共查询到20条相似文献,搜索用时 353 毫秒
1.
Plant roots are known to orient growth through the soil by gravitropism, hydrotropism, and thigmotropism. Recent observations
of plant roots that developed in a microgravity environment in space suggested that plant roots may also orient their growth
toward oxygen (oxytropism). Using garden pea (Pisum sativum L. cv. Weibul's Apollo) and an agravitropic mutant (cv. Ageotropum), root oxytropism was studied in the controlled environment
of a microrhizotron. A series of channels in the microrhizotron allowed establishment of an oxygen gradient of 0.8 mmol · mol−1 · mm−1. Curvature of seedling roots was determined prior to freezing the roots for subsequent spectrophotometric determinations
of alcohol dehydrogenase activity. Oxytropic curvature was observed all along the gradient in both cultivars of pea. The normal
gravitropic cultivar showed a maximal curvature of 45° after 48 h, while the agravitropic mutant curved to 90°. In each cultivar,
the amount of curvature declined as the oxygen concentration decreased, and was linearly related to the root elongation rate.
Since oxytropic curvature occurred in roots exposed to oxygen concentrations that were not low enough to induce the hypoxically
responsive protein alcohol dehydrogenase, we suspect that the oxygen sensor associated with oxytropism does not control the
induction of hypoxic metabolism. Our results indicate that oxygen can play a critical role in determining root orientation
as well as impacting root metabolic status. Oxytropism allows roots to avoid oxygen-deprived soil strata and may also be the
basis of an auto-avoidance mechanism, decreasing the competition between roots for water and nutrients as well as oxygen.
Received: 14 January 1998 / Accepted: 10 February 1998 相似文献
2.
Molecular cloning and analysis of a pea cDNA that is expressed in darkness and very rapidly induced by gibberellic acid 总被引:6,自引:0,他引:6
Using cDNA representational difference analysis (cDNA RDA), we isolated a cDNA named GDA-1 from a cDNA library constructed
with mRNA from short-day (SD) grown G2 pea apical tissue. The amino acid sequence deduced from GDA-1 shares partial identity
with the B2 protein which is expressed during embryogenesis of carrot cells. Northern analysis showed that GDA-1 mRNA is abundant
in SD-grown G2 pea apical buds. In long-day (LD) conditions, there was almost no detectable GDA-1 mRNA. When LD-grown G2 peas
were kept in continuous darkness for 24 h, the GDA-1 mRNA content reached a level equivalent to about 50% of that in the SD
samples. On the other hand, when SD-grown peas were transferred into the light for 24 h, the amount of hybridizable GDA-1
mRNA dropped to the same as that of LD-grown plants. GDA-1 expression was found to be independent of flower initiation time.
GA3 application in vitro resulted in rapid accumulation of GDA-1 mRNA in LD-grown G2 pea apical buds, which is compatible with
its delaying effect on apical senescence. Time-course experiments revealed that GDA-1 is induced within 15 min of GA3 application. Exogenous GA3 did not influence the expression of GDA-1 in SD-grown G2 peas. Since both photoperiod and GA induce the expression of GDA-1,
we speculate that they may activate similar signal transduction pathways in G2 peas. Our work also shows that photoperiod
may change the efficiency of gibberellin perception by plants.
Received: 27 March 1998 / Accepted: 2 June 1998 相似文献
3.
Mycorrhizal and nonmycorrhizal roots of Allium schoenoprasum were tested for activities of α-mannosidase, β-glucosidase and arabinosidase. Mannosidase activity was higher by a factor
of two in mycorrhizal than in nonmycorrhizal root extracts. The apparent molecular weight of the enzyme was 152 kDa and its
KM was 1.25 mM in colonized roots and 1.85 mM in uncolonized roots. α-Mannosidase activity was further characterized by an acid
pH optimum and Zn2+ dependency. No significant differences could be found between mycorrhizal and nonmycorrhizal roots for β-glucosidase and
arabinosidase activities.
Accepted: 28 August 1995 相似文献
4.
Walter Maier Jürgen Schmidt Victor Wray Michael Herbert Walter Dieter Strack 《Planta》1999,207(4):620-623
Tobacco (Nicotiana tabacum L.) plants were grown with and without the arbuscular mycorrhizal fungus, Glomus intraradices Schenk & Smith. High-performance liquid chromatographic analyses of methanolic extracts from mycorrhizal and non-mycorrhizal
tobacco roots revealed marked fungus-induced changes in the patterns of UV-detectable products. The UV spectra of these products,
obtained from an HPLC photodiode array detector, indicated the presence of several blumenol derivatives. The most predominant
compound among these derivatives was spectroscopically identified as 13-hydroxyblumenol C 9-O-gentiobioside (“nicoblumin”), i.e. the 9-O-(6′-O-β-glucopyranosyl)-β-glucopyranoside of 13-hydroxy-6-(3-hydroxybutyl)-1,1,5-trimethyl-4-cyclohexen-3-one, a new natural product.
This is the first report on the identification of blumenol derivatives in mycorrhizal roots of a non-gramineous plant.
Received: 28 August 1998 / Accepted: 26 October 1998 相似文献
5.
I. R. Sanders R. Streitwolf-Engel M. G. A. van der Heijden T. Boller A. Wiemken 《Oecologia》1998,117(4):496-503
Prunella vulgaris was inoculated with different arbuscular mycorrhizal fungi (AMF) and grown at two concentrations of CO2 (ambient, 350 μl l−1, and elevated, 600 μl l−1) to test whether a plants response to elevated CO2 is dependent on the species of AMF colonizing the roots. Using compartments accessible only to AMF hyphae but not to roots,
we also tested whether elevated CO2 affects the growth of external AMF hyphae. Plant biomass was significantly greater at elevated than at ambient CO2; the biomass of the root system, for example, increased by a factor of 2. The colonization of AMF inside the root remained
constant, indicating that the total AMF inside the root system also increased by a factor of 2. The length of external AMF
hyphae at elevated CO2 was up to 5 times that at ambient CO2, indicating that elevated CO2 promoted allocation of AMF biomass to the external hyphae. The concentration and content of phosphorus in the stolons differed
significantly between ambient and elevated CO2 but this resulted in either an increase or a decrease, according to which AMF isolate occupied the roots. We hypothesized
that an increase in external hyphal growth at elevated CO2 would result in increased P acquistion by the plant. To test this we supplied phosphorus, in a compartment only accessible
to AMF hyphae. Plants did not acquire more phosphorus at elevated CO2 when phosphorus was added to this compartment. Large increases in AMF hyphal growth could, however, play a significant role
in the movement of fixed carbon to the soil and increase soil aggregation.
Received: 28 March 1998 / Accepted: 27 August 1998 相似文献
6.
The influence of mycorrhizal colonization on beech (Fagus sylvatica L.) root tannin (procyanidin polymer) and its putative precursors catechin and epicatechin was investigated by high performance
liquid chromatography. Seedlings planted in a sterile mixture of litter, compost, soil and sand were inoculated with brown
beech ectomycorrhizas collected from a woodland (Lactarius subdulcis Bull ex Fr. × F. sylvatica). The seedlings were not fertilized during the first year of growth. Nonmycorrhizal control plants showed severe nutrient-deficiency
symptoms on their leaves and grew less well than mycorrhizal plants. Mycorrhizal roots contained significantly less catechin,
epicatechin and procyanidin polymer than nonmycorrhizal roots. In the second year of growth, the plants were fertilized and
procyanidin formation in roots was investigated. None of the fertilized plants showed mineral-deficiency symptoms. Fertilized
mycorrhizal roots consistently contained significantly less catechin and epicatechin than nonmycorrhizal controls, but procyanidin
polymer content varied between replicate experiments. The possible function of catechin and epicatechin in ectomycorrhizal
formation is discussed.
Accepted: 11 July 1997 相似文献
7.
In arbuscular mycorrhizas, H+-ATPase is active in the plant membrane around arbuscules but absent from plant mutants defective in arbuscule development
(Gianinazzi-Pearson et al. 1995, Can J Bot 73: S526–S532). The proton-pumping H+-ATPase is encoded by a family of genes in plants. Immunocytochemical studies and promoter-gusA fusion assays were performed in transgenic tobacco (Nicotiana tabacum L.) to determine whether the periarbuscular enzyme activity results from de-novo activation of plant genes by an arbuscular
mycorrhizal fungus. The H+-ATPase protein was localized in the plant membrane around arbuscule hyphae. The enzyme was absent from non-colonized cortical
cells. Regulation of seven H+-ATPase genes (pma) was compared in non-mycorrhizal and mycorrhizal roots by histochemical detection of β-glucuronidase (GUS) activity. Two
genes (pma2, pma4) were induced in arbuscule-containing cells of mycorrhizal roots but not in non-mycorrhizal cortical tissues or senescent
mycorrhiza. It is concluded that de-novo H+-ATPase activity in the periarbuscular membrane results from selective induction of two H+-ATPase genes, which can have diverse roles in plant-fungal interactions at the symbiotic interface.
Received: 23 October 1999 / Accepted: 7 February 2000 相似文献
8.
The Glomus mosseae 3-phosphoglycerate kinase (PGK) gene encodes a polypeptide of 416 amino acids. A synthetic peptide was designed to the C-terminus of the polypeptide for
the production of a polyclonal antibody. The antibody was tested against the synthetic peptide in an immuno-dot blot and was
then used to investigate the asymbiotic and symbiotic accumulation of the PGK protein. Western blot analysis revealed that
a polypeptide of approximately 45 kDa accumulated in G. mosseae-colonised tomato roots; this is similar to the theoretical molecular weight of 44.764 kDa. The protein was not detected in
non-mycorrhizal roots. Quantitative immuno-dot blotting revealed that the polypeptide accumulated in germinating spores and
hyphae of G. mosseae and also in tomato roots colonised by G. mosseae. The amount detected in the mycorrhizal root system was significantly higher than that found in germinating sporocarps. The
variation in the levels of glycolytic activity in the symbiotic and asymbiotic developmental stages of G. mosseae is discussed.
Accepted: 20 April 2000 相似文献
9.
The gene dak1 encoding a dihydroxyacetone kinase (DHAK) isoenzyme I, one of two isoenzymes in the Schizosaccharomyces pombe IFO 0354 strain, was cloned and sequenced. The dak1 gene comprises 1743 bp and encodes a protein of 62 245 Da. The deduced amino acid sequence showed a similarity to a putative
DHAK of Saccharomyces cerevisiae and DHAK of Citrobacter freundii. The dak1 gene was expressed at a high level in Escherichia coli, and the recombinant enzyme was purified to homogeneity and characterized. The acetone powder of recombinant E. coli cells was used to produce dihydroxyacetone phosphate.
Received: 25 August 1998 / Received revision: 22 September 1998 / Accepted: 11 October 1998 相似文献
10.
A new amperometric enzyme-linked immunoassay for specific enumeration of Nitrobacter has been developed. This assay uses an electrode made of glassy carbon, on which the immunological reaction is carried out.
The method is based on a competitive immunoassay principle, utilising monoclonal primary antibody and alkaline-phosphatase-labelled
secondary antibody. The enzyme substrate 5-bromo-4-chloro-3-indolyl phosphate generates an electroactive product which is
amperometrically detected. The effects of different parameters on the performance of the sensor have been studied. Quantitative
detection of Nitrobacter using the immunosensor has been compared to a previously developed enzyme-linked immunosorbent assay showing compatible results.
In addition, the overall assay time can be shortened with this new sensor. A detection limit of approximately 3 × 106
Nitrobacter cells/ml was obtained.
Received: 27 May 1998 / Received revision: 28 August 1998 / Accepted: 28 August 1998 相似文献
11.
J. Q. Liu M. Odani T. Dairi N. Itoh S. Shimizu H. Yamada 《Applied microbiology and biotechnology》1999,51(5):586-591
A new enzymatic resolution process was established for the production of l-threo-3-[4-(methylthio)phenylserine] (MTPS), an intermediate for synthesis of antibiotics, florfenicol and thiamphenicol, using
the recombinant low-specificity d-threonine aldolase from Arthrobacter sp. DK-38. Chemically synthesized dl-threo-MTPS was efficiently resolved with either the purified enzyme or the intact recombinant Escherichiacoli cells overproducing the enzyme. Under the optimized experimental conditions, 100 mM (22.8 g l−1) l-threo-MTPS was obtained from 200 mM (45.5 g l−1) dl-threo-MTPS, with a molar yield of 50% and a 99.6% enantiomeric excess.
Received: 2 September 1998 / Received revision: 27 October 1998 / Accepted: 29 November 1998 相似文献
12.
B. H. R. Ranamalie Amarasinghe Guy L. de Bruxelles Marysha Braddon Ignatius Onyeocha Brian G. Forde Michael K. Udvardi 《Planta》1998,206(1):44-52
A full-length cDNA, GmNRT2, encoding a putative high-affinity nitrate transporter was isolated from a Glycine max (L.) root cDNA library and sequenced. The deduced GmNRT2 protein is 530 amino acids in length and contains 12 putative membrane-spanning
domains and a long, hydrophilic C-terminal domain. GmNRT2 is related to high-affinity nitrate transporters in the eukaryotes
Chlamydomonas reinhardtii and Aspergillus nidulans, and to putative high-affinity nitrate transporters in barley and tobacco. Southern blot analysis indicated that GmNRT2 is part of a small, multigene family in soybean. Expression of GmNRT2 in roots was regulated by the type of nitrogen source provided to plants: GmNRT2 mRNA levels were barely detectable in ammonium-grown plants, higher in nitrogen-deprived plants, and highest in nitrate-grown
plants. Induction of GmNRT2 mRNA levels in roots occurred within 1 h after exposure of plants to nitrate. Nitrate induction of GmNRT2 mRNA levels was accompanied by a fourfold increase in net nitrate uptake by soybean roots at 100 μM external nitrate. The
molecular and physiological evidence indicates that GmNRT2 is probably a high-affinity nitrate transporter involved in nitrate
uptake by soybean roots.
Received: 22 November 1997 / Accepted: 26 January 1998 相似文献
13.
A. Martins Margarida Santos Helena Santos Maria Salomé Pais 《Trees - Structure and Function》1999,13(3):168-172
31P-Nuclear Magnetic Resonance (NMR) was used to assess phosphate distribution in ectomycorrhizal and nonmycorrhizal roots of
Castanea sativa Mill. as well as in the mycorrhizal fungus Pisolithus tinctorius in order to gain insight into phosphate trafficking in these systems. The fungus P. tinctorius accumulated high levels of polyphosphates during the rapid phase of growth. Mycorrhizal and nonmycorrhizal roots accumulate
orthophosphate. Only mycorrhizal roots presented polyphosphates. The content in polyphosphates increased along the 3 months
of mycorrhiza formation. In mycorrhizal roots of plants cultured under axenic conditions, the orthophosphate pool decreased
along the culture time. In nonmycorrhizal roots the decrease in the orthophosphate content was less pronounced. The level
of orthophosphate in mycorrhizal roots was significantly lower than in nonmycorrhizal ones, which indicates that this system
relies upon the fungal polyphosphates as a major source of phosphate.
Received: 28 July 1998 / Accepted: 21 October 1998 相似文献
14.
The effects of inorganic phosphate levels and the presence of arbuscular mycorrhiza on disease severity of Aphanomyces euteiches in pea roots were studied. Disease severity on roots and epicotyl as well as the oospore number within infected root tissue
were correlated with the phosphorus (P) level in the growth medium. The arbuscular mycorrhizal fungus Glomus intraradices increased P uptake and the P concentration in the plant but reduced disease development in peas. Polyacrylamide gel electrophoresis
followed by densitometry of glucose-6-phosphate dehydrogenase specific to A.euteiches was used to measure the activity of the pathogen in roots. The enzyme activity increased with disease severity and disease
incidence, except in plants supplemented with P at the highest level, where a peak in activity was seen 12 days after inoculation
with the pathogen, followed by a decrease in activity. The epicotyl of mycorrhizal plants showed a reduction in disease severity
although this part of the plants was not mycorrhizal. Thus, an induced systemic factor may be responsible for increased resistance
in mycorrhizal plants.
Accepted: 21 August 1998 相似文献
15.
The entry of calcium and magnesium from external sources into mycorrhizal roots of 3-year-old Norway spruce trees (Piceaabies [L.] Karst.) was monitored. Roots of intact plants were exposed for various periods of time, ranging from 2 min to 48 h,
to nutrient solutions which contained the stable-isotope tracers 25Mg and 44Ca. After labelling, samples of roots were excised from the plants, shock-frozen, cryosubstituted and embedded. The resulting
isotope composition in this material was analysed by a laser-microprobe-mass-analyser (LAMMA) at relevant positions within
cross-sections of the roots. For both elements, we determined (i) the fractions of the isotopes originating from the plant
prior to labelling, and (ii) the fraction of isotopes originating from the corresponding tracer that penetrated into the root.
Both divalent cations rapidly penetrated across the cortical apoplast and reached the endodermis. After 2 min of exposure
to the labelling solution, an initial transient gradient of the tracers could be observed within the root cortex. Subsequently,
calcium as well as magnesium equilibrated between the apoplast of the entire cortex and the external tracer with a half-time,
t1/2, of about 3 min. In contrast, the kinetics of radial movement into the vascular stele showed a delay with a t1/2 of 100–120 min. We take this as strong evidence that there exists a free apoplastic path for divalent cations in the cortex
and that the endodermis is a major barrier to the further passage of Mg and Ca into the xylem. While 25Mg in the labelling solution exchanged rapidly with Mg in the cortical apoplast, the exchange across the plasma membrane with
Mg present in the protoplasm of the same cortical cells was almost 2 orders of magnitude slower. The kinetics of Ca and Mg
entry at +6 °C were similar to those obtained at a root temperature of +22 °C.
Received: 23 December 1998 / Accepted: 17 September 1999 相似文献
16.
Psidium guajava L.) plantlets was determined during acclimatization and plant establishment. Guava plantlets were asexually propagated through
tissue culture and grown in a glasshouse for 18 weeks. Half of the plantlets were inoculated with a mixed endomycorrhiza isolate
from Mexico, ZAC-19, containing Glomus diaphanum, G. albidum and G. claroides. Plantlets were fertilized with modified Long Ashton nutrient solution that supplied 11 μg P ml−1. Gas exchange measurements were taken at 2, 4, 8, and 18 weeks after inoculation using a portable photosynthesis system.
All micropropagated guava plantlets survived transplant shock. After 6 weeks, mycorrhizal plantlets had greater shoot growth
rates and leaf production than non-mycorrhizal plantlets. This also corresponded with increased photosynthetic rates and stomatal
conductance of mycorrhizal plants. By 18 weeks, mycorrhizal plantlets had greater shoot length, leaf area, leaf, stem, and
root dry mass. However, gas exchange was comparable among treatments, in part because the container size was restricting growth
of the larger mycorrhizal plantlets. Non-mycorrhizal plantlets had greater leaf area ratios and specific leaf areas than mycorrhizal
plantlets. Increased leaf tissue mineral levels of P, Mg, Cu, and Mo also occurred with mycorrhizal plantlets. Roots of inoculated
guava plantlets were heavily colonized with arbuscules, vesicles and endospores. Guava plantlets were highly mycotrophic with
a mycorrhizal dependency index of 103%.
Accepted: 27 December 1999 相似文献
17.
To study the metabolic interactions between mesophyll and bundle-sheath cells of C4 plants, protein kinases possibly involved in the regulatory processes and signal transduction pathways have been cloned and
characterized. A receptor-like protein kinase (RLK) cDNA clone from the C4 plant Sorghum bicolor (L.) Moench has been identified. The deduced protein was designated SbRLK1 for receptor-like protein kinase from S. bicolor. The putative cytoplasmic domain of SbRLK1 contains all amino acids that are characteristic of protein kinases. The extracellular
domain contains five leucine-rich repeats. The mRNA of the SbRLK1 gene accumulated to much higher levels in mesophyll cells than in the bundle-sheath and was almost undetectable in roots.
This expression pattern indicates that SbRLK1 might be involved in the regulation of specific processes in mesophyll cells.
Received: 13 August 1998 / Accepted: 22 December 1998 相似文献
18.
The pea (Pisum sativum L.) mutants dgl and brz are defective in the regulation of iron uptake. Enhanced proton extrusion and constitutively high Fe(III) reductase activities
in the roots lead to an accumulation of iron and other divalent cations in different organs of the mutants. Ultrastructural
investigations of the basal leaflets of the mutants revealed in the cytoplasm, in mitochondria and especially in, or close
to the endoplasmic reticulum numerous electron-dense particles which were absent in the corresponding wild type plants DGV
and Sparkle. By means of electron-spectroscopic imaging and electron-energy-loss spectroscopy it could be shown that these
electron-dense particles consist mainly of iron. Some of the iron deposits were immunocytochemically identified as the iron-storage
protein ferritin. It is suggested that the precipitation of excessive iron in the dgl and brz mutant leaves in the form of electron-dense iron particles combined with the accumulation of ferritin is part of the plant
defense mechanism against Fe-mediated oxidative stress.
Received: 17 February 1998 / Accepted: 4 July 1998 相似文献
19.
Polyclonal rat antibodies were raised to a bovine serum albumin-sinigrin conjugate and used to immunolocalize sinigrin (2-propenylglucosinolate)
in imbibed seeds and developing seedlings of Brassica juncea. (L.) Czern. Sinigrin was localized to protein bodies in aleurone-like cells but shown to be absent from myrosin cells. Double
labelling techniques were used to co-localize both myrosinase (β-thioglucoside glucohydrolase, EC 3.2.3.1) and sinigrin. Myrosin
grains were labelled only with the anti-myrosinase antibody, but aleurone cells were labelled with both anti-myrosinase and
anti-sinigrin antibodies. High-performance liquid chromatographic analysis of conventionally fixed and dehydrated seed tissues
(4 h post imbibition in water), indicated a high proportion of sinigrin was retained in fixed tissues. Over a time course
of 100 h, protein bodies within aleurone-like cells degraded, fused to form the cell vacuole and lost all myrosinase labelling
but retained residual sinigrin labelling. The degradation of protein bodies corresponded to a decrease in retention of sinigrin
in the fixed tissues. The results describe for the first time the co-localization of a plant enzyme and its substrate, a secondary
metabolite.
Received: 8 January 1998 / Accepted: 27 February 1998 相似文献
20.
Repeated application of carvone-induced bacteria to enhance biodegradation of polychlorinated biphenyls in soil 总被引:4,自引:0,他引:4
Carvone, the principal component of spearmint oil, induces biodegradation of polychlorinated biphenyls (PCB) by Arthrobacter sp. strain B1B. This study investigated the effectiveness of the repeated application of carvone-induced bacteria for bioremediation
of Aroclor-1242-contaminated soil. Control treatments compared a single inoculation of carvone-induced cells, repeated applications
of noninduced cells, and repeated applications of cell-free carvone/fructose medium. The results showed that repeated application
of carvone-induced bacteria was the most effective treatment for mineralizing PCB, resulting in 27 ± 6% degradation of Aroclor
1242 after 9 weeks; whereas a single application of cells resulted in no significant degradation. Addition of cell-free, carvone/fructose
medium resulted in 10% degradation of PCB, which suggests that this treatment stimulated biodegradation of PCB by the indigenous
microflora. The di- and trichlorobiphenyls were the most readily degraded congeners. More highly chlorinated congeners, which
had been previously shown to be degraded in liquid culture, were not substantially degraded in soil, indicating that low bioavailability
may have limited their degradation. With the development of new technology, which permits automated in situ fermentation and
delivery of degrader microorganisms, the repeated application of carvone-induced bacteria may facilitate bioremediation of
PCB-contaminated soils.
Received: 7 January 1998 / Received revision: 18 June 1998 / Accepted: 27 June 1998 相似文献