共查询到20条相似文献,搜索用时 0 毫秒
1.
The pollination of one plant species can be facilitated by the presence of one or more neighboring plant species and evidence
has been found in some rewardless species of orchid that benefit from the presence of rewarding plant species in the neighborhood.
There are two pollination mechanisms by which a non-rewarding orchid attracts pollinators and increases its reproductive success:
(1) A magnetic species effect that occurs even though the flowers do not resemble those of the other species, and (2) floral
mimicry where the mimic’s flower resembles that of the model plant species. Oncidium cosymbephorum is a Mexican rewardless epiphytic orchid whose flowers look like those of the rewarding shrub Malpighia glabra (Malpighiaceae). The resemblance of O. cosymbephorum to the oil-offering flowers of M. glabra attracts the same pollinators, and the fitness of the orchid is higher when M. glabra is present than when it is absent. We evaluated the facilitation by M. glabra of the orchid’s pollination for natural and artificial clumps of O. cosymbephorum close to and far from M. glabra over 4 years. Two experiments were performed at five different study sites to evaluate the effect of the presence and absence
of M. glabra on the reproductive success of O. cosymbephorum. In experiment 1, we recorded fruit set production in natural and artificial monospecific clumps of the orchid, and in natural
and artificial heterospecific clumps of O. cosymbephorum and M. glabra. In experiment 2, we recorded the fruit set of O. cosymbephorum at different sites where individuals grow in monospecific clumps, both before and after cultivated individuals of oil-producing
M. glabra had been planted in their vicinity. Both experiments showed that the reproductive success of O. cosymbephorum was greater in the presence of M. glabra than it was in its absence. This study provides experimental evidence for the magnetic species effect. Floral similarity
between O. cosymbephorum and M. glabra, should be experimentally tested to determine whether it is adaptive. 相似文献
2.
Variation in plant resistance to pathogen infection is commonly observed in interactions between wild plants and their foliar
pathogens. Models of host–pathogen interactions indicate that a large cost of infection is generally necessary to maintain
this variation, yet there is limited evidence that foliar pathogens cause detectable fitness reductions in wild host plants.
Most published work has focused on fungal pathogens. Pseudomonas viridiflava, a common bacterial pathogen of the annual weed Arabidopsis thaliana across its range, comprises two distinct genetic clades that cause disease symptoms of different severity. Here we measured
the extent of infection of wild A. thaliana populations in the Midwest, USA, and examined the effect on seed production, in field and growth-chamber experiments, of
experimental inoculation with isolates from the two clades. We found infection with P. viridiflava varied from 0 to 56% in Midwest A. thaliana populations, with the possibility of several leaves per plant infected later in the growing season. In the growth chambers,
experimental inoculation reduced seed set by averages of 15 and 11% for clades A and B, respectively. In the field experiment,
only clade A affected plant fitness significantly, reducing seed set by an average of 38%. Underlying these average effects
we observed both negative and positive effects of infection, and variation in both fitness among plant genotypes and sensitivity
to environmental conditions. 相似文献
3.
Common yew (Taxus baccata L.) stands are recognized as prioritary habitats for biodiversity conservation within the European Union. The effects of
browsing on the regeneration capacity and spatial dispersal of T. baccata recruits at the European southern limit of the species in the Mediterranean Basin have been herein studied. The efficacy
of T. baccata recruitment has been evaluated at six localities in the Northern Sardinia mountains, which have similar altitude, climate,
soil, and vegetation but have different types of uses (three were grazed by livestock and three were not). At each site, five
habitats have been identified for T. baccata seed dispersal: reproductive female T. baccata canopy, reproductive female Ilex aquifolium canopy, non-fleshy-fruited tree canopy, fleshy-fruited shrubs, and open areas. The density of seedlings was found to be greater
under fleshy-fruited trees (reproductive female T. baccata and I. aquifolium) than under shrubs, whereas the sapling density was higher in shrubby habitats, especially at grazed sites due to the mechanical
protection afforded by the spiny shrubs against herbivores. Land use (LU) has been found to be the most important factor in
determining the spatial distribution of seedlings and saplings in relation to forest habitats. Although browsers had an ephemeral
but positive effect on seed germination through their trampling and the resultant scarification, this process eventually became
ineffective as was shown by the occurrence of the lowest density of saplings in those habitats where the density of seedlings
was the highest. The ultimate and most important effect of browsing was the sharp decrease in the density of saplings, and
their almost complete extinction, in non-shrubby habitats. This study highlights the result that, in Mediterranean ecosystems,
browsing constitutes the main negative factor on T. baccata seedling-sapling transition and furthermore confirms the necessity to preserve shrubby patches in the vicinity of reproductive
female T. baccata and I. aquifolium to permit the regeneration of T. baccata in the presence of livestock. Moreover, at ungrazed sites, T. baccata is able to colonize non-shrubby shady habitats. The application of different management strategies to ungrazed and grazed
sites should therefore be the main direction in the management and preservation of T. baccata stands in the Mediterranean region. 相似文献
4.
Elizabete S. Cândido Jackeline L. Pereira Alice M. Quezado-Duval Eliane F. Noronha Ricardo H. Krüger Betania F. Quirino 《World journal of microbiology & biotechnology》2008,24(2):163-170
Bacterial spot caused by Xanthomonas spp. is an important tomato and pepper disease worldwide. Recent outbreaks of bacterial spot disease in Central Brazil and
Canada have been attributed to Xanthomonas gardneri, which is also recognized as group D of Xanthomonas campestris pv. vesicatoria. Carotenoid-like pigments called xanthomonadins, which are diagnostic for yellow Xanthomonas spp., were extracted from X. gardneri. It was shown that the model plant Arabidopsis thaliana, member of the Brassicaceae family, can develop disease symptoms in response to different isolates of X. gardneri. Secretion of enzymes has been shown to play an important role in pathogenicity for different pathogens, and to begin to
understand the interaction of X. gardneri and A. thaliana, a biochemical analysis of secreted proteins in the presence of A. thaliana leaves was performed. Different enzymatic activities such as for cellulase, α-arabinofuranosidase, pectinase, invertase and
xylanase were assayed. In the presence of leaves, cellulase activity was highest after 60 and 72 h of growth and α-arabinofuranosidase
activity was detected between 12 and 72 h of growth. Pectinase, invertase and xylanase activities were not detected. Cellulase
and α-arabinofuranosidase activities may be important for X. gardneri acquisition of plant nutrients through degradation of cellulose fibers and hemicellulose of the cell wall, respectively,
to the invasion of the host tissue and/or may generate signal molecules that are recognized by the plant. This is the first
study to address how X. gardneri responds to host plant tissue. 相似文献
5.
Kevin J. Delaney 《Plant Ecology》2008,199(2):187-200
Insect herbivory has variable effects on plant physiology; so greater understanding is needed about how injury alters photosynthesis
on individual injured and uninjured leaves. Gas exchange and light-adapted leaf chlorophyll fluorescence measurements were
collected from uninjured and mechanical partial leaf defoliation in two experiments with Nerium oleander (Apocynaceae) leaves, and one experiment with Danaus plexippus herbivory on Asclepias curassavica (Asclepiadaceae) leaves. Gas exchange impairment (lower photosynthetic rate (P
n
), stomatal conductance (g
s)) indicates water stress in a leaf, suggests stomatal limitations causing injury P
n
impairment. The same pattern of gas exchange impairment also occurred on uninjured leaves opposite from injured leaves in
both N. oleander experiments. This is an interesting result because photosynthetic impairment is rarely reported on injured leaves near injured
leaves. No photosynthetic changes occurred in uninjured A. curassavica leaves opposite from D. plexippus-fed leaves. Partially defoliated leaves that had P
n
and g
s reductions lacked any significant changes in intercellular leaf [CO2], C
i. These results neither support, nor are sufficient to reject, stomatal limitations to photosynthesis. Manually imposed midrib
vein severance in N. oleander experiment #1 significantly increased leaf C
i, indicating mesophyll limitations to photosynthesis. Maximal light-adapted leaf photochemical efficiency () and also non-photochemical quenching (q
N) were reduced by mechanical or insect herbivory to both study species, suggesting leaf trouble handling excess light energy
not used for photochemistry. Midrib injury on N. oleander leaves and D. plexippus herbivory on A. curassavica leaves also reduced effective quantum yield (ΦPSII) and photochemical quenching (q
P); so reduced plastoquinone pools could lead to additional PSII reaction center closure. 相似文献
6.
Carlos Neira Lisa A. Levin Edwin D. Grosholz Guillermo Mendoza 《Biological invasions》2007,9(8):975-993
In coastal wetlands, invasive plants often act as ecosystem engineers altering flow, light and sediments which, in turn, can
affect benthic animal communities. However, the degree of influence of the engineer will vary significantly as it grows, matures
and senesces, and surprisingly little is known about how the influence of an ecosystem engineer varies with ontogeny. We address
this issue on the tidal flats of San Francisco Bay where hybrid Spartina (foliosa × alterniflora) invaded 30 years ago. The invasion has altered the physico-chemical properties of the sediment habitat, which we predicted
should cause changes in macrofaunal community structure and function. Through mensurative and manipulative approaches we investigated
the influence of different growth stages of hybrid Spartina on macrobenthos and the underlying mechanisms. Cross-elevation sampling transects were established covering 5 zones (or stages)
of the invasion, running from the tidal flat (pre-invasion) to an unvegetated dieback zone. Additionally, we experimentally
removed aboveground plant structure in the mature (inner) marsh to mimic the ’unvegetated areas’. Our results revealed four
distinct faunal assemblages, which reflected Spartina-induced changes in the corresponding habitat properties along an elevation gradient: a pre-invaded tidal flat, a leading
edge of immature invasion, a center of mature invasion, and a senescing dieback area. These stages of hybrid Spartina invasion were accompanied by a substantial reduction in macrofaunal species richness and an increase in dominance, as well
as a strong shift in feeding modes, from surface microalgal feeders to subsurface detritus/Spartina feeders (mainly tubificid oligochaetes and capitellid polychaetes). Knowledge of the varying influence of plant invaders
on the sediment ecosystem during different phases of invasion is critical for management of coastal wetlands. 相似文献
7.
Summary. A novel practical method for the synthesis of N-methyl-DL-aspartic acid 1 (NMA) and new syntheses for N-methyl-aspartic acid derivatives are described. NMA 1, the natural amino acid was synthesized by Michael addition of methylamine to dimethyl fumarate 5. Fumaric or maleic acid mono-ester and -amide were regioselectively transformed into beta-substituted aspartic acid derivatives.
In the cases of maleamic 11a or fumaramic esters 11b, the α-amide derivative 13 was formed, but hydrolysis of the product provided N-methyl-DL-asparagine 9 via base catalyzed ring closure to DL-α-methylamino-succinimide 4, followed by selective ring opening. Efficient methods were developed for the preparation of NMA-α-amide 13 from unprotected NMA via sulphinamide anhydride 15 and aspartic anhydride 3 intermediate products. NMA diamide 16 was prepared from NMA dimethyl ester 6 and methylamino-succinimide 4 by ammonolysis. Temperature-dependent side reactions of methylamino-succinimide 4 led to diazocinone 18, resulted from self-condensation of methylamino-succinimide via nucleophyl ring opening and the subsequent ring-transformation. 相似文献
8.
The relationship between Sporidiobolus johnsonii and S. salmonicolor was investigated using rDNA sequence data. Two statistically well-supported clades were obtained. One clade included the
type strain of S. johnsonii and the other included the type strain of S. salmonicolor. However, some mating strains of S. salmonicolor were found in the S. johnsonii group. These strains belonged to mating type A2 and were sexually compatible with mating type A1 strains from the S. salmonicolor group. DNA–DNA reassociation values were high within each clade and moderate between the two clades. In the re-investigation
of teliospore germination, we observed that the basidia of S. salmonicolor were two-celled. In S. johnsonii, basidia were not formed and teliospore germination resulted in direct formation of yeast cells. We hypothesize that the
S. johnsonii clade is becoming genetically isolated from the S. salmonicolor group and that a speciation process is presently going on. We suspect that the observed sexual compatibility between strains
of the S. johnsonii and S. salmonicolor groups and the possible genetic flow between the two species has little biological relevance because distinct phenotypes
have been fixed in the two taxa and intermediate (hybrid) sequences for LSU and ITS rDNAs have not been detected.
An erratum to this article can be found at 相似文献
9.
Three C-glycosylflavones in the leaves of Oxalis corniculata, the host plant of the lycaenid butterfly pale grass blue (Pseudozizeeria maha), were identified as 6-C-glucosylluteolin (isoorientin), 6-C-glucosylapigenin (isovitexin) and isovitexin 7-methyl ether (swertisin). Comparative spectral and HPLC analyses between the
leaf extract of the host plants and the wings of P. maha showed selective uptake of the host-plant flavonoid isovitexin to the wings of the butterfly. 相似文献
10.
Divol F Vilaine F Thibivilliers S Amselem J Palauqui JC Kusiak C Dinant S 《Plant molecular biology》2005,57(4):517-540
Little is known about the molecular processes involved in the phloem response to aphid feeding. We investigated molecular responses to aphid feeding on celery (Apium graveolenscv. Dulce) plants infested with the aphid Myzus persicae, as a means of identifying changes in phloem function. We used celery as our model species as it is easy to separate the phloem from the surrounding tissues in the petioles of mature leaves of this species. We generated a total of 1187 expressed sequence tags (ESTs), corresponding to 891 non-redundant genes. We analysed these ESTs in silico after cDNA macroarray hybridisation. Aphid feeding led to significant increase in RNA accumulation for 126 different genes. Different patterns of deregulation were observed, including transitory or stable induction 3 or 7days after infestation. The genes affected belonged to various functional categories and were induced systemically in the phloem after infestation. In particular, genes involved in cell wall modification, water transport, vitamin biosynthesis, photosynthesis, carbon assimilation and nitrogen and carbon mobilisation were up-regulated in the phloem. Further analysis of the response in the phloem or xylem suggested that a component of the response was developed more specifically in the phloem. However, this component was different from the stress responses in the phloem driven by pathogen infection. Our results indicate that the phloem is actively involved in multiple adjustments, recruiting metabolic pathways and in structural changes far from aphid feeding sites. However, they also suggest that the phloem displays specific mechanisms that may not be induced in other tissues.EST, macroarray and clustering data are available from our website [http://www-biocel.versailles.inra.fr/phloem]. Data deposition: The sequences reported in this paper have been deposited in the Genbank database (Accession nos.: AY607692-AY607700, AY611007, CN253939-CN255151, CV512445-CV512447 and CV651120-CV651121). 相似文献
11.
Chemical defense,mycorrhizal colonization and growth responses in <Emphasis Type="Italic">Plantago lanceolata</Emphasis> L. 总被引:1,自引:0,他引:1
Gerlinde Barbra De Deyn A. Biere W. H. van der Putten R. Wagenaar J. N. Klironomos 《Oecologia》2009,160(3):433-442
Allelochemicals defend plants against herbivore and pathogen attack aboveground and belowground. Whether such plant defenses
incur ecological costs by reducing benefits from plant mutualistic symbionts is largely unknown. We explored a potential trade-off
between inherent plant chemical defense and belowground mutualism with arbuscular mycorrhizal fungi (AMF) in Plantago lanceolata L., using plant genotypes from lines selected for low and high constitutive levels of the iridoid glycosides (IG) aucubin
and catalpol. As selection was based on IG concentrations in leaves, we first examined whether IG concentrations covaried
in roots. Root and leaf IG concentrations were strongly positively correlated among genotypes, indicating genetic interdependence
of leaf and root defense. We then found that root AMF arbuscule colonization was negatively correlated with root aucubin concentration.
This negative correlation was observed both in plants grown with monocultures of Glomus intraradices and in plants colonized from whole-field soil inoculum. Overall, AMF did not affect total biomass of plants; an enhancement
of initial shoot biomass was offset by a lower root biomass and reduced regrowth after defoliation. Although the precise effects
of AMF on plant biomass varied among genotypes, plants with high IG levels and low AMF arbuscule colonization in roots did
not produce less biomass than plants with low IG and high AMF arbuscule colonization. Therefore, although an apparent trade-off
was observed between high root chemical defense and AMF arbuscule colonization, this did not negatively affect the growth
responses of the plants to AMF. Interestingly, AMF induced an increase in root aucubin concentration in the high root IG genotype
of P. lanceolata. We conclude that AMF does not necessarily stimulate plant growth, that direct plant defense by secondary metabolites does
not necessarily reduce potential benefits from AMF, and that AMF can enhance concentrations of root chemical defenses, but
that these responses are plant genotype-dependent. 相似文献
12.
The reserve ovary model is a key hypothesis proposed to explain why plants produce surplus flowers and posits that plants may utilize surplus flowers
to compensate for losses from floral herbivory. We tested this hypothesis in the prairie plant Eryngium yuccifolium and its floral herbivore Coleotechnites eryngiella. At five Illinois tallgrass prairie sites, we collected central, primary lateral, and secondary lateral inflorescences from
E. yuccifolium to determine whether damage by the larvae of C. eryngiella to the flowers in earlier developing inflorescences would be compensated for in later developing inflorescences. Coleotechnites eryngiella does extensive damage to the central and primary inflorescences and little damage to the secondary inflorescences. Later
maturing inflorescences did not compensate for early damage by increasing seed production in later inflorescences. The secondary
inflorescences of E. yuccifolium may only compensate for catastrophic damage done to the central and primary inflorescences early on in development, serve
as additional advertisements for pollinators, act as pollen donors, or allow the plant to take advantage of “ecological windows”
of high pollinator and low herbivore abundance. Our findings were spatially and temporally consistent and did not support
the predictions of the reserve ovary model in the E. yuccifolium–C. eryngiella system suggesting that in this system, alternate, proximate, and ultimate causes need to be explored for the production of
surplus flowers. 相似文献
13.
Animals that consume plant parts or rewards but provide no services in return are likely to have significant impacts on the
reproductive success of their host plants. The effects of multiple antagonists to plant reproduction may not be predictable
from studying their individual effects in isolation. If consumer behaviors are contingent on each other, such interactions
may limit the ability of the host to evolve in response to any one enemy. Here, we asked whether nectar robbing by a bumblebee
(Bombus occidentalis) altered the likelihood of pre-dispersal seed predation by a fly (Hylemya sp.) on a shared host plant, Ipomopsis aggregata (Polemoniaceae). We estimated the fitness consequences of the combined interactions using experimental manipulations of nectar
robbing within and among sites. Within sites, nectar robbing reduced the percentage of fruits destroyed by Hylemya. However, the negative effects of robbing on seed production outweighed any advantages associated with decreased seed predation
in robbed plants. We found similar trends among sites when we manipulated robbing to all plants within a local population,
although the results were not statistically significant. Taken together, our results suggest that seed predation is not independent
of nectar robbing. Thus, accounting for the interactions among species is crucial to predicting their ecological effects and
plant evolutionary response. 相似文献
14.
Summary. Polyamines, in particular spermine, as well as some natural and synthetic polyamine derivatives have been found to be blockers
of N-methyl-d-aspartate receptors. We developed novel, polyamine-based channel blockers to analyze the structure of NMDA receptors. Anthraquinone
polyamines block NMDA receptors with some selectivity compared to other glutamate receptors. Results using mutant NR1 and
NR2 subunits identified amino acid residues that influence blockade by anthraquinone polyamines. The head group (anthraquinone)
may be positioned at the selectivity filter/narrowest constriction of the channel and the polyamine tail penetrates this constriction
into the inner vestibule below the level of the selectivity filter. The results are consistent with other work showing that
NR1 (Asn616) and NR2B (Asn616), but not NR2B (Asn615), make the narrowest constriction of NMDA channel, and that the M3 segments
from the two subunits, which form the outer vestibule, are likely staggered relative to each other in the vertical axis of
the channel. 相似文献
15.
Summary. Hydrogensquarates of dipeptide l-threonyl-l-serine (H-Thr-Ser-OH) and l-serine (HSq × Ser) have been synthesized, isolated and spectroscopic characterized by solid-state linear-polarized IR-spectroscopy, 1H- and 13C-NMR, ESI-MS and HPLC with tandem masspectrometry (MS-MS) methods. The structures of the salts and neutral dipeptide have
been predicted theoretically by ab initio calculations. In the case of H-Thr-Ser-OH the theoretical data are supported by IR-LD ones. The hydrogensquarates consist in positive charged dipeptide or amino acid
moiety and negative hydrogensquarate anion (HSq) stabilizing by strong intermolecular hydrogen bonds. The data about the l-serine hydrogensquarate are compared with known crystallographic data thus indicating a good correlation between the theoretical
predicted structures and experimentally obtained by single crystal X-ray diffraction. 相似文献
16.
Allopatric populations sometimes display reproductive barriers in incipient form, and may thus reveal potential mechanisms
of speciation. We conducted mating trials to estimate the degree of precopulatory (behavioral) and postcopulatory (gametic)
prezygotic isolation between African and Asian populations of the seed beetle Callosobruchus maculatus. The populations differ in several fitness-related traits, and have been associated with different legume hosts. In single-pair
trials, the probability of copulation within 10 min was lower when Asian females were paired with African males than it was
in the other three pairing combinations. This pairing also provided evidence for gametic isolation, as Asian females mated
once to African males laid fewer eggs than did females in the other treatments. Variation in fecundity could not be explained
by the duration of copulation, which did not differ among pairing combinations. There was also no effect of pairing combination
on the number of copulation attempts, latency to copulation, or rate of egg hatch. When females were simultaneously presented
a male from each population, Asian males obtained a disproportionate share of the matings, and were more likely to disturb
a pair already in copulo. Surprisingly, male size did not influence the probability of copulation in the single-male trials, the outcome of male–male
competition, or the fecundity of once-mated females. Although the African and Asian populations showed some evidence of mating
incompatibility, the absence of symmetrical isolating factors suggests minimal barriers to gene flow. 相似文献
17.
Crop to weed transgene flow, which could result in more competitive weed populations, is an agricultural biosafety concern.
Crop Brassica napus to weedy Brassica rapa hybridization has been extensively characterized to better understand the transgene flow and its consequences. In this study,
weedy accessions of B. rapa were transformed with Bacillus thuringiensis (Bt) cry1Ac- and green fluorescence protein (gfp)-coding transgenes using Agrobacterium to assess ecological performance of the wild biotype relative to introgressed hybrids in which the transgenic parent was
the crop. Regenerated transgenic B. rapa events were characterized by progeny analysis, Bt protein enzyme-linked immunosorbent assay (ELISA), Southern blot analysis,
and GFP expression assay. GFP expression level and Bt protein concentration were significantly different between independent
transgenic B. rapa events. Similar reproductive productivity was observed in comparison between transgenic B. rapa events and B. rapa × B. napus introgressed hybrids in greenhouse and field experiments. In the greenhouse, Bt transgenic plants experienced significantly
less herbivory damage from the diamondback moth (Plutella xylostella). No differences were found in the field experiment under ambient, low, herbivore pressure. Directly transformed transgenic
B. rapa plants should be a helpful experimental control to better understand crop genetic load in introgressed transgenic weeds. 相似文献
18.
Correlation between plant size and reproductive output may be modified by herbivory in accordance with host plant density
and the presence of nonhost plants. To elucidate the effects of nonhost plant density and host plant density on the intensity
of herbivory and reproductive output of the host plant in relation to plant size under natural conditions, we investigated
the abundance of three lepidopteran insects, Plutella maculipennis, Anthocharis scolymus, and Pieris rapae the intensity of herbivory, and fruit set of their host plant, Turritis glabra (Cruciferae). To elucidate the effects of nonhost and host plant density, we selected four categories of plots under natural
conditions: low density of nonhost and high density of host plants; low density of both nonhost and host plants; high density
of both nonhost and host plants; and high density of nonhost and low density of host plants. The plant size indicated by stem
diameter was a good predictor of the abundance of all herbivorous species. The effects of density of nonhost and host plants
on the abundance of insects varied among species and stages of insects. As the abundance of insects affected the intensity
of herbivory, herbivory was more apparent on larger host plants in plots with low density of both nonhost and host plants.
Consequently, the correlation between plant size and the number of fruits disappeared in low plots with density of both nonhost
and host plants. In this T. glabra– herbivorous insect system, the density of nonhost plants and host plants plays an important role in modifying the relationship
between plants and herbivores under natural conditions.
Received: July 19, 1999 / Accepted: June 15, 2000 相似文献
19.
Kottakis F Lamari F Matragkou Ch Zachariadis G Karamanos N Choli-Papadopoulou T 《Amino acids》2008,34(3):413-420
Summary. Arabino-Galactan Proteins (AGPs) were isolated from Chios mastic gum (CMG) by using a buffer containing 0.1 M NaCl, 20 mM
Tris–HCl, pH 7.5. Protein analytical methods, combined with specific procedures for carbohydrate characterization, indicated
the presence of highly glycosylated protein backbone. In particular, staining by Yariv reagent of the electrophoretically
separated molecules revealed the existence of arabinose and galactose and such a modification is characteristic for AGPs.
After experiments involving extensive dialysis of the isolated extracts against water and atomic absorption, there was evidence
of the existence of zinc ions that are probably covalently bound to the AGPs. By using anion-exchange chromatography, capillary
electrophoresis, colorimetric methods and GC-MS, it was found that the extracts were separated into three major populations
(A, B, and C), which were consistent with their respective negative charge content namely, uronic acid. The characterization
of neutral sugars that was investigated with GC-MS showed the existence of arabinose and galactose in different amounts for
each group.
Experiments concerning the inhibition of growth of Helicobacter pylori in the presence of AGPs, as is shown for other CMG constituents, showed that the extracts of at least 1.4 g CMG affected
the viability of the bacterium. There is no evidence as to whether the AGPs provoke abnormal morphologies of H. pylori, as is reported for the total CMG, or for O-glycans that possess terminal α1, 4-linked N-acetylglucosamine and are expressed
in the human gastric mucosa; this has to be further investigated.
Authors’ address: Theodora Choli-Papadopoulou, Laboratory of Biochemistry, School of Chemistry, Aristotle University of Thessaloniki,
TK 54124 Thessaloniki, Greece 相似文献
20.
Jorge A. Zavala Clare L. Casteel Paul D. Nabity May R. Berenbaum Evan H. DeLucia 《Oecologia》2009,161(1):35-41
Elevated levels of CO2, equivalent to those projected to occur under global climate change scenarios, increase the susceptibility of soybean foliage to herbivores by down-regulating the expression of genes related to the defense hormones jasmonic acid and ethylene; these in turn decrease the gene expression and activity of cysteine proteinase inhibitors (CystPIs), the principal antiherbivore defenses in foliage. To examine the effects of elevated CO2 on the preference of Japanese beetle (JB; Popillia japonica) for leaves of different ages within the plant, soybeans were grown at the SoyFACE facility at the University of Illinois at Urbana-Champaign. When given a choice, JB consistently inflicted greater levels of damage on older leaves than on younger leaves, and there was a trend for a greater preference for young leaves grown under elevated CO2 compared to those grown under ambient CO2. More heavily damaged older leaves and those grown under elevated CO2 had reduced CystPI activity, and JB that consumed leaves with lower CystPI activity had correspondingly greater gut proteinase activity. Younger leaves with higher CystPI activity and photosynthetic rates may contribute disproportionately to plant fitness and are more protected against herbivore attack than older foliage. Cysteine proteinase inhibitors are potent defenses against JB, and the effectiveness of this defense is modulated by growth under elevated CO2 as well as leaf position. 相似文献