bluuebunny/crossref_metadata_2025 huggingface dataset:
Up‐regulation of matrix metalloproteinase‐1 expression in U937 cells by low‐density lipoprotein‐containing immune complexes requires the activator protein‐1 and the Ets motifs in the distal and the proximal promoter regions
Authors: Maldonado Alejandro , Game Bryan A. , Song Lanxi , Huang Yan
Published: July 2003

We reported previously that low‐density lipoprotein (LDL)‐containing immune complexes (LDL‐IC) stimulated matrix metalloproteinase‐1 (MMP‐1) expression in U937 histiocytes through Fc gamma receptor (FcγR)‐mediated extracellular signal‐regulated kinase pathway. The present study has explored the transcriptional mechanisms involved in the stimulation. Deletion analysis showed that LDL‐IC stimulated MMP‐1 promoter activity in cells transfected with the Construct 1 that contained a 4,334‐bp MMP‐1 promoter fragment, but had no effect in cells transfected with other constructs that had shorter MMP‐1 promoter (2685‐bp or less), suggesting that cis‐acting elements located between −4334 and −2685 are required for the promoter stimulation. The mutation study further indicated that the activator protein‐1 (AP‐1) (−3471) or Ets (−3836) motifs in this distal region were essential for the LDL‐IC‐stimulated MMP‐1 expression. Moreover, although above deletion analysis showed that LDL‐IC did not stimulate MMP‐1 promoter activity in cells transfected with constructs that contained the proximal AP‐1 (−72) and Ets (−88) in the promoter fragments that are 2685‐bp or less, the mutations of the −72 AP‐1 or the −88 Ets motif in the construct 1 abolished the stimulation of MMP‐1 expression by LDL‐IC, suggesting that a long promoter sequence is required for the −72 AP‐1 and −88 Ets motifs to be involved in the stimulation. Finally, electrophoretic mobility shift assay showed that LDL‐IC stimulated the activities of transcription factors AP‐1 and Ets. In conclusion, the present study shows that both the distal and proximal AP‐1 and Ets motifs are required for LDL‐IC‐stimulated MMP‐1 expression in U937 histiocytes.
Genomic structure around joining segments and constant regions of swine T‐cell receptor α/δ (TRA/TRD) locus
Authors: Uenishi Hirohide , Hiraiwa Hideki , Yamamoto Ryuji , Yasue Hiroshi , Takagaki Yohtaroh , Shiina Takashi , Kikkawa Eri , Inoko Hidetoshi , Awata Takashi
Published: July 2003

A complete genomic region of 131·2 kb including the swine T‐cell receptor α/δ constant region (TRAC/TRDC) and joining segments (TRAJ/TRDJ) was sequenced. The structure of this region was strikingly conserved in comparison to that of human or mouse. All of the 61 TRAJ segments detected in the human genomic sequence were detected in the swine sequence and the sequence of the protein binding site of T early alpha, the sequence of the α enhancer element and the conserved sequence block between TRAJ3 and TRAJ4 are highly conserved. Insertion of the repetitive sequences that interspersed after the differentiation of the species in mammals such as short interspersed nucleotide elements is markedly suppressed in comparison to other genomic regions, while the composition of the mammalian‐wide interspersed sequences is relatively conserved in human and swine. This observation indicates the existence of a highly selective pressure to conserve this genomic region around TRAJ throughout the evolution of mammals.
Hepatitis B virus‐induced defect of monocyte‐derived dendritic cells leads to impaired T helper type 1 response in vitro: mechanisms for viral immune escape
Authors: Beckebaum Susanne , Cicinnati Vito R. , Zhang Xia , Ferencik Stanislav , Frilling Andrea , Grosse‐Wilde Hans , Broelsch Christoph Erich , Gerken Guido
Published: July 2003

Dendritic cells (DC) are the most potent antigen‐presenting cells and play a central role in the induction of antiviral immune responses. Recently, we have shown that monocyte‐derived DC (MoDC) from patients with chronic hepatitis B virus (HBV) infection are functionally impaired. In our present study MoDC from healthy subjects were propagated in vitro and inoculated with HBV particles to investigate the precise mechanisms that underly MoDC dysfunction. T‐cell proliferation assays revealed an impaired allostimulatory capacity of HBV‐inoculated MoDC (HBV‐MoDC) as well as a lower potential of stimulating autologous T cells against a recall antigen in comparison to control‐MoDC. Interleukin‐2, tumour necrosis factor‐α and interferon‐γ production by T cells in proliferation assays with HBV‐MoDC was significantly lower than with control‐MoDC and correlated with lower IL‐12 production in HBV‐MoDC cultures. The presence of the nucleoside analogue lamivudine (3TC), an inhibitor of HBV replication, restored impaired allostimulatory function of HBV‐MoDC and up‐regulated major histocompatibility complex class II expression. These results show that HBV infection compromises the antigen‐presenting function of MoDC with concomitant impairment of T helper cell type 1 responses. This may play an important role for viral immune escape leading to chronic HBV infection. However, 3TC treatment can overcome HBV‐MoDC‐related T‐cell hyporeactivity and this underscores its important role in enhanced immune responses to HBV.
Human secretory immunoglobulin A may contribute to biofilm formation in the gut
Authors: Randal Bollinger R. , Everett Mary Lou , Palestrant Daniel , Love Stephanie D. , Lin Shu S. , Parker William
Published: July 2003

It is critical, both for the host and for the long‐term benefit of the bacteria that colonize the gut, that bacterial overgrowth with subsequent bacterial translocation, which may lead to sepsis and death of the host, be avoided. Secretory IgA (sIgA) is known to be a key factor in this process, agglutinating bacteria and preventing their translocation in a process termed ‘immune exclusion’. To determine whether human sIgA might facilitate the growth of normal enteric bacteria under some conditions, the growth of human enteric bacteria on cultured, fixed human epithelial cells was evaluated in the presence of sIgA or various other proteins. Human sIgA was found to facilitate biofilm formation by normal human gut flora and by Escherichia coli on cultured human epithelial cell surfaces under conditions in which non‐adherent bacteria were repeatedly washed away. In addition, the presence of sIgA resulted in a 64% increase in adherence of E. coli to live cultured epithelial cells over a 45‐min period. Mucin, another defence factor thought to play a key role in immune exclusion, was found to facilitate biofilm formation by E. coli. Our findings suggest that sIgA may contribute to biofilm formation in the gut.
Effects of population size and genetic variation on the response of Succisa pratensis to eutrophication and acidification
Authors: Vergeer Philippine , Rengelink Ramses , Ouborg N. Joop , Roelofs Jan G. M.
Published: July 2003

Succisa pratensis, a characteristic plant species of biodiverse, slightly acidic grasslands (NARDETEA), has declined in the Netherlands over recent decades. This process has mainly been attributed to environmental stress caused by anthropogenic acidification and eutrophication, although genetic deterioration and decreasing population size may also be involved.

We analysed the combined effects of environmental stress, genetic variation and population size on the performance of Succisa pratensis.

Individual plant performance was negatively affected by eutrophication and, to a smaller extent, by acidification. Plants originating from smaller populations performed less well and showed less genetic variation and higher inbreeding coefficients than plants from large populations. Strong interactions between population size and stress treatments reflected the fact that plants from small populations suffered more from deteriorating soil conditions than those from large populations.

abitat fragmentation may reinforce the negative effects of environmental stress, leading to even the less effective treatment (acidification) having serious consequences.
Community assembly along proglacial chronosequences in the high Arctic: vegetation and soil development in north‐west Svalbard
Authors: Hodkinson Ian D. , Coulson Stephen J. , Webb Nigel R.
Published: July 2003

Community assembly is described for two contrasting high Arctic chronosequences representing glacial regression of up to 2000 years on Svalbard. The chronosequences included a nutrient‐poor glacier foreland (Midtre Lovénbre) and a series of nutrient‐enriched islands (Lovén Islands) progressively released from below a tidewater glacier.

Soil development and community assembly paralleled proglacial sequences elsewhere but time scales were extended and mature vegetation types comprised species‐poor prostrate communities.

Initial colonization by Cyanobacteria stabilized soil surfaces and raised nutrient status. Cyanobacteria formed the dominant ground cover (up to 34%) for 60 years, after when they declined.

Vascular plants established slowly and represented minor components of ground cover for the first 100 years. Earliest colonizers were often species with ectomycorrhizal associations, followed by mid‐successional species that tended to disappear as ground cover increased. Some species present in the mature vegetation at the oldest sites, established only after 60+ years.

Species richness of vascular plants increased for c. 100 years, beyond when only occasional species were added. Bryophytes became increasingly dominant with time.

Soil development on the Midtre Lovénbre and Lovén Island chronosequences was similar after 100 years. Differences subsequently developed, with organic horizon depth, percentage organic matter and water content on the older Lovén islands significantly greater than at equivalent Midtre Lovénbre sites. This was associated with increased bryophyte cover but lower vascular plant species richness. One explanation is a slightly more favourable microclimate, coupled with nutrient input from nesting birds.

Communities progressively recruit from a limited pool of effectively dispersed species, each with particular ecological requirements that determine their point of entry into the community. A measure of determinism by default is suggested in the way communities assembled.

Under climate warming, in the absence of nutrient enrichment, community development will accelerate but will be constrained by nutrient limitations and a restricted species pool. Where nutrients are less limiting, acceleration towards a moss‐dominated community is expected, with a lower species richness of vascular plants.
Floral neighbourhoods in the sea: how floral density, opportunity for outcrossing and population fragmentation affect seed set in Zostera marina
Authors: Reusch Thorsten B. H.
Published: July 2003

Almost nothing is known about how the floral neighbourhood affects reproductive output in plants with subaqueous pollination (hydrophily), such as seagrasses, an ecologically important group of some 60 marine angiosperms.

I studied how floral density, genetic diversity and population fragmentation affect seed set in Zostera marina (eelgrass), a functionally hermaphrodite seagrass with extensive clonal propagation.

In a field experiment in the south‐western Baltic Sea, I increased or decreased the density of flowering shoots in 6 × 6 m plots. Early seed set was a positive, saturation‐type function of density suggesting pollen limitation below approximately 5 flowering shoots m−2.

Using molecular markers, I determined local genotypic diversity and outcrossing rates as indicators of outcrossing opportunities. I found only non‐significant effects of these variables on early seed set, suggesting that density of the floral neighbourhood is more important than genetic composition.

Early seed set was 22% lower in isolated vegetation patches compared to continuous eelgrass meadow (> 50 m2).

Given the spatial scale of the observed pollen limitation, and low natural densities of flowering shoots in the field, pollen limitation may be widespread in Z. marina and, possibly, other plant species with subaqueous pollination.
Luxury consumption of soil nutrients: a possible competitive strategy in above‐ground and below‐ground biomass allocation and root morphology for slow‐growing arctic vegetation?
Authors: Van Wijk M. T. , Williams M. , Gough L. , Hobbie S. E. , Shaver G. R.
Published: July 2003

A field‐experiment was used to determine how plant species might retain dominance in an arctic ecosystem receiving added nutrients. We both measured and modelled the above‐ground and below‐ground biomass allocation and root morphology of non‐acidic tussock tundra near Toolik Lake, Alaska, after 4 years of fertilization with nitrogen and phosphorus.

Compared with control plots, the fertilized plots showed significant increases in overall root weight ratio, and root biomass, root length and root nitrogen concentration in the upper soil layers. There was a strong trend towards relatively more biomass below ground.

We constructed an individual teleonomic (i.e. optimality) plant allocation and growth model, and a competition model in which two plants grow and compete for the limiting resources.

The individual plant model predicted a strong decrease in root weight ratio with increased nutrient availability, contrary to the results obtained in the field.

The increased investment in roots in the fertilized plots found in the field could be explained in the competition model in terms of luxury consumption of nutrients (i.e. the absorbance of nutrients in excess of the immediate plant growth requirements). For slow‐growing species with relatively low phenological and physiological plasticity it can be advantageous to increase relative investment into root growth and root activity. This increased investment can limit nutrient availability to other fast‐growing species and, thereby, preclude the successful invasion of these species.

These results have implications for the transient response of communities and ecosystems to global change.
Response of forest plant species to land‐use change: a life‐history trait‐based approach
Authors: Verheyen Kris , Honnay Olivier , Motzkin Glenn , Hermy Martin , Foster David R.
Published: July 2003

Classifying species by shared functional characteristics is important if common functional response groups are to be identified among different taxa.

We investigated plant traits that determine the response of forest plant species to land use changes using literature data. Sources from eight European countries and four North‐eastern American states, comprising 20 field studies yielded information on 216 forest plant species. For these species, data on 13 life history traits were collected.

Trait correlation structure was similar in the European and American data‐sets and corresponded well to those described in the literature. The European and American herbs and the European graminoids were clustered into distinct emergent groups based on their plant traits. The profiles of the European and American emergent groups were similar.

Herb species belonging to emergent groups characterized by low dispersability (i.e. large seeds, low fecundity, unassisted dispersal) were relatively slow colonizers. Dispersability (and not recruitment) seems to be a key factor limiting the colonization of some forest plant species. The relationship between dispersability and colonizing capacity was less clear for graminoids.

A life history trait‐based approach offers good opportunities to gain insight into the mechanisms behind species response to land‐use change.
The dynamics of nitrogen movement in an Arctic salt marsh in response to goose herbivory: a parameterized model with alternate stable states
Authors: Walker N. A. , Henry H. A. L. , Wilson D. J. , Jefferies R. L.
Published: July 2003

LPBN is a parameterized simulation model of flows of nitrogen (N) in an ecosystem of cyanobacteria, grass and grazers, based on the N dynamics of a grazed Puccinellia lawn in an intertidal marsh on Hudson Bay. This system shows two alternate stable states: (a) lawns that either support a foraging population of lesser snow geese, or are not grazed by geese; and (b) exposed saline sediments that support little or no vegetation. The model represents the flow of N from cyanobacterial fixation, the major N input into the system, to the geese that migrate in autumn; those that do not return represent the major N output from the system. We have modelled N fixation, the transformations of N in the soil, plant growth, lawn regeneration, and goose grazing and grubbing.

The model simulates steady‐state flows of N similar to those observed in the field at zero and at moderate goose density, and it also simulates the transition to the state of zero plant biomass, a consequence of increased grubbing at high goose density. The simulated steady‐state flows are found to be more sensitive to changes in the parameters that describe N fixation and goose biology, than to similar changes in the parameters describing plant biology.

Because the model shows the alternate stable states and the transition between them, with values for the state variables that are consistent with field data, we conclude that N dynamics are crucial in determining the stability of the real salt marsh‐goose system. The determining factor is the loss of the input of N from fixation when lawn area is reduced because the rate of goose grubbing exceeds that of plant re‐establishment.
Plant amino acid uptake, soluble N turnover and microbial N capture in soils of a grazed Arctic salt marsh
Authors: Henry Hugh A. L. , Jefferies Robert L.
Published: July 2003

The uptake of free amino acids by the grass Puccinellia phryganodes was investigated in soils of an Arctic coastal salt marsh, where low temperatures and high salinity limit inorganic nitrogen (N) availability, and the availability of soluble organic N relative to inorganic N is often high.

Following the injection of 13C15N‐amino acid, 15N‐ammonium and 15N‐nitrate tracers into soils, rates of soluble nitrogen turnover and the incorporation of 13C and 15N into plant roots and shoots were assessed. Chloroform fumigation‐extraction was used to estimate the partitioning of labelled substrates into microbial biomass.

Free amino acids turned over rapidly in the soil, with half‐lives ranging from 8.2 to 22.8 h for glycine and 8.9 to 25.2 h for leucine, compared with 5.6 to 14.7 h and 5.6 to 15.6 h for ammonium and nitrate, respectively. 15N from both organic and inorganic substrates was incorporated rapidly into plant tissue and the ratio of 13C/15N incorporation into plant tissue indicated that at least 5–11% of 13C15N‐glycine was absorbed intact.

Microbial C and N per unit soil volume were 1.7 and 5.4 times higher, respectively, than corresponding values for plant C and N. Plant incorporation of 15N tracer was 56%, 83% and 68% of the comparable incorporation by soil microorganisms of glycine, ammonium and nitrate ions, respectively.

These results indicate that P. phryganodes can absorb amino acids intact from the soil despite competition from soil microorganisms, and that free amino acids may contribute substantially to N uptake in this important forage grass utilized by lesser snow geese in the coastal marsh.
Lack of relationship between below‐ground competition and allocation to roots in 10 grassland species
Authors: Cahill James F.
Published: July 2003

A field experiment in a native grassland in Central Alberta, Canada, tested whether plants alter relative allocation to roots vs. shoots in response to below‐ground competition, and whether the mass of a species’ root system accounts for interspecific differences in below‐ground competitive response.

Seedlings of each of 10 native species were transplanted into the naturally occurring vegetation in the field at the start of the growing season. Root interactions between the target plants and their neighbours were manipulated through the use of PVC root exclusion tubes, with target plants grown with or without potential root interactions with their neighbours. Neighbour shoots were also tied back, forcing any target–neighbour interactions to be below ground.

Below‐ground competition generally reduced plant growth, with its relative magnitude varying among species.

An allometric analysis indicated that competition below ground did not result in an increase in the relative biomass allocated to roots for any of the 10 target species. This is counter to the growth‐balance hypothesis (and optimal foraging theory). Below‐ground competition did increase root : shoot ratios, but this was due to reduced plant size (small plants have larger root : shoot ratios), rather than adaptive plasticity.

A species’ below‐ground competitive ability was not related to its root system size. Although this finding is counter to commonly made assumptions, it is supported by other work demonstrating below‐ground competition to be generally size‐symmetric.

Despite the majority of plant–plant interactions in grasslands being below ground, our understanding of plant competition above ground is significantly more robust. Several wide‐spread assumptions regarding below‐ground competition are suspect, and more multispecies studies such as this are required to provide a fuller picture of how plants respond to, and compete for, soil resources.
Habitat fragmentation affects the common wetland specialist Primula farinosa in north‐east Switzerland
Authors: Lienert Judit , Fischer Markus
Published: July 2003

Fragmentation reduces size and increases isolation of plant habitats, and increases the ratio between edge and centre area. Consequences of habitat fragmentation have rarely been studied for common plants, and edge effects are rarely studied for plants in general. We studied density, population structure, fitness components and biotic interactions in the locally abundant distylous fen plant Primula farinosa in the centres and at the edges of 27 Swiss fen habitats of different size and degree of isolation.

Population sizes ranged from 80 to 106 450 flowering plants and were larger in larger fen habitats than in smaller ones.

The densities of plants were lower in more isolated habitats (by 26–46% depending on developmental stage). In the less isolated habitats, the density of seedlings and juveniles was higher in larger habitats. Plant densities were lower at the edge than in the centre of habitats (34–55%), and edges had fewer plants of younger developmental states. Densities of reproductive plants differed only in the centres of habitats, where they were higher in larger habitats, while at the edges these densities were independent of habitat area.

Flower morph proportions were independent of size and isolation of habitats.

Plants in larger habitats had larger rosette diameters and tended to have more flowers.

At edges, seed set was on average 11% lower, and occurrence and degree of herbivory more than 50% higher, than in centres. Capsule frugivory was less likely in larger habitats. Infection by the smut fungus Urocystis primulicola was more likely in larger habitats.

We conclude that size, isolation and edge to centre ratio of fen habitats all affect the abundant P. farinosa and recommend that edge effects and more common species are given more attention.
Facilitated invasion by hybridization of Sarcocornia species in a salt‐marsh succession
Authors: Figueroa M. E. , Castillo J. M. , Redondo S. , Luque T. , Castellanos E. M. , Nieva F. J. , Luque C. J. , Rubio‐Casal A. E. , Davy A. J.
Published: July 2003

We examined salt marsh development over 17 years (1984–2001) in a rapidly accreting, well‐drained lagoon of a macrotidal marsh in south‐west Spain. Scattered, elevated tussocks of colonizing Spartina maritima expanded radially until they either coalesced or were separated only by narrow drainage channels. We recorded changes in elevation of the tussocks and investigated the cover and biomass of successive species invading them.

Sediment accretion produced a mean annual increase in tussock elevation of 3.5 cm. Sarcocornia perennis had begun to invade the raised centres of the tussocks by 1984, subsequently displacing Spartina maritima radially to become dominant by 1990. A hybrid form of Sarcocornia, which appeared on some of the tussocks occupied by S. perennis in 1997, also expanded radially and had achieved dominance on many of the invaded tussocks by 2001, by virtue of its more erect growth form and rapid accumulation of high above‐ and below‐ground biomass.

Tussocks not yet invaded by the hybrid remain dominated by S. perennis and have maintained sediment accretion rates and redox potentials similar to those that have been invaded.

Genetic analysis, using random amplified DNA (RAPD) markers, indicated that the hybrid was a cross between the diploid Sarcocornia perennis (2n = 18) and the octaploid S. fruticosa (2n = 72), a high‐marsh species, and suggested that each hybrid individual may have resulted from a separate pollination of an indigenous S. perennis plant.

Invasion by the new hybrid thus probably occurred as a result of pollen flow from high‐marsh S. fruticosa, some 1 km distant, to the stigmas of the established dominant S. perennis. Succession might therefore be facilitated genetically rather than simply by the enhanced sediment accretion, which ameliorated the effects of submersion and low sediment redox potentials that presumably exclude S. fruticosa from lower parts of the marsh.
Self/non‐self discrimination in roots
Authors: Falik Omer , Reides Perla , Gersani Mordechai , Novoplansky Ariel
Published: July 2003

Competition usually involves the allocation of limiting resources to non‐reproductive functions. Natural selection is expected to favour mechanisms that increase competition with non‐self neighbours and limit wasteful competition with self.

We used Pisum sativum plants that had two roots and ‘double plants’ with two shoots and two roots that could be either longitudinally separated into two genetically identical but physiologically distinct individuals or left intact.

Root development was significantly greater in split‐root plants whose neighbours belonged to different plants. Furthermore, root development was relatively greater in the presence of roots of a different plant, regardless of its identity. This discrimination had a vectorial component whereby plants developed more and longer lateral roots towards neighbouring roots of different plants than towards other roots of the same plant.

The results thus demonstrate a mechanism of avoiding self‐competition that is based on physiological co‐ordination among different organs of the same plant rather than on allochemical recognition that depends on genetic differences.

The ability to discriminate between self and non‐self could be expected to increase resource use efficiency and ecological performance in plants. It could also be expected that tight physiological co‐ordination will be selected for between organs of the same plant that have greater probability of being engaged in direct competitive interactions with each other.
Long‐term canopy dynamics analysed by aerial photographs in a temperate old‐growth evergreen broad‐leaved forest
Authors: Fujita Takashi , Itaya Akemi , Miura Masahiro , Manabe Tohru , Yamamoto Shin‐Ichi
Published: July 2003

We used aerial photographs to analyse canopy dynamics over 32 years in a 4‐ha permanent plot of an old‐growth evergreen broad‐leaved forest in the Tatera Forest Reserve, south‐western Japan.

We used aerial photographs taken in 1966, 1983, 1993 and 1998 to create digital elevation models (on a 2.5‐m grid) of the canopy surface in a 10‐ha area that included the 4‐ha plot. A topographic map of the ground surface of the 4‐ha plot was also created from ground measurements taken in 1990. The canopy height at each location was calculated and the ‘vegetation height profile technique’ was applied to quantify canopy dynamics.

The size distributions of gaps at each observation time showed peaks at both small and intermediate sizes. The total number of gaps and gap density increased over the study period, while total gap area, mean gap size and maximum gap size fluctuated. While the overall mean rates of gap formation and closure (0.58 vs. 0.50% year−1) were nearly balanced, we found large temporal variation.

Of the 6400 of 2.5 × 2.5‐m quadrats, 3.4% remained as gaps throughout the 32‐year period. These tended to be in the centres of large, old gaps, whereas those that experienced re‐disturbance (2.5%) were distributed along the edges of old gaps. A large proportion (74.5%) maintained a closed canopy state.

Meteorological data suggested that the variation in gap formation and gap closure rates may be related to year‐to‐year variations in the number and severity of typhoons.

This study suggests that long‐term and large openings are essential for the establishment of deciduous broad‐leaved and shade intolerant pioneer species in predominantly evergreen broad‐leaved forests.
Seed dispersal patterns produced by white‐faced monkeys: implications for the dispersal limitation of neotropical tree species
Authors: Wehncke E. V. , Hubbell S. P. , Foster R. B. , Dalling J. W.
Published: July 2003

Primate frugivores are important seed dispersers for a large fraction of tree species in many tropical forests. The movement, diet preferences and defecation patterns produced by primates may therefore strongly influence seed dispersion patterns and seedling recruitment success. Here we examine the pattern of seed dispersal generated by white‐faced monkeys (Cebus capucinus) in relation to adult tree distribution in the 50‐ha plot on Barro Colorado Island (BCI), Panamá.

Diet breadth of Cebus was remarkably wide. Over four months they consumed fruits of 95 out of an estimated 240 species available. Seeds of 67 species passed intact through the gut and 28 were spat out.

Dispersal effectiveness of Cebus was also high. Two Cebus groups on average spent < 10 min feeding in individual trees, had large home ranges (> 150 ha), travelled 1–3 km day−1 and defecated seeds in small clumps throughout the day.

Mean dispersal distance of ingested seeds was 216 m (range 20–844 m), with the highest probability of dispersal 100–200 m from the parent plant. For six of nine species studied, the distance between defecation sites and nearest conspecific adults of seeds in faeces was not significantly different from random expectations.

The scattered dispersal pattern produced by Cebus suggests that this species contributes relatively little to dispersal limitation (sensu) compared to other dispersers in the community. Long‐distance dispersal by Cebus resulted in substantial movement of seeds in and out of the 50 ha plot, and suggests that inverse modelling procedures to estimate dispersal functions from trap data may not adequately describe dispersal patterns generated by this primate.
The effects of spatial pattern of nutrient supply on yield, structure and mortality in plant populations
Authors: Day Kieron J. , Hutchings Michael J. , John Elizabeth A.
Published: July 2003

Early in growth, plant populations subjected to heterogeneous conditions can achieve significantly higher yields than populations grown in homogeneous conditions that provide the same amount of nutrients. We hypothesized that this yield enhancement would be ephemeral, and that yields of populations grown under different patterns of nutrient supply will converge as time passes. We also predicted that plant size frequency distributions will continue to differ between populations in heterogeneous and homogeneous conditions, that spatial patterns of mortality will differ, and that greater mortality will occur in populations under heterogeneous conditions. An experiment was carried out on Cardamine hirsuta to test these hypotheses.

The experiment was harvested after 60 days, when flowering had begun in all populations. At this time, populations grown with the same nutrient supply but different patterns of supply did not differ in yield. Populations grown at higher nutrient levels had greater yields but suffered more mortality.

In heterogeneous conditions, plants in nutrient‐rich locations were larger than plants in nutrient‐poor locations, and larger than plants in identical positions in populations growing under homogeneous conditions. Plants in nutrient‐rich patches in heterogeneous treatments suffered more mortality than plants in nutrient‐poor patches. Contrary to prediction, total mortality at all levels of nutrient supply was significantly higher in populations in homogeneous conditions.

Coefficient of variation in shoot sizes was higher in populations at higher nutrient levels, but unaffected by pattern of nutrient supply. CV of root mass per unit of substrate was greater under heterogeneous than homogeneous conditions.

Frequency distributions of shoot size, and root mass per unit of substrate, were strikingly different between populations grown under different patterns of nutrient supply. The differences are interpreted as showing that under homogeneous conditions all parts of the habitat are heavily exploited, giving rise to uniformly high levels of interplant competition. In contrast, nutrient‐poor patches in the heterogeneous treatments contain low root masses. Plants in these patches remain small, but have a high probability of survival. We propose that these differences in intensity of habitat occupation, and presumably in competition, explain the lower mortality in populations growing under heterogeneous conditions.
Asymmetric competition and the evolution of propagule size
Authors: Rodríguez‐Gironés M. A. , Sandsten H. , Santamaría L.
Published: July 2003

In an asexually reproducing plant (Potamogeton pectinatus L.) the competitive advantage of a larger propagule over a smaller one was determined by a single parameter (α, the competitive asymmetry coefficient), independent of sowing density or average propagule size. Competitive advantage was determined by the relative size difference between propagules instead of their absolute difference.

Productivity per germination site increased with the number and size of propagules present, even at densities high enough to result in decreased per capita yield due to plant competition.

Both the number of propagules produced by a plant and their size increased with increasing per capita resource capture. Therefore, propagule size was neither equal to the size of the propagule from which the plant germinated nor independent of resource status.

Our results clarify what assumptions should be made in ecological and evolutionary models dealing with competition for resources between seedlings. In particular, the use of relative size differences instead of absolute ones should lead to the evolution of smaller propagules than those expected if competitive advantage grew with absolute propagule size.
Spatial patterns of maternal lineages and clones of Galium odoratum in a large ancient woodland: inferences about seedling recruitment
Authors: Ziegenhagen Birgit , Bialozyt Ronald , Kuhlenkamp Vivian , Schulze Inge , Ulrich Andreas , Wulf Monika
Published: July 2003

We investigated spatial genetic patterns in the clonal herbaceous plant species Galium odoratum L., which has previously been shown to be significantly associated with ancient woodlands.

A maternally inherited chloroplast DNA marker was developed for G. odoratum. Seven chloroplast haplotypes were detected in the study area and mapped at different spatial scales. Their spatial patterns suggest that both local and non‐local gene flow occurs via seeds.

Fingerprints from DIG‐labelled AFLP technology were validated as markers for G. odoratum clone identification. A single primer–enzyme combination was sufficient to distinguish between clones. A typical patch of G. odoratum is composed of numerous genets, mainly occurring in separate clusters of ramets, which may be several meters in diameter.

Pairwise similarities, calculated from the AFLP banding patterns, were used for spatial autocorrelation analysis. The distinct spatial genetic structure at the patch level may be due to the genetic similarity of neighbouring genets or to clonal growth.

The spatial patterns obtained using the two DNA markers, suggest that a mixture of local and non‐local gene flow via both seeds and pollen is occurring. Repeated seedling recruitment (RSR) would be consistent with the life history of G. odoratum in ancient woodlands with long‐term spatial continuity.
Chemokine Upregulation Follows Cytokine Expression in Chronic Relapsing Experimental Autoimmune Encephalomyelitis
Authors: Glabinski A. R. , Bielecki B. , Ransohoff R. M.
Published: July 2003

Chronic relapsing experimental autoimmune encephalomyelitis (ChREAE) is an autoimmune disease of the central nervous system (CNS) induced by CNS myelin components. In the early active stage, both ChREAE and multiple sclerosis (MS) are characterized by the presence of perivascular inflammatory cuffs disseminated in the CNS. There is growing evidence that chemoattractant cytokines (chemokines) play an important role in this process. The main goal of the present study was to analyse the hypothesis that chemokine expression in the CNS during autoimmune inflammation is regulated by proinflammatory cytokines. To address this concept, we analysed temporal relations between chemokine and cytokine expression during ChREAE. Phasic upregulation of gene expression for chemokines T‐cell activation gene 3 (TCA‐3)/CCL1, monocyte chemoattractant protein‐1 (MCP‐1)/CCL2, macrophage inflammatory protein‐1 alpha (MIP‐1α)/CCL3, MIP‐1β/CCL4, regulated on activation normal T cell expressed and secreted (RANTES)/CCL5 and MIP‐2/CXCL2–3 as well as cytokines tumour necrosis factor‐α (TNF‐α), ‐β, LT‐β, interferon‐γ (IFN‐γ) and transforming growth factor‐β1 (TGF‐β1) in the CNS was observed during attacks of ChREAE. Expression of cytokines TNF‐β and LT‐β preceded, and the expression of TGF‐β1 followed chemokine upregulation. Our results suggest that chemokine expression during CNS autoimmune inflammation may be regulated by some proinflammatory cytokines.
The dynamin‐like protein ADL1C is essential for plasma membrane maintenance during pollen maturation
Authors: Kang Byung‐Ho , Rancour David M. , Bednarek Sebastian Y.
Published: July 2003

Dynamin‐related GTPases regulate a wide variety of dynamic membrane processes in eukaryotes. Here, we investigated the function of ADL1C, a member of the Arabidopsis 68 kDa dynamin‐like protein family. Analysis of heterozygous adl1C‐1 indicates that the mutation specifically affects post‐meiotic male gametogenesis. Fifty percent of the mature pollen from heterozygous adl1C‐1 androecia are shriveled and fail to germinate in vitro. During microspore maturation, adl1C‐1 pollen grains display defects in the plasma membrane and intine morphology, suggesting that ADL1C is essential for the formation and maintenance of the pollen cell surface and viability during desiccation. Consistent with a role in cell‐surface dynamics, immunofluorescence microscopy indicates that ADL1C is localized to the cell plate of dividing somatic cells and to the tip of expanding root hairs. We propose that ADL1C functions in plasma membrane dynamics, and we discuss the role of the ADL1 family in plant growth and development.
Microfilaments and microtubules control the morphology and movement of non‐green plastids and stromules in Nicotiana tabacum
Authors: Kwok Ernest Y. , Hanson Maureen R.
Published: July 2003

Plastid stromules are stroma‐filled tubular extensions of the plastid envelope membrane. These structures, which have been observed in a number of species, allow transfer of proteins between interconnected plastids. The dramatic shape of stromules and their dynamic movement within the cell provide an opportunity to study the control of morphology and motion of plastids. Using inhibitors of actin and tubulin, we found that both microfilaments and microtubules affect the shape and motility of non‐green plastids. Actin and tubulin control plastid and stromule structure by independent mechanisms, while plastid movement is promoted by microfilaments but inhibited by microtubules. The presence or absence of stromules does not affect the motility of plastids. Photobleaching experiments indicate that actin and tubulin are not necessary for the bulk of green fluorescent protein (GFP) movement between plastids via stromules.
Signaling of systemic acquired resistance in tobacco depends on ethylene perception
Authors: Verberne Marianne C. , Hoekstra Jan , Bol John F. , Linthorst Huub J.M.
Published: July 2003

The hypersensitive interaction between Tobacco mosaic virus (TMV) and tobacco results in accumulation of salicylic acid (SA), defense gene expression, and development of systemic acquired resistance (SAR) in uninfected leaves. The plant hormones SA and ethylene have been implicated in SAR. From a study with ethylene‐insensitive (Tetr) tobacco, we concluded that ethylene perception is required to generate the systemic signal molecules in TMV‐infected leaves that trigger SA accumulation, defense gene expression, and SAR development in uninfected leaves. Ethylene perception was not required for the responses of the plant to the systemic signal that leads to SAR development.
Mutations in the huge Arabidopsis gene BIG affect a range of hormone and light responses
Authors: Kanyuka Konstantin , Praekelt Uta , Franklin Keara A. , Billingham Olivia E. , Hooley Richard , Whitelam Garry C. , Halliday Karen J.
Published: July 2003

In independent genetic screens, for shade‐avoidance response and cytokinin sensitivity, we identified two Arabidopsis mutants, attenuated shade avoidance 1 (asa1) and umbrella1 (umb1), which have very similar pleiotropic phenotypes. asa1 and umb1 are allelic to tir3‐1, and are caused by mutations in BIG, which is required for normal auxin efflux. They have a compact rosette, fewer lateral roots, delayed flowering, more secondary inflorescence, smaller seeds and, in the Laer‐0 background, much shorter internodes between adjacent flowers, suggesting an interaction between BIG and ERECTA. These mutants have organ‐specific defects in response to cytokinins, ethylene, N‐1‐naphthylphthalamic acid (NPA) and gibberellin (GA). The phenotype of the asa1 ga1‐3 double mutant is consistent with defects in GA signalling. There are subtle effects in responses to auxins, abscisic acid and brassinolide. Elongation growth associated with shade avoidance in phyA phyB null mutants is suppressed by asa1 in all organs other than the hypocotyl. Therefore, we here provide evidence that BIG is a key player not just in auxin signalling, but in a multitude of light and hormone pathways.
Where do gibberellin biosynthesis and gibberellin signaling occur in rice plants?
Authors: Kaneko Miyuki , Itoh Hironori , Inukai Yoshiaki , Sakamoto Tomoaki , Ueguchi‐Tanaka Miyako , Ashikari Motoyuki , Matsuoka Makoto
Published: July 2003

To identify where gibberellin (GA) biosynthesis and signaling occur, we analyzed the expression of four genes involved in GA biosynthesis, GA 20‐oxidase1 and GA 20‐oxidase2 (OsGA20ox1 and OsGA20ox2), and GA 3‐oxidase1 and GA 3‐oxidase2 (OsGA3ox1 and OsGA3ox2), and two genes involved in GA signaling, namely, the gene encoding the α‐subunit of the heterotrimeric GTP‐binding protein (Gα), and SLENDER RICE1 (SLR1), which encodes a repressor of GA signaling. At the vegetative stage, the expression of OsGA20ox2, OsGA3ox2, Gα, and SLR1 was observed in rapidly elongating or dividing organs and tissues, whereas the expression of OsGA20ox1 or OsGA3ox1 could not be detected. At the inflorescence or floral stage, the expression of OsGA20ox2, OsGA3ox2, Gα, and SLR1 was also observed in the shoot meristems and stamen primordia. The overlapping expression of genes for GA biosynthesis and signaling indicates that in these tissues and organs, active GA biosynthesis occurs at the same site as does GA signaling. In contrast, no GA‐biosynthesis genes were expressed in the aleurone cells of the endosperm; however, the two GA‐signaling genes were actively expressed, indicating that the aleurone does not produce bioactive GAs, but can perceive GAs. The expression of OsGA20ox1 and OsGA3ox1 was observed only in the epithelium of the embryo and the tapetum of the anther. Based on the specific expression pattern of OsGA20ox1 and OsGA3ox1 in these tissues, we discuss the unique nature of the epithelium and the tapetum in terms of GA biosynthesis. The epithelium and the tapetum are considered to be an important source of bioactive GAs for aleurone and other organs of the flower, respectively.
Vacuolar malate uptake is mediated by an anion‐selective inward rectifier
Authors: Hafke Jens B. , Hafke Yuliya , Smith J. Andrew C. , Lüttge Ulrich , Thiel Gerhard
Published: July 2003

Electrophysiological studies using the patch‐clamp technique were performed on isolated vacuoles from leaf mesophyll cells of the crassulacean acid metabolism (CAM) plant Kalanchoë daigremontiana to characterize the malate transport system responsible for nocturnal malic acid accumulation. In the presence of malate on both sides of the membrane, the current–voltage relations of the tonoplast were dominated by a strongly inward‐rectifying anion‐selective channel that was active at cytoplasmic‐side negative voltages. Rectification of the macroscopic conductance was reflected in the voltage‐dependent gating of a 3‐pS malate‐selective ion channel, which showed a half‐maximal open probability at −43 mV. Also, the time‐averaged unitary currents following a step to a negative voltage corresponded to the time‐dependent kinetics of the macroscopic currents, suggesting that the activity of this channel underlies the anion‐selective inward rectifier. The inward rectifier showed saturation kinetics with respect to malate (apparent Km of 2.5 mm malate2− activity), a selectivity sequence of fumarate2− > malate2− > Cl− > maleate2– ≈ citrate3–, and greater activity at higher pH values (with an apparent pK of 7.1 and maximum activity at around pH 8.0). All these properties were in close agreement with the characteristics of malate transport observed in isolated tonoplast vesicles. Further, 100 µm niflumate reversibly blocked the activity of the 3‐pS channel and inhibited both macroscopic currents and malate transport into tonoplast vesicles to the same extent. The macroscopic current densities recorded at physiological voltages and the estimated channel density of 0.2 µm−2 are sufficient to account for the observed rates of nocturnal malic acid accumulation in this CAM plant, suggesting that the 3‐pS, inward‐rectifying, anion‐selective channel represents the principal pathway for malate influx into the vacuole.
Visualization of abscisic acid‐perception sites on the plasma membrane of stomatal guard cells
Authors: Yamazaki Daiki , Yoshida Shigeo , Asami Tadao , Kuchitsu Kazuyuki
Published: July 2003

Abscisic acid (ABA) is a phytohormone that plays a key role as a stress signal, regulating water relations during drought conditions, by inducing stomatal closure. However, to date, no putative ABA receptor(s) has been reported at the protein sequence, gene family, or cellular localization levels. We used biotinylated ABA (bioABA) to characterize the ABA‐perception sites in the stomatal guard cells of Vicia faba. Treatment with bioABA induced stomatal closure and shrinkage of guard cell protoplasts (GCPs). The ABA‐perception sites were visualized by fluorescence microscopy and confocal laser scanning microscopy (CLSM), using bioABA and fluorescence‐labeled avidin. Fluorescent particles were observed in patches on the surface of the GCPs. Fluorescence intensity was quantified by flow cytometry (FCM) as well as by CLSM. Binding of bioABA was inhibited by ABA in a dose‐dependent manner. Pre‐treatment of GCPs with proteinase K also blocked the binding of bioABA. Binding of bioABA was inhibited by RCA‐7a, an ABA analog that induces stomatal closure, but not by RCA‐16, which has no effect on stomatal aperture. Another ABA analog, PBI‐51, inhibited ABA‐induced stomatal closure. This ABA antagonist also inhibited binding of bioABA to the GCPs. These results suggest that ABA is perceived on the plasma membrane of stomatal guard cells, and that the present experimental methods constitute valuable tools for characterizing the nature of the ABA receptor(s) that perceives physiological ABA signals. These imaging studies allow us to demonstrate the spatial distribution of the ABA‐perception sites. Visualization of the ABA‐perception sites provides new insights into the nature of membrane‐associated ABA receptor(s).