bluuebunny/crossref_metadata_2025_split huggingface dataset:
A monocarpic tree species in a polycarpic world: how can Tachigali vasquezii maintain itself so successfully in a tropical rain forest community?
Authors: POORTER LOURENS , ZUIDEMA PIETER A. , PEÑA‐CLAROS MARIELOS , BOOT RENE G. A. 
Published: March 2005

Summary

Although monocarpy is rare among long‐lived plant species that grow in stable habitats, one monocarpic species, Tachigali vasquezii, is extremely abundant in the rain forests of the Bolivian Amazon. We analyse how T. vasquezii is able to maintain itself successfully by comparing its life‐history traits with those of polycarpic tree species of the same community. We then evaluate the relative importance of such traits using population matrix models.
Monocarpic species are expected to have a high fecundity. Seed production per basal area for T. vasquezii is indeed nearly twice that of an average polycarpic species, but this is not sufficient to maintain stable populations.
Life‐history theory predicts that a monocarpic strategy is advantageous if juvenile survival rates are high compared with adult survival. Although seedlings of T. vasquezii have a lower mortality rate than polycarpic species, its sapling have higher mortality.
We found that the success of T. vasquezii is due to its very high diameter growth rates in the larger size classes, which are four times higher than that of an average, co‐occurring polycarpic species. Fast diameter growth is enabled by investment in large, leafy crowns and by a low wood density. Applying this high diameter growth in a population model yielded a population growth rate close to that of polycarpic species. Life table response experiment analysis of Tachigali and polycarp models showed that higher growth compensated for the negative demographic effect of 100% adult mortality following reproduction.
Rapid growth enables T. vasquezii to reach reproductive maturity in only 49 years, compared with 79 years for an average polycarpic species. It also reduces the risk of dying before reproducing, and 50% more seedlings survive to maturity for T. vasquezii compared with polycarpic species.
The dramatic negative demographic consequences of one‐time flowering can therefore be completely balanced by taking a shorter time to reach maturity. Taking a time perspective, it appears that Tachigali vasquezii has an advanced, rather than a delayed, reproduction.
Ectomycorrhizal fungal communities at forest edges
Authors: A. DICKIE IAN , REICH PETER B. 
Published: March 2005

Summary

Ectomycorrhizal fungi are spatially associated with established ectomycorrhizal vegetation, but the influence of distance from established vegetation on the presence, abundance, diversity and community composition of fungi is not well understood.
We examined mycorrhizal communities in two abandoned agricultural fields in Minnesota, USA, using Quercus macrocarpa seedlings as an in situ bioassay for ectomycorrhizal fungi from 0 to 20 m distance from the forest edge.
There were marked effects of distance on all aspects of fungal communities. The abundance of mycorrhiza was uniformly high near trees, declined rapidly around 15 m from the base of trees and was uniformly low at 20 m. All seedlings between 0 and 8 m distance from forest edges were ectomycorrhizal, but many seedlings at 16–20 m were uninfected in one of the two years of the study. Species richness of fungi also declined with distance from trees.
Different species of fungi were found at different distances from the edge. ‘Rare’ species (found only once or twice) dominated the community at 0 m, Russula spp. were dominants from 4 to 12 m, and Astraeus sp. and a Pezizalean fungus were abundant at 12 m to 20 m. Cenococcum geophilum, the most dominant species found, was abundant both near trees and distant from trees, with lowest relative abundance at intermediate distances.
Our data suggest that seedlings germinating at some distance from established ectomycorrhizal vegetation (15.5 m in the present study) have low levels of infection, at least in the first year of growth. Distance from established vegetation represents an important gradient for ectomycorrhizal fungi, with different species occupying distinct niches along this gradient. This provides support for niche differentiation as a factor contributing to ectomycorrhizal fungal diversity.
Ectomycorrhizal infection of seedlings is spatially complex, with high infection and high fungal diversity near trees, high infection but lower diversity at intermediate distances, and low infection and low fungal diversity distant from trees. This spatial complexity should be considered as a factor potentially influencing the establishment of ectomycorrhizal vegetation.
Variation in growth pattern and response to slug damage among native and invasive provenances of four perennial Brassicaceae species
Authors: BUSCHMANN H. , EDWARDS P.J. , DIETZ H. 
Published: March 2005

Summary

The EICA (evolution of increased competitive ability) hypothesis suggests that release from natural enemies and pathogens results in higher vigour of invasive plants as a result of the selection of less defended but rapidly growing genotypes. Slug diversity and abundance appear to be low in North America compared with Europe, and we therefore hypothesized that release from slug herbivory contributes to the invasiveness of European Brassicaceae species in North America.
In common garden and glasshouse experiments we compared life history and fitness parameters in native (NP) and introduced (IP) provenances of four invasive Brassicaceae species (Barbarea vulgaris, Bunias orientalis, Cardaria draba, Rorippa austriaca) that were subjected to herbivory by Arion lusitanicus. In climate chamber bioassays we investigated slug damage to seedlings and leaf discs using the same sources of plant material.
In all species except B. orientalis we found significant but not always consistent differences in growth and reproductive characteristics between IP and NP plants. Plants of B. vulgaris and R. austriaca from the introduced range had a considerably higher growth rate than those from the native range. While IP plants of the non‐clonal B. vulgaris allocated more resources to seed production than NP plants, the IP plants of the clonal R. austriaca showed a decreased number of seeds.
Contrary to expectation, there were no differences between NP plants and IP plants in the number of damaged leaves and leaf area consumed by slugs, or in the proportion of seedlings damaged and killed. Nor were there interaction effects between slug treatments and provenance.
The results suggest that there are genetically based differences in growth and reproductive parameters between NP and IP plants. As there were no differences in herbivore damage between the provenances, this genetic differentiation is probably due to factors such as competition rather than herbivore effects.
In order to make progress in understanding why some species become invasive, more comparative experimental studies are needed that investigate how different kinds of antagonists (generalist and specialist herbivores and pathogens) influence the performance of plants at different life stages.
Bacterial Endotoxin (lipopolysaccharide) Stimulates Interleukin‐6 Production and Inhibits Growth of Pituitary Tumour Cells Expressing the Toll‐Like Receptor 4
Authors: Tichomirowa M. , Theodoropoulou M. , Lohrer P. , Schaaf L. , Losa M. , Uhl E. , Lange M. , Arzt E. , Stalla G. K. , Renner U. 
Published: March 2005

AbstractMembers of the Toll receptor (Tlr) family have a crucial role in the innate immune response following bacterial infection. The effects of Gram‐negative bacteria‐derived endotoxins (lipopolysaccharide, LPS) are predominantly mediated by Tlr4, and we have recently shown that pituitary folliculostellate cells express functional Tlr4. In the present study, we investigated whether Tlr4 is also present in normal and transformed endocrine epithelial pituitary cell types. By reverse transcriptase‐polymerase chain reaction, Tlr4 mRNA expression was found in some pituitary epithelial tumour cell lines (AtT20, HP75), whereas others were negative (GH3, αT3‐1). Tlr4 protein was detected by immunohistochemistry in a few epithelial cells in normal human anterior pituitaries and in 26 out of 67 human pituitary tumours analysed. LPS had no effect on adrenocorticotropic hormone secretion in Tlr4‐positive AtT20 cells, but it suppressed the growth of these cells in a dose‐dependent manner. As expected, neither hormone secretion, nor growth of Tlr4‐negative GH3 cells was affected by LPS. In cell cultures of Tlr4‐positive pituitary adenomas, LPS dose‐dependently stimulated the production of interleukin (IL)‐6, which is known to induce growth and hormone production in pituitary tumours. The LPS‐induced IL‐6 production was blocked by the specific p38αMAP kinase inhibitor, SB203580, and by the synthetic glucocorticoid, dexamethasone. The data suggest that, during Gram‐negative bacteria‐induced infections or inflammatory processes, LPS could affect pituitary tumour pathophysiology and progression in the subset of Tlr4‐expressing pituitary adenomas.
Oestradiol Effect on Galanin‐Immunoreactive Neurones in the Diencephalon of the Ewe
Authors: Tourlet S. , Ziyazetdinova G. , Caraty A. , Tramu G. , Delsol G. , Tillet Y. 
Published: March 2005

AbstractGalanin is a neuropeptide involved in the regulation of numerous functions such as reproduction. In female rats, this peptide stimulates gonadotropin‐releasing hormone (GnRH)/luteinizing hormone release and its synthesis is stimulated by oestradiol. It could therefore be an intermediary between the oestrogenic signal from the ovaries and the GnRH neurones (e.g. during the time course leading to the preovulatory GnRH surge). However, although the involvement of galanin is well‐known in rodents, it is poorly understood in ewes. Using immunohistochemistry with a specific antigalanin antiserum, we detected the peptide in neurones of two groups of ovariectomized ewes treated for 6 h with subcutaneous implants, either with oestradiol (experimental group) or empty (control group). The galanin‐immunoreactive neurones were counted in three areas, the preoptic area, the bed nucleus of the stria terminalis and the infundibular nucleus, using a computerized image analysis system. There was no change in the mean number of galanin‐immunoreactive (GAL‐ir) neurones in the infundibular nucleus (37 ± 12 neurones/section in treated animals and 31 ± 11 in controls) or in the bed nucleus of the stria terminalis (22 ± 5 neurones/section in treated animals and 16 ± 4 in controls), but the number of GAL‐ir neurones was higher in the preoptic area in treated than in control ewes (35 ± 4 versus 14 ± 10, P < 0.001). To determine whether the neurones of the preoptic area were directly sensitive to oestradiol, we performed double immunohistochemical labelling for oestradiol receptor alpha and galanin. More than 50% of the GAL‐ir neurones contained the oestradiol receptor alpha and therefore could be directly regulated by oestradiol. These results indicate that oestradiol might act directly on a GAL‐ir neuronal population situated in the preoptic area, without any effect on the GAL‐ir neurones of the infundibular nucleus or the bed nucleus of the stria terminalis. Because a 6‐h oestradiol treatment can induce a preovulatory GnRH surge in ewes, the GAL‐ir neuronal population of the preoptic area might be one of the neuronal systems by which oestradiol activates the GnRH neurones. However, although the morphological relationships between galanin and GnRH neurones have been described in rodents, they remain to be demonstrated in the ewe.
A bacterial hormone (the SCB1) directly controls the expression of a pathway‐specific regulatory gene in the cryptic type I polyketide biosynthetic gene cluster of Streptomyces coelicolor
Authors: Takano Eriko , Kinoshita Hiroshi , Mersinias Vassilis , Bucca Giselda , Hotchkiss Graham , Nihira Takuya , Smith Colin P. , Bibb Mervyn , Wohlleben Wolfgang , Chater Keith 
Published: March 2005

SummaryGamma‐butyrolactone signalling molecules are produced by many Streptomyces species, and several have been shown to regulate antibiotic production. In Streptomyces coelicolor A3(2) at least one γ‐butyrolactone (SCB1) has been shown to stimulate antibiotic production, and genes encoding proteins that are involved in its synthesis (scbA) and binding (scbR) have been characterized. Expression of these genes is autoregulated by a complex mechanism involving the γ‐butyrolactone. In this study, additional genes influenced by ScbR were identified by DNA microarray analysis, and included a cryptic cluster of genes for a hypothetical type I polyketide. Further analysis of this gene cluster revealed that the pathway‐specific regulatory gene, kasO, is a direct target for regulation by ScbR. Gel retardation and DNase I footprinting analyses identified two potential binding sites for ScbR, one at −3 to −35 nt and the other at −222 to −244 nt upstream of the kasO transcriptional start site. Addition of SCB1 eliminated the DNA binding activity of ScbR at both sites. The expression of kasO was growth phase regulated in the parent (maximal during transition phase), undetectable in a scbA null mutant, and constitutively expressed in a scbR null mutant. Addition of SCB1 to the scbA mutant restored the expression of kasO, indicating that ScbR represses kasO until transition phase, when presumably SCB1 accumulates in sufficient quantity to relieve kasO repression. Expression of the cryptic antibiotic gene cluster was undetectable in a kasO deletion mutant. This is the first report with comprehensive in vivo and in vitro data to show that a γ‐butyrolactone‐binding protein directly regulates a secondary metabolite pathway‐specific regulatory gene in Streptomyces.
Understanding the control of Pseudomonas aeruginosa alginate synthesis and the prospects for management of chronic infections in cystic fibrosis
Authors: Ramsey Deborah M. , Wozniak Daniel J. 
Published: March 2005

SummaryDecades of research have been dedicated to the study of the opportunistic pathogen Pseudomonas aeruginosa, a Gram‐negative, environmental bacterium that secretes the exopolysaccharide alginate during chronic lung infection of cystic fibrosis (CF) patients. Although P. aeruginosa utilizes a variety of factors to establish a successful infection in the lungs of CF patients, alginate has stood out as one of the best‐studied prognostic indicators of chronic lung infection. While the genetics, biosynthesis and regulation of alginate are well understood, questions still remain concerning its role in biofilm development and its potential as a therapeutic target. The purpose of this review is to provide a brief summary of alginate biosynthesis and regulation, and to highlight recent discoveries in the areas of alginate production, biofilm formation and vaccine design. This information is placed in context with a proposed P. aeruginosa infectious pathway, highlighting avenues for the use of existing therapies as well as the potential for novel agents to reduce or eliminate chronic infections in CF patients.
Regulation of azole drug susceptibility by Candida albicans protein kinase CK2
Authors: Bruno Vincent M. , Mitchell Aaron P. 
Published: March 2005

SummaryFluconazole resistance of the fungal pathogen Candida albicans can arise through several mechanisms, but the responsible genes and pathways are poorly understood. We report here that mutations in CKA2, identified through an insertional mutagenesis screen, confer fluconazole resistance. CKA2 and its homologue CKA1 specify catalytic subunits of protein kinase CK2. Although cka1 mutations have little effect on fluconazole resistance, CKA1 overexpression suppresses the fluconazole resistance of a cka2 mutant. This observation, along with synthetic cka1–cka2 interactions, argues that Cka1p and Cka2p carry out similar functions. cka2 mutants overexpress CDR1 and CDR2, two fluconazole efflux transporter genes, and a cdr1 mutation decreases resistance of a cka2 mutant, as expected if CDR1 and CDR2 overexpression is responsible for fluconazole resistance of the cka2 mutant. The protein phosphatase calcineurin is required for azole tolerance, and we find that the calcineurin inhibitor cyclosporin reverses fluconazole resistance of cka2 mutants. In addition, a mutation in CRZ1, which specifies a homologue of the Saccharomyces cerevisiae transcription factor that is a major target of calcineurin, suppresses fluconazole resistance  of  cka2 mutants.  Expression  analysis  of Cka2p‐responsive genes argues that Cka2p and Crz1p act through distinct mechanisms. Several clinical fluconazole‐resistant isolates overexpress some Cka2p‐responsive genes. We suggest that a Cka2p‐dependent regulatory pathway is altered by clinically derived azole resistance mutations.
Evaluation of Usefulness of Daily Mean Temperature Studies on Impact of Climate Change
Authors: Chauhan S. , Khandelwal R. S. , Prabhu K. V. , Sinha S. K. , Khanna‐Chopra R. 
Published: March 2005

AbstractThe impact of global warming on rise in temperature in different regions has often been expressed as a change in mean temperature (Tmean). The recent results suggest that this change could be both in diurnal and interannual temperatures. Therefore it is important to assess the impact of diurnal variation with the same mean temperature on crop plants for understanding the impact of climate change on agriculture, and also assess the possibility of genetic variation in adaptation. The present study in wheat (Triticum aestivum) varieties examines the effect of varying Tmax and Tmin, while maintaining the same mean temperature on phenology, growth and productivity. The mean temperatures examined are 18 °C with Tmax/Tmin combination of 18/18, 20/16, 22/14 and 24/12 °C. These wheat varieties differed considerably in their response to varying Tmax and Tmin with respect to days to ear emergence, anthesis, biomass accumulation and grain yield. The wheat variety HD2329, a popular Mexican dwarf high yielding cultivar showed maximum adaptation in the temperature combinations examined. The results suggest the need to refine the crop ideotypes in the context of the changing global scenario. This may require detailed experimental studies on various phenological phases. Such studies would help in assessing genotypes which may be having adaptation and thus identify the potential donors for further improvement of crops.
Remobilization of Nitrogen and Carbohydrate from Stems of Bread Wheat in Response to Heat Stress during Grain Filling
Authors: Tahir I. S. A. , Nakata N. 
Published: March 2005

AbstractWhen wheat (Triticum aestivum L.) is grown under heat‐stress conditions during grain filling, preanthesis stored total non‐structural carbohydrates (TNC) and nitrogen (N) could serve as alternative source of assimilates. This study was performed to evaluate wheat genotypes for their ability to accumulate and remobilize TNC and N stored in their stem to support grain filling under heat stress. Eighteen genotypes were used for N remobilization study while nine of them were used for TNC remobilization study. They were grown in pots and placed in a vinyl house with the maximum temperature kept below 30 °C. Five days after anthesis (5DAA), half of the pots were taken to phytotrons where temperature was gradually increased and the maximum was set at 38 °C. Grain yield and grain weight decreased by about 35 % under heat stress. Significant differences were found among genotypes in percentage reduction in grain yield, grain weight, grain filling duration and harvest index because of heat stress. The N and TNC concentrations of the stem at 5DAA were significantly different among genotypes. Heat stress significantly reduced the N remobilization efficiency of most of genotypes. However, heat stress significantly increased TNC remobilization efficiency and significant variation were observed among genotypes. N remobilization efficiency across treatments significantly correlated with grain yield, grain weight, harvest index and grain filling duration. TNC at 5DAA negatively correlated with N at 5DAA and harvest index, but the TNC remobilization efficiency under heat stress positively correlated with mainstem grain yield, grain weight and harvest index. The rate of chlorophyll loss from flag leaf positively correlated with N and TNC remobilization efficiencies under heat stress suggesting a link between leaf senescence and remobilization efficiency. The results indicate that heat stress negatively affected grain yield, its components and N remobilization while it increased TNC remobilization because of the increasing demand for resources.
Increased Yield and Revenue with a Seedling Transplanting System for Hybrid Seed Production in Bt Cotton
Authors: Dong H. Z. , Li W. J. , Tang W. , Li Z. H. , Zhang D. M. 
Published: March 2005

AbstractRapid adoption of Bacillus thuringiensis (Bt) transgenic hybrid cotton (Gossypium hirsutum L.) in China is greatly attributed to high‐quality hybrid seed produced in northern Shandong cotton production area; however, seed yield has reached a plateau in this area in recent years. Shifting the growing season earlier in the year by planting earlier in a greenhouse‐like hut and transplanting the raised seedlings to the open fields later may allow the crop to produce more seeds. Four‐year consecutive experiments conducted in Huimin County (northern Shandong, China) showed that early‐season chilling stress on seedlings was avoided in such a hut, and that the blooming period was extended by about 1 week longer and the peak blooming occurred 5 days earlier in the year in the transplanting system than in the normal planting system. The number of early‐season blooms and the number of bolls retained per unit area in transplanting system were significantly higher than those in normal planting system, but there were no significant differences in boll size and lint percentage between the two planting systems. Seed yield and quality parameters were significantly improved in the transplanting system through the increased number of bolls per square metre and earlier blooming respectively. As a result of improvement in seed yield and quality, the net revenue for seed producers with the transplanting system was increased by 20.8 and 22.5 % in 2002 and 2003, respectively, compared with the corresponding net revenue in the normal planting system. Seedling transplanting is a potent way to enhance hybrid seed production in Bt transgenic cotton.