bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for a genetic component of female fecundity in British Roe Deer from studies of cranial morphometrics
Authors: HEWISON A. J. M.
Published: November 2003

1. The fecundity of adult female Roe Deer varies by a factor of 2·35 among populations across Britain. Although much of this variation may be related to environmental differences, there could also be a genetic influence on this component of fitness. In this paper, the relationship between morphological variation of the skull and female fecundity in Roe Deer from 13 populations across the deer’s entire range in Britain is investigated.

2. First, principal components analysis of cranial data was used to infer genetic relationships among populations. Three distinct morphological types were identified, all significantly differentiated from the others in terms of both size and shape. The results are compared with earlier analyses of biochemical variation among the same sites; a possible native morph is identified.

3. Subsequently, canonical ordination techniques (redundancy analysis) were used to control for the effects of ‘environmental’ variation (female body mass, density, climate) and, with the residual variation, the correlation between skull morphology and female fecundity was investigated. This correlation is significant for both the extracted axes (R>0·7), indicating that there are heritable differences between populations affecting female fecundity.

4. The analysis suggests that Roe Deer native to Britain are of a genetically less fecund type relative to populations established by introductions from the continent.
Haematocrit correlates with tail ornament size in three populations of the Barn Swallow (Hirundo rustica)
Authors: SAINO N. , CUERVO J. J. , NINNI P. , DE LOPE F. , MØLLER A. P.
Published: November 2003

1. Handicap models of sexual selection propose that male ornaments are indicators of male quality and that honesty is enforced by the costs imposed by the exaggerated ornamental traits. In long‐distance migratory birds that feed on the wing, the aerodynamic cost of exaggerated ornamental characters should be particularly high because the size of the ornaments deviates from the natural selection optimum. During migration, birds are expected to raise their oxygen consumption in relation to the energetic demands imposed by their morphology. An increase of haematocrit is an adaptive response to enhance oxygen uptake and efficiency of transfer to the muscular tissues during spells of intense muscular activity.

2. The change of haematocrit of Barn Swallows (Hirundo rustica) after their arrival to the breeding sites, and the relationships between haematocrit values recorded after migration and the size of ordinary and sexually selected morphological characters in three Barn Swallow populations were analysed.

3. Males had higher haematocrit values than females. Individual haematocrit values declined after arrival to the breeding sites. Haematocrit values of males were significantly and positively correlated with the size of their ornamental tail but not correlated with other characters, thus suggesting that well‐ornamented males, in order to arrive early, have to raise their haematocrit above the level of short‐tailed males.

4. Males and females of similar tail length did not differ in their haematocrit, thus suggesting that sexual dimorphism in haematocrit might be functionally related to dimorphism in tail length.

5. Our results are consistent with the handicap principle because long‐tailed males experience lower mortality and larger seasonal reproductive success compared with short‐tailed males.
Fruit size in wild olives: implications for avian seed dispersal
Authors: REY P. J. , GUTIÉRREZ J. E. , ALCÁNTARA J. , VALERA F.
Published: November 2003

1. The response of frugivorous birds to an enlargement of fruit size, and the consequences for both birds and plants, are analysed for the interaction between avian seed dispersers and olives (Olea europaea).

2. The enlargement of fruit size promotes a shift in frugivorous birds’ feeding behaviour, from swallowing fruits whole to pecking pieces of pulp. The relative frequency of olive consumption using each feeding behaviour was assessed by combining field data on frequency of appearance of olive pulp and seeds with data from laboratory trials.

3. Sardinian Warblers (Sylvia melanocephala) and European Robins (Erithacus rubecula) were mainly peckers both on cultivated and wild olives. Blackcaps (Sylvia atricapilla) consumed wild olives mainly by swallowing but consumed cultivated olives (larger than the wild ones) primarily by pecking. Song Thrushes (Turdus philomelos) were primarily swallowers of both types of fruits.

4. Laboratory trials with Song Thrushes, Blackcaps and European Robins showed that: (a) all were able to peck fruits; (b) fruit size determined a shift from swallowing to pecking, as pecking frequency increased with the enlargement of the fruit size; (c) all the species had an increased fruit handling failure rate when trying to swallow increasingly large fruits; and (d) from the birds’ perspective, small shifts in fruit size may have important consequences on fruit profitability.

5. Pecking on olives turns the mutualistic fruit–frugivore interaction into a fruit‐pulp predator interaction, thus arising a conflict between the plant and frugivorous birds.

6. This study shows that heavy dependence on fruit is not always simply related to seed dispersal. The same frugivorous bird species can act as a seed disperser or a pulp predator for the same plant species. The threshold between these roles is highly influenced by the ratio gape size/fruit size.
Response of Deer Mice (Peromyscus maniculatus) to shrubs in shortgrass prairie: linking small‐scale movements and the spatial distribution of individuals
Authors: STAPP P. , VAN HORNE B.
Published: November 2003

1. Organisms respond to the abundance and spatial distribution of resources at both individual and population scales but there have been relatively few attempts to link insights from studies of these different phenomena, especially for wide‐ranging vertebrates.

2. Deer Mice (Peromyscus maniculatus) were live‐trapped and tracked across a gradient of shrub cover in shortgrass prairie to determine patterns of abundance, microhabitat use and movements.

3. In areas with few shrubs, mice preferred shrub microhabitats and their movement trails were relatively straight. Both trail tortuosity and population density increased with increasing shrub cover, so that mice tended to accumulate in areas where their trails were most convoluted. However, movements were also linear where shrubs were dense, presumably because mice could achieve the benefits of association with shrubs without travelling directly beneath them. Areas with dense shrubs also had high but variable population densities, suggesting that other factors such as intraspecific interactions may have affected movements on a larger, home‐range scale.

4. Apparent thresholds in the selective vs random use of shrubs, movement patterns and abundance occurred over a narrow range of shrub cover where shrubs were most aggregated, underscoring the importance of both shrub density and dispersion. Non‐linear relationships in the response to resources at both behavioural and population scales thus may complicate our ability to predict abundance from individual movements across a broad range of resource distributions.
Thermoregulation in four species of British grasshoppers (Orthoptera: Acrididae)
Authors: WILLOTT S. J.
Published: November 2003

1. This study examines the extent to which thermal balance and thermoregulatory ability may contribute to habitat partitioning in insect herbivores.

2. The distribution of four species of grasshopper on a Breckland grass heath is described. Myrmeleotettix maculatus is restricted to short swards, Omocestus viridulus is restricted to long swards, and Chorthippus brunneus and Stenobothrus lineatus are found on swards of intermediate length.

3. Short swards are warmer on average than long swards, but lack cooler refuges on hot days.

4.
Chorthippus brunneus and O. viridulus are better able to raise their body temperatures at low ambient temperatures than M. maculatus and S. lineatus. Omocestus viridulus is less able to reduce body temperature at high ambient temperature.

5.
Myrmeleotettix maculatus may be precluded from inhabiting cooler long swards because of its inability to raise body temperatures at low ambient temperatures. Omocestus viridulus may avoid short swards because of the danger of overheating.

6. Thermoregulatory ability is a good predictor of the distribution of the grasshoppers in swards of differing length and microclimate.
Nitrogen‐use efficiency in six perennial grasses from contrasting habitats
Authors: VÁZQUEZ DE ALDANA B. R. , BERENDSE F.
Published: November 2003

1. We studied the nitrogen‐use efficiency (NUE) in six perennial grasses adapted to a wide range of nutrient availability. The glasshouse experiment was carried out in pots containing nutrient solution, with two fertility treatments. Nitrogen‐use efficiency was considered as the product of nitrogen productivity and mean residence time of the nitrogen in the plant (calculated using 15N pulse labelling).

2. The species investigated are characteristic of habitats ranging from very nutrient rich to extremely nutrient poor, in the following order: Lolium perenne, Arrhenatherum elatius, Festuca rubra, Anthoxanthum odoratum, Festuca ovina and Molinia caerulea.

3.
Lolium perenne (adapted to nutrient‐rich habitats) had higher nitrogen productivity (A) than M. caerulea (species adapted to nutrient‐poor habitats) but lower than that of F. rubra (from habitats with an intermediate availability of nutrients).

4. In the low fertility treatment, species with the lowest nitrogen‐use efficiency had the lowest N productivity and the highest mean nitrogen residence time (MRT); however, although species with the highest nitrogen use efficiency had the highest N productivity they did not have the lowest MRT. In all species the nitrogen‐use efficiency decreased with increasing N supply. The two components of the NUE (A and MRT) are inversely correlated along gradients of nutrient availability, but not at very high levels of nutrient availability.

5. The nitrogen‐use efficiency of species at constant levels of nutrient supply tends to increase with increasing nutrient availability in their preferred habitat, according to the Clausman nutrient index, up to a certain nutrient availability and then decreases. The results support the contention that species from nutrient‐poor sites are not necessarily adapted by a high nitrogen‐use efficiency, but by low nutrient loss rates (high mean residence time of N in the plant).
Relationships between branch spacing, growth rate and light in tropical forest saplings
Authors: KING D. A. , LEIGH E. G. , CONDIT R. , FOSTER R. B. , HUBBELL S. P.
Published: November 2003

1. The spacing of branches along central stems was related to growth rate and light level in forest saplings and trees in tropical moist forest on Barro Colorado Island (BCI), Panama. The study included 14 species with tiers of plagiotropic branches (having planar leaf arrangements) and four species with continuous distributions of plagiotropic branches.

2. All species showed increases in branch spacing with increasing light and growth rate of diameter, similar to the patterns in leaf spacing noted previously in species which initially bear large leaves on unbranched stems.

3. Non‐tiered species had shorter internodes than tiered species but because the latter bear more branches per node, both groups had similar numbers of branches per unit stem length, when compared at similar growth rates.

4. Differences in the relationship between internode length and growth rate among tiered species were related to demographic characteristics, suggesting that tree architecture may influence forest composition.

5. The strong correlation observed between branch spacing and growth rate suggests that branch spacing may be used to estimate past growth histories of forest tree species with plagiotropic branches.
Genetic variation in photosynthetic capacity, carbon isotope discrimination and mesophyll conductance in provenances of Castanea sativa adapted to different environments
Authors: LAUTERI M. , SCARTAZZA A. , GUIDO M. C. , BRUGNOLI E.
Published: November 2003

1. Provenances of Castanea sativa from populations adapted to different climatic areas of Turkey were grown in a field trial in Italy. Carbon isotope discrimination (Δ) in leaf dry matter and in leaf soluble sugar, were measured, along with photosynthesis, stomatal conductance and mesophyll conductance, to study the variability of primary productivity and its ecological significance in European Chestnut.

2. Genetic variations were found in RuBP carboxylase, chlorophyll, leaf soluble protein and leaf thickness.

3. Carbon isotope discrimination (Δ) in leaf dry matter was greater in drought‐adapted than in wet‐adapted provenances. A similar variation of Δ was observed in leaf soluble carbohydrates either under watered or drought conditions. Possible environmental effects of variables such as vapour pressure difference, on the relationship between transpiration efficiency and carbon isotope discrimination are discussed, on the basis of short‐term and long‐term results.

4. Generally low values of Δ encountered among provenances were explained not only by low values of intercellular CO2 partial pressure but also by consistently low values of mesophyll conductance leading to reduced chloroplastic CO2 partial pressure. A decrease in mesophyll conductance was induced by water shortage. Co‐ordination was found between stomatal and mesophyll conductance, with the drought‐adapted provenances showing much higher mesophyll conductance than the wet‐adapted provenances. Variations in mesophyll conductance were related to differences in leaf protein content.

5. Possible ecophysiological adaptive mechanisms are discussed taking into account stomatal sensitivity, modulation of photosynthetic capacity and water‐use efficiency under drought conditions.
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.
SH2 and SH3‐containing adaptor proteins: redundant or independent mediators of intracellular signal transduction
Authors: Birge Raymond B. , Knudsen Beatrice S. , Besser Daniel , Hanafusa Hidesaburo
Published: November 2003

Molecules which contain Src Homology 2 (SH2) and SH3 domains provide one of the principal ways by which signals are transduced in cells using protein–protein interactions between proline‐rich motifs and SH3 domains and induced interactions between phosphotyrosine residues and SH2 domains. The simplest of SH2/SH3‐containing proteins are the Crk, Grb2 and Nck adaptor proteins which contain SH2 and SH3 domains but no intrinsic catalytic activity. Whereas Grb2 connects activated receptor tyrosine kinases with Sos and activates p21ras, recent evidence suggests that this may not be the major mechanism by which Crk and Nck signal to downstream effectors. Identification of novel binding partners for Crk, Grb2 and Nck indicate that these adaptor proteins control distinct aspects of tyrosine kinase signalling.
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.
Regulation and conservation of the heat‐shock transcription factor σ32
Authors: Yura Takashi
Published: November 2003

Heat shock and other stresses induce a set of genes encoding molecular chaperones and proteases through increase in the level of transcription factor σ32 in Escherichia coli. Some of the cis‐and trans‐acting factors involved in the control of synthesis (translation), degradation and activity of σ32 have been identified and characterized. These studies contribute to our understanding of early events of the heat‐shock response, including modes of interaction between chaperones and σ32. Besides, analysis of σ32 homologues from diverse bacteria reveals new insights into evolution of the regulatory mechanisms.
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.
NAP‐I is a functional homologue of TAF‐I that is required for replication and transcription of the adenovirus genome in a chromatin‐like structure
Authors: Kawase Hiroyuki , Okuwaki Mitsuru , Miyaji Mary , Ohba Reiko , Handa Hiroshi , Ishimi Yukio , Fujii‐Nakata Tomoko , Kikuchi Akihiko , Nagata Kyosuke
Published: November 2003

Background:
For the activation of replication and transcription from DNA in a chromatin structure, a variety of factors are thought to be needed that alter the chromatin structure. Template activating factor‐I (TAF‐I) has been identified as such a host factor required for replication of the adenovirus (Ad) genome complexed with viral basic core proteins (Ad core). TAF‐I also stimulates transcription from the Ad core DNA.

Results:
Using mutant TAF‐I proteins, we have demonstrated that the acidic stretch present in the carboxyl terminal region is essential for the stimulation of transcription from the Ad core. A genomic footprinting experiment with restriction endonuclease has revealed that TAF‐I causes a structural change in the Ad core. TAF‐I has been shown to have significant amino acid similarity to nucleosome assembly protein‐I (NAP‐I), which is involved in the formation of the chromatin structure. We have shown that TAF‐I can be substituted by NAP‐I in the activation of the cell‐free Ad core transcription system. Two of the tripartite acidic regions and the region homologous to TAF‐I in NAP‐I are required for the maximal TAF‐I activity of NAP‐I. Furthermore, TAF‐I has been shown to have NAP‐I activity, and the acidic region of TAF‐I is required for this activity.

Conclusions:
Since TAF‐I causes the structural change of the Ad core and thereby activates transcription, TAF‐I is thought to be one of the proteins which is involved in chromatin remodeling. NAP‐I is structurally related to TAF‐I and functionally substitutes for TAF‐I. Furthermore, TAF‐I has NAP‐I activity. These observations suggest that this type of molecule has dual functions, possibly by participating in facilitating the assembly of the chromatin structure as well as perturbing the chromatin structure to allow transcription to proceed.
Mesodermal‐ vs. neuronal‐specific expression of MafK is elicited by different promoters
Authors: Motohashi Hozumi , Igarashi Kazuhiko , Onodera Kou , Takahashi Satoru , Ohtani Haruo , Nakafuku Masato , Nishizawa Makoto , Engel James Douglas , Yamamoto Masayuki
Published: November 2003

Background: Small members of the Maf family of transcriptional regulatory proteins share similar basic‐leucine zipper domains but have no intrinsic ability to activate transcription. One member of the family (MafK) has been shown to mediate both negative and positive regulation: in addition to forming a homodimer which represses transcription, MafK can also form a heterodimer with p45 (the large subunit of erythroid transcription factor NF‐E2) to activate transcription.

Results: We examined the expression of mafK during murine development. mafK mRNA was first detected in 7.5 days post coitus (dpc) embryonic mesoderm and persisted in mesodermal derivatives (mesenchymal and haematopoietic cells) thereafter. However, around 13 dpc mafK was also strongly induced in neuronal cells and it is broadly expressed in neurones in postnatal mouse. The neuronal expression of mafK is directed by a distinct promoter located 6 kbp 3′ to the mesoderm‐specific promoter. mafK in neurones associates with a different partner molecule from p45. In transgenic mice, a regulatory domain in the immediate vicinity of the mesodermal promoter was found to direct mesenchymal, but not haematopoietic, expression of mafK.

Conclusion: The cell type‐ and developmental stage‐specific expression of MafK suggests that, in addition to its demonstrated role in erythroid transcriptional regulation, MafK also plays an important regulatory role in other mesodermally and neuroectodermally derived tissues during mouse embryonic development.
Differential thermoregulation of two highly homologous cold‐shock genes, cspA and cspB, of Escherichia coli
Authors: Etchegaray Jean‐Pierre , Jones Pamela G. , Inouye Masayori
Published: November 2003

Background The major cold‐shock protein in Escherichia coli is CspA, a 7.4 kDa protein. A CspA family has been found which consists of four additional proteins, CspB, CspC, CspD and CspE. The expression of cspB, unlike the other homologues, is cold‐shock inducible like cspA

Results: We examined the cold‐shock induction of CspA and CspB at various temperatures. The cspA induction is observed by temperature shift from 37 to 30 °C and high levels of CspA production are observed between 24 and 10 °C. In contrast, CspB production occurs only by temperature shift to below 20 °C, with maximum induction at 15 °C. Both cspA and cspB expressions were found to be induced at the level of transcription as determined by primer extension.

Conclusions: These results show that cspA and cspB expressions are differentially regulated at low temperature indicating that E. coli contains at least two different biothermostats or thermoregulators that are likely to play important roles in cellular adaptation to low temperature. The cspB promoter shows sequence similarity to the cspA promoter. Furthermore, both cspA and cspB mRNAs have unusually long 5′ untranslated regions (159 and 161 bases, respectively), both of which are able to form similar extensive secondary structures. These features are considered to contribute to the nature of the thermostats for cspA and cspB
MutT‐related error avoidance mechanism for DNA synthesis
Authors: Sekiguchi Mutsuo
Published: November 2003

Mutator mutants that show an increased frequency of spontaneous mutation have led to the elucidation of the multiple pathways of spontaneous mutagenesis. 8‐Oxo‐dGTP (8‐oxo‐7,8‐dihydrodeoxyguanosine triphosphate) is formed in the nucleotide pool of a cell during normal cellular metabolism, and when it is incorporated into DNA causes mutation. MutT protein of Escherichia coli and related mammalian enzymes specifically degrade 8‐oxo‐dGTP to 8‐oxo‐dGMP, thereby preventing occurrence of transversion mutation. The gene encoding the human enzyme, designated MTH1 (for mutT homologue 1), maps to chromosome 7p22. These proteins may be responsible for genomic stability.
Specification of posterior midbrain region in zebrafish neuroepithelium
Authors: Miyagawa Terumi , Amanuma Hiroshi , Kuroiwa Atsushi , Takeda Hiroyuki
Published: November 2003

Background: The developing vertebrate nervous system displays a pronounced anterior–posterior (A‐P) pattern, but the mechanism that generates this pattern is poorly understood. We examined through cell‐transplantation experiments, when and how the cells in the zebrafish posterior midbrain acquire regional specificity along the A‐P axis as shown by pax[b] gene expression.

Results: Labelled donor cells from the presumptive midbrain region at various stages were transplanted into more anterior part of unlabelled host embryos of the same developmental stage, and the expression of pax[b] in the donor cells were examined by in situ hybridization. The results indicated that, in the cells from the presumptive midbrain region, expression of pax[b] was determined as early as the 55%‐epiboly (6.5 h, early gastrulation) when the underlying hypoblastic layer reached the presumptive midbrain region. We also found that when transplanted heterotopically, anterior, but not posterior, hypoblast cells induced expression of pax[b] in the overlying ectoderm.

Conclusions: Expression of a midbrain specific gene is determined during early gastrulation and the hypoblastic layer plays an important role in this determination process.
Schizosaccharomyces pombe gad7+ encodes a phosphoprotein with a bZIP domain, which is required for proper G1 arrest and gene expression under nitrogen starvation
Authors: Kanoh Junko , Watanabe Yoshinori , Ohsugi Miho , Iino Yuichi , Yamamoto Masayuki
Published: November 2003

Background: Fission yeast cells arrest at G1 phase when starved of nitrogen. The molecular mechanism that ensures this arrest is poorly understood. We took a genetic approach to this problem.

Results: The fission yeast gad7‐1 mutant failed to arrest at G1 when starved of nitrogen, and was poor in mating and sporulation. The gad7 gene was cloned by complementation. The deduced gad7 gene product was a bZIP protein of 566 amino acids, which could bind to the CRE (cAMP response element) sequence in vitro. Disruption of gad7 resulted in the same phenotypes as gad7‐1. Expression of ste11, which encodes a key transcription factor for sexual development, was not inducible in the disruptant. Gad7 was co‐immunoprecipitated with another bZIP protein Pcr1, suggesting that the two proteins form a heterodimer in vivo. Gad7 was phosphorylated, and the state of its phosphorylation appeared to be modified in pka1Δ or wis1Δ cells.

Conclusions: Gad7, a CRE‐binding protein that cooperates with Pcr1, is required for proper G1 arrest and gene expression under nitrogen starvation. Gad7 is a phosphoprotein, whose activity may be regulated by protein kinases including the cAMP‐dependent protein kinase (Pka1) and Wis1 osmosensory MAP kinase kinase.