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971.
James Beardmore 《Journal of inorganic biochemistry》2009,103(2):205-209
We have used a systems biology approach to address the hitherto insoluble problem of the quantitative analysis of non-equilibrium binding of aqueous metal ions by competitive ligands in heterogeneous media. To-date, the relative proportions of different metal complexes in aqueous media has only been modelled at chemical equilibrium and there are no quantitative analyses of the approach to equilibrium. While these models have improved our understanding of how metals are used in biological systems they cannot account for the influence of kinetic factors in metal binding, transport and fate. Here we have modelled the binding of aluminium, Al(III), in blood serum by the iron transport protein transferrin (Tf) as it is widely accepted that the biological fate of this non-essential metal is not adequately described by experiments, invitro and insilico, which have consistently demonstrated that at equilibrium 90% of serum Al(III) is bound by Tf. We have coined this paradox ‘the blood-aluminium problem’ and herein applied a systems biology approach which utilised well-found assumptions to pare away the complexities of the problem such that it was defined by a comparatively simple set of computational rules and, importantly, its solution assumed significant predictive capabilities. Here we show that our novel computational model successfully described the binding of Al(III) by Tf both at equilibrium and as equilibrium for AlTf was approached. The model predicted significant non-equilibrium binding of Al by ligands in competition with Tf and, thereby, provided an explanation of why the distribution of Al(III) in the body cannot be adequately described by its binding and transport by Tf alone. Generically the model highlighted the significance of kinetic in addition to thermodynamic constraints in defining the fate of metal ions in biological systems. 相似文献
972.
David?NoshadEmail author Saber?Miresmaili Andrew?Riseman Abul?Ekramoddoullah 《Plant Cell, Tissue and Organ Culture》2009,96(2):201-209
Cultures of seven Daphne species: Daphne caucasica, D. cneorum, D. giraldii, D. retusa, D. jasminea, D. laureola and D. tangutica were established in vitro on MS/WPM based media. Five of the species responded best on MS-based media (D. tangutica, D. laureola, D. caucasica, D. retusa and D. giraldii), while the remaining two species performed best on WPM-based media (D. cneorum, and D. jasminea). Shoot proliferation was achieved from both apical and nodal explants. Shoots were sub-cultured from stock cultures, cut
into nodal explants 3–5 cm long and place vertically on basal media supplemented with different concentrations and combinations
of cytokinins and auxins. Individual species displayed different responses to the various cytokinins and auxins. Among species,
D. jasminea produced the greatest proliferation rate with an average of 7.84 + 0.6 shoots per explant on WPM supplemented with 2.32 μM
BA + 0.0045 μM TDZ + 0.054 μM NAA, while the best multiplication rate for the same species grown on the same media supplemented
with a single cytokinin (BA) and no auxin was 2.60 + 1.3 shoots per explant. Following multiplication, new shoots transferred
to the elongation trails and then 50–100 mm Shoots used for rooting experiments. Increased rooting efficiencies were observed
on in vitro-generated shoots with the two-layer medium or dipping methods over when PGRs were uniformly incorporated into
the medium. Maximum rooting frequencies (average) ranged from 59% in D. tangutica to 85% in D. jasminea. Following in vitro rooting, rooted shoots immersed in 0.01% solution of humates and planted into a standard horticultural
substrate composed and watered weekly with a solution containing half-strength MS salts. 相似文献
973.
Effects of brassinosteroids on barley root growth,antioxidant system and cell division 总被引:1,自引:0,他引:1
Gonul Kartal Aslihan Temel Ercan Arican Nermin Gozukirmizi 《Plant Growth Regulation》2009,58(3):261-267
Homobrassinolide (HBR), which is one of the most biologically active forms of Brassinosteroids (BRs), was used to examine
the potential effects of hormone on root germination, antioxidant system enzymes and cell division of barley (Hordeum vulgare L.). Seeds were germinated between filter papers in 0.1, 0.5 and 1.0 μM HBR-supplemented distilled water for 48 h at dark
with their controls. HBR application increased especially the primary root growth significantly with increasing concentrations
when compared with the control materials and reached two fold increase in 1.0 μM HBR treated material. Treated and untreated
control group roots were fixed in 1:3 aceto-alcohol and aceto-orcein preparations were made. Roots treated with HBR showed
more mitotic activity, mitotic abnormalities and significant enlargements at the root tips when compared with control material.
HBR application decreased total soluble protein content, superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6) and peroxidase
(EC 1.11.1.11) activities significantly at 1.0 μM HBR concentration. Data presented here is one of the first detailed analyses
of HBR effect on barley root development. 相似文献
974.
Sandra J. Bucci Fabian G. Scholz Guillermo Goldstein Frederick C. Meinzer Maria E. Arce 《Oecologia》2009,160(4):631-641
Adaptations of species to capture limiting resources is central for understanding structure and function of ecosystems. We
studied the water economy of nine woody species differing in rooting depth in a Patagonian shrub steppe from southern Argentina
to understand how soil water availability and rooting depth determine their hydraulic architecture. Soil water content and
potentials, leaf water potentials (ΨLeaf), hydraulic conductivity, wood density (ρw), rooting depth, and specific leaf area (SLA) were measured during two summers. Water potentials in the upper soil layers
during a summer drought ranged from −2.3 to −3.6 MPa, increasing to −0.05 MPa below 150 cm. Predawn ΨLeaf was used as a surrogate of weighted mean soil water potential because no statistical differences in ΨLeaf were observed between exposed and covered leaves. Species-specific differences in predawn ΨLeaf were consistent with rooting depths. Predawn ΨLeaf ranged from −4.0 MPa for shallow rooted shrubs to −1.0 MPa for deep-rooted shrubs, suggesting that the roots of the latter
have access to abundant moisture, whereas shallow-rooted shrubs are adapted to use water deposited mainly by small rainfall
events. Wood density was a good predictor of hydraulic conductivity and SLA. Overall, we found that shallow rooted species
had efficient water transport in terms of high specific and leaf specific hydraulic conductivity, low ρw, high SLA and a low minimum ΨLeaf that exhibited strong seasonal changes, whereas deeply rooted shrubs maintained similar minimum ΨLeaf throughout the year, had stems with high ρw and low hydraulic conductivity and leaves with low SLA. These two hydraulic syndromes were the extremes of a continuum with
several species occupying different portions of a gradient in hydraulic characteristics. It appears that the marginal cost
of having an extensive root system (e.g., high ρw and root hydraulic resistance) contributes to low growth rates of the deeply rooted species. 相似文献
975.
The dicarboxylic acid malate has long been thought to play important roles in plant physiology. In addition to being a major photosynthate in C4 and CAM plants and an intermediate of the tricarboxylic acid cycle it has been proposed to play essential roles in pH regulation and important roles in pathogen response, as a component of the root exudates and as a regulatory osmolyte affecting stomatal function. Recent years have seen the cloning and functional analysis of a wide range of enzymes and transporters associated with malate metabolism. Here we attempt to provide a synthesis of research in this field as well as re-evaluating the role of this metabolite in mediating guard cell function. 相似文献
976.
Evarcha culicivora is an unusual salticid spider because each sex actively courts the other and both sexes make distinctive mate-choice decisions. Here we use olfactometer experiments for investigating the ability of each sex to identify potential mates on the basis of odour alone. Test spiders spent more time in the vicinity of opposite-sex conspecific source spiders, regardless of whether or not these source spiders had previously mated, when the alternatives were conspecific individuals of the same sex, juveniles or a control (no odour source). This trend held regardless of the test spider's and source spider's age after reaching maturity and, for male test spiders, it held regardless of the test spider's mating status. However, after females had mated they no longer expressed a preference for male odour. 相似文献
977.
The response regulator PhoP negatively regulates Yersinia pseudotuberculosis and Yersinia pestis biofilms 总被引:1,自引:0,他引:1
A few Yersinia pseudotuberculosis strains form biofilms on the head of the nematode Caenorhabditis elegans , but numerous others do not. We show that a widely used Y. pseudotuberculosis strain, YPIII, is biofilm positive because of a mutation in phoP , which encodes the response regulator of a two-component system. For two wild-type Y. pseudotuberculosis that do not make biofilms on C. elegans , deletion of phoP was sufficient to produce robust biofilms. In Yersinia pestis , a phoP mutant made more extensive biofilms in vitro than did the wild type. Expression of HmsT, a diguanylate cyclase that positively regulates biofilms, is diminished in Y. pseudotuberculosis strains with functional PhoP. 相似文献
978.
Hanne N. Rasmussen Bjarke Veierskov Jens Hansen-Møller Rikke Nørbæk Ulrik Bräuner Nielsen 《Journal of Plant Growth Regulation》2009,28(2):154-166
Conifer trees are routinely manipulated hormonally to increase flowering, branching, or adjust crown shape for production
purposes. This survey of internal cytokinin levels provides a background for such treatments in Abies nordmanniana, a tree of great economic interest. Reference points in the crown and root system were sampled destructively in 4- and 6-year-old
trees and analyzed for a range of cytokinins by LC-MS/MS. No seasonal patterns were detected in the root samples, and a major
portion of cytokinin was in conjugated forms. Dramatic and consistent seasonal changes occurred in the crown, at levels 17–65 times
higher than in the root. Predominant among crown cytokinins was ZR, except in the needles where IPR was also prominent. Within
the crown, cytokinin profiles in different organs differed consistently. The leader bud showed a pronounced mid-June minimum,
and a maximum later in summer. Subapical buds showed the same June minimum but peaked in mid autumn at a much lower level.
Maxima in these buds were preceded by peaks in the subapical stem. Parallel patterns were observed in homologous tissues on
branches.This pattern is consistent with two surges beginning in the uppermost stem tissues leading to subsequent accumulation
or stimulated production within the buds. Strong differential hormonal profiles between adjacent buds with different fates
agree with recent evidence of localized cytokinin production. The data suggest a reduced role of root-derived cytokinins in
crown development. Practical cytokinin treatments for crown-shape regulation require close attention to dosage as well as
precise timing and positioning. 相似文献
979.
Hiroki Miwa Atsuko Kinoshita Hiroo Fukuda Shinichiro Sawa 《Journal of plant research》2009,122(1):31-39
The plant meristems, shoot apical meristem (SAM) and root apical meristem (RAM), are unique structures made up of a self-renewing
population of undifferentiated pluripotent stem cells. The SAM produces all aerial parts of postembryonic organs, and the
RAM promotes the continuous growth of roots. Even though the structures of the SAM and RAM differ, the signaling components
required for stem cell maintenance seem to be relatively conserved. Both meristems utilize cell-to-cell communication to maintain
proper meristematic activities and meristem organization and to coordinate new organ formation. In SAM, an essential regulatory
mechanism for meristem organization is a regulatory loop between WUSCHEL (WUS) and CLAVATA (CLV), which functions in a non-cell-autonomous manner. This intercellular signaling network coordinates the development of the
organization center, organ boundaries and distant organs. The CLAVATA3/ESR (CLE)-related genes produce signal peptides, which act non-cell-autonomously in the meristem regulation in SAM. In RAM, it has
been suggested that a similar mechanism can regulate meristem maintenance, but these functions are largely unknown. Here,
we overview the WUS–CLV signaling network for stem cell maintenance in SAM and a related mechanism in RAM maintenance. We also discuss conservation
of the regulatory system for stem cells in various plant species.
S. Sawa is the recipient of the BSJ Award for Young Scientist, 2007. 相似文献
980.
Jukka Sakari Pumpanen Jussi Heinonsalo Terhi Rasilo Kaj-Roger Hurme Hannu Ilvesniemi 《Trees - Structure and Function》2009,23(3):611-621
Carbon dioxide is released from the soil to the atmosphere in heterotrophic respiration when the dead organic matter is used
for substrates for soil micro-organisms and soil animals. Respiration of roots and mycorrhiza is another major source of carbon
dioxide in soil CO2 efflux. The partitioning of these two fluxes is essential for understanding the carbon balance of forest ecosystems and for
modelling the carbon cycle within these ecosystems. In this study, we determined the carbon balance of three common tree species
in boreal forest zone, Scots pine, Norway spruce, and Silver birch with gas exchange measurements conducted in laboratory
in controlled temperature and light conditions. We also studied the allocation pattern of assimilated carbon with 14C pulse labelling experiment. The photosynthetic light responses of the tree species were substantially different. The maximum
photosynthetic capacity (P
max) was 2.21 μg CO2 s−1 g−1 in Scots pine, 1.22 μg CO2 s−1 g−1 in Norway spruce and 3.01 μg CO2 s−1 g−1 in Silver birch seedlings. According to the pulse labelling experiments, 43–75% of the assimilated carbon remained in the
aboveground parts of the seedlings. The amount of carbon allocated to root and rhizosphere respiration was about 9–26%, and
the amount of carbon allocated to root and ectomycorrhizal biomass about 13–21% of the total assimilated CO2. The 14CO2 pulse reached the root system within few hours after the labelling and most of the pulse had passed the root system after
48 h. The transport rate of carbon from shoot to roots was fastest in Silver birch seedlings. 相似文献