bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigating the caffeine effects in the yeast Saccharomyces cerevisiae brings new insights into the connection between TOR, PKC and Ras/cAMP signalling pathways
Authors: Kuranda Klaudia , Leberre Veronique , Sokol Serguei , Palamarczyk Grazyna , François Jean 
Published: August 2006

SummaryCaffeine is a natural purine analogue that elicits pleiotropic effects leading ultimately to cell's death by a largely uncharacterized mechanism. Previous works have shown that this drug induces a rapid phosphorylation of the Mpk1p, the final mitogen‐activated protein (MAP) kinase of the Pkc1p‐mediated cell integrity pathway. In this work, we showed that this phosphorylation did not necessitate the main cell wall sensors Wsc1p and Mid2p, but was abolished upon deletion of ROM2 encoding a GDP/GTP exchange factor of Rho1p. We also showed that the caffeine‐induced phosphorylation of Mpk1p was accompanied by a negligible activation of its main downstream target, the Rlm1p transcription factor. This result was consolidated by the finding that the loss of RLM1 had no consequence on the increased resistance of caffeine‐treated cells to zymolyase, indicating that the cell wall modification caused by this drug is largely independent of transcriptional activation of Rlm1p‐regulated genes. Additionally, the transcriptional programme elicited by caffeine resembled that of rapamycin, a potent inhibitor of the TOR1/2 kinases. Consistent with this analysis, we found that the caffeine‐induced phosphorylation of Mpk1p was lost in a tor1Δ mutant. Moreover, a tor1Δ mutant was, like mutants defective in components of the Pkc1p‐Mpk1p cascade, highly sensitive to caffeine. However, the hypersensitivity of a tor1 null mutant to this drug was rescued neither by sorbitol nor by adenine, which was found to outcompete caffeine effects specially on mutants in the PKC pathway. Altogether, these data indicated that Tor1 kinase is a target of caffeine, whose inhibition incidentally activates the Pkc1p‐Mpk1p cascade, and that the caffeine‐dependent phenotypes are largely dependent on inhibition of Tor1p‐regulated cellular functions. Finally, we found that caffeine provoked, in a Rom2p‐dependent manner, a transient drop in intracellular levels of cAMP, that was followed by change in expression of genes implicated in Ras/cAMP pathway. This result may pose Rom2p as a mediator in the interplay between Tor1p and the Ras/cAMP pathway.
Identification by functional proteomics of a deubiquitinating/deNeddylating enzyme in Plasmodium falciparum
Authors: Artavanis‐Tsakonas Katerina , Misaghi Shahram , Comeaux Christy A. , Catic Andre , Spooner Eric , Duraisingh Manoj T. , Ploegh Hidde L. 
Published: August 2006

SummaryUbiquitination is a post‐translational modification implicated in a variety of cellular functions, including transcriptional regulation, protein degradation and membrane protein trafficking. Ubiquitin and the enzymes that act on it, although conserved and essential in eukaryotes, have not been well studied in parasites, despite sequencing of several parasite genomes. Several putative ubiquitin hydrolases have been identified in Plasmodium falciparum based on sequence homology alone, with no evidence of expression or function. Here we identify the first deubiquitinating enzyme in P. falciparum, PfUCH54, by its activity. We show that PfUCH54 also has deNeddylating activity, as assayed by a mammalian Nedd8‐based probe. This activity is absent from mammalian homologues of PfUCH54. Given the importance of parasitic membrane protein trafficking as well as protein degradation in the virulence of this parasite, this family of enzymes may represent a target for pharmacological intervention with this disease.
Purification and functional studies of a potent modified quorum‐sensing peptide and a two‐peptide bacteriocin in Streptococcus mutans
Authors: Petersen Fernanda Cristina , Fimland Gunnar , Scheie Anne Aamdal 
Published: August 2006

SummaryBacteria use quorum‐sensing signals or autoinducers to communicate. The signals in Gram‐positive bacteria are often peptides activated by proteolytic removal of an N‐terminal leader sequence. While investigating stimulation of antimicrobial peptide production by the Streptococcus mutans synthetic competence stimulating peptide signal (21‐CSP), we found a peptide similar to the 21‐CSP, but lacking the three C‐terminal amino acid residues (18‐CSP). The 18‐CSP was more potent in inducing competence, biofilm formation, and antimicrobial activity than the 21‐CSP. Our results indicate that cleavage of the three C‐terminal residues occurred post export, and was not regulated by the CSP‐signalling system. Deletion of comD encoding the CSP receptor abolished the competence and biofilm responses to the 21‐CSP and the 18‐CSP, suggesting that signal transduction via the ComD receptor is involved in the responses to both CSPs. In S. mutans GS5, beside the 18‐CSP we also purified to homogeneity a two‐peptide bacteriocin which production was stimulated by the 18‐CSP and the 21‐CSP. Partial sequence of the two‐peptide bacteriocin revealed the product of the smbAB genes recently described. We found that the peptide SmbB was slightly different from the deduced sequence, and confirmed the prediction that both peptides constituting SmbAB bacteriocin are post‐translationally modified. SmbAB exhibited antimicrobial activity against 11 species of streptococci, Enterococcus faecalis and Staphylocococcus epidermidis. Taken together, the findings support the involvement of the CSP response in bacteriocin production by streptococci and suggest a novel strategy to potentiate autoinducer activity.
The bacterial chromosome segregation protein Spo0J spreads along DNA from parS nucleation sites
Authors: Murray Heath , Ferreira Henrique , Errington Jeff 
Published: August 2006

SummaryRegulation of chromosome inheritance is essential to ensure proper transmission of genetic information. To accomplish accurate genome segregation, cells organize their chromosomes and actively separate them prior to cytokinesis. In Bacillus subtilis the Spo0J protein is required for accurate chromosome segregation and it regulates the developmental switch from vegetative growth to sporulation. Spo0J is a DNA‐binding protein that recognizes at least eight identified parS sites located near the origin of replication. As judged by fluorescence microscopy, Spo0J forms discrete foci associated with the oriC region of the chromosome throughout the cell cycle. In an attempt to determine the mechanisms utilized by Spo0J to facilitate productive chromosome segregation, we have investigated the DNA binding activity of Spo0J. In vivo we find Spo0J associates with several kilobases of DNA flanking its specific binding sites (parS) through a parS‐dependent nucleation event that promotes lateral spreading of Spo0J along the chromosome. Using purified components we find that Spo0J has the ability to coat non‐specific DNA substrates. These ‘Spo0J domains’ provide large structures near oriC that could potentially demark, organize or localize the origin region of the chromosome.
Development and application of molecular‐based diagnosis for ‘Candidatus Liberibacter asiaticus’, the causal pathogen of citrus huanglongbing
Authors: Wang Z. , Yin Y. , Hu H. , Yuan Q. , Peng G. , Xia Y. 
Published: August 2006

Conventional PCR and two real‐time PCR (RTi‐PCR) methods were developed and compared using the primer pairs CQULA03F/CQULA03R and CQULA04F/CQULA04R, and TaqMan probe CQULAP1 designed from a species‐specific sequence of the rplJ/rplL ribosomal protein gene, for diagnosis of citrus huanglongbing (HLB) disease in southern China. The specificity and sensitivity of the three protocols for detecting ‘Candidatus Liberibacter asiaticus’ in total DNA extracts of midribs collected from infected citrus leaves with symptoms in Guangxi municipality, Jiangxi Province and Zhejiang Province, were tested. Sensitivities using extracted total DNA (measured as copy number, CN per µL of recombinant plasmid solution) were 439·0 (1·30 × 105 CN µL−1), 4·39 (1·30 × 103 CN µL−1) and 0·44 fg µL−1 (1·30 × 102 CN µL−1) for conventional PCR, TaqMan and SYBR Green I (SGI) RTi‐PCR, respectively. SGI RTi‐PCR was the most sensitive, but its specificity needed to be confirmed by running a melt‐curve assay. The TaqMan RTi‐PCR assay was rapid and had the greatest specificity. Concerning the correlation of PCR detection results with the various HLB symptoms, uneven mottling of leaves had the highest positive rate (96·50%), indicating that leaf mottling was the most reliable symptom for field surveys. Dynamic analysis results from the TaqMan assays showed that the titre (CN) g−1 citrus tissue of ‘Ca. L. asiaticus’ was highest between October and December (threshold cycle (Ct) average = 29·3, CN = 3·35 × 107) and lowest between March and May (Ct average = 32·0, CN = 5·10 × 106) in 2004 and 2005. The optimized molecular‐based assays should prove useful for presymptom diagnosis of HLB disease, monitoring and identification of ‘Ca. L. asiaticus’, and field epidemic regulation.
The phs1‐3 mutation in a putative dual‐specificity protein tyrosine phosphatase gene provokes hypersensitive responses to abscisic acid in Arabidopsis thaliana
Authors: Quettier Anne‐Laure , Bertrand Claire , Habricot Yvette , Miginiac Emile , Agnes Christiane , Jeannette Emmanuelle , Maldiney Régis 
Published: August 2006

SummaryThe plant hormone abscisic acid (ABA) controls numerous physiological traits: dormancy and germination of seeds, senescence and resistance to abiotic stresses. In order to get more insight into the role of protein tyrosine phosphatase (PTP) in ABA signalling, we obtained eight homozygous T‐DNA insertion lines in Arabidopsis thaliana PTP genes. One mutant, named phs1‐3, exhibited a strong ABA‐induced inhibition of germination as only 26% of its seeds germinated after 3 days instead of 92% for the Columbia (Col‐0) line. Genetic and molecular analyses of phs1‐3 showed that it bears a unique T‐DNA insertion in the promoter of the gene and that the mutation is recessive. PHS1 expression in the mutant is about half that of the Col‐0 line. The upregulation of two ABA‐induced genes (At5g06760, RAB18) and the downregulation of two ABA‐repressed genes (AtCLC‐A, ACL) are enhanced in the phs1‐3 mutant compared with the wild‐type. The ‘in planta’ aperture of phs1‐3 stomata is reduced and the inhibition of the light‐induced opening of stomata by ABA is stronger in phs1‐3 leaves than in Col‐0 leaves. Finally, PHS1 expression is upregulated in the presence of ABA in both phs1‐3 and Col‐0 but more intensively in the mutant. Thus, phs1‐3 is hypersensitive to ABA. Taken together, these results show that PHS1, which encodes a dual‐specificity PTP, is a negative regulator of ABA signalling.
Mutation of SAD2, an importin β‐domain protein in Arabidopsis, alters abscisic acid sensitivity
Authors: Verslues Paul E. , Guo Yan , Dong Chun‐Hai , Ma Wujun , Zhu Jian‐Kang 
Published: August 2006

SummaryA number of protein and RNA‐processing mutants have been shown to affect ABA sensitivity. A new mutant, sad2‐1, was isolated from a T‐DNA mutagenized population of RD29A:LUC plants and shown to have increased luminescence after ABA, salt, cold or polyethylene glycol treatments. Expression of several ABA‐ and stress‐responsive genes was higher in the mutant than in the wild type. sad2‐1 also exhibited ABA hypersensitivity in seed germination and seedling growth. SAD2 was found to encode an importin β‐domain family protein likely to be involved in nuclear transport. SAD2 was expressed at a low level in all tissues examined except flowers, but SAD2 expression was not inducible by ABA or stress. Subcellular localization of GFP‐tagged SAD2 showed a predominantly nuclear localization, consistent with a role for SAD2 in nuclear transport. Knockout of the closest importin β homolog of SAD2 in Arabidopsis did not duplicate the sad2 phenotype, indicating that SAD2 plays a specific role in ABA signaling. Analysis of RD29A:LUC luminescence and ABA and stress sensitivity in double mutants of sad2‐1 and sad1 or abh1‐7, a newly isolated allele of ABH1 also in the RD29A:LUC background, suggested that SAD2 acts upstream of or has additive effects with these two genes. The results suggest a role for nuclear transport in ABA signal transduction, and the possible roles of SAD2 in relation to that of SAD1 and ABH1 are discussed.
The Arabidopsis thaliana TIR‐NB‐LRR R‐protein, RPP1A; protein localization and constitutive activation of defence by truncated alleles in tobacco and Arabidopsis
Authors: Michael Weaver L. , Swiderski Michal R. , Li Yan , Jones Jonathan D. G. 
Published: August 2006

SummarySpecific recognition of Hyaloperonospora parasitica isolate Cala2 by Arabidopsis thaliana Ws‐0 is mediated by the resistance gene RPP1A. Transient expression of different truncations of RPP1A in tobacco leaves revealed that its TIR‐NB‐ARC portion is sufficient to induce an elicitor‐independent cell death. In stable transgenic lines of Arabidopsis, overexpression of the RPP1A TIR‐NB‐ARC domains (E12) using the 35S promoter leads to broad‐spectrum resistance to virulent strains of H. parasitica and Pseudomonas syringae DC3000. The TIR‐NB‐ARC‐mediated constitutive immunity is due to activation of the salicylic acid‐dependent resistance pathway and is relieved by either a mutation in EDS1 or the presence of the salicylate hydroxylase gene, NahG. Growth of 35S::E12 plants is reduced, a phenotype observed in many constitutively resistant mutants. RPP1A carries a hydrophobic peptide at its N‐terminus that directs the RPP1A protein into membranes, though it may not be the sole determinant mediating membrane association of RPP1A. Two‐phase partitioning and sucrose density gradient sedimentation established that RPP1A resides in the endoplasmic reticulum and/or Golgi apparatus.
SERRATE is a novel nuclear regulator in primary microRNA processing in Arabidopsis
Authors: Yang Li , Liu Ziqiang , Lu Feng , Dong Aiwu , Huang Hai 
Published: August 2006

SummaryThe Arabidopsis gene SERRATE (SE) controls leaf development, meristem activity, inflorescence architecture and developmental phase transition. It has been suggested that SE, which encodes a C2H2 zinc finger protein, may change gene expression via chromatin modification. Recently, SE has also been shown to regulate specific microRNAs (miRNAs), miR165/166, and thus control shoot meristem function and leaf polarity. However, it remains unclear whether and how SE modulates specific miRNA processing. Here we show that the se mutant exhibits some similar developmental abnormalities as the hyponastic leaves1 (hyl1) mutant. Since HYL1 is a nuclear double‐stranded RNA‐binding protein acting in the DICER‐LIKE1 (DCL1) complex to regulate the first step of primary miRNA transcript (pri‐miRNA) processing, we hypothesized that SE could play a previously unrecognized and general role in miRNA processing. Genetic analysis supports that SE and HYL1 act in the same pathway to regulate plant development. Consistently, SE is critical for the accumulation of multiple miRNAs and the trans‐acting small interfering RNA (ta‐siRNA), but is not required for sense post‐transcriptional gene silencing. We further demonstrate that SE is localized in the nucleus and interacts physically with HYL1. Finally, we provide evidence that SE and HYL1 probably act with DCL1 in processing pri‐miRNAs before HEN1 in miRNA biogenesis. In plants and animals, miRNAs are known to be processed in a stepwise manner from pri‐miRNA. Our data strongly suggest that SE plays an important and general role in pri‐miRNA processing, and it would be interesting to determine whether animal SE homologues may play similar roles in vivo.
EFFETS DU CHLORATE DE SODIUM SUR LES MICROORGANISMES DU SOL, LEUR RESPIRATION ET LEUR ACTIVITE ENZYMATIQUE
Authors: KARKI A. B. , COUPIN L. , KAISER P. , MOUSSIN M. 
Published: August 2006

Résumé. En vue de dé terminer les effets du chlorate de sodium sur les microorganisms du sol, leur respiration ct leur activité enzymatique, celui‐ci a été appliqué sous forme granulée à la dose normale (150 kg/ha comme matière active) aux partellcs enherbées ou nouvellemcnt dé sherbé es. Les é chantillons ont été recueillis apré s 5, 27 et 150 jours à une profondeur de 0–20 cm sur des parcelles traité es et non traité es.Le nombre total de la microflore, des actinomycètes, des cellulolytiques aérobies, des bactéries ammonifiantes de même que des bactéries nitrifiantes et dénitrifiantes n'est pas affecté par l'herbicide. En ce qui concerne les échantillons prélevés après 27 jours, la production de CO2était, initialement, identique dans les sols traités ou non traités, mais elle diminue ensuite dans le sol traité au chlorate, ce qui indique une diminution du métabolisme global microbien. Le chlorate réduit l'activite déshydrogénasique des échantillons recueillis aprés 5, 27 et 150 jours; ceci est attribuéà l'apparition de l'oxygène à partir de chlorate, ce dernier étant, après 150 jours, complètement éliminé du sol.Die Wirkung von Natriumchlorat auf Bodenmikroorganismen, ihre Atmung und Enzymaktivität
The addition of ammonium salts or a phosphate ester to herbicides to control Agropyron repens (L) Beauv.
Authors: BLAIR A. M. 
Published: August 2006

Summary: Résumé: ZusammenfassungN‐(phosphonomethyl)glycine (glyphosate) at 0·5‐1·0 kg a.i./ha controlled Agropyron repens grown in specially established 1‐m2 field plots in three out of four experiments. The addition of butyl acid phosphate or ammonium sulphate to the spray liquid improved the level of control given by glyphosate alone, where there was scope for such improvement: the addition of ammonium nitrate had no effect. When ammonium sulphate was added to either dalapon or asulam there was also no increased control of A. repens. However, when added to activated aminotriazole at 2·0 kg a.i./ha, ammonium sulphate significantly increased the level of control of A. repens in one experiment. Addition de sets d'ammonium ou d'un ester phosphorique à des herbicides en vue de la destruction de l'Agropyron repens (L) Beauv. La N‐ (phosphonométhyl) glycine (glyphosate) à al dose de 0.5–1.0 kg m.a./ha a été efficace contre l'Agropyron repens poussant au champ dans des parcelles spécialement établies de 1‐m2 dans trois essais sur quatre. L'addition de phosphate acide de butyle ou de sulfate d'ammonium au liquide pulvérisé a augments le niveau d'efflcacité obtenu avec le glyphosate seul, là oú il y avait possibilité de réaliser cette amélioration; l'addition de nitrate d'ammonium fut sans effet. Lorsque le sufate d'ammonium fut ajouté soit au dalapon, soit à l'asulame, il n'y eut pas non plus augmentation de l'efficacité contre A. repens. Toutefois, lorsque fut ajouté de l'aminotriazole activéà raison de 2 kg m.a./ha, le sulfate d'ammonium dans un essai accrut significativement le niveau d'efficacité contre A. repens. Der Zusatz von Ammoniumsalzen oder eines Phosphatesters zu Herbiziden zur Bekämpfung von Agropyron repens (L) Beauv.In drei von vier Versuchen wurde Agropyron repens in 1 m2 grossen Feldparzellen durch 0.5–1.0 kg A.S./ha von N‐(Phosphonomethyl)glycin (Glyphosate) bekämpft. Die Zugabe von Phosphorsäure‐dibutylester oder von Ammoniumsulfat zur Spritzbrühe erhöhte die Wirkung, verglichen mit Glyphosate alleine. Der Zusatz von Ammoniumnitrat brachte keine Verbesserung. Auch wenn Ammoniumsulfat zu Dalapon oder zu Asulam zugesetzt wurde, wurde die Bekämpfung von A. repens nicht verbessert. Wenn aber zu ‘aktiviertem’ Aminotrizol (Aminotriazol+Ammonium‐rhodanid) bei 2,0 kg A.S./ha Ammoniumsulfat zugegeben wurde, wurde in einem Versuch die Bekämpfung von A. repens deutlich verbessert.
Field emergence of Avena fatua L. and A. sterilis ssp. ludoviciana (Dur.) Nym. in Aragón, Spain
Authors: AIBAR J. , OCHOA M. J. , ZARAGOZA C. 
Published: August 2006

Summary:Emergence of Avena fatua and A. sterilis ssp. ludoviciana infesting winter cereals during two years and at two sites in Aragon began after sowing in late October and continued for 23 weeks, with 75% of seedlings appearing in the first 9 weeks. The start of emergence was associated with a fall in minimum air temperature to below 9°C and a maximum of less than 20°C. Soil moisture was not limiting, and during winter flushes of seedlings tended to be associated with rises in mean temperature. In contrast with results from other latitudes, A. fatua emerged mainly in autumn at the same time as A. sterilis ssp. ludoviciana.
Competitive interactions among two specialist predators and a generalist predator of hemlock woolly adelgid, Adelges tsugae (Hemiptera: Adelgidae) in south‐western Virginia
Authors: Flowers R. W. , Salom S. M. , Kok L. T. 
Published: August 2006

Abstract1 Competitive interactions among two specialist predators, Laricobius nigrinus and Sasajiscymnus (Pseudoscymnus) tsugae, and a generalist predator, Harmonia axyridis Pallas, of hemlock woolly adelgid, Adelges tsugae were evaluated in hemlock stands in south‐western Virginia. The two specialist predators are part of a biological control program for A. tsugae, and the potential for competition among these species and previously established generalist predators in the field is unknown.2 Adult predators were evaluated in branch cages during spring and summer at two field sites infested with A. tsugae. Using females only in 2003 and sexual pairs in 2004, predator survival and net reproduction were examined, as well as their feeding and impact on A. tsugae when present alone and in conspecific and heterospecific groupings.3 Predator survival was not affected by the presence of additional predators. Total feeding was greater for all species when placed in predator groupings, suggesting that interactions do not significantly interfere with feeding activity. Net reproduction per predator was negatively affected by conspecifics, but unaffected by heterospecifics, indicating that direct or indirect intraspecific interference may occur. In spring, L. nigrinus showed the greatest impact on A. tsugae, and H. axyridis had the greatest impact during summer.4 These results suggest that it would be beneficial to utilize multiple predator species combinations over single species when implementing biological control for A. tsugae. Low‐density releases are also recommended to reduce intraspecific interference.