bluuebunny/crossref_metadata_2025_split huggingface dataset:
Below‐ground architectural and mycorrhizal responses to elevated CO2 in Betula alleghaniensis populations
Authors: BERNTSON G. M. , WAYNE P. M. , BAZZAZ F. A. 
Published: November 2003

1. Replicate populations of crowded, regenerating stands of Betula alleghaniensis were grown in ambient and elevated (700p.p.m.) atmospheric CO2 concentrations in monoliths of forest soil. Early in the second year the seedlings were harvested and detailed measurements of individual plant root architectural parameters and ectomycorrhizal colonization were made. 2. Comparing the average responses of individual plants within the populations, elevated CO2 had no significant effects on architectural parameters that improve a plant’s ability to forage for and acquire soil resources. In contrast, the intensity and magnitude of mycorrhizal colonization, and whole plant C/N ratios were significantly enhanced with elevated CO2. 3. The allometric scaling relationship between total plant biomass and root biomass was not affected by CO2, suggesting that relative allocation between roots and shoots was not affected. However, the allometric scaling relationships between root architectural parameters and plant biomass, and between fine root biomass and woody root biomass were significantly altered by elevated CO2. For all of these relationships, elevated CO2 reduced the ‘size bias’ of architectural components in relation to plant size within the populations; in elevated CO2 root architectural size (e.g. root length) per unit biomass was more similar between the smallest and largest individuals within the population than was the case for ambient CO2. 4. Overall, the results of this study suggest that the average individual seedling biomass and architectural growth responses within populations of plants exposed to elevated atmospheric CO2 levels may be unresponsive, but that mycorrhizal responses and interactions among plants within populations may be altered significantly. These findings have important implications for how we make predictions about plant growth responses to elevated CO2 in natural ecosystems. Significant increases in mycorrhizal infection rates and architecture–biomass allometries suggest that below‐ground competitive interactions within plant populations may be reduced in elevated CO2. Alterations in competitive interactions may lead to shifts in productivity and plant population structure.
Disproportional increases in photosynthesis and plant biomass in a Californian grassland exposed to elevated CO2: a simulation analysis
Authors: LUO Y. , CHEN J.‐L. , REYNOLDS J.F. , FIELD C.B. , MOONEY H.A. 
Published: November 2003

1. Elevated CO2 concentrations often lead to increased photosynthetic carbon uptake in plants, but this does not necessarily result in a proportional increase in plant biomass. We examined this paradox for grasslands in northern California that have been exposed to elevated CO2 since 1992. We evaluated the effects of physiological adjustments on plant growth and carbon balance of the dominant species, Avena barbata, using a plant growth model. 2. Without physiological adjustments, an observed 70% increase in leaf photosynthesis in elevated CO2 was predicted to increase plant biomass by 97% whereas experimental measurements suggested 5 and 13% decreases in 1992 and 1993, respectively, and a 40% increase in 1994. 3. Simulations with an increase in carbon allocation to roots by 29%, or leaf death rate by 80%, or non‐structural carbohydrate storage by 60%, or leaf mass per unit area by 25% each predicted an approximately 40% increase in plant biomass in 1994 under elevated CO2. It follows that greater suppression of the biomass responses to elevated CO2 in 1992 and 1993 resulted from variable combinations of these physiological adjustments. 4. This modelling study concludes that (a) an increase in carbon loss or (b) a decrease in carbon‐use efficiency or (c) an increase in carbon allocation to root growth will result in an increase in biomass growth that is less than that in leaf photosynthesis under elevated CO2. Alternatively, if carbon loss is reduced (e.g. depressed respiration) and/or carbon allocation to leaf growth is increased, biomass growth may be stimulated more than leaf photosynthesis by atmospheric CO2 concentration. Moreover, this modelling exercise suggests that physiological adjustments may have substantial effects on ecosystem carbon processes by varying ecosystem carbon influx, litterfall and litter quality.
Multiple breeding in the Great Tit. A trade‐off between successive reproductive attempts?
Authors: VERHULST S. , TINBERGEN J. M. , DAAN S. 
Published: November 2003

1. Multiple breeding (raising more than one batch of young per breeding season) is a common life‐history tactic that has received very little attention. A simple static optimization model was developed, applicable to iteroparous animals with parental care, that predicts: (1) when an animal should be a multiple breeder, (2) the optimal interval between successive clutches, and (3) when a clutch should be deserted. 2. More specifically, it was predicted that (I) animals should invest less in a clutch when it is followed by another clutch in the same season, and (II) as a consequence the contribution of the first clutch to the parents’ fitness will be reduced. 3. These predictions were tested experimentally in a population of Great Tits (ParusM. major L.). The experiment consisted of the removal of second clutches. When second clutches were removed, parents tended their first brood fledglings for a longer period than undisturbed control pairs, in agreement with the first prediction. Removal of second clutches did not affect fledgling survival, but recruits enjoyed higher reproductive success in their first year of breeding when the second clutch of their parents had been removed, in agreement with the second prediction. 4. It is concluded that a trade‐off exists between successive reproductive attempts, which will affect the optimal rate of reproductive attempts.
Feeding behaviour, food consumption, and growth efficiency of hemiclonal and parental tadpoles of the Rana esculenta complex
Authors: RIST L. , SEMLITSCH R. D. , HOTZ H. , REYER H.‐U. 
Published: November 2003

1. Clonally reproducing species are often assumed to lack sufficient genetic variability to evolve specific local adaptations to cope with environmental perturbation and competition from sexual species. Yet, many asexuals are extremely successful judged by abundance and wide range, suggesting high competitive abilities in resource exploitation. 2. In this study, food use and its effects on larval growth in a water frog system consisting of the two parental sexual species, Rana lessonae (Camerano 1882) and Rana ridibunda (Pallas 1771), and three different coexisting hemiclones of their hybrid, Rana esculenta (Linnaeus 1758) were investigated. 3.
R. esculenta tadpoles spent 18·6% more time feeding than did tadpoles of either parental species, but feeding time was not affected by interspecific mixture. 4.
R. esculenta tadpoles consumed 50·8% more food over the whole test period than did tadpoles of the two parental species. 5.
R. esculenta tadpoles exhibited higher growth rates than did tadpoles of either parental species. 6.
R. lessonae tadpoles had the highest and R. ridibunda tadpoles the lowest growth efficiencies with the R. esculenta tadpoles ranging between the two parentals. 7. The results obtained indicate that hemiclonal hybridogenetic R. esculenta tadpoles display significant phenotypic variation among coexisting hemiclones as well as out‐perform tadpoles of the parental sexual species R. lessonae and R. ridibunda. The primary mechanism for success of the hybrid tadpoles is probably behavioural, through increased feeding time and food consumption, and not physiological via growth efficiency.
Where is the cost in copper tolerance in Mimulus guttatus? Testing the trade‐off hypothesis
Authors: HARPER F. A. , SMITH S. E. , MACNAIR M. R. 
Published: November 2003

1. It is frequently asserted that the adaptation of metal tolerance involves a cost, i.e. tolerant individuals have a lowered fitness on uncontaminated soil. To date, however, evidence for a cost has been highly circumstantial. One well‐known example of metal tolerance, copper tolerance in Mimulus guttatus, is used in this paper to search for a cost. 2. The absence of highly tolerant plants in the field, despite the ability to select, rapidly and artificially, for extreme levels of tolerance, indicates that strong selection against extreme tolerance occurs in this species. 3. Negative genetic correlations between plants selected for increased degree of tolerance and other fitness traits were sought to test the trade‐off hypothesis that energy/resources needed to manifest tolerance are diverted away from other essential traits. 4. The case for using replicated selection lines when using this methodology to demonstrate a cost is put forward. It is argued that replication is required to show unambiguously that any correlations found result from the pleiotropic effects of the gene(s) that govern the adaptation and not the consequence of linkage disequilibrium. 5. No clear evidence to support the trade‐off hypothesis was found.
A generic plant functional attribute set and grammar for dynamic vegetation description and analysis
Authors: GILLISON A. N. , CARPENTER G. 
Published: November 2003

1. Conventional methods of vegetation description rarely convey the behavioural or response‐based information needed to describe effectively the world’s vegetation for conservation and management purposes. The information required for these purposes may be derived from a generic set of plant functional attributes (PFAs). 2. A grammar provides a syntactic rule base for generating and comparing individuals as functional models or modi based on specific PFA combinations. 3. The method facilitates rapid and uniform assessment of plant response to variation in the physical environment at differing spatial scales independently of species. This is illustrated by local, regional and global case studies.
Processing of the Nedd2 precursor by ICE‐like proteases and granzyme B
Authors: Harvey Natasha L. , Trapani Joseph A. , Fernandes‐Alnemri Teresa , Litwack Gerald , Alnemri Emad S. , Kumar Sharad 
Published: November 2003

Background: The Nedd2/Ich‐1 protein belongs to a growing family of mammalian cysteine proteases similar to interleukin‐1β converting enzyme (ICE). Because of their similarity to the Caenorhabditiselegans cell death protein CED‐3, the ICE‐like proteins are thought to play a key role in the execution of apoptosis. The active form of ICE is a tetramer consisting of two heterodimers (p20 + p10)2 derived from the cleavage of the pro‐enzyme. Results: In the present communication we show that the p51 Nedd2 precursor (pro‐Nedd2) is also cleaved into p20‐like (p19) and p10‐like (p12) subunits by extracts prepared from cultured cell lines. Extracts from apoptotic NIH‐3T3 cells but not normal growing NIH‐3T3 cells also contained pro‐Nedd2 cleaving activity. The processing of pro‐Nedd2 by cell extracts was inhibited by characteristic inhibitors of ICE‐like proteases. Additionally we show that pro‐Nedd2 (p51) can be processed in vitro by active CPP32 and ICE, and to a lesser extent by Mch2 and Nedd2. Granzyme B, a serine protease required for cytotoxic T lymphocyte (CTL) mediated killing of target cells, also cleaved pro‐Nedd2 to p19 + p12 subunits. Conclusions: Our observations suggest that Nedd2 activation requires cleavage by one or more ICE‐like proteases that lie upstream in the proteolytic cascade. Cleavage of pro‐Nedd2 by granzyme B indicates that Nedd2 may be one of the downstream effectors in the CTL‐mediated killing of target cells.
Clamp loading, unloading and intrinsic stability of the PCNA, β and gp45 sliding clamps of human, E. coli and T4 replicases
Authors: Yao Nina , Turner Jennifer , Kelman Zvi , Stukenberg P. Todd , Dean Frank , Shechter David , Pan Zhen‐Qiang , Hurwitz Jerard , O'Donnell Mike 
Published: November 2003

Background: The high speed and processivity of replicative DNA polymerases reside in a processivity factor which has been shown to be a ring‐shaped protein. This protein (‘sliding clamp’) encircles DNA and tethers the catalytic unit to the template. Although in eukaryotic, prokaryotic and bacteriophage‐T4 systems, the processivity factors are ring‐shaped, they assume different oligomeric states. The Escherichia coli clamp (the β subunit) is active as a dimer while the eukaryotic and T4 phage clamps (PCNA and gp45, respectively) are active as trimers. The clamp can not assemble itself on DNA. Instead, a protein complex known as a clamp loader utilizes ATP to assemble the ring around the primer‐template. This study compares properties of the human PCNA clamp with those of E. coli and T4 phage. Results: The PCNA ring is a stable trimer down to a concentration below 100 nm (Kd ≈ 21 nm). On DNA, the PCNA clamp slides freely and dissociates from DNA slowly (t1/2 ≈ 24 min). β is more stable in solution (Kd < 60 pm) and on DNA (t1/2 ≈ 1 h) than PCNA which may be explained by its simpler oligomeric state. The T4 gp45 clamp is a much less stable trimer than PCNA (Kd ≈ 250 nm) and requires association with the polymerase to stabilize it on DNA as observed previously. The consequence of this cooperation between clamp and polymerase is that upon finishing a template and dissociation of the polymerase from DNA, the gp45 clamp spontaneously dissociates from DNA without assistance. However, the greater stability of the PCNA and β clamps on DNA necessitates an active process for their removal. The clamp loaders (RF‐C and γ complex) were also capable of unloading their respective clamps from DNA in the presence of ATP. Conclusions: The stability of the different clamps in solution correlates with their stability on DNA. Thus, the low stability of the T4 clamp explains the inability to isolate gp45 on DNA. The stability of the PCNA and β clamps predicts they will require an unloading factor to recycle them on and off DNA during replication. The clamp loaders of PCNA and β double as clamp unloaders presumably for the purpose of clamp recycling.
Essential and non‐redundant roles of p48 (ISGF3γ) and IRF‐1 in both type I and type II interferon responses, as revealed by gene targeting studies
Authors: Kimura Tohru , Kadokawa Yuzo , Harada Hisashi , Matsumoto Masahito , Sato Mitsuharu , Kashiwazaki Yasuo , Tarutani Masahito , Sok‐Pin Tan Rosemary , Takasugi Tomohiro , Matsuyama Toshifumi , Mak Tak W. , Noguchi Shigeru , Taniguchi Tadatsugu 
Published: November 2003

Background: Interferons (IFNs) are a class of cytokines which confer cellular resistance against viral infections. Type I (IFN‐α and ‐β) and type II (IFN‐γ) IFNs utilize distinct receptors, the stimulation of which results in the induction of downstream target genes. These target genes usually contain within their promoter region an IFN responsive element, termed ISRE (IFN stimulated response element) which binds a heterotrimeric transcription factor, ISGF3 (IFN‐stimulated gene factor 3) consisting of p48 (ISGF3 γ), Stat1 (Signal transducers and activators of transcription‐1; α or β), and Stat2. The ISRE sequence overlaps with that of IRF‐E which binds another IFN‐inducible factor, IRF‐1 (IFN regulatory factor‐1). Results: We generated mice lacking p48 by gene targeting. We show that p48 plays an essential role in both type I and type II IFN responses; activation of IFN‐inducible genes and establishment of the antiviral state by IFN‐α or ‐γ are both severely impaired, and ISRE‐binding activities induced by both IFNs are absent in the p48‐negative embryonic fibroblasts (EFs). Furthermore, we generated mice deficient for both p48 and IRF‐1 and found that at least one IFN‐inducible gene is dependent on both factors. Conclusions: p48 and IRF‐1 do not perform redundant functions in the cell, but rather complement one another in both type I and II IFN responses.
Involvement of Rho and Rac small G proteins and Rho GDI in Ca2+‐dependent exocytosis from PC12 cells
Authors: Komuro Ryutaro , Sasaki Takuya , Takaishi Kenji , Orita Satoshi , Takai Yoshimi 
Published: November 2003

Background: The Rho small G protein family, which includes the Rho, Rac and Cdc42 subfamilies, is implicated in various cell functions such as cell shape change, cell motility and cytokinesis, through the reorganization of actin filaments. Rho GDI is an inhibitory regulator of the Rho small G protein family and inhibits the Rho family dependent cell functions. Reorganization of actin filaments is also known to regulate Ca2+‐dependent exocytosis. Results: We have examined here whether the Rho family members are also involved in Ca2+‐dependent exocytosis. We have found, by the use of the human growth hormone (GH) co‐expression assay system on PC12 cells, that overexpression of Rho GDI inhibits high K+‐induced, Ca2+‐dependent GH release. This inhibitory action of Rho GDI is restored by co‐expression of a dominant active mutant of RhoA or Rac1, but not of a dominant active mutant of Cdc42. C3 transferase, known to ADP‐ribosylate Rho and to inhibit its function, also inhibits this GH release. Overexpression of a dominant active mutant of RhoA or Rac1 alone shows only a small effect on GH release. Moreover, immunocytochemical studies show that the overexpression of Rho GDI prevents a partial disruption of the cortical actin network which accompanies exocytosis. Conclusions: These results suggest that RhoA, Rac1 and Rho GDI are involved in Ca2+‐dependent exocytosis at least partly through the reorganization of actin filaments, and that the activation of RhoA or Rac1 alone is not sufficient for this reaction.
Protein inheritance: λ plasmid replication perpetuated by the heritable replication complex
Authors: We¸grzyn Alicja , We¸grzyn Grzegorz , Herman Anna , Taylor Karol 
Published: November 2003

Background: Replication of a plasmid derived from the Escherichia coli phage λ initiates by binding of the λO protein initiator to the origin of λ DNA replication, oriλ. The λP protein participates in subsequent steps of assembly of the λ replication complex. A function of λP required for replication complex assembly is inactivated at 43°C by the ts1 mutation. Results: We found that the λ replication complex assembled at 30°C survives the temperature upshift in λcrotsPts1 plasmid‐harbouring bacteria. We present several lines of evidence that in this system (in which the replication complex assembly does not occur), the replication complex assembled prior to the temperature upshift is inherited by one of two daughter plasmid copies at each replication round for more than 30 cell generations. The ‘old’ replication complex‐driven replication is chloramphenicol‐resistant and rifampicin‐sensitive. This replication is dependent on λO and host dnaK, dnaJ and grpE chaperone gene functions. Conclusions: The λO‐containing replication complex is inherited together with DNA and bears information how to initiate the next round of replication at oriλ; thus, we consider that this phenomenon deserves to be called protein inheritance.
Mouse MCM proteins: complex formation and transportation to the nucleus
Authors: Kimura Hiroshi , Ohtomo Takatsugu , Yamaguchi Masato , Ishii Atsushi , Sugimoto Kazunori 
Published: November 2003

Background: The members of the MCM protein family, including MCM2, MCM3, Cdc21, CDC46, Mis5 and CDC47, are considered to be involved in the control of a single round of DNA replication during S phase in eukaryotes. They bind to chromatin during G1 and detach from it during S phase as if they license the chromatin to replicate. However, unlike the originally proposed ‘licensing factor’ and the budding yeast homologues, mammalian MCM2 and P1MCM3 proteins appeared to be localized in the nucleus during the interphase. Results: We purified mCdc21 and its associated proteins from mouse cell extract by anti‐mCdc21 immunoaffinity chromatography. Three proteins which co‐purified with mCdc21 were identified as mCDC47, mMis5 and mMCM2, all were MCM proteins. Glycerol gradient centrifugation analysis showed that all the mouse MCM proteins were detected at 450–600 kDa, an indication of the sum of their calculated molecular weights from their amino acid sequences. mCdc21 was displaced from replicated chromatin in a similar way to P1MCM3 and MCM2 during S phase. Among the six mouse MCM proteins, only mMCM2 and mP1MCM3 showed nuclear localization when overexpressed in COS cells. Conclusions: We conclude that in the mouse, six MCM proteins form a single protein complex of molecular weight 450–600 kDa, which may enter the nucleus by nuclear localization signals in the mMCM2 and mP1MCM3 subunits.
Otx1 function overlaps with Otx2 in development of mouse forebrain and midbrain
Authors: Suda Yoko , Matsuo Isao , Kuratani Shigeru , Aizawa Shinichi 
Published: November 2003

Background: We previously reported that the homozygous mutation of Otx2 gene, a mouse cognate of the Drosophila head gap gene orthodenticle, causes failure in the development of the rostral head anterior to rhombomere 3, which may correspond to earlier Otx2 expression in cells destined for the anterior mesoendoderm. At the same time, the Otx2 heterozygous mutation displayed a phenotype characterized as otocephaly, probably related to expression in the anterior neuroectoderm at the subsequent pharyngula stage. Defects were characteristic in the most anterior and posterior regions of Otx2 expression where Otx1, another mouse cognate of orthodenticle, is not or weakly expressed. They were not found in the region where Otx1 is expressed. Results: In the present work, Otx1 null mutant mice were generated by gene targeting in embryonic stem cells. No defects were apparent in the regionalization of the early embryonic rostral brain. The newborn brain defects were subtle and most likely related to later Otx1‐unique expression. Otx1 and Otx2 double heterozygous mutant brains, however, exhibited marked defects throughout the fore‐ and midbrains, where defects were not apparent with a single mutation alone. Conclusions:
Otx1 and Otx2 play synergistic roles in the development of the forebrain and midbrain where both genes are expressed.