bluuebunny/crossref_metadata_2025 huggingface dataset:
Detailed Genomic Analysis of the Wβ and γ Phages InfectingBacillus anthracis: Implications for Evolution of Environmental Fitness and Antibiotic Resistance
Authors: Schuch Raymond , Fischetti Vincent A.
Published: April 2006

Phage-mediated lysis has been an essential laboratory tool for rapidly identifyingBacillus anthracisfor more than 40 years, relying on the γ phage derivative of aBacillus cereusprophage called W. The complete genomic sequences of the temperate W phage, referred to as Wβ, and its lytic variant γ were determined and found to encode 53 open reading frames each, spanning 40,864 bp and 37,373 bp, respectively. Direct comparison of the genomes showed that γ evolved through mutations at key loci controlling host recognition, lysogenic growth, and possibly host phenotypic modification. Included are a cluster of point mutations at thegp14tail fiber locus of γ, encoding a protein that, when fused to green fluorescent protein, binds specifically toB. anthracis. A large 2,003-bp deletion was also identified at the γ lysogeny module, explaining its shift from a temperate to a lytic lifestyle. Finally, evidence of recombination was observed at a dicistronic Wβ locus, encoding putative bacterial cell surface-modifying proteins, replaced in γ with a locus, likely obtained from aB. anthracisprophage, encoding demonstrable fosfomycin resistance. Reverse transcriptase PCR analysis confirmed strong induction at the dicistronic Wβ locus and at four other phage loci inB. anthracisand/orB. cereuslysogens. In all, this study represents the first genomic and functional description of two historically important phages and is part of a broader investigation into contributions of phage to theB. anthracislife cycle. Initial findings suggest that lysogeny ofB. anthracispromotes ecological adaptation, rather than virulence, as with other gram-positive pathogens.
Structural Alterations of the Cysteine Desulfurase IscS of
Salmonella enterica
Serovar Typhimurium Reveal Substrate Specificity of IscS in tRNA Thiolation
Authors: Lundgren Hans K. , Björk Glenn R.
Published: April 2006

The cysteine desulfurase IscS in
Salmonella enterica
serovar Typhimurium is required for the formation of all four thiolated nucleosides in tRNA, which is thought to occur via two principally different biosynthetic pathways. The synthesis of 4-thiouridine (s
4
U) and 5-methylaminomethyl-2-thiouridine (mnm
5
s
2
U) occurs by a transfer of sulfur from IscS via various proteins to the target nucleoside in the tRNA, and no iron-sulfur cluster protein participates, whereas the synthesis of 2-thiocytidine (s
2
C) and
N
6
-(4-hydroxyisopentenyl)-2-methylthioadenosine (ms
2
io
6
A) is dependent on iron-sulfur cluster proteins, whose formation and maintenance depend on IscS. Accordingly, inactivation of IscS should result in decreased synthesis of all thiolated nucleosides. We selected mutants defective either in the synthesis of a thiolated nucleoside (mnm
5
s
2
U) specific for the iron-sulfur protein-independent pathway or in the synthesis of a thiolated nucleoside (ms
2
io
6
A) specific for the iron-sulfur protein-dependent pathway. Although we found altered forms of IscS that influenced the synthesis of all thiolated nucleosides, consistent with the model, we also found mutants defective in subsets of thiolated nucleosides. Alterations in the C-terminal region of IscS reduced the level of only ms
2
io
6
A, suggesting that the synthesis of this nucleoside is especially sensitive to minor aberrations in iron-sulfur cluster transfer activity. Our results suggest that IscS has an intrinsic substrate specificity in how it mediates sulfur mobilization and/or iron-sulfur cluster formation and maintenance required for thiolation of tRNA.
Upregulated Transcription of Plasmid and Chromosomal Ribulose Monophosphate Pathway Genes Is Critical for Methanol Assimilation Rate and Methanol Tolerance in the Methylotrophic Bacterium
Bacillus methanolicus
Authors: Jakobsen Øyvind M. , Benichou Aline , Flickinger Michael C. , Valla Svein , Ellingsen Trond E. , Brautaset Trygve
Published: April 2006

The natural plasmid pBM19 carries the key
mdh
gene needed for the oxidation of methanol into formaldehyde by
Bacillus methanolicus
. Five more genes,
glpX
,
fba
,
tkt
,
pfk
, and
rpe
, with deduced roles in the cell primary metabolism, are also located on this plasmid. By using real-time PCR, we show that they are transcriptionally upregulated (6- to 40-fold) in cells utilizing methanol; a similar induction was shown for two chromosomal genes,
hps
and
phi
. These seven genes are involved in the fructose bisphosphate aldolase/sedoheptulose bisphosphatase variant of the ribulose monophosphate (RuMP) pathway for formaldehyde assimilation. Curing of pBM19 causes higher methanol tolerance and reduced formaldehyde tolerance, and the methanol tolerance is reversed to wild-type levels by reintroducing
mdh
. Thus, the RuMP pathway is needed to detoxify the formaldehyde produced by the methanol dehydrogenase-mediated conversion of methanol, and the in vivo transcription levels of
mdh
and the RuMP pathway genes reflect the methanol tolerance level of the cells. The transcriptional inducer of
hps
and
phi
genes is formaldehyde, and not methanol, and introduction of multiple copies of these two genes into
B. methanolicus
made the cells more tolerant of growth on high methanol concentrations. The recombinant strain also had a significantly higher specific growth rate on methanol than the wild type. While pBM19 is critical for growth on methanol and important for formaldehyde detoxification, the maintenance of this plasmid represents a burden for
B. methanolicus
when growing on mannitol. Our data contribute to a new and fundamental understanding of the regulation of
B. methanolicus
methylotrophy.
A CsgD-Independent Pathway for Cellulose Production and Biofilm Formation inEscherichia coli
Authors: Da Re Sandra , Ghigo Jean-Marc
Published: April 2006

Bacterial growth on a surface often involves the production of a polysaccharide-rich extracellular matrix that provides structural support for the formation of biofilm communities. InSalmonella, cellulose is one of the major constituents of the biofilm matrix. Its production is regulated by CsgD and the diguanylate cyclase AdrA that activates cellulose synthesis at a posttranscriptional level. Here, we studied a collection ofEscherichia coliisolates, and we found that the ability to produce cellulose is a common trait shared by more than 50% of the tested strains. We investigated the genetic determinants of cellulose production and its role in biofilm formation in the commensal strainE. coli1094. By contrast with theSalmonellacellulose regulatory cascade, neither CsgD nor AdrA is required inE. coli1094 to regulate cellulose production. In this strain, an alternative cellulose regulatory pathway is used, which involves the GGDEF domain protein, YedQ. Although AdrA1094is functional, it is weakly expressed inE. coli1094 compared to YedQ, which constitutively activates cellulose production under all tested environmental conditions. The study of cellulose regulation in several otherE. coliisolates showed that, besides the CsgD/AdrA regulatory pathway, both CsgD-independent/YedQ-dependent and CsgD-independent/YedQ-independent pathways are found, indicating that alternative cellulose pathways are common inE. coliand possibly in other cellulose-producingEnterobacteriaceae.
Effects of Phosphorelay Perturbations on Architecture, Sporulation, and Spore Resistance in Biofilms ofBacillus subtilis
Authors: Veening Jan-Willem , Kuipers Oscar P. , Brul Stanley , Hellingwerf Klaas J. , Kort Remco
Published: April 2006

The spore-forming bacteriumBacillus subtilisis able to form highly organized multicellular communities called biofilms. This coordinated bacterial behavior is often lost in domesticated or laboratory strains as a result of planktonic growth in rich media for many generations. However, we show here that the laboratory strainB. subtilis168 is still capable of forming spatially organized multicellular communities on minimal medium agar plates, exemplified by colonies with vein-like structures formed by elevated bundles of cells. In line with the current model for biofilm formation, we demonstrate that overproduction of the phosphorelay components KinA and Spo0A stimulates bundle formation, while overproduction of the transition state regulators AbrB and SinR leads to repression of formation of elevated bundles. Time-lapse fluorescence microscopy studies ofB. subtilisgreen fluorescent protein reporter strains show that bundles are preferential sites for spore formation and that flat structures surrounding the bundles contain vegetative cells. The elevated bundle structures are formed prior to sporulation, in agreement with a genetic developmental program in which these processes are sequentially activated. Perturbations of the phosphorelay by disruption and overexpression of genes that lead to an increased tendency to sporulate result in the segregation of sporulation mutations and decreased heat resistance of spores in biofilms. These results stress the importance of a balanced control of the phosphorelay for biofilm and spore development.
EspF of Enteropathogenic
Escherichia coli
Binds Sorting Nexin 9
Authors: Marchès Oliver , Batchelor Miranda , Shaw Robert K. , Patel Amit , Cummings Nicola , Nagai Takeshi , Sasakawa Chihiro , Carlsson Sven R. , Lundmark Richard , Cougoule Celine , Caron Emmanuelle , Knutton Stuart , Connerton Ian , Frankel Gad
Published: April 2006

EspF of enteropathogenic
Escherichia coli
targets mitochondria and subverts a number of cellular functions. EspF consists of six putative Src homology 3 (SH3) domain binding motifs. In this study we identified sorting nexin 9 (SNX9) as a host cell EspF binding partner protein, which binds EspF via its amino-terminal SH3 region. Coimmunoprecipitation and confocal microscopy showed specific EspF-SNX9 interaction and non-mitochondrial protein colocalization in infected epithelial cells.
Mechanism ofhilARepression by 1,2-Propanediol Consists of Two Distinct Pathways, One Dependent on and the Other Independent of Catabolic Production of Propionate, inSalmonella entericaSerovar Typhimurium
Authors: Nakayama Shu-ichi , Watanabe Haruo
Published: April 2006

A glycerol dehydrogenase gene was selected as a multicopy suppressor rescuing the reducedhilAexpression in theSalmonella entericaserovar TyphimuriumcpxAmutant. A substrate of the enzyme, 1,2-propanediol, repressedhilAexpression. The 1,2-propanediol-mediated repression at 150 mM, but not that at 300 mM, was abrogated by blocking the catabolism producing propionate from 1,2-propanediol.
Sigma L Is Important for Cold Shock Adaptation of
Bacillus subtilis
Authors: Wiegeshoff Frank , Beckering Carsten L. , Debarbouille Michel , Marahiel Mohamed A.
Published: April 2006

Although sigma factor-dependent transcriptional regulation was shown to be essential for adaptation to different environmental stimuli, no such sigma factor has been related to the regulation of the cold shock response in
Bacillus subtilis
. In this study, we present genetic evidence for participation of σ
L
(σ
54
) and the two σ
L
-dependent transcriptional enhancers BkdR and YplP in the cold shock response of
Bacillus subtilis
JH642. Single-gene deletion of either
sigL
,
bkdR
, or
yplP
resulted in a cold-sensitive phenotype.
Independent Regulation of MucD, an HtrA-Like Protease in
Pseudomonas aeruginosa
, and the Role of Its Proteolytic Motif in Alginate Gene Regulation
Authors: Wood Lynn F. , Ohman Dennis E.
Published: April 2006

Expression of
mucD
, encoding a homologue of the HtrA(DegP) family of endoserine proteases, was investigated in
Pseudomonas aeruginosa
. Expressed from the
algT-mucABCD
operon, MucD was detected in mucoid (FRD1) and nonmucoid (PAO1) parental strains and also when polar insertions were placed upstream in
algT
or
mucB
. A transcriptional start site for a
mucD
promoter (P
mucD
) was mapped within
mucC
. Expression of single-copy
mucD217
, encoding MucD altered in the protease motif (S217A), was defective in temperature resistance and alginate gene regulation.
Two Putative
c
-Type Multiheme Cytochromes Required for the Expression of OmcB, an Outer Membrane Protein Essential for Optimal Fe(III) Reduction in
Geobacter sulfurreducens
Authors: Kim Byoung-Chan , Qian Xinlei , Leang Ching , Coppi Maddalena V. , Lovley Derek R.
Published: April 2006

Deletion of two homologous
Geobacter sulfurreducens c
-type cytochrome genes,
omcG
and
omcH
, decreased the rate of Fe(III) reduction and decreased the level of an outer membrane cytochrome critical for Fe(III) reduction, OmcB, without affecting its transcription. Expression of either gene restored Fe(III) reduction and OmcB expression, suggesting functional similarity.
Characterization of a Gene Encoding an Acetylase Required for Pyoverdine Synthesis in
Pseudomonas aeruginosa
Authors: Lamont Iain L. , Martin Lois W. , Sims Talia , Scott Amy , Wallace Mary
Published: April 2006

Strains of
Pseudomonas aeruginosa
secrete one of three pyoverdine siderophores (types I to III). We have characterized a gene,
pvdY
II
(for the
pvdY
gene present in type II
P. aeruginosa
strains), that is only present in strains that make type II pyoverdine. A mutation in
pvdY
II
prevented pyoverdine synthesis. Bioinformatic, genetic, and biochemical approaches indicate that the PvdYII enzyme catalyzes acetylation of hydroxyornithine. Expression of
pvdY
II
is repressed by the presence of iron and upregulated by the presence of type II pyoverdine. Characterization of
pvdY
II
provides insights into the molecular basis for production of different pyoverdines by different strains of
P. aeruginosa
.
Levels of Glycine Betaine in Growing Cells and Spores of
Bacillus
Species and Lack of Effect of Glycine Betaine on Dormant Spore Resistance
Authors: Loshon Charles A. , Wahome Paul G. , Maciejewski Mark W. , Setlow Peter
Published: April 2006

Bacteria of various
Bacillus
species are able to grow in media with very high osmotic strength in part due to the accumulation of low-molecular-weight osmolytes such as glycine betaine (GB). Cells of
Bacillus
species grown in rich and minimal media contained low levels of GB, but GB levels were 4- to 60-fold higher in cells grown in media with high salt. GB levels in
Bacillus subtilis
cells grown in minimal medium were increased ∼7-fold by GB in the medium and 60-fold by GB plus high salt. GB was present in spores of
Bacillus
species prepared in media with or without high salt but at lower levels than in comparable growing cells. With spores prepared in media with high salt, GB levels were highest in
B. subtilis
spores and ≥20-fold lower in
B. cereus
and
B. megaterium
spores. Athough GB levels in
B. subtilis
spores were elevated 15- to 30-fold by GB plus high salt in sporulation media, GB levels did not affect spore resistance. GB levels were similar in wild-type
B. subtilis
spores and spores that lacked major small, acid-soluble spore proteins but were much lower in spores that lacked dipicolinic acid.
Identification of Nudix Hydrolase Family Members with an Antimutator Role in
Mycobacterium tuberculosis
and
Mycobacterium smegmatis
Authors: Dos Vultos T. , Blázquez J. , Rauzier J. , Matic I. , Gicquel B.
Published: April 2006

Mycobacterium tuberculosis
and
Mycobacterium smegmatis
MutT1, MutT2, MutT3, and Rv3908 (MutT4) enzymes were screened for an antimutator role. Results indicate that both MutT1, in
M. tuberculosis
and
M. smegmatis
, and MutT4, in
M. smegmatis
, have that role. Furthermore, an 8-oxo-guanosine triphosphatase function for MutT1 and MutT2 is suggested.
A comparative cytological analysis of fungal endophytes in the sporophyte rhizomes and vascularized gametophytes of Tmesipteris and Psilotum
Authors: Duckett Jeffrey G. , Ligrone Roberto
Published: April 2006

This article describes the results of a light and electron microscopic study of the fungal endophytes and vascular anatomy in the rhizomes and gametophytes of Tmesipteris and Psilotum. The parenchymatous cortical cells of the rhizomes and subterranean gametophytes of Tmesipteris and Psilotum contain intracellular aseptate glomeromycotean fungi resembling the “Paris-type” of arbuscular mycorrhizas found in seed plants. The fungi differentiate into multinucleate vesicles and hyphal coils, both containing bacteria-like structures and accumulating lipid masses and crystals as they age. After several cycles of infection in the same cell, degenerate hyphae form amorphous masses encased by host wall material. Nearly identical host–fungus cytology between the autotrophic sporophytes and the heterotrophic gametophytes suggests that these psilophyte associations are exploitative of the fungus in both generations. Following the description of tracheids nearly 60 years ago in the gametophytes of Psilotum, vascular elements are described for the first time in the haploid generation of Tmesipteris. Close similarities between the water- and food-conducting elements in both generations, viz. vessel elements with scalariform perforation plates and sieve cells with refractive spherules and lacking callose at all stages in their develoment, add support to the homologous theory of the alternations of generations. Mitochondrial aggregations, cross-linked by small electron-opaque rods, are common in the stelar cells of both generations and appear to be a unique feature of the psilophyte clade.
The effect of Frankia and Paxillus involutus on the performance of Alnus incana subsp. rugosa in mine tailings
Authors: Markham John H.
Published: April 2006

The purpose of this study was to determine whether symbiotic nitrogen-fixing bacteria and mycorrhizal fungi act synergistically to improve plant performance when grown on heavy metal mine tailings. Seedlings were inoculated with Frankia, Paxillus involutus (Batsch) Fr., or a combination of both and grown in 100% peat, a 1:1 mix of peat and tailings, or 100% tailings for 20 weeks. Mortality of plants grown on pure tailings (15.0%) and peat–tailings (17.9%) was significantly greater than mortality of plants grown on peat (3.5%). The rate of nodulation and mycorrhizae formation decreased from 90.0% and 66.7%, respectively, on the peat, to 11.9% and 2.6% on the tailings. Frankia-inoculated plants grown on peat–tailings showed twice the mortality rate (38.5%) of any other inoculation treatment. Plants grown on media containing tailings had greater root/shoot ratios than plants grown on peat. Inoculating plants grown in the presence of tailings with either Frankia and (or) P. involutus increased root thickness. Inoculating plants with both symbionts increased colonization rates and shoot yield on the peat and peat–tailings media, suggesting that these symbionts act synergistically to improve plant performance. However, inoculating plants with Frankia decreased shoot relative growth rate in the early part of the experiment when plants were not fixing nitrogen, which, coupled with the higher mortality effect, suggests that nodule development is a stress for plants. It may be advisable that plants have fully functioning nodules before transplanting if they are to be used in revegetation programs.
Architectural differences in saplings of temperate versus tropical angiosperms; consequences of the deciduous habit?
Authors: King David A.
Published: April 2006

The architecture of saplings of temperate deciduous species of the southeastern United States was compared with that of tropical evergreen species of Central America, Borneo, and northeastern Australia. The deciduous species were more planar in the understory than were the tropical species, because of (i) more planar leaf displays within branches, (ii) a high frequency of arching, plagiotropic main stems (associated with greater plasticity in crown symmetry in relation to light), and (iii) a lower height of first branching. The deciduous species also had more planar branches than did subtropical and temperate evergreen angiosperms. This greater planarity in temperate deciduous understories may be associated with the simultaneous positioning of most leaves during a single flush in the spring. In contrast, saplings in tropical understories typically bear multiple leaf cohorts and position new leaves at the peripheries of existing leaf displays. These results and those of other studies suggest that there are adaptive links between plant architecture and phenology. Other factors, such as latitudinal variation in sun angles, may influence crown shape in overstory trees, but did not seem to be involved here, possibly because the filtering effect of the canopy results in smaller latitudinal shifts in understory illumination angles during the growing season. Thus, by favouring the deciduous habit, the cold winters and warm, humid summers of the eastern deciduous biome of North America appear to have had a notable influence on sapling architecture.
Revisions toPenicilliumser.Corymbifera: agents responsible for blue mould storage rot of various flower and vegetable bulbs
Authors: Overy D.P. , Valdez J.G. , Frisvad J.C.
Published: April 2006

Fifteen strains representing each Penicillium ser. Corymbifera taxa were compared using phenotypic and chemotaxonomic characters by cluster analysis and discriminant partial least squares regression. Variability in phenotypic expression of species strains resulted in a more fragmented classification compared with secondary metabolite expression. Although the observed phenotypic expression varied for strains cultured upon the same media, it was possible to classify strains into species groupings based only upon a few distinctive phenotypic traits. Data analysis of secondary metabolite profiles generated from HPLC-diode array dectection analysis gave reliable strain classification when more than one media type was employed. Depending on the species, Czapek yeast autolysate agar typically yielded the greatest chemical diversity; however, several metabolites (terrestric acid, corymbiferone, the corymbiferan lactones, and daldinin D) were only produced when strains were grown on either yeast extract sucrose or oatmeal agar. For the classification of strains based on a binary data matrix, application of the Yule coefficient gave the best clustering. Several secondary metabolites, of importance for the classification of ser. Corymbifera strains, were identified by discriminant-partial least squares regression analysis. A diagnostic key based on phenotypic, chemotaxonomic, and pathogenic traits is provided as an aid for species identification.
Aluminum accumulation in the roots of Melastoma malabathricum, an aluminum-accumulating plant
Authors: Watanabe Toshihiro , Misawa Seiji , Osaki Mitsuru
Published: April 2006

Generally, plants that have Al levels of at least 1000 mg·kg–1 in their leaves are defined as Al accumulators. These plants are often found in very acid soils in the tropics. The mechanisms of Al uptake in strong Al accumulators are still unclear. In this study, we investigated the characteristics of Al uptake and accumulation in the roots of Melastoma malabathricum L., an Al-accumulating plant that grows in acidic soils in the tropics. Melastoma malabathricum roots hardly absorb any La, possibly because of lower affinity of the root apoplast to La than to Al. Exposure to La did not affect the concentration of citrate in the roots; however, application of Al increased the citrate level considerably, corresponding with the amount of Al accumulation in the symplast. 27Al NMR analysis revealed that Al complexes with oxalate, but not with citrate, in the roots of M. malabathricum. This investigation revealed that oxalate, which occurs constitutively at high concentrations, is a ligand for Al accumulation in both root and shoot tissue, and that citrate, the synthesis of which is induced by Al application, is a ligand mainly used for Al translocation from the roots to the shoots.
Isozyme variation and the conservation genetics of Garry oak
Authors: Ritland K. , Meagher L.D. , Edwards D.G.W. , El-Kassaby Y.A.
Published: April 2006

Garry oak ( Quercus garryana Dougl. ex Hook) has a long north–south distribution along the inland Pacific coast. In British Columbia, it is a keystone species in a unique and endangered “Garry oak meadow” ecosystem. Here, we apply isozyme markers to address issues in the conservation and phylogeography of Garry oak. Among 42 populations and 23 gene loci, gene diversity (expected heterozygosity) averaged 0.17, and number of alleles per locus averaged 1.84. These values are about one-half of those found in other white oak species. Using progeny arrays, we found outcrossing rates in two Vancouver Island populations to average 0.96, with no detectable biparental inbreeding; also inbreeding coefficients of the 42 populations averaged near zero (0.025); thus inbreeding is not a significant concern. Cluster analysis of genetic distances identified two major groups of populations: southern Washington – Oregon and Vancouver Island – Gulf Islands; populations within the island region were particularly homogenous. An isolated mainland British Columbia population near Sumas, British Columbia, perhaps of anthropogenic origin, showed the least genetic variability and greatest genetic distance. Generally, geographically isolated populations were more genetically depauperate, which may place handicaps on their survival, but also more genetically distinct, providing a greater evolutionary legacy to the species.
Coordinated variation in ecophysiological properties among life stages and tissue types in an invasive perennial forb of semiarid shrub steppe
Authors: Hill Judson P. , Germino Matthew J.
Published: April 2006

Semiarid lands of North America are vulnerable to invasion by exotic forbs that frequently have an extended phenology compared with native herbaceous species. We hypothesized that photosynthetic stems, rosette leaves, and cauline leaves of Centaurea maculosa Lam. (knapweed) would differ in ecophysiological specialization and that these differences would enhance plant carbon uptake across seasonal variations in microclimate. Photosynthesis, water relations, and morphological features of C. maculosa were measured under natural variations in temperature and soil water, and under manipulated light environments, in adults compared with seedlings having only rosette leaves. Carbon gain was greater in adults than in seedlings owing to high photosynthesis in cauline and rosette leaves when water was abundant. Otherwise, photosynthesis was relatively lower but persistent through drought in all tissues and ages until senescence. Photosynthesis decreased with water stress in all tissues except stems. Stems comprised up to 36% of photosynthetic area following senescence of rosette leaves during seasonal drought. Seedlings expressed shade acclimation compared with rosette and especially cauline leaves of adults, although adult rosette leaves had flexible photosynthetic light responses. Contrasting ecophysiological specializations of photosynthetic tissues enhance carbon gain of adult C. maculosa as light, water, and temperature vary during its relatively long growth season.
The biology ofStellaria longipes(Caryophyllaceae)
Authors: Chinnappa C.C. , Donald Gillian M. , Sasidharan Rashmi , Emery R.J. Neil
Published: April 2006

During the past 30 years of research on Stellaria longipes Goldie, much has been learned about the taxonomy, cytology, reproductive biology, genetic variation, and phenotypic plasticity of this highly successful, circumpolar species. The conclusion that a S. longipes complex exists where two diploid progenitors ( Stellaria longifolia Muhl. (2n = 26) and Stellaria porsildii Chinnappa (2n = 26)) hybridized to produce polyploid S. longipes (2n = 52, 2n = 78, 2n = 104) was determined following extensive cytological and morphological studies. Interspecific hybridization is also common with S. borealis (2n = 52). The genetic variation and phenotypic plasticity contributing to the population differentiation within the S. longipes complex was investigated using isozyme, RFLP, and RAPD analyses, and comparative morphological studies. In later years, the focus shifted to elucidating the physiological and molecular aspects regulating the stem elongation plasticity observed in response to different temperatures, photoperiods, and different red/far red ratios. The roles of the phytohormones, ethylene, gibberellins, and abscisic acid were investigated in alpine and prairie ecotypes of S. longipes, and the phytochrome multigene family members were cloned. The presence of multigene families and a complex phytohormone interaction are postulated to underlie the extensive phenotypic plasticity observed in S. longipes.
Computed tomography scanning for three-dimensional imaging and complexity analysis of developing root systems
Authors: Lontoc-Roy Melinda , Dutilleul Pierre , Prasher Shiv O. , Han Liwen , Smith Donald L.
Published: April 2006

To improve our understanding of the role of root systems in soil-based resource acquisition by plants and eventually model it completely, root system complexity must be quantified, in addition to other morphometric traits. In this note, we introduce a new approach in which computed tomography (CT) scan data are collected on crop root systems in three-dimensional (3-D) space nondestructively and noninvasively, thus allowing for repeated measurements and a relevant complexity analysis of root systems. The experimental crop is maize ( Zea mays L.). Four potted seedlings were CT scanned under wet soil conditions on the day of emergence, and each of the two following days. Specifically, a high-resolution X-ray CT scanner formerly used for medical purposes produced 3 × 500 CT images of 0.1 mm thick cross-sections for each seedling. The fractal dimension of each root system on each day was estimated on a skeletonized 3-D image reconstructed from CT scan data. We found that the mean fractal dimension value was not significantly greater than 1 on day 1 (1.015 ± 0.015), contrary to days 2 and 3 (1.037 ± 0.015, 1.065 ± 0.016). Our results, including original 3-D images, provide support for a novel type of root system studies based on the collection and advanced analysis of CT scan data.
Calcium oxalate crystal macropatterns in leaves of species from groups Glycine and Shuteria (Glycininae; Phaseoleae; Papilionoideae; Fabaceae)
Authors: Cervantes-Martinez Teresa , Horner Harry T. , Palmer Reid G. , Hymowitz Theodore , Brown A.H.D.
Published: April 2006

Calcium oxalate crystal macropatterns in leaves were characterized for 69 species (and two Glycine tomentella cytotypes) from 14 of 16 genera in two legume groups, Glycine and Shuteria, to determine whether they share a common macropattern. A leaf clearing method was used to visualize the crystals. All 69 species (and two Glycine tomentella cytotypes) displayed prismatic crystals associated with leaf veins and vein endings. In contrast, mesophyll crystals occurred in 76.8% of 69 species and two G. tomentella cytotypes, and varied from a few to many. Conversely, only 40.9% of 22 Glycine species (in group Glycine) lacked mesophyll crystals, while 8.7% of 23 species of six genera associated with Glycine (in group Glycine) lacked mesophyll crystals. Thus 24.4% of 45 species of seven combined genera in group Glycine lacked mesophyll crystals. With seven genera in group Shuteria, 20.8% of 24 species lacked mesophyll crystals. The consistently present vein crystals varied in size and shape, so their length–width (Stubby versus Long) crystal ratios were determined for primary, secondary, and tertiary veins, and vein endings. Two trends were evident: Long-crystal ratios increased from primary veins to vein endings in species in both groups, and the perennial and annual Glycine species showed this condition to a greater extent than all the non-Glycine species. In some cases, taxonomically closely associated species were quite similar in their macropattern and presence or absence of mesophyll crystals. These results should be of value to future studies dealing with taxonomy and phylogeny of species in these two leguminous groups.
Proximate factors causing mast seeding in Fagus crenata: the effects of resource level and weather cues
Authors: Kon Hirokazu , Noda Takashi , Terazawa Kazuhiko , Koyama Hiromasa , Yasaka Michiyasu
Published: April 2006

To examine the proximate factors causing mast seeding in Fagus crenata Blume in Hokkaido, northern Japan, we analyzed a 13-year time series of seed production in relation to both previous reproduction and weather conditions. In an autocorrelation analysis we observed a significant negative correlation in 1-year time lags for the log-transformed total seed crop. This indicates that internal resource dynamics are important for mast seeding. A strong negative correlation was observed between the total seed crop and minimum temperature from late April to mid-May in the year preceding flowering. The critical minimum temperature from late April to mid-May for total seed crop at all five sites was about 1.0 °C higher than the 22-year (1979–2000) mean of the minimum temperatures, above which very few seeds were produced. These results show that a weather cue triggers the cessation of reproduction in F. crenata. Regression models that included reproduction in the previous year and minimum temperature explained 57.8%–83.1% of the total seed crop at the five study sites. Therefore, resource dynamics and weather cues are clearly involved in mast seeding in F. crenata.
The effects of the smut fungus Microbotryum bistortarum on survival and growth of Polygonum viviparum in Svalbard, Norway
Authors: Tojo Motoaki , Nishitani Satomi
Published: April 2006

The effect of the smut fungus Microbotryum bistortarum (de Candolle) K. Vánky on Polygonum viviparum L. was investigated in the High Arctic region, Svalbard, Norway, from 2000 to 2004. Ninety-two plants in a field plot were monitored for disease occurrence, plant survival, and plant growth. The disease, initially identified in 20 plants, only spread to one additional plant in 4 years. Once infected, the plants remained infected. Although a few of the 71 uninfected plants disappeared or died without any apparent signs of disease, the majority remained healthy without smut throughout the study. The percent survival among smut-infected plants was significantly lower than that of healthy plants in 2004 (P < 0.001). The number of bulbils, the number of flowers, and the size of the largest leaves of smut-infected plants were significantly lower than those of healthy plants. These results suggest infection by M. bistortarum can negatively impact populations of P. viviparum in the High Arctic region by lowering plant growth and longevity. Teliospore surface characteristics and germination patterns of the High Arctic specimens of M. bistortarum were also documented.
Different characteristics of nitrogen utilization between lupin and soybean: can lupin utilize organic nitrogen in soils?
Authors: Watanabe Toshihiro , Okamoto Miwa , Misawa Seiji , Urayama Masaru , Osaki Mitsuru
Published: April 2006

It is well known that lupin forms cluster roots, which help in dissolving insoluble P in soils. In nonleguminous species, cluster roots also appear to contribute to the utilization of organic N in soils. In white lupin ( Lupinus albus L.), however, the characteristics of its organic N utilization have not been studied. Therefore, we examined whether white lupin can utilize organic N in soils. Soybean ( Glycine max (L.) Merr.), which does not form cluster roots, was used as a control plant. Seedlings of lupin and soybean were cultivated in soils with different N sources (non-N, ammonium sulphate, ammonium sulphate plus cattle farmyard manure, or cattle farmyard manure). The rate of glycine uptake by excised roots was determined in a hydroponic experiment to investigate the ability of lupin and soybean to directly utilize amino acids. Nitrogen accumulation in soybean corresponded to the decrease in inorganic N in the soils. In contrast, N accumulation in lupin was higher than the decrease in inorganic N in the soil, especially with the cattle farmyard manure treatment, indicating that lupin derived more N from an organic N source. Wheat ( Triticum aestivum L.) cultivated with lupin in a pot accessed more available N than wheat with soybean or wheat in monoculture, suggesting that lupin roots themselves or the lupin rhizosphere microorganisms were able to decompose organic N in soils. Excised roots of lupin, especially cluster roots, exhibited higher rates of glycine uptake than roots of soybean. In conclusion, lupin decomposed organic N in the rhizosphere and was able to absorb amino acids from decomposition in addition to any inorganic N produced by further microbial decomposition.
Evolutionary analysis of Pinus leiophylla: a study using an Intron II sequence fragment of mitochondrial nad1
Authors: Mendoza Carlos Fabián Vargas , Rodríguez-Banderas Abril
Published: April 2006

A phylogenetic analysis was done using a mitochondrial marker to study the relationship between Pinus leiophylla Schiede & Deppe and Californian, Mesoamerican, European, and Asian pines. The type II intron between the nad1 b and c exons was chosen for the analysis. Nineteen otus (15 species with mitotypes in two species) from the Pinus and Picea genera were used. Amplification using the two primers generated an approximately 1000 bp product, depending on species. Parsimony branch and bound analysis resulted in 135 shortest trees with 1323 steps (CI = 0.9131 and RI = 0.9511). The strict consensus tree showed P. leiophylla associated with Eurasian pines. Though unusual, it is not the first time this association has been proposed. Given these results, P. leiophylla is likely one of the oldest pine species in the Americas and probably arose from a Eurasian ancestor that initially invaded North America at between 25°N and 35°N latitude and later colonized Mexico.
Maturation temperature regulates germinability and chemical constituents of Scotch thistle (Onopordum acanthium) cypselas
Authors: Qaderi Mirwais M. , Cavers Paul B. , Hamill Allan S. , Downs Michael P. , Bernards Mark A.
Published: April 2006

The effects of maturation temperature on germinability and chemical constituents of Scotch thistle ( Onopordum acanthium L.) cypselas (fruits) were determined as part of our ongoing investigation into the causes of intermittent germination in this species. Mature cypselas were collected from plants that were grown under higher (28 or 30 °C) and lower (20 or 22 °C) temperature regimes in greenhouses in 2000 and 2001. Two collections were made, from early- and late-ripening capitula. Germinability and the amounts of moisture, wax, phenolic compounds, and lignin were determined for cypselas from all collections. Cypselas that matured in the first year had lower amounts of moisture and wax than second-year cypselas, but did not differ in amounts of other components. Cypselas that matured under the higher temperatures generally had lower amounts of moisture, wax, and phenolic compounds, faster germination, and higher germination percentages. Early-matured cypselas had higher amounts of moisture and wax, faster germination, and higher germination percentages, but lower amounts of phenolic compounds. However, maturation temperature and collection date did not affect lignin content. Consistent and significant differences in germination patterns and chemical constituents between cypselas that matured under contrasting temperatures confirmed that maturation temperature altered the germinability of O. acanthium cypselas. Thus, under field conditions, cypselas that mature under low temperatures can have stronger dormancy and exhibit greater intermittency in germination/emergence patterns than those that mature under high temperatures.
Annual growth of the spring ephemeral Erythronium americanum as a function of temperature and mycorrhizal status
Authors: Lapointe Line , Lerat Sylvain
Published: April 2006

The capacity of the spring ephemeral Erythronium americanum L. to grow and absorb nutrient either as nonmycorrhizal (NM) or mycorrhizal (M) plants under the low temperature regime characteristic of its growth period was investigated. Specimens of E. americanum were collected in the field as either NM (early September) or as M plants (late October). Both groups of plants were submitted to different nutrient regimes during the hypogeous growth period at 5 °C, and during the subsequent epigeous growth period conducted at temperature regimes of either 12 °C day : 10 °C night or 17 °C day : 15 °C night. Nutrient regime influenced bulb nutrient content only during the epigeous growth period. The presence of mycorrhizas did not influence nutrient content, but favoured a greater bulb biomass at the final harvest (epigeous growth period), as did the lower temperature regime. Net nutrient uptake was not reduced at lower temperatures and appeared to follow plant demand. These findings confirm that E. americanum is adapted to perform better under a low temperature regime and that mineral nutrition in this species occurs mainly in spring in response to active growth. Arbuscular mycorrhizal fungi benefit E. americanum maybe through less expensive nutrient uptake or sustained carbon sink demand.
Banque de graines du sol et succession végétale dans les Alpes du Sud : effets des facteurs historiques et écologiques
Authors: Marage Damien , Rameau Jean-Claude , Garraud Luc
Published: April 2006

Dans un bassin versant des Alpes du Sud, nous avons étudié la densité, la richesse et la similarité, de la banque de graines du sol et de la végétation, au cours d’une succession secondaire soumise ou non au pâturage. Un plan d’échantillonnage stratifié, bâti sous système d’information géographique, a permis de retenir des facteurs historico-écologiques pertinents et de les mettre en relation avec la banque de graines et la végétation. Nos résultats ont montré que (i) la densité et la richesse de la banque de graines des pelouses et des fruticées sont supérieures dans les zones non pâturées comparées aux zones pâturées, (ii) que la similarité entre la végétation et la banque de graines augmente au cours de la succession, puis décroît dans les forêts anciennes, et que (iii) la banque de graines de ces forêts est très différente de celle des forêts récentes. Les tests de corrélations de matrices montrent que ce sont des variables pédologiques qui structurent, quelque soit le stade dynamique, la banque de graines. Dans ce contexte montagnard, la végétation privilégie la reproduction végétative aux dépens de la création de banque de graines longévives. Par conséquent, seul le maintien du pastoralisme permettra la persistance de la biodiversité en place.
Seed size variation in cold and freezing tolerance during seed germination of winterfat (Krascheninnikovia lanata) (Chenopodiaceae)
Authors: Wang Ruojing , Bai Yuguang , Low Nicholas H. , Tanino Karen
Published: April 2006

Native plants have adaptations to their local environments and elucidation of these traits has implications in both agronomy and restoration ecology. Winterfat ( Krascheninnikovia lanata (Pursh) A.D.J. Meeuse & Smit) is a native perennial shrub in North America capable of germinating at low temperatures. The effect of seed size on germination ability at low and subzero temperatures and the physiological mechanisms were investigated. Winterfat seeds achieved 50%–72% germination at –3 °C, a temperature slightly above the base temperature estimated using thermal time models. Small seeds required a longer time to reach 50% germination at subzero temperatures than large seeds. Large seeds maintained stable water uptake rate for both the seed and the embryo when temperatures decreased from 5 to –1 °C. In contrast, faster water uptake and greater relative K+leakage in small seeds indicated possible damage to membrane integrity at subzero temperatures. Carbohydrate conversion efficiency (Rq/RCO2) of large seeds was significantly higher than that of small seeds at 10 °C but not at 20 °C. Higher cold resistance in large seeds was also correlated with higher concentrations of glucose, raffinose, and sucrose. This study revealed the potential basis of the low-temperature germination advantage of large seeds and provided the first direct evidence of germination under freezing temperatures in winterfat.
Photosynthesis and physiological traits of evergreen broadleafed saplings during winter under different light environments in a temperate forest
Authors: Miyazawa Yoshiyuki , Kikuzawa Kihachiro
Published: April 2006

Photosynthetic traits of the evergreen broadleafed species Camellia japonica L. and Quercus glauca Thunb. were continuously investigated during autumn and winter using saplings that grew in different light environments (gap, deciduous canopy understory, and evergreen canopy understory) in a temperate forest. Light-saturated rates of net photosynthesis in midwinter and spring were lower than those in autumn. Photosynthetic capacity, scaled to a common leaf temperature of 25 °C, increased or remained stable after autumn and then decreased in spring in most leaves. Photosynthetic traits per unit leaf area were different among leaves in different light environments of both Camellia and Quercus during most periods. However, photosynthetic traits per unit leaf mass did not differ among leaves in different light environments, suggesting that differences in photosynthetic traits were mainly due to different leaf mass per area among leaves. Photosynthetic rates under light availability typical in the environment were lower in winter than in autumn in leaves in the sun in a gap but were not different in leaves in the shade under evergreen canopy trees. Thus, the importance of winter carbon gain for annual carbon gain is small in leaves in a gap but is large in leaves under evergreen canopy trees.
Contrasting terrestrial lichen, liverwort, and moss diversity between old-growth and young second-growth forest on two soil textures in central British Columbia
Authors: Botting Rachel S. , Fredeen Arthur L.
Published: April 2006

The diversity and abundance of terrestrial lichens, mosses, and liverworts were examined and compared between two ages of forest (old-growth and young second-growth) on two dominant soil types (fine- and coarse-textured soils) in subboreal spruce forests in central British Columbia. Major differences in species composition were found between forest ages, with 30% of species found only in old-growth forest and 21% found only in young second-growth forest. Liverworts were much more common in old-growth sites with half the liverwort species found exclusively in old-growth, and 90% of the recorded liverwort observations occurring there. Different moss species assemblages dominated old-growth and second-growth sites, with much of the terrestrial cover of second-growth sites composed of Polytrichum juniperinum Hedw. Young second-growth forest had higher cover of lichen species than old-growth forest. Lichens and bryophytes used different terrestrial substrates in each forest age, with higher cover of mosses and lichens occurring on woody substrates in old-growth, irrespective of substrate availability. Nonmetric multidimensional scaling ordination clearly separated plots by forest age and also showed soil texture to be a defining variable. Though not statistically significant, there was increased bryophyte diversity on coarse-textured soils and increased lichen cover on fine-textured soils.
Studies inCrataegusseriesCoccineae. I. Delimitation of series
Authors: Macklin J.A. , Phipps J.B.
Published: April 2006

The conventional concept of Crataegus series Coccineae was used as an hypothesis to test its validity when subjected to a morphometric analysis. Putative outgroups Crataegus ellwangeriana Sarg., ser. Molles , and ser. Dilatatae were included to test the limits of ser. Coccineae, and more distantly related ser. Punctatae and ser. Crataegus were included to provide scale. Multivariate studies based on substantial sample sizes and attribute lists were used to determine optimal group structure. We demonstrate that the group customarily called ser. Coccineae is cohesive. Crataegus ellwangeriana clearly proves to be outside of ser. Coccineae as are the close outgroups ser. Molles and ser. Dilatatae.