bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative genome hybridization reveals widespread aneuploidy in Candida albicans laboratory strains
Authors: Selmecki Anna , Bergmann Sven , Berman Judith 
Published: February 2005

SummaryClinical strains of Candida albicans are highly tolerant of aneuploidies and other genome rearrangements. We have used comparative genome hybridization (CGH), in an array format, to analyse the copy number of over 6000 open reading frames (ORFs) in the genomic DNA of C. albicans laboratory strains carrying one (CAI‐4) to three (BWP17) auxotrophies. We find that during disruption of the HIS1 locus all genes telomeric to HIS1 were deleted and telomeric repeats were added to a 9 nt sequence within the transforming DNA. This deletion occurred in ∼10% of transformants analysed and was stably maintained through two additional rounds of transformation and counterselection of the transformation marker. In one example, the deletion was repaired, apparently via break‐induced replication. Furthermore, all CAI‐4 strains tested were trisomic for chromosome 2 although this trisomy appears to be unstable, as it is not detected in strains subsequently derived from CAI‐4. Our data indicate CGH arrays can be used to detect monosomies and trisomies, to predict the sites of chromosome breaks, and to identify chromosomal aberrations that have not been detected with other approaches in C. albicans strains. Furthermore, they highlight the high level of genome instability in C. albicans laboratory strains exposed to the stress of transformation and counterselection on 5‐fluoro‐orotic acid.
Leishmania salvage and remodelling of host sphingolipids in amastigote survival and acidocalcisome biogenesis
Authors: Zhang Kai , Hsu Fong‐Fu , Scott David A. , Docampo Roberto , Turk John , Beverley Stephen M. 
Published: February 2005

SummarySphingolipids (SLs) play essential roles in most eukaryotes, but in the trypanosomatid protozoan Leishmania major their functions differ significantly. Previously we showed that null mutants defective in de novo sphingoid base synthesis (spt2–) lacked SLs but grew well and retained lipid rafts while replicating as promastigotes in vitro. However, they experienced catastrophic defects in membrane trafficking on entry into stationary phase, and failed to differentiate to the infective metacyclic form. Here we showed this mutant retained the ability to enter macrophages silently and inhibit activation, although as expected most parasites were destroyed. However, in mouse infections, after a delay rapidly progressive lesions appeared, and purified amastigotes were fully virulent to macrophages and mice. Mass spectrometry of spt2– amastigote lipids revealed the presence of high levels of parasite‐specific inositol phosphorylceramides (IPCs) not synthesized by the mammalian hosts. Inhibitor studies showed that salvage occurs at the level of complex SLs, suggesting that parasites carry out ‘headgroup’ remodelling. Additionally, we describe a new defect of the spt2– promastigotes involving ‘empty’ acidocalcisomes (ACs), which may point to the origin of this organelle from the lysosome‐related organelle/multivesicular body biogenesis pathway. However, ACs in spt2– amastigotes appeared quantitatively and morphologically normal. Thus salvage of SLs and other molecules by intracellular amastigotes play key roles in AC biogenesis and parasite survival in the host.
Differential binding specificities of oral streptococcal antigen I/II family adhesins for human or bacterial ligands
Authors: Jakubovics Nicholas S. , Strömberg Nicklas , Van Dolleweerd Craig J. , Kelly Charles G. , Jenkinson Howard F. 
Published: February 2005

SummaryThe antigen I/II (AgI/II) family polypeptides, ranging from 1310 to 1653 amino acid (aa) residues, are cell wall anchored adhesins expressed by most indigenous species of oral streptococci. The polypeptides interact with a wide range of host molecules, in particular salivary agglutinin glycoprotein (SAG or gp340), and with ligands on other oral bacteria. To determine the receptor recognition properties of six different AgI/II family polypeptides from strains of Streptococcus gordonii, Streptococcus intermedius and Streptococcus mutans, the genes were cloned and expressed on the surface of the surrogate host Lactococcus lactis. The S. gordonii SspA and SspB polypeptides mediated higher binding levels of L. lactis cells to surface immobilized gp340 than did S. intermedius Pas protein, or S. mutans SpaP or PAc proteins. However, the AgI/II proteins were all similar in their abilities to mediate aggregation of lactococci by fluid phase gp340. The SpaPI polypeptide from S. mutans Ingbritt, which was C‐terminally truncated by approximately 400 aa residues, did not bind gp340. Lactococci expressing AgI/II proteins, including SpaPI, were aggregated by a synthetic 16 aa residue peptide SRCRP2 derived from the aa repeat block sequences within gp340. In coaggregation assays, SspB from S. gordonii was unique in mediating coaggregation with only group A and group E strains of Actinomyces naeslundii. All the other AgI/II polypeptides mediated coaggregation with group C and group D strains of A. naeslundii. Analysis of chimeric protein constructs revealed that coaggregation specificity was determined by sequences within the N‐terminal half of AgI/II protein. A synthetic peptide (20 aa residues), which defines a putative adhesion epitope within the C‐terminal region of polypeptide, inhibited AgI/II‐mediated aggregation by gp340 but did not affect coaggregation with A. naeslundii. These results suggest that different mechanisms operate in interactions of AgI/II family polypeptides with native gp340, gp340 SRCR domain peptide, and A. naeslundii. Specificity of these interactions appears to be determined by discontinuous but interacting regions of the polypeptides, thus providing flexibility in receptor recognition for streptococcal colonization of the human host.
Linking isoprene with plant thermotolerance, antioxidants and monoterpene emissions
Authors: PEÑUELAS J. , LLUSIÀ J. , ASENSIO D. , MUNNÉ‐BOSCH S. 
Published: February 2005

ABSTRACTThe purpose of the present study was to test the possible plant thermotolerance role of isoprene and to study its relationship with non‐enzymatic antioxidants and terpene emissions. The gas exchange, chlorophyll fluorescence, extent of photo‐ and oxidative stress, leaf damage, mechanisms of photo‐ and antioxidant protection, and terpene emission were measured in leaves of Quercus ilex seedlings exposed to a ramp of temperatures of 5 °C steps from 25 to 50 °C growing with and without isoprene (10 µL L−1) fumigation. The results showed that isoprene actually conferred thermotolerance (shifted the decrease of net photosynthetic rates from 35 to 45 °C, increased Fv/Fm at 50 °C from 0.38 to 0.65, and decreased the leaf area damaged from 27 to 15%), that it precluded or delayed the enhancement of the antioxidant non‐enzymatic defence conferred by α‐tocopherol, ascorbic acid or β‐carotene consumption in response to increasing temperatures, and that it decreased by approximately 70% the emissions of monoterpenes at the highest temperatures. This suggests that there are inducible mechanisms triggered by the initial stages of thermal damage that up‐regulate these antioxidant compounds at high temperatures and that these mechanisms are somehow suppressed in the presence of exogenous isoprene, which seems to already exert an antioxidant‐like behaviour.
Adjustment of leaf photosynthesis to shade in a natural canopy: reallocation of nitrogen
Authors: EICHELMANN H. , OJA V. , RASULOV B. , PADU E. , BICHELE I. , PETTAI H. , MÄND P. , KULL O. , LAISK A. 
Published: February 2005

ABSTRACTThe present study was performed to investigate the adjustment of the constituents of the light and dark reactions of photosynthesis to the natural growth irradiance in the leaves of an overstorey species,Betula pendulaRoth, a subcanopy speciesTilia cordataP. Mill., and a herbSolidago virgaureaL. growing in a natural plant community in Järvselja, Estonia. Shoots were collected from the site and properties of individual leaves were measured in a laboratory, by applying a routine of kinetic gas exchange and optical measurements that revealed photosystem II (PSII), photosystem I (PSI), and cytochrome b6f densities per leaf area and the distribution of excitation (or chlorophyll, Chl) between the two photosystems. In parallel, N, Chl and ribulose‐bisphosphate carboxylase‐oxygenase (Rubisco) content was measured from the same leaves. The amount of N in photosynthetic proteins was calculated from the measured contents of the components of the photosynthetic machinery. Non‐photosynthetic N was found as the residual of the budget. Growth in shade resulted in the decrease of leaf dry mass to a half of the DW in sun leaves in each species, but the total variation, from the top to the bottom of the canopy, was larger. Through the whole cross‐section of the canopy, leaf dry weight (DW) and Rubisco content per area decreased by a factor of four, N content by a factor of three, but Chl content only by a factor of 1.7. PSII density decreased by a factor of 1.9, but PSI density by a factor of 3.2. The density of PSI adjusted to shade to a greater extent than the density of PSII. In shade, the distribution of N between the components of the photosynthetic machinery was shifted toward light‐harvesting proteins at the expense of Rubisco. Non‐photosynthetic N decreased the most substantially, from 54% in the sun leaves ofB. pendulato 11% in the shade leaves ofT. cordata. It is concluded that the redistribution of N toward light‐harvesting Chl proteins in shade is not sufficient to keep the excitation rate of a PSII centre invariant. Contrary to PSII, the density of PSI – the photosystem that is in immediate contact with the carbon assimilation system – shade‐adjusts almost proportionally with the latter, whereas its Chl antenna correspondingly increases. Even under N deficiency, a likely condition in the natural plant community, a substantial part of N is stored in non‐photosynthetic proteins under abundant irradiation, but much less under limiting irradiation. At least in trees the general sequence of down‐regulation due to shade adjustment is the following: (1) non‐protein cell structures and non‐photosynthetic proteins; (2) carbon assimilation proteins; (3) light reaction centre proteins, first PSI; and (4) chlorophyll‐binding proteins.
Identification of rice root proteins regulated by gibberellin using proteome analysis
Authors: KONISHI H. , KITANO H. , KOMATSU S. 
Published: February 2005

ABSTRACTGibberellin (GA) promoted rice (Oryza sativa L.) root elongation in a concentration‐dependent manner with roots grown in 0.1 µm GA3 being 13.8% longer than controls. On the other hand, the roots of Tan‐ginbozu, a semi‐dwarf cultivar were 69.8% shorter in comparison with Nipponbare, a normal cultivar. Treatments with 10 µm uniconazole‐P and 10 µm abscisic acid (ABA) caused decreases in root length in Tan‐ginbozu by 44.6 and 79.2%, respectively. To investigate how GA influences rice root growth, proteome analysis techniques were applied. Extracted proteins were separated by two‐dimensional polyacrylamide gel electrophoresis and analysed using an automated protein sequencer and mass spectrometer. Sixteen proteins show differences in accumulation levels as a result of treatment with GA3, uniconazole‐P and ABA treatment and/or the difference between the semi‐dwarf cultivar, Tan‐ginbozu, and normal cultivars. Among these proteins, fructose‐bisphosphate aldolase (EC 4.1.2.13) increased in roots treated with GA3, occurred in low levels in Tan‐ginbozu roots, and decreased in roots treated with uniconazole‐P or ABA. Moreover, roots from seedlings grown in 100 µm glucose were 9.1% longer than controls. These results indicate that increases in fructose‐bisphosphate aldolase activity stimulate the glycolytic pathway and may play an important role in the GA‐induced growth of roots.
Regulation of the expression of OsIPS1 and OsIPS2 in rice via systemic and local Pi signalling and hormones
Authors: HOU X. L. , WU P. , JIAO F. C. , JIA Q. J. , CHEN H. M. , YU J. , SONG X. W. , YI K. K. 
Published: February 2005

ABSTRACTTwo genes with a common region that is characteristic of the TPSI1/Mt4 family were cloned from a Pi‐starvation‐induced cDNA library of rice roots using suppression subtracted hybridization (SSH). Based on the consensus sequence of these two genes, members of the TPSI1/Mt4 family were found in maize, wheat and barley. blast and a cluster analysis in the eight members of the TPSI1/Mt4 family showed two classes of four genes each among monocots. The first gene from rice was designated OsIPS1 based on a comparison of the consensus sequence with AtIPS1, and consequently the second gene, which has been previously reported as OsPI1, was designated OsIPS2. Accumulation of the mRNA of OsIPS1/2 was examined by northern blotting and quantitative reverse transcriptase‐polymerase chain reaction in whole‐root and split‐root experiments under treatment with phosphate (Pi) and the Pi analogue phosphite (Phi). OsIPS1 showed much higher mRNA accumulation in roots than OsIPS2, and an opposite trend was seen in shoots. OsIPS1/2 showed both systemic and local responses to Pi starvation, and less than 10% of the overall induced mRNA level was due to the local Pi concentration in roots. The results indicate that Phi may interfere with earlier events in roots that are associated with a local Pi signalling pathway. An analysis of transgenic plants showed that OsIPS1/2 are independently responsive to Pi signalling and are mainly expressed in lateral roots and in the vascular cylinder in the primary root. Exogenous cytokinin (6‐BA) almost completely suppressed systemic Pi starvation signalling and partially suppressed local Pi signalling. Exogenous abscisic acid remarkably reduced Pi starvation signalling. In contrast, exogenous auxin enhanced Pi signalling, especially local Pi signalling in roots. Exogenous ethylene (ethyphon) and the ratio of auxin to cytokinins did not appear to affect the expression of these two genes.
Ectopic expression of nicotianamine synthase genes results in improved iron accumulation and increased nickel tolerance in transgenic tobacco
Authors: DOUCHKOV D. , GRYCZKA C. , STEPHAN U. W. , HELL R. , BÄUMLEIN H. 
Published: February 2005

ABSTRACTHeavy metals are essential for basic cellular processes but toxic in higher concentrations. This requires the precise control of their intracellular concentrations, a process known as homeostasis. The metal‐chelating, non‐proteinogenous amino acid nicotianamine (NA) is a key component of plant metal assimilation and homeostasis. Its precise function is still unknown. Therefore, this article aims to contribute new information on the in vivo function of NA and to evaluate its potential use for plant nutrition and crop fortification. For this purpose, a nicotianamine synthase gene of Arabidopsis thaliana was ectopically expressed in transgenic tobacco plants. The presence of extra copies of the nicotianamine synthase gene co‐segregated with up to 10‐fold elevated levels of NA in comparison with wild type. The increased NA level led to: (a) a significantly increased iron level in leaves of adult plants; (b) the accumulation of zinc and manganese, but not copper; (c) an improvement of the iron use efficiency in adult plants grown under iron limitation; and (d) an enhanced tolerance against up to 1 m m nickel. Taken together, the data predict that NA may be a useful tool for improved plant nutrition on adverse soils and possibly for enhanced nutritional value of leaf and seed crops.
Growth at moderately elevated temperature alters the physiological response of the photosynthetic apparatus to heat stress in pea (Pisum sativumL.) leaves
Authors: HALDIMANN PIERRE , FELLER URS 
Published: February 2005

ABSTRACTThe impact of heat stress on the functioning of the photosynthetic apparatus was examined in pea (Pisum sativumL.) plants grown at control (25 °C; 25 °C‐plants) or moderately elevated temperature (35 °C; 35 °C‐plants). In both types of plants net photosynthesis (Pn) decreased with increasing leaf temperature (LT) and was more than 80% reduced at 45 °C as compared to 25 °C. In the 25 °C‐plants, LTs higher than 40 °C could result in a complete suppression ofPn. Short‐term acclimation to heat stress did not alter the temperature response ofPn. Chlorophyllafluorescence measurements revealed that photosynthetic electron transport (PET) started to decrease when LT increased above 35 °C and that growth at 35 °C improved the thermal stability of the thylakoid membranes. In the 25 °C‐plants, but not in the 35 °C‐plants, the maximum quantum yield of the photosystem II primary photochemistry, as judged by measuring theFv/Fmratio, decreased significantly at LTs higher than 38 °C. A post‐illumination heat‐induced reduction of the plastoquinone pool was observed in the 25 °C‐plants, but not in the 35 °C‐plants. Inhibition ofPnby heat stress correlated with a reduction of the activation state of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco). Western‐blot analysis of Rubisco activase showed that heat stress resulted in a redistribution of activase polypeptides from the soluble to the insoluble fraction of extracts. Heat‐dependent inhibition ofPnand PET could be reduced by increasing the intercellular CO2concentration, but much more effectively so in the 35 °C‐plants than in the 25 °C‐plants. The 35 °C‐plants recovered more efficiently from heat‐dependent inhibition ofPnthan the 25 °C‐plants. The results show that growth at moderately high temperature hardly diminished inhibition ofPnby heat stress that originated from a reversible heat‐dependent reduction of the Rubisco activation state. However, by improving the thermal stability of the thylakoid membranes it allowed the photosynthetic apparatus to preserve its functional potential at high LTs, thus minimizing the after‐effects of heat stress.
Effects of moderate heat stress on photosynthesis: importance of thylakoid reactions, rubisco deactivation, reactive oxygen species, and thermotolerance provided by isoprene
Authors: SHARKEY THOMAS D. 
Published: February 2005

ABSTRACTPhotosynthesis is particularly sensitive to heat stress and recent results provide important new insights into the mechanisms by which moderate heat stress reduces photosynthetic capacity. Perhaps most surprising is that there is little or no damage to photosystem II as a result of moderate heat stress even though moderate heat stress can reduce the photosynthetic rate to near zero. Moderate heat stress can stimulate dark reduction of plastoquinone and cyclic electron flow in the light. In addition, moderate heat stress may increase thylakoid leakiness. At the same time, rubisco deactivates at moderately high temperature. Relationships between effects of moderate heat on rubisco activation and thylakoid reactions are not yet clear. Reactive oxygen species such as H2O2 may also be important during moderate heat stress. Rubisco can make hydrogen peroxide as a result of oxygenase side reactions and H2O2 production by rubisco was recently shown to increase substantially with temperature. The ability to withstand moderately high temperature can be improved by altering thylakoid lipid composition or by supplying isoprene. In my opinion this indicates that thylakoid reactions are important during moderate heat stress. The deactivation of rubisco at moderately high temperature could be a parallel deleterious effect or a regulatory response to limit damage to thylakoid reactions.
First year donation patterns predict long‐term commitment for first‐time donors
Authors: Schreiber G. B. , Sharma U. K. , Wright D. J. , Glynn S. A. , Ownby H. E. , Tu Y. , Garratty G. , Piliavin J. , Zuck T. , Gilcher R. ,   for the Retrovirus Epidemiology Donor Study
Published: February 2005

Background and Objectives  Converting first‐time donors to become regular donors continues to be a challenge facing blood centres. We examined whether first‐time donors with frequent return in the first 12 months were more likely to become regular donors.Subjects and Methods  The donation histories of 179 409 community whole‐blood donors, whose first‐time donation in 1991 was negative on donor screening tests, were evaluated. Donors were categorized by the number of donations made in the 12 months after (and including) their first donation. The donor return pattern in the subsequent 6 years, and its association with first‐year donation frequency and demographics, was evaluated by using logistic regression analysis. A ‘regular donor’ was defined as one who returned to donate in at least 4 of the 6 years of follow‐up.Results  First‐year donation frequency was significantly correlated with long‐term donor return (P < 0·0001). Among those giving 1, 2, 3, 4 and ≥ 5 donations in the first year, 4%, 11%, 21%, 32% and 42%, respectively, became regular donors (P < 0·0001). Similar associations between donation pattern and donor return behaviour were observed after adjusting for demographic variables (P < 0·0001).Conclusions  Strategies aimed at encouraging current donors to donate more frequently during the first year may help to establish a regular donation behaviour.
Strict red blood cell transfusion guideline reduces the need for transfusions in very‐low‐birthweight infants in the first 4 weeks of life: a multicentre trial
Authors: Miyashiro A. M. , Dos Santos N. , Guinsburg R. , Kopelman B. I. , De Araújo Peres C. , De Lima Taga M. F. , Shinzato A. R. , De Paula Fiod Costa H. 
Published: February 2005

Background and Objectives  Very‐low‐birthweight infants are among the most heavily transfused patients. The objective of this study was to verify if the introduction of a strict guideline would reduce the need for red blood cell transfusions in the first 4 weeks of life in these neonates.Materials and Methods  This was a multicentre prospective study of two cohorts of very‐low‐birthweight infants transfused in accordance with the recommendations of a neonatologist (Phase 1) or according to previously published guidelines (Phase 2).Results  In the first 28 days of life, 102 patients (68·5%) in Phase 1 and 117 (59·7%) in Phase 2 were transfused. The number of transfusions was 1·9 ± 2·0 in Phase 1 and 1·4 ± 1·6 in Phase 2 (P = 0·01). After adjusting for gestational age, blood loss and the presence of respiratory distress syndrome, the strict guideline reduced the number of transfusions in 17·6% (IC 95%−30·5% to −2·6%).Conclusions  The strict guideline was effective in reducing erythrocyte transfusions in very‐low‐birthweight infants.