binding box that harbours the nucleophile involved in sucrose hydrolysis (Asp164). Subsequent research into the individual amino acids responsible for the enhanced transglycosylation activity revealed that mutations in amino acids Trp161 and Asn166, can give rise to a shift towards polymerase activity. Changing the amino acid at either of these positions in the sucrose‐binding box increases the transglycosylation capacity of invertases two‐ to threefold compared to wild type. Combining the two mutations had an additive effect on transglycosylation ability, resulting in an approximately fourfold enhancement. The mutations generated correspond with natural variation present in the sucrose‐binding boxes of vacuolar invertases and fructosyltransferases. These relatively small changes that increase the transglycosylation capacity of invertases might explain the polyphyletic origin of the fructan accumulation trait.
Insecticidal and antifeedant activities of proteins secreted by entomopathogenic fungi against Spodoptera littoralis (Lep., Noctuidae)
Authors: Quesada‐Moraga E. , Carrasco‐Díaz J.‐A. , Santiago‐Álvarez C.
Published: August 2006

Abstract:  Entomopathogenic fungi are a poorly exploited source of insecticidal proteins, which may be used for the development of new natural insecticides and as alternative molecules for transgenic deployment. The crude soluble protein extracts in Adamek's liquid medium of 25 fungal isolates belonging to the fungal species Metarhizum anisopliae, Beauveria bassiana, Beauveria brongniartii and Scopulariopsis brevicaulis were screened by per os toxicity on Spodoptera littoralis larvae. Whilst extracts from two M. anisopliae and two B. bassiana isolates gave significant mortalities when applied either on alfalfa leaf discs or incorporated into artificial diet, the one from M. anisopliae 01/58‐Su isolate was the only most toxic that showed promise for S. littoralis control. In leaf disc assays, this extract exhibited strong dose‐related toxic and antifeedant activity against the larvae. At 10, 20 and 40 μg protein/insect, the extract gave 61.3%, 96.6% and 100.0% mortality, respectively, and average survival time of 5.7, 4.3 and 3.1 days respectively. Not only the antifeeding index was dose‐related, but it significantly increased over time in a dose‐related manner. Longer exposure times led to a dose‐related significant increase in larval mortality. The exposure times for 50% mortality were 91.3 h and 62.1 h for 20 and 40 μg protein/insect respectively. The crude extract when exposed to higher temperature or protease treatment lost toxicity, indicating that toxicity was protein mediated. In addition, the liquid medium composition did not influence its insecticidal activity. The effects of the protein extract on midgut cells of second instar larvae of S. littoralis were investigated by using both light and electron microscopy. A progressive bleeding of the midgut epithelium into the gut lumen was observed along with lysis of the epithelium and deterioration of the microvilli.