bluuebunny/crossref_metadata_2025_split huggingface dataset:
A novel protein kinase family in Plasmodium falciparum is differentially transcribed and secreted to various cellular compartments of the host cell
Authors: Nunes Marta C. , Goldring J. P. Dean , Doerig Christian , Scherf Artur 
Published: December 2006

SummaryProcesses at the surface of Plasmodium falciparum‐infected erythrocytes such as antigenic variation and cytoadhesion may be modulated by active signalling between host and parasite. Potential candidates for this role include the putative kinases of the FIKK family. The novel Apicomplexa‐specific FIKK gene has expanded in P. falciparum to 20 sequence‐related members distributed between 11 chromosomes. Specific antibodies raised against different members indicated that most FIKK proteins locate to punctate foci in the erythrocyte cytoplasm that colocalized with Maurer's clefts proteins. One FIKK member dissociates at the trophozoite stage from the Maurer's clefts and relocates with the erythrocyte cytoskeleton. Another FIKK protein, despite having a PEXEL motif, remains located within the parasite. FIKK proteins possess the essential residues for phosphotransferase activity. We show that protein kinase activity was detected in immunoprecipitates obtained with two anti‐FIKK antibodies. Quantitative PCR analysis revealed differential gene transcription of the FIKK paralogues in asexual blood stages parasites. We observed significant changes in the transcription pattern between parasites with different adhesion phenotypes. Our data suggest a role of FIKK proteins in the remodelling of the erythrocyte surface and reveal the existence of an adaptable parasite system able to sense intra‐ and possibly extracellular changes.
Interplay between primase and replication factor C in the hyperthermophilic archaeonSulfolobus solfataricus
Authors: Wu Kangyun , Lai Xiaoqin , Guo Xin , Hu Jinchuan , Xiang Xiaoyu , Huang Li 
Published: December 2006

SummaryThe heterodimeric primase from the hyperthermophilic archaeonSulfolobus solfataricussynthesizes long RNA and DNA productsin vitro. How primer synthesis by primase is coupled to primer extension by DNA polymerase in this organism is unclear. Here we show that the small subunit of the clamp loader replication factor C (RFC) ofS. solfataricusinteracted with both the catalytic and non‐catalytic subunits of the primase by yeast two‐hybrid and co‐immunoprecipitation assays. Further, the primase–RFC interaction was also identified in the cell extract ofS. solfataricus. Deletion analysis indicated that the small subunit of RFC interacted strongly with the N‐terminal domain of the catalytic subunit of the primase. RFC stimulated dinucleotide formation but decreased the amount of primers synthesized by the primase. The inhibition of primer synthesis is consistent with the observation that RFC reduced the affinity of the primase for DNA templates. On the other hand, primase stimulated the ATPase activity of RFC. These findings suggest that the primase–RFC interaction modulates the activities of both enzymes and therefore may be involved in the regulation of primer synthesis and the transfer of primers to DNA polymerase in Archaea.
Antimicrobial peptides activate the Vibrio choleraeσE regulon through an OmpU‐dependent signalling pathway
Authors: Mathur Jyoti , Davis Brigid M. , Waldor Matthew K. 
Published: December 2006

Summary Vibrio cholerae, an enteric pathogen, is subject to assault by several membrane‐acting, host gut‐derived antimicrobial peptides (AP). We previously found that a major V. cholerae outer membrane protein, OmpU, confers resistance to polymyxin B and to a bioactive peptide (P2) derived from the human bactericidal/permeability‐increasing protein. Here, we report that the alternative sigma factor σE also plays a critical role in determining V. cholerae resistance to AP and that OmpU and σE lie in the same pathway. In fact, we found that OmpU is a key determinant of basal σE expression. We also found that sublethal AP exposure activates σE and the σE‐mediated periplasmic stress response. σE is not activated by P2 in V. cholerae cells lacking OmpU or DegS, a periplasmic protease that controls σE activity. The lack of AP‐elicited σE activation in a strain harbouring a point mutation in OmpU's putative DegS‐binding residues provides support for a link between OmpU and DegS‐mediated activation of σE. We propose that AP‐induced membrane perturbations change the conformation of OmpU to trigger a DegS‐dependent σE‐activating cascade. Thus, OmpU appears to act as a sensor component in a signal transduction pathway.
The small nucleoid protein Fis is involved in Vibrio cholerae quorum sensing
Authors: Lenz Derrick H. , Bassler Bonnie L. 
Published: December 2006

SummaryQuorum sensing is a process of cell–cell communication that bacteria use to relay information to one another about the cell density and species composition of the bacterial community. Quorum sensing involves the production, secretion and population‐wide detection of small signalling molecules called autoinducers. This process allows bacteria to synchronize group behaviours and act as multicellular units. The human pathogen, Vibrio cholerae, uses quorum sensing to co‐ordinate such complex behaviours as pathogenicity and biofilm formation. The quorum‐sensing circuit of V. cholerae consists of two autoinducer/sensor systems, CAI‐1/CqsS and AI‐2/LuxPQ, and the VarS/A‐CsrA/BCD growth‐phase regulatory system. Genetic analysis suggests that an additional regulatory arm involved in quorum sensing exists in V. cholerae. All of these systems channel information into the histidine phosphotransfer protein, LuxU, and/or the response regulator, LuxO. LuxO, when phosphorylated, activates the expression of four genes encoding the Qrr (quorum regulatory RNAs) small RNAs (sRNAs). The Qrr sRNAs destabilize the hapR transcript encoding the master regulator of quorum sensing, HapR. Here we identify the nucleoid protein Fis as playing a major role in the V. cholerae quorum‐sensing circuit. Fis fulfils the predictions required to be the putative additional component that inputs information into the cascade: its expression is regulated in a growth phase‐dependent manner; it requires LuxO but acts independently of LuxU, and it regulates all four qrr genes and, in turn, HapR by directly binding to the qrr gene promoters and modulating their expression.
A semiselective medium for the isolation of Acidovorax valerianellae from soil and plant debris
Authors: Grondeau C. , Manceau C. , Samson R. 
Published: December 2006

Bacterial black spot of corn‐salad (Valerianella locusta) caused by Acidovorax valerianellae appeared in France in the beginning of the 1990s. The disease is now widespread in the main area of corn‐salad production and is responsible for high depreciation and significant economic losses every year. A semiselective medium is described for the detection of the bacterium in various environments and to identify primary sources of inoculum. The medium TSAV (tryptic soy broth, 3 g L−1, agar 15 g L−1, 5‐fluorouracyl 5 mg L−1, novobiocin 5 mg L−1, propiconazole 5 mg L−1) increased chances of obtaining cultures of A. valerianellae from naturally infested soil and from root‐debris. Using TSAV, the pathogen was detected in root‐debris up to 39 days after the harvest of a diseased crop. As only a few days usually separates harvest from the next sowing date, soil is likely to be an important source of inoculum for the next crop.
Characterization of Rhizoctonia solani from potato in Great Britain
Authors: Woodhall J. W. , Lees A. K. , Edwards S. G. , Jenkinson P. 
Published: December 2006

One hundred and thirty five isolates of Rhizoctonia solani were obtained from British potato crops between 2001 and 2003. Isolates were assigned to anastomosis group (AG) using conventional PCR assays for AG2‐1 or AG3 or through the observation of hyphal interactions, where appropriate. A previously published primer set was modified in this study to enhance specificity for AG3PT. Most of the isolates (92·6%) belonged to AG3PT whilst some (6·7%) belonged to AG2‐1. Only one isolate recovered (0·7%) belonged to AG5. Isolates of AG2‐1 were diverse, with variation in both the length of the rDNA intergenic spacer 1 (IGS1) region and the categories of hyphal interaction observed between pairings of AG2‐1 isolates. No variation in the length of the rDNA IGS1 region was observed amongst the AG3 isolates collected. Tests carried out on potato stems with a sub‐set of the isolates revealed a wide range of aggressiveness amongst AG2‐1 isolates. Sequencing of the rDNA internal transcribed spacer (ITS) region of the AG2‐1 isolates and construction of a neighbour joining tree with other AG2‐1 sequences available indicated that AG2‐1 isolates with the short IGS1 region were closely related. This is the first investigation which provides evidence of the relative AG composition of R. solani populations causing disease in potato crops in Great Britain.
Genetic diversity of Pseudomonas syringae pv. lachrymans strains isolated from cucumber leaves collected in Poland
Authors: Olczak‐Woltman H. , Masny A. , Bartoszewski G. , Płucienniczak A. , Niemirowicz‐Szczytt K. 
Published: December 2006

Several strains of Pseudomonas syringae pathovar (pv.) lachrymans and related bacterial pathogens were isolated from cucumber (Cucumis sativus) leaves collected in central and southern Poland in 2001 and 2002. Twenty five original strains, together with five reference strains of P. syringae pv. lachrymans, pv. syringae and pv. tomato, were genetically characterized by PCR‐RFLP (polymerase chain reaction − restriction fragment length polymorphism), ADSRRS (amplification of DNA fragments surrounding rare restriction sites), and PCR‐MP (PCR − melting profiles) fingerprinting techniques. Genetic similarity analyses of the PCR‐RFLP and ADSRRS fingerprints showed that strains of P. syringae pv. lachrymans form distinct clusters. The results also indicated that the ADSRRS and the PCR‐MP fingerprinting techniques may serve as more efficient tools for evaluating genetic similarity among pathovars and strains of P. syringae than PCR‐RFLP. The 25 strains showed diverse pathogenicity to cucumber seedlings and biochemical tests were varied. The syrB gene was identified in four cucumber strains, characterized as P. syringae pv. syringae.
Sympatric ascochyta complex of wild Cicer judaicum and domesticated chickpea
Authors: Frenkel O. , Shtienberg D. , Abbo S. , Sherman A. 
Published: December 2006

The aim of this study was to isolate, identify and characterize ascochyta blight pathogens from Cicer judaicum, a wild annual Cicer species which grows in Israel and other Mediterranean countries in sympatric distribution with legume crops, and determine their virulence and aggressiveness to other wild and domesticated legumes. Native C. judaicum plants exhibited symptoms resembling ascochyta diseases of grain legume crops. Two distinct pathogens were isolated and identified as Phoma pinodella and Didymella rabiei using morphological and molecular tools; their infectivity was verified using Koch's postulates. The virulence of these pathogens was examined on 13 legume species, of which P. pinodella was virulent to Pisum sativum, P. fulvum, C. judaicum, C. arietinum, C. reticulatum, C. pinnatifidum and C. bijugum. Didymella rabiei infected all these Cicer species, but not the other legume species tested. Aggressiveness of the pathogens was tested on wild and domesticated chickpea and pea. Didymella rabiei isolated from C. judaicum had significantly higher (P < 0·001) aggressiveness than P. pinodella from C. judaicum on both wild and domesticated chickpea. Disease severity on the former species ranged from 62·5% to 70% and on the latter from 41% to 56%. Phoma pinodella isolates from C. judaicum were more aggressive on C. arietinum and P. sativum than on C. judaicum and P. fulvum. Results of the current study suggest that C. judaicum may serve as an alternative host to ascochyta pathogens that endanger chickpea and possibly other crops and wild species growing in close proximity.
An oligonucleotide microarray‐based assay for identification of phytoplasma 16S ribosomal groups
Authors: Nicolaisen M. , Bertaccini A. 
Published: December 2006

A method using consensus PCR followed by oligonucleotide microarray hybridization was developed for identification of phytoplasma 16Sr ribosomal groups. The array consisted of 21– to 33‐nt‐long oligonucleotides which were designed to hybridize to individual 16Sr groups. Two oligonucleotides were designed to detect all phytoplasma groups. The array could efficiently identify samples from 16SrI, 16SrII, 16SrIII, 16SrV, 16SrVI, 16SrVII, 16SrIX, 16SrX and 16SrXII ribosomal groups. This microarray‐based test represents a rapid method for detection of phytoplasmas in unknown samples and for identification of most 16Sr groups.
In vitro somatic growth and reproduction of phenylamide‐resistant and ‐sensitive isolates of Phytophthora erythroseptica from infected potato tubers in Idaho
Authors: Porter L. D. , Miller J. S. , Nolte P. , Price W. J. 
Published: December 2006

Pink rot of potato, most commonly caused by Phytophthora erythroseptica, is a major field and post‐harvest problem in southern Idaho, USA, particularly since 1998 when isolates resistant to the phenylamide fungicide metalaxyl‐M (mefenoxam) were detected. Isolates of P. erythroseptica were collected from infected tubers in 2001 and 2002 from six Idaho counties and tested for resistance to metalaxyl‐M on amended agar. Metalaxyl‐M resistant (MR) and metalaxyl‐M‐sensitive (MS) isolates were identified in six counties; 160 isolates were highly resistant, seven moderately resistant and 57 sensitive to metalaxyl‐M with mean EC50 values of 182, 23 and 0·5 mg L−1 ai metalaxyl‐M, respectively. Mycelial growth rates and oospore production in agar were assessed for 20 MS and 20 MR isolates at 10, 15, 20, 25 and 30°C. Growth rates of MR isolates were between 2·5 and 3·1 times greater (P < 0·05) than those of MS isolates at 10, 15, 20 and 25°C, and oospore production was between 6·8 and 20·5 times greater (P < 0·0001) for MR than for MS isolates at the same temperatures. Colony growth in V8 broth at 18°C was greater for MR than MS isolates (P < 0·0032). However, zoospore production at 18°C was greater for MS than for MR isolates (P < 0·0109), and zoospore production mm−1 of colony circumference was also greater for MS than for MR isolates, 14 191 and 9959, respectively (P = 0·0109). Sexual reproduction of MR isolates in nature may be greater than MS isolates, but MS isolates may be more asexually fit based on the fitness parameters studied.
Erosional and depositional characteristics of regional overwash deposits caused by multiple hurricanes
Authors: WANG PING , HORWITZ MARK H. 
Published: December 2006

AbstractRegional‐scale washover deposits along the Florida Gulf and Atlantic coasts induced by multiple hurricanes in 2004 and 2005 were studied through coring, trenching, ground‐penetrating radar imaging, aerial photography, and prestorm and poststorm beach‐profile surveys. Erosional and depositional characteristics in different barrier‐island sub‐environments, including dune field, interior wetland and back‐barrier bay were examined. Over the eroded dune fields, the washover deposits are characterized by an extensive horizontal basal erosional surface truncating the old dune deposits and horizontal to slightly landward‐dipping stratification. Over the marshes in the barrier‐island interior, the washover deposits are characterized by steep tabular bedding, with no erosion at the bottom. Overwash into the back‐barrier bay produced the thickest deposits characterized by steep, prograding sigmoidal bedding. No significant erosional feature was observed at the bottom. Washover deposits within the dense interior mangrove swamp demonstrate both normal and reversed graded bedding. The washover deposits caused by hurricanes Frances (2004) and Jeanne (2004) along the southern Florida Atlantic coast barrier islands are substantially different from those along the northern Florida barrier islands caused by Ivan (2004) and Dennis (2005) in terms of regional extension, erosional features and sedimentary structures. These differences are controlled by different overall barrier‐island morphology, vegetation type and density, and sediment properties. The homogeneity of sediment along the northern Florida coast makes distinguishing between washover deposits from Ivan and Dennis difficult. In contrast, along the Atlantic coast barrier islands, the two overwash events, as demonstrated by two phases of graded bedding of the bimodal sediments, are easily distinguishable.
Histidine kinases play important roles in the perception and signal transduction of hydrogen peroxide in the cyanobacterium, Synechocystis sp. PCC 6803
Authors: Kanesaki Yu , Yamamoto Hiroshi , Paithoonrangsarid Kalyanee , Shumskaya Maria , Suzuki Iwane , Hayashi Hidenori , Murata Norio 
Published: December 2006

SummaryOxidative stress caused by reactive oxygen species and, in particular, to hydrogen peroxide (H2O2) has a major impact on all biological systems, including plants and microorganisms. We investigated the H2O2‐inducible expression of genes in the cyanobacterium Synechocystis sp. PCC 6803 using genome‐wide DNA microarrays. Our systematic screening of a library of mutant lines with defects in histidine kinases (Hiks) by RNA slot‐blot hybridization and DNA‐microarray analysis suggested that four Hiks, namely, Hik33, Hik34, Hik16 and Hik41, are involved in the perception and transduction of H2O2 signals that regulate the gene expression of 26 of the 77 H2O2‐inducible genes with induction factors higher than 4.0. Among the four Hiks, Hik33 was the main contributor and was responsible for 22 of the 26 H2O2‐inducible genes under the control of the Hiks. By contrast to Hik33, PerR encoding putative peroxide‐sensing protein is involved in the regulation of only nine H2O2‐inducible genes.
Subfunctionalization of PhyB1 and PhyB2 in the control of seedling and mature plant traits in maize
Authors: Sheehan Moira J. , Kennedy Lisa M. , Costich Denise E. , Brutnell Thomas P. 
Published: December 2006

SummaryPhytochromes are the primary red/far‐red photoreceptors of higher plants, mediating numerous developmental processes throughout the life cycle, from germination to flowering. In seed plants, phytochromes are encoded by a small gene family with each member performing both distinct and redundant roles in mediating physiological responses to light cues. Studies in both eudicot and monocot species have defined a central role for phytochrome B in mediating responses to light in the control of several agronomically important traits, including plant height, transitions to flowering and axillary branch meristem development. Here we characterize Mutator‐induced alleles of PhyB1 and a naturally occurring deletion allele of PhyB2 in Zea mays (maize). Using single and double mutants, we show that the highly similar PhyB1 and PhyB2 genes encode proteins with both overlapping and non‐redundant functions that control seedling and mature plant traits. PHYB1 and PHYB2 regulate elongation of sheath and stem tissues of mature plants and contribute to the light‐mediated regulation of PhyA and Cab gene transcripts. However, PHYB1 and not PHYB2 contributes significantly to the inhibition of mesocotyl elongation under red light, whereas PHYB2 and to a lesser extent PHYB1 mediate the photoperiod‐dependent floral transition. This sub functionalization of PHYB activities in maize has probably occurred since the tetraploidization of maize, and may contribute to flowering time variation in modern‐day varieties.
Spatial variation in H2O2 response of Arabidopsis thaliana root epidermal Ca2+ flux and plasma membrane Ca2+ channels
Authors: Demidchik Vadim , Shabala Sergey N. , Davies Julia M. 
Published: December 2006

SummaryHydrogen peroxide is an important regulatory agent in plants. This study demonstrates that exogenous H2O2 application to Arabidopsis thaliana root epidermis results in dose‐dependent transient increases in net Ca2+ influx. The magnitude and duration of the transients were greater in the elongation zone than in the mature epidermis. In both regions, treatment with the cation channel blocker Gd3+ prevented H2O2‐induced net Ca2+ influx, consistent with application of exogenous H2O2 resulting in the activation of plasma membrane Gd3+‐sensitive Ca2+‐influx pathways. Application of 10 mm H2O2 to the external plasma membrane face of elongation zone epidermal protoplasts resulted in the appearance of a hyperpolarization‐activated Ca2+‐permeable conductance. This conductance differed from that previously characterized as being responsive to extracellular hydroxyl radicals. In contrast, in mature epidermal protoplasts a plasma membrane hyperpolarization‐activated Ca2+‐permeable channel was activated only when H2O2 was present at the intracellular membrane face. Channel open probability increased with intracellular [H2O2] and at hyperpolarized voltages. Unitary conductance decreased thus: Ba2+ > Ca2+ (14.5 pS) > Mg2+ > Zn2+ (20 mm external cation, 1 mm H2O2). Lanthanides and Zn2+ (but not TEA+) suppressed the open probability without affecting current amplitude. The results suggest spatial heterogeneity and differential sensitivity of Ca2+ channel activation by reactive oxygen species in the root that could underpin signalling.
Stability of lymphocytes and Epstein–Barr virus during red blood cell storage
Authors: Qu L. , Triulzi D. J , Rowe D. T. , Griffin D. L. , Donnenberg A. D. 
Published: December 2006

Background  The Epstein–Barr virus (EBV) establishes and maintains latent infection in B lymphocytes of the healthy adults. Lymphocytes remain viable during red blood cell (RBC) storage. The effect of RBC storage on the stability of EBV‐infected B lymphocytes and EBV genome is not known.Study Design and Methods  Eight randomly selected non‐leukoreduced AS‐5 RBC units were stored for 42 days under standard blood bank refrigerated at 1–6 °C. Cell count and EBV genomes in CD19+ B lymphocytes were measured in fresh products and weekly for 6 weeks. Total white blood cells (CD45+), T lymphocyte (CD3+), and B lymphocyte (CD19+) were quantified by a single platform flow cytometric assay. EBV genomes were quantified by real‐time polymerase chain reaction using DNA purified from CD19+ B cells.Results  Viable white blood cell, T and B lymphocytes followed a biphasic decline curve during RBC storage consisting of a steep steady decline during the first 3 weeks followed by a plateau for the remainder of the storage. At the end of the RBC shelf‐life, 19% of the original T and B cells remained viable. EBV genomes per 105 CD19+ B lymphocytes remained constant during RBC storage. However, the total EBV genomes in the RBC units decline by more than 80% of their original value at the end of RBC storage due to loss of viable B lymphocytes.Conclusions  The results indicate that lymphocytes and EBV latently infected B cells can survive the normal storage conditions for RBC.