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1.
Root and stem xylem embolism,stomatal conductance,and leaf turgor in Acer grandidentatum populations along a soil moisture gradient 总被引:1,自引:0,他引:1
The objective of this study was to determine how adjustment in stomatal conductance (g
s) and turgor loss point (tlp) between riparian (wet) and neighboring slope (dry) populations of Acer grandidentum Nutt. was associated with the susceptibility of root versus stem xylem to embolism. Over two summers of study (1993–1994), the slope site had substantially lower xylem pressures (px) and g
s than the riparian site, particularly during the drought year of 1994. The tlp was also lower at the slope (-2.9±0.1 MPa; all errors 95% confidence limits) than at riparian sites (-1.9±0.2 MPa); but it did not drop in response to the 1994 drought. Stem xylem did not differ in vulnerability to embolism between sites. Although slope-site stems lost a greater percentage of hydraulic conductance to embolism than riparian stems during the 1994 drought (46±11% versus 27±3%), they still maintained a safety margin of at least 1.7 MPa between midday px and the critical pressure triggering catastrophic xylem embolism (pxCT). Root xylem was more susceptible to embolism than stem xylem, and there were significant differences between sites: riparian roots were completely cavitated at -1.75 MPa, compared with -2.75 MPa for slope roots. Vulnerability to embolism was related to pore sizes in intervessel pit membranes and bore no simple relationship to vessel diameter. Safety margins from pxCT averaged less than 0.6 MPa in roots at both the riparian and slope sites. Minimal safety margins at the slope site during the drought of 1994 may have led to the almost complete closure of stomata (g
s=9±2 versus 79±15 mmol m-2 s-1 at riparian site) and made any further osmotic adjustment of tlp non-adaptive. Embolism in roots was at least partially reversed after fall rains. Although catastrophic embolism in roots may limit the minimum for gas exchange, partial (and reversible) root embolism may be adaptive in limiting water use as soil water is exhausted. 相似文献
2.
To explore the possible physiological mechanism of salt tolerance in peanut, we investigated the effect of salinity on antioxidant enzyme activity, fatty acid composition, and chlorophyll fluorescence parameters. Seedlings at the initial growth stage had been treated with 0, 100, 150, 200, 250, and 300 mM NaCl for 7 days. Results showed that fresh mass and dry mass decreased with the rise of the NaCl concentration. They decreased significantly when the NaCl concentration was more than 200 mM. The PSII’s highest photochemical efficiency (F v/F m) was not affected before treating 250 mM NaCl. However, the PSII (ΦPSII)’s actual photochemical efficiency of decreased after treating 200 mM NaCl. Both the initial fluorescence (F o) and non-photochemical quenching (NPQ) increased after 200 mM NaCl treatment. PSI oxidoreductive activity (ΔI/I o) was not affected before 200 mM NaCl. The malondialdehyde (MDA) content increased with the rise of the NaCl concentration. The activities of ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities increased first and then decreased, while the content of H2O2 and O 2 ?· decreased first and then increased. Treated with 150 mM NaCl, the linolenic acid (18:3) and linoleic acid (18:2) of monogalactosyldiacylglycerols (MGDG), digalactosyldiacylglycerols (DGDG), sulphoquinovosyldiacylglycerols (SQDG) as well as phosphatidylglycerols (PG), the ratio of DGDG/MGDG increased, and the opposite results were obtained with 300 mM NaCl. The double bond index (DBI) of MGDG, DGDG, SQDG, and PG also increased after treating 150 mM NaCl. These conclusions verified that increased unsaturated fatty acid content in membrane lipid of peanut leaves could improve salt tolerance by alleviating photoinhibition of PSII and PSI. 相似文献
3.
4.
Long noncoding RNAs (lncRNAs) act important roles in a wide range of biological processes. The regulatory roles of lncRNAs are still poorly understood. One of the major problems of limiting plant productivity is the salinity in the worldwide that barley (Hordeum vulgare L.) seems to be relatively well adapted to salinity environments. The aim of this study is the investigation of lncRNAs’ expression levels on four barley genotypes (Hasat, Beysehir 99, Konevi 98 and Tarm 92) to 150 mM salt stress application during 3 days germination. Grains were placed randomly in petri dishes containing filter paper soaked in (a) only H2O (control), (b) 150 mM NaCl for 72 h. RNA extraction were carried out using TriPure® reagent from root and shoot samples obtained after 150 mM salt treatment. Expression levels of CNT0018772 and CNT0031477 were determined by qPCR. Expression analysis demonstrated salinity effected expression levels of CNT0018772 and CNT0031477 on roots and shoots during germination. The expression levels of CNT0018772 for 150 mM salt applied groups were down-regulated raged between (log2–0.52 and–35.65) compared controls on roots and shoot. The expression levels of CNT0031477 in 150 mM salt applied groups were also down-regulated ranged between (log2–10.40 and 33.59) compared controls on roots and shoot except for Tarm 92 variety. On the contrary, expression levels of CNT0031477 were up-regulated on root and shoot of Tarm 92. Comparison of CNT0018772 and CNT0031477 expression levels on roots, there was no significant difference between barley varieties compared to controls (p > 0.05). However, it was found there was statistically significant difference between 150 mM salt treatment and control groups for CNT0031477 expression levels (p < 0.05). It was determined Konevi 98 shoot control expression level was statistically higher than Tarm 92 shoot control. This is the first report about the lncRNAs expression levels of barley under salinity. 相似文献
5.
Excision and subsequent incubation of the apices (1 cm) of wheat (Triticum aestivum L.) seedling roots in simple media severely reduced elongation from 28 mm·(24 h)-1 in intact roots to a maximum of 2 mm·(24 h)-1 in excised roots. The reduction in growth was accompanied by a loss of cell turgor in the growing zone but was correlated with a hardening of the cell walls in this region. Rheological properties were measured as percent extensibility (both plastic and elastic) using a tensiometer, and as instantaneous volumetric elastic modulus (
i) using the pressure probe. Excision decreased plastic and elastic properties with a half-time of some 60 min. Plastic extension was reduced from 2.5% to 0.9% and elastic from 4.8% to 2.6% for an 8-g load. By contrast,
i was increased by excision. The observed reduction in root elongation rate was accompained by a reduction in mature cell length from 240 m to 40 m and a shortening of the zone of cell expansion.Symbol
i
instantaneous volumetric elastic modulus 相似文献
6.
Stephen C. Wood Kjell Johansen 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1974,89(2):145-158
Summary The objectives of this study included directin vivo measurements of circulating blood gases, pH, heart rate, and blood pressure during voluntary dives of unrestrained Nile monitor lizards. A Radiometer flow-through cuvette was employed for continuous recording of arterial PO2, PCO2 and pH. Hematological properties revealed no particular adaptations for diving. Mean values were: hematocrit = 24%; hemoglobin concentration = 7.1 g %; oxygen capacity = 9.3 vol %; red cell dimensions = 22×12 ; red cell count = 0.67 million/l. The respiratory properties of the blood, studiedin vitro andin vivo, show distinct adaptations to habitual diving. Oxygen affinity of blood is low (P50 = 42.4 mm Hg at pH 7.45, 25 °) and the dissociation curve is markedly sigmoid (n = 3.1). These features, coupled with a Bohr factor ( logP
50/pH) of –0.48, ensure increased utilization of oxygen while maintaining relatively high tissue PO2. Arterial pH decreases during diving from about 7.5 to 7.1 due to combined respiratory and metabolic acidosis. High plasma bicarbonate (30 mM/l at PCO2 = 25 mm Hg) and a buffering capacity of H C3
–O/ pH = 18.9 mM/l increase the tolerance to this acidosis and prolong diving time. Thein vivo oxygen dissociation curve shows a 90 % depletion of arterial oxygen content during typical dives. Diving elicited a rapidly developing bradycardia with maximum of 85 % reduction in heart rate. The temperature sensitivity of HbO2 binding was very low (H = –3kcal). This would minimize the HbO2 affinity increase accompanying the decrease in body temperature likely to occur in lizards going from sun basking to submergence in water.Supported by a grant from the Danish Natural Science Research Council. 相似文献
7.
The relative importance of endogenous abscisic acid (ABA), as well as Na+ and Cl– in NaCl-induced responses related to growth in roots of rice seedlings were investigated. The increase in ammonium, proline and H2O2 levels, and cell wall peroxidase (POD) activity has been shown to be related to NaCl-inhibited root growth of rice seedlings. Increasing concentrations of NaCl from 50 to 150 mM progressively decreased root growth and increased both Na+ and Cl–. Treatment with NaCl in the presence of 4,4-diisothiocyano-2,2-disulfonic acid (DIDS, a nonpermeating amino-reactive disulfonic acid known to inhibit the uptake of Cl–) had less Cl– level in roots than that in the absence of DIDS, but did not affect the levels of Na+, and responses related to growth in roots. Treatment with 50 mM Na-gluconate (the anion of which is not permeable to membrane) had similar Na+ level in roots as that with 100 mM NaCl. It was found that treatment with 50 mM Na-gluconate effected growth reduction and growth-related responses in roots in the same way as 100 mM NaCl. All these results suggest that Cl– is not required for NaCl-induced responses in root of rice seedlings. Endogenous ABA level showed no increase in roots of rice seedlings exposed to 150 mM NaCl. It is unlikely that ABA is associated with NaCl-inhibited root growth of rice seedlings. 相似文献
8.
Zusammenfassung Der Gehalt an reduzierten Nicotinamid-adenin-dinucleotiden bei Rhodospirillum rubrum, Rhodopseudomonas spheroides und Rps. capsulata wird beim Absenken des pO2 erst zwischen 0,2 und 0,5 mm Hg deutlich erhöht.Beim schnellen Wechsel (dichte Bakteriensuspension) zur Anaerobiose tritt bei R. rubrum eine deutliche Überreduktion der Nicotinamid-adenin-dinucleotide ein und bei erneuter Belüftung eine Überoxydation.Der Reduktionszustand der Cytochrome b+c2 und c2 (Differenzspektren 422 m bzw. 426 m oder 428 m minus 405 m und 550 m minus 545 m bzw. 550 m minus 560 m) erhöht sich etwa zur gleichen Zeit wie die Konzentration von NAD(P)H. Bei erneuter Belüftung tritt immer eine Überoxydation ein, die über 1 min andauern kann.Die änderung des Redoxgleichgewichts von NAD(P)+/NAD(P)H und der Cytochrome ist korreliert mit dem Zusammenbruch des Energiestoffwechels (oxydative Phosphorylierung), zeigt aber keine Beziehung zum Beginn der Bakteriochlorophyll-synthese unter semiaeroben Wachstumsbedingungen, die schon bei höherem pO2 erfolgt.Damit konnte gezeigt werden, daß die Induktion der BChl.-Synthese in Dunkelkulturen durch Änderung des O2-Partialdruckes in keinem direkten Zusammenhang zur Änderung des Redoxgleichgewichtes von NAD(P)+/NAD(P)H und der Cytochrome b und c2 steht.
Abkürzungen NAD(P) Nicotinamid-adenin-dinucleotid + Nicotinamid-adenin-dinucleotid-phosphat - pO2 Sauerstoffpartialdruck - BChl. Bacteriochlorphyll 相似文献
The influence of the pO2 on the redox balance of NAD(P) and of cytochrome b and c2 in some Athiorhodaceae
Summary If the oxygen partial pressure in growing cultures of Rhodospirillum rubrum, Rhodopseudomonas spheroides, and Rhodopseudomonas capsulata is slowly lowered the level of reduced nicotinamide-adenine dinucleotide is strongly increased but not before the pO2 is dropped beneath 0.2–0.5 mm Hg.A very quick change from aerobic to strict anaerobic conditions in a dense suspension of R. rubrum causes a significant overreduction of the nicotinamide-adenine dinucleotides. After switching on the aeration an overoxidation is observable.The reduction of cytochromes b and c2 obeys the same kinetics as the reduction of NAD(P)+. A sudden aeration is followed by an overoxidation, which continues for more than 1 min.The changes in the ratio of the reduced to the oxidised states of the nicotinamide-adenine dinucleotide and the cytochromes are correlated to the breakdown of the metabolism (oxidative phosphorylation). But the synthesis of bacteriochlorophyll is induced by a decrease of oxygen partial pressure down to 50- mm Hg (depended from the organism). It has been shown in these experiments that the induction of the synthesis of bacteriochlorophyll in the dark by changing the pO2 is not directly correlated to the change in the redox state of NAD(P)+/NAD(P)H and of the cytochromes b and c2.
Abkürzungen NAD(P) Nicotinamid-adenin-dinucleotid + Nicotinamid-adenin-dinucleotid-phosphat - pO2 Sauerstoffpartialdruck - BChl. Bacteriochlorphyll 相似文献
9.
Y. Yamagata H. Kojima K. Ejiri K. Inomata 《Origins of life and evolution of the biosphere》1982,12(4):333-337
Possible formation of a P4O10 molecule in magma, the stability of the molecule in hydrous volcanic gas at high temperatures and a possible prebiotic phosphate cycle were discussed in relation to chemical evolution. To demonstrate the utility of phosphorus pentoxide as a phosphorylating agent, aqueous solutions of adenosine (0.02M) and phosphorus pentoxide (0.2M) were incubated at 37°C for 5 months. The pH of the solutions was adjusted every day or every few days to each fixed value (9.0, 10.5, 11.5, 12.5) with 10 N NaOH. The HPLC analysis showed the formation of 2-AMP, 3-AMP, 5-AMP, cyclic (2–3)-AMP and cyclic (3–5)-AMP. The main components of the products were 2- and 3-AMP, though cyclic (2–3)-AMP was the main component in the early period of the incubation at pH 9.0. The yields (conversion rate of adenosine to AMPs) were increased almost linearly with the incubation time for 5 months in the case of pH 9.0. The final yields were about 3% (pH 9.0), 6% (pH 9.0, 1 M NaCl), 5% (pH 9.0, 0.01 M CaCl2, 0.01 M MgCl2), 7% (pH 9.0, 0.5 M NaCl, 0.01 M CaCl2, 0.01 M MgCl2), 9% (pH 9.0, 1 M NaCl, 0.01 M CaCl2, 0.01 M MgCl2), 32% (pH 10.5), 43% (pH 11.5), 35% (pH 12.5). 相似文献
10.
J. F. Siebenaller T. F. Murray 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,163(8):626-632
To investigate, the effects of hydrostatic pressure on transmembrane signaling in cold-adapted marine fishes, we examined the high-affinity GTPase activity in two congeneric marine fishes, Sebastolobus alascanus and S. altivelis. In brain membranes there are two GTPase activities, one with a low K
m and one with a high K
m for GTP. The high-affinity GTPase activity, characteristic of the subunits of the guanine nucleotide binding protein pool, was stimulated by the A1 adenosine receptor agonists N
6(R-phenylisopropyl)adenosine and N
6-cyclopentyladenosine, and the muscarinic cholinergic agonist carbamyl choline. Pertussis toxin-catalyzed ADP-ribosylation of the membranes for 2 h at 5°C prior to the GTPase assay decreased the basal GTPase activity 30–40% and abolished N
6 (R-phenylisopropyl)adenosine stimulation of GTP hydrolysis. Basal high-affinity hydrolysis of GTP, measured at 0.3 mol·1-1GTP, was stimulated 22% in both species by 340 atm pressure. At 340 atm pressure, the apparent K
m of GTP is decreased approximately 10% in each of the species, and the V
max values are increased 11 and 15.9% in S. alascanus and S. altivelis, respectively. The apparent volume changes associated with the decreased K
m of GTP and the increased V
max ranged from-7.0 to-9.9 ml·mol-1. Increased pressure markedly decreased the efficacy of N
6 (R-phenylisopropyl) adenosine, N
6-cylcopentyladenosine and carbamyl choline in stimulating GTPase activity. The effects of increased hydrostatic pressure on transmembrane signal transduction by the A1 adenosine receptor-inhibitory guanine nucleotide binding protein-adenylyl cyclase system may stem, at least in part, from pressure-increased GTP hydrolysis and the concomitant termination of inhibitory signal transduction.Abbreviations [3H] DPCPX
3H cyclopentyl-1, 3-dipropylxanthine
- AppNHp
5-adenylylimidodiphosphate
- cpm
counts per minute
- CPA
N
6-cyclopentyladenosine
- EDTA
ethylenediaminetetra acetic acid
- EGTA
ethyleneglycol-bis (-aminoethylether) N, N, N, N-totra-acctic acid
- G protein
guanine nucleotide binding protein
- Gi
inhibitory G protein
- Go
other G protein, common in brain membranes
- Gs
stimulatory G protein
- GTPase
guanosine triphosphatase
-
K
i
inhibition constant
-
K
m
Michaelis constant
- pK
a
log of the dissociation constant
- R-PIA
N
6 (R-phenylisopropyl) adenosine
- TRIS
tris[hydroxymethyl]aminomethane
- Vmax
maximal velocity
- [-32P]GTP
[-32P] guanosine 5-triphosphate (tetra (triethylammonium) salt) 相似文献
11.
Filamentous gametophytes of the fernO. sensibilis were exposed to paired combinations of light of different qualities, hormones and cations in the attempt to elucidate the underlying processes that regulate cell expansion. Simultaneous treatments with high-pH buffers or the auxin antagonistp-chlorophenoxyisobutyric acid abolished blue-light-mediated expansion but did not influence growth in red light. In contrast, the red-light response was preferentially altered by the ethylene absorbant KMnO4 or the Ca2+ chelator ethyleneglycol-bis(-aminoethyl ether) N,N-tetraacetic acid. The Ca2+ ionophore A23187 caused a significant reduction in cell expansion under both blue and red irradiation. A marked promotion of expansion was mediated by high concentrations of indole-3-acetic acid, but this effect was dependent on the presence of low-pH buffers. The ethylene-generating agent 2-chloroethylphosphonic acid decreased the magnitudes of both photoresponses; this inhibition was further enhanced by high Ca2+ concentrations. These findings and those with other plants are interpreted in terms of two independent control mechanisms for cell expansion: 1) a blue light photoreceptor-auxin-hydrogen ion system, and 2) a phytochrome-ethylene-calcium ion system.Abbreviations APW-X
artificial pond water (the associated number designates pH)
- CEPA
2-chloroethylphosphonic acid
- EGTA
ethyleneglycol-bis(-aminoethyl ether)N,N-tetraacetic acid
- IAA
indole-3-acetic acid
- PCIB
p-chlorophenoxyisobutyric acid 相似文献
12.
Langenfeld-Heyser R Gao J Ducic T Tachd P Lu CF Fritz E Gafur A Polle A 《Mycorrhiza》2007,17(2):121-131
In order to characterise the effect of ectomycorrhiza on Na+-responses of the salt-sensitive poplar hybrid Populus × canescens, growth and stress responses of Paxillus involutus (strain MAJ) were tested in liquid cultures in the presence of 20 to 500 mM NaCl, and the effects of mycorrhization on mineral
nutrient accumulation and oxidative stress were characterised in mycorrhizal and non-mycorrhizal poplar seedlings exposed
to 150 mM NaCl. Paxillus involutus was salt tolerant, showing biomass increases in media containing up to 500 mM NaCl after 4 weeks growth. Mycorrhizal mantle
formation on poplar roots was not affected by 150 mM NaCl. Whole plant performance was positively affected by the fungus because
total biomass was greater and leaves accumulated less Na+ than non-mycorrhizal plants. Energy dispersive X-ray microanalysis using transmission electron microscopy analysis of the
influence of mycorrhization on the subcellular localisation of Na+ and Cl− in roots showed that the hyphal mantle did not diminish salt accumulation in root cell walls, indicating that mycorrhization
did not provide a physical barrier against excess salinity. In the absence of salt stress, mycorrhizal poplar roots contained
higher Na+ and Cl− concentrations than non-mycorrhizal poplar roots. Paxillus involutus hyphae produced H2O2 in the mantle but not in the Hartig net or in pure culture. Salt exposure resulted in H2O2 formation in cortical cells of both non-mycorrhizal and mycorrhizal poplar and stimulated peroxidase but not superoxide dismutase
activities. This shows that mature ectomycorrhiza was unable to suppress salt-induced oxidative stress. Element analyses suggest
that improved performance of mycorrhizal poplar under salt stress may result from diminished xylem loading of Na+ and increased supply with K+. 相似文献
13.
Hend Askri Samia Daldoul Anis Ben Ammar Saloua Rejeb Rahma Jardak Mohamed Nejib Rejeb Ahmed Mliki Abdelwahed Ghorbel 《Acta Physiologiae Plantarum》2012,34(3):957-968
The physiological and molecular response to salt stress was studied in two wild grapevine (Vitis vinifera L. ssp. sylvestris or Vitis sylvestris) accessions “Khédhayria” and “Houamdia”, previously identified as salt-tolerant and salt-sensitive pair wise. Plants from
both accessions were subjected to a progressive salt stress by the use of a nutritional solution containing up to 150 mM NaCl
for 2 weeks. Salt stress adversely affected growth and water potential since the first day of exposure to 150 mM NaCl. However,
chlorophyll fluorescence parameters were unchanged until 14 days of salt exposure. At that time point the predawn water potential
(ΨPD), the non-photochemical quenching of fluorescence (NPQ) and the coefficient of photochemical quenching (qp) were significantly less altered in the tolerant accession. At the molecular level semi-quantitative RT-PCR assays revealed
a differential expression of (Vs α-gal/SIP and Vs DHN) genes within these contrasting accessions after exposure to 24 h and 14 days of salt. Comparably, the Vs RD22 gene had increased slightly after only 14 days of treatment in both accessions. These results were the first pieces of information
reported on the early and late regulation of salt response genes in wild grapevines. Furthermore, genotype-dependent parameters
such as NPQ, qp, mRNA levels of Vs α-gal/SIP and Vs DHN could be used to screen salt-tolerant wild grapevine genotypes. 相似文献
14.
Kathryn H. Engler Steven L. Kelly Raymond D. Coker Ivor H. Evans 《Biotechnology letters》2000,22(1):3-8
Microsomes from Kluyveromyces marxianus GK1005 examined by carbon monoxide difference spectroscopy showed no evidence of cytochrome P450, in contrast to microsomes isolated from a control strain of Saccharomyces cerevisiae. Benzo[a]pyrene produced a typical Type I-binding spectrum with microsomes of both yeasts, with K
s values of 82 M (S. cerevisiae) and 70 M (K. marxianus). While aflatoxin B1 generated a typical Type I-binding spectrum with microsomes from S. cerevisiae (K
s of 178 M), the toxin did not produce a recognisable binding spectrum with microsomes from K. marxianus. 相似文献
15.
Twenty-nine randomly chosen, soluble antigens, many of them highly complex, were used to immunize mice of two strains, C3H and B10.RIII. Lymphnode cells from the immunized mice were restimulated in vitro with the priming antigens and the proliferative response of the cells was determined. Both strains were responders to 28 of 29 antigens. Eight antigens were then used to immunize 11 congenic strains carrying different H-2 haplotypes, and the T-cell proliferative responses of these strains were determined. Again, all the strains responded to seven of the eight antigens. These experiments were then repeated, but this time -antibodies specific for the A (AA) or E (EE) molecules were added to the culture to block the in vitro responsiveness. In all but one of the responses, inhibition with both A-specific and E-specific antibodies was observed. The response to one antigen (Blastoinyces) was exceptional in that some strains were nonresponders to this antigen. Furthermore, the response in the responder strains was blocked with A-specific, but not with E-specific, antibodies. The study demonstrates that responses to antigens not controlled by Irr genes nevertheless require participation of class II Mhc molecules. In contrast to Ir gene-controlled responses involving either the A- or the E-molecule controlling loci (but never both), the responses not Ir-controlled involve participation of both A- and E-controlling loci. The lack of Ir-gene control is probably the result of complexity of the responses to multiple determinants. There is thus no principal difference between responses controlled and those not controlled by Ir genes: both types involve the recognition of the antigen, in the context of Mhc molecules.Abbreviations used in this paper A
class II MHC molecule consisting of the A and A chains
- ADH
alcohol dehydrogenase
- APC
antigen-presenting cell
- cpm
counts per minute
- E
class II Mhc molecule onsisting of the E and A chains
-
Ir
immune response
- KLH
key-hole limpet hemocyanin
- Mhc
major histocompatibility complex
- PBS
phosphate buffered salt solution
- SD
standard deviation
- SI
stimulation index
- SN
supernatant of Sendai-virus preparation 相似文献
16.
Structure of a rice β-glucanase gene regulated by ethylene,cytokinin, wounding,salicylic acid and fungal elicitors 总被引:6,自引:0,他引:6
Carl R. Simmons James C. Litts Ning Huang Raymond L. Rodriguez 《Plant molecular biology》1992,18(1):33-45
A rice -glucanase gene was sequenced and its expression analyzed at the level of mRNA accumulation. This gene (Gns1) is expressed at relatively low levels in germinating seeds, shoots, leaves, panicles and callus, but it is expressed at higher levels in roots. Expression in the roots appears to be constitutive. Shoots expressGns1 at much higher levels when treated with ethylene, cytokinin, salicylic acid, and fungal elicitors derived from the pathogenSclerotium oryzae or from the non-pathogenSaccharomyces cereviseae. Shoots also expressGns1 at higher levels in response to wounding. Expression in the shoots is not significantly affected by auxin, gibberellic acid or abscisic acid. The -glucanase shows 82% amino acid similarity to the barley 1,3;1,4--D-glucanases, and from hybridization studies it is the -glucanase gene in the rice genome closest to the barley 1,3;1,4--glucanase EI gene. The mature peptide has a calculated molecular mass of 32 kDa. The gene has a large 3145 bp intron in the codon for the 25th amino acid of the signal peptide. The gene exhibits a very strong codon bias of 99% G+C in the third position of the codon in the mature peptide coding region, but only 61% G+C in the signal peptide region.Abbreviations ABA
abscisic acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- EtBr
ethidium bromide
- GA
gibberellic acid
- n.p.
nucleotide position in gene sequence
- PCR
polymerase chain reaction
- 1×SSPE
150 mM NaCl, 10 mM NaH2PO4, 1 mM EDTA pH 7.4 相似文献
17.
Phaseolus vulgaris (cv. Hawkesbury Wonder) was grown over a range of NaCl concentrations (0–150 mM), and the effects on growth, ion relations and photosynthetic performance were examined. Dry and fresh weight decreased with increasing external NaCl concentration while the root/shoot ratio increased. The Cl- concentration of leaf tissue increased linearly with increasing external NaCl concentration, as did K+ concentration, although to a lesser degree. Increases in leaf Na+ concentration occurred only at the higher external NaCl concentrations (100 mM). Increases in leaf Cl- were primarily balanced by increases in K+ and Na+. X-ray microanalysis of leaf cells from salinized plants showed that Cl- concentration was high in both the cell vacuole and chloroplast-cytoplasm (250–300 mM in both compartments for the most stressed plants), indicating a lack of effective intracellular ion compartmentation in this species. Salinity had little effect on the total nitrogen and ribulose-1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) content per unit leaf area. Chlorophyll per unit leaf area was reduced considerably by salt stress, however. Stomatal conductance declined substantially with salt stress such that the intercellular CO2 concentration (C
i) was reduced by up to 30%. Salinization of plants was found to alter the 13C value of leaves of Phaseolus by up to 5 and this change agreed quantitatively with that predicted by the theory relating carbon-isotope fractionation to the corresponding measured intercellular CO2 concentration. Salt stress also brought about a reduction in photosynthetic CO2 fixation independent of altered diffusional limitations. The initial slope of the photosynthesis versus C
i response declined with salinity stress, indicating that the apparent in-vivo activity of RuBP carboxylase was decreased by up to 40% at high leaf Cl- concentrations. The quantum yield for net CO2 uptake was also reduced by salt stress.Abbreviations and symbols A
net CO2 assimilation rate
- C
a
ambient CO2 concentration
-
C
i
intercellular CO2 concentration
- RuBP
ribulose-1,5-bisphosphate
- 13C
ratio of 13C to 12C relative to standard limestone 相似文献
18.
Zahid Mozaffar Kazuhiro Nakanishi Ryuichi Matsuno 《Applied microbiology and biotechnology》1987,25(5):426-429
Summary The oligosaccharide-producing activity of -galactosidase-1, one of the isomers of -galactosidase (-d-galactoside galactohydrolase, EC 3.2.1.23) from Bacillus circulans was changed after immobilization onto porous silica gel (Merckogel) by crosslinkage with glutaraldehyde. The reason for this modification was studied by treating the free enzyme with glutaraldehyde. Glutaraldehyde of 0.025% to 3% modified 40% to 90% of the free amino groups with or without intermolecular crosslinking. The maximum yield of oligosaccharides increased from 12% to 40% depending upon degree of modification, while native enzyme gave only 6% trisaccharides during hydrolysis of 127 mM lactose. The K
m
value for the enzyme treated with glutaraldehyde was also increased. 相似文献
19.
Recent findings have suggested that H2O2 is an important signaling molecule for regulating plant responses to abiotic stress. H2O2 plays a critical role in NaCl stress. Heme oxygenase (HO) is known to play a protective role against oxidative stress. In this study, we examined the possible involvement of H2O2 in regulating NaCl-promoted HO activity in rice roots. Treatment with NaCl increased HO activity and H2O2 content in rice roots. As well, NaCl could induce OsHO1 mRNA expression. NaCl (150 mM) and NaNO3 (150 mM) were equally effective in inducing HO activity. However, mannitol at the concentration (276 mM) iso-osmotic with 150 mM NaCl had no effect on HO activity. NaCl-promoted HO activity and OsHO1 expression in rice roots was reduced by NADPH oxidase inhibitors i.e. dipehnyleneiodonium and imidazole. Moreover, exogenous application of H2O2 enhanced the activity of HO and the mRNA level of OsHO1. Our data suggest that H2O2 production plays a positive role in NaCl- induced HO activity by enhancing its mRNA level in rice roots. 相似文献
20.
With 3-O-methylfluorescein phosphate (3-OMFP) as substrate for the phosphatase reaction catalyzed by the (Na+ + K+)-ATPase, a number of properties of that reaction differ from those with the common substratep-nitrophenyl phosphate (NPP): theK
m is 2 orders of magnitude less and the Vmax is two times greater, and dimethyl sulfoxide (Me2SO) inhibits rather than stimulates. In addition, reducing the incubation pH decreases both theK
m and Vmax for K+-activated 3-OMFP hydrolysis as well as theK
0.5 for K+ activation. However, reducing the incubation pH increases inhibition by Pi and the Vmax for 3-OMFP hydrolysis in the absence of K+. When choline chloride is varied reciprocally with NaCl to maintain the ionic strength constant, NaCl inhibits K+-activated 3-OMFP hydrolysis modestly with 10 mM KCl, but stimulates (in the range 5–30 mM NaCl) with suboptimal (0.35 mM) KCl. In the absence of K+, however, NaCl stimulates increasingly over the range 5–100 mM when the ionic strength is held constant. These observations are interpreted in terms of (a) differential effects of the ligands on enzyme conformations; (b) alternative reaction pathways in the absence of Na+, with a faster, phosphorylating pathway more readily available to 3-OMFP than to NPP; and (c) a (Na+ + K+)-phosphatase pathway, most apparent at suboptimal K+ concentrations, that is also more readily available to 3-OMFP.Abbreviations Et3N
triethyl amine
- FITC
fluorescein isothiocyanate
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonate
- MES
2-(N-morpholino)ethanesulfonate
- Me2SO
dimethyl sulfoxide
- NPP
p-nitrophenyl phosphate
- 3-OMFP
3-O-methylfluorescein phosphate
- TNP-ATP
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