共查询到20条相似文献,搜索用时 15 毫秒
1.
B. Jongsareejit R. N. Z. A. Rahman S. Fujiwara T. Imanaka 《Molecular genetics and genomics : MGG》1997,254(6):635-642
The gltA gene encoding a glutamate synthase (GOGAT) from the hyperthermophilic archaeon Pyrococcus sp. KOD1 was cloned as a 6.6?kb HindIII-BamHI fragment. Sequence analysis indicates that gltA encodes a 481- amino acid protein (53?269?Da). The deduced amino acid sequence of KOD1-GltA includes conserved regions that are found in the small subunits of bacterial GOGAT: two cysteine clusters, an adenylate-binding consensus sequence and an FAD-binding consensus sequence. However, no sequences homologous to the large subunit of bacterial GOGAT were found in the upstream or downstream regions. In order to examine whether GltA alone can act as a functional GOGAT, GltA was overexpressed in Escherichia coli BL21 (DE3) cells using an expression plasmid. GltA was purified to homogeneity and shown to be functional as a homotetramer of approximately 205?kDa, which is equivalent to the molecular weight of the native GOGAT from KOD1, thus indicating that KOD1-GOGAT is the smallest known active GOGAT. GltA is capable of both glutamine-dependent and ammonia-dependent synthesis of glutamate. Synthesis of glutamate by KOD1-GltA required NADPH, indicating that this enzyme is an NADPH-GOGAT (EC 1.4.1.13). The optimum pH for both activities was 6.5. However, GltA exhibited different optimum temperatures for activity depending on the reaction assayed (glutamine-dependent reaction, 80°?C; ammonia-dependent reaction, 90°?C). 相似文献
2.
Indolepyruvate ferredoxin oxidoreductase (IOR) catalyzes the oxidative decarboxylation of arylpyruvates. Gene cloning and
sequencing analysis of the IOR gene from the hyperthermophilic archaeon Pyrococcus sp. KOD1 was performed. Two genes, iorA and iorB, encoding α and β subunits of IOR were found to be tandemly arranged, which suggests that gene expression is translationaly
coupled. Sequence analysis showed the C-terminal region of the α subunit to have a typical ferredoxin-type [4Fe-4S] cluster
motif (CXXCXXCXXCXXXCP), which is similar to that present in the δ subunits of other oxidoreductases such as pyruvate ferredoxin
oxidoreductase (POR) and 2-ketoisovalerate ferredoxin oxidoreductase (VOR). We suggest that the α subunit of KOD1-IOR has
a mosaic structure composed of features characteristic of the α, β and δ subunits from POR and VOR. KOD1-IOR was overproduced
in anaerobically incubated Escherichia coli cells and the crude enzyme was extracted under anaerobic conditions. The optimal temperature for activity of recombinant
IOR was 70° C and the half-life of this enzyme in the presence of air was 15 min at 25° C.
Received: 25 September 1996 / Accepted: 20 December 1996 相似文献
3.
Bernd Schröder Ina Rittmann Ernst Pfeffer Gerhard Breves 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(1):43-51
Unidirectional flux rates of Ca2+ across gastrointestinal tissues from sheep and goats were measured in vitro by applying the Ussing-chamber technique. Except for the sheep duodenum, mucosal to serosal Ca2+ flux rates (J
ms) exceeded respective flux rates in the opposite direction (J
sm) in both species and in all segments of the intestinal tract. This resulted in net Ca2+ flux rates␣(J
net = J
ms − J
sm) ranging between −2 and 9 nmol · cm−2 · h−1 in sheep and between 10 and 15 nmol cm−2 · h−1 in goats. In sheep, only J
net in jejunum, and in goats, J
netin duodenum and jejunum were significantly different from zero. Using sheep rumen wall epithelia, significant J
net of Ca2+ of around 5 nmol · cm−2 · h−1 could be detected. Since the experiments were carried out in the absence of an electrochemical gradient, significant net
Ca2+ absorption clearly indicates the presence of active mechanisms for Ca2+ transport. Dietary Ca depletion caused increased calcitriol plasma concentrations and induced significant stimulations of
net Ca2+ absorption in goat rumen. J
net of Ca2+ across goat rumen epithelia was significantly reduced by 1 mmol · l −1 verapamil in the mucosal buffer solution. In conclusion, there is clear evidence for the rumen as a main site for active
Ca2+ absorption in small ruminants. Stimulation of active Ca2+ absorption by increased plasma calcitriol levels and inhibition by mucosal verapamil suggest mechanistic and regulatory similarities
to active Ca2+ transport as described for the upper small intestines of monogastric species.
Accepted: 31 July 1996 相似文献
4.
Isabelle Sendowski Gustave Savourey Yves Besnard Jacques Bittel 《European journal of applied physiology and occupational physiology》1997,75(6):471-477
To study the physiological responses induced by immersing in cold water various areas of the upper limb, 20 subjects immersed
either the index finger (T1), hand (T2) or forearm and hand (T3) for 30 min in 5°C water followed by a 15-min recovery period.
Skin temperature of the index finger, skin blood flow (Qsk) measured by laser Doppler flowmetry, as well as heart rate (HR) and mean arterial blood pressure (ˉBPa) were all monitored during the test. Cutaneous vascular conductance (CVC) was calculated as Qsk / ˉBPa. Cold induced vasodilatation (CIVD) indices were calculated from index finger skin temperature and CVC time courses. The
results showed that no differences in temperature, CVC or cardiovascular changes were observed between T2 and T3. During T1,
CIVD appeared earlier compared to T2 and T3 [5.90 (SEM 0.32) min in T1 vs 7.95 (SEM 0.86) min in T2 and 9.26 (SEM 0.78) min
in T3, P < 0.01]. The HR was unchanged in T1 whereas it increased significantly at the beginning of T2 and T3 [+13 (SEM 2) beats · min−1 in T2 and +15 (SEM 3) beats · min−1 in T3, P < 0.01] and then decreased at the end of the immersion [−12 (SEM 3) beats · min−1 in T2, and −15 (SEM 3) beats · min−1 in T3, P < 0.01]. Moreover, ˉBPaincreased at the beginning of T1 but was lower than in T2 and T3 [+9.3 (SEM 2.5) mmHg in T1, P < 0.05; +20.6 (SEM 2.6) mmHg and 26.5 (SEM 2.8) mmHg in T2 and T3, respectively, P < 0.01]. The rewarming during recovery was faster and higher in T1 compared to T2 and T3. These results showed that general
and local physiological responses observed during an upper limb cold water test differed according to the area immersed. Index
finger cooling led to earlier and faster CIVD without significant cardiovascular changes, whereas hand or forearm immersion
led to a delayed and slower CIVD with a bradycardia at the end of the test.
Accepted: 26 November 1996 相似文献
5.
S. J. Brown R. B. Child S. H. Day A. E. Donnelly 《European journal of applied physiology and occupational physiology》1997,75(4):369-374
Indirect indices of exercise-induced human skeletal muscle damage and connective tissue breakdown were studied following
a single bout of voluntary eccentric muscle contractions. Subjects (six female, two male), mean (SD) age 22 (2) years performed
a bout of 50 maximum voluntary eccentric contractions of the knee extensors of a single leg. The eccentric exercise protocol
induced muscle soreness (P < 0.05 Wilcoxon test), chronic force loss, and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio
[P < 0.01, repeated measures analysis of variance (ANOVA)]. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) activities
were elevated (P < 0.01, repeated measures ANOVA) following the bout. The mean (SD) CK and LDH levels recorded 3 days post-exercise were 2815
(4144) IU · l–1 and 375 (198) IU · l–1, respectively. Serum alkaline phosphatase activity showed no changes throughout the study, and a non-significant increase
(P = 0.058, repeated measures ANOVA) in pyridinoline was recorded following the bout. Urinary hydroxyproline (HP) and hydroxylysine
(HL) excretion, expressed in terms of creatinine (Cr) concentration, increased after exercise (P < 0.05 and P < 0.01, respectively, repeated measures ANOVA). An increased HP:Cr was recorded 2 days post-exercise and HL:Cr was increased
above baseline on days 2, 5, and 9 post-exercise. This indirect evidence of exercise-induced muscle damage suggests that myofibre
disruption was caused by the eccentric muscle contractions. Elevated urine concentrations of indirect indices of collagen
breakdown following eccentric muscle contractions suggests an increased breakdown of connective tissue, possibly due to a
localised inflammatory response.
Accepted: 9 October 1996 相似文献
6.
Michael J. Webster Timothy P. Scheett Matthew R. Doyle Matthew Branz 《European journal of applied physiology and occupational physiology》1997,75(6):520-524
The purpose of this study was to investigate the effect of a thiamin derivative, thiamin tetrahydrofurfuryl disulfide (TTFD),
on oxygen uptake (˙VO2), lactate accumulation and cycling performance during exercise to exhaustion. Using a randomized, double-blind, cross-over
design with a 10-day washout between trials, 14 subjects ingested either 1 g · day−1 of TTFD or a placebo (PL) for 4 days. On day 3, subjects performed a progressive exercise test to exhaustion on a cycle ergometer
for the determination of ˙VO2submax, ˙VO2peak, lactate concentration ([La− ]), lactate threshold (ThLa) and heart rate ( f
c). On day 4, subjects performed a maximal 2000-m time trial on a cycle ergometer. A one-way analysis of variance (ANOVA) with
repeated measures was used to determine significant differences between trials. There were no significant differences detected
between trials for serial measures of ˙VO2submax, [La−] or f
c. Likewise, ˙VO2peak [PL 4.06 (0.19) TTFD 4.12 (0.19) l · min−1, P = 0.83], ThLa [PL 2.47 (0.17), TTFD 2.43 (0.16) l · min−1, P = 0.86] and 2000-m performance time [PL 204.5 (5.5), TTFD 200.9 (4.3) s, P = 0.61] were not significantly different between trials. The results of this study suggest that thiamin derivative supplementation
does not influence high-intensity exercise performance.
Accepted: 19 December 1996 相似文献
7.
A transposable element, Flipper, was isolated from the phytopathogenic fungus Botrytis cinerea. The element was identified as an insertion sequence within the coding region of the nitrate reductase gene. The Flipper
sequence is 1842 bp long with perfect inverted terminal repeats (ITRs) of 48 bp and an open reading frame (ORF) of 533 amino
acids, potentially encoding for a transposase; the element is flanked by the dinucleotide TA. The encoded protein is very
similar to the putative transposases of three elements from other phytopathogenic fungi, Fot1 from Fusarium oxysporum, and Pot2 and MGR586 from Magnaporthe grisea. The number of Flipper elements in strains of B. cinerea varied from 0 to 20 copies per genome. Analysis of the descendants of one cross showed that the segregation ratio of Flipper
elements was 2:2 and that the copies were not linked.
Received: 4 December 1996 / Accepted: 21 January 1997 相似文献
8.
Ralph Beneke Katharina Meyer 《European journal of applied physiology and occupational physiology》1997,75(3):246-251
The effect of a 3-week exercise programme on performance and economy of walking was analysed in 16 male patients with chronic
heart failure [mean age 51.8 (SD 6.9) years, height 174.9 (SD 6.3) cm, body mass 75.3 (SD 11.5) kg, ejection fraction 20.8
(SD 5.0)%]. They were submitted to a cardiopulmonary exercise test on a cycle ergometer and a 6-min walking test on a treadmill
before and after the period of exercise training. The training programme consisted of interval cycle (five times a week for
15 min), and treadmill ergometer training (three times a week for 10 min) at approximately 70% cycling peak oxygen uptake
(O2peak) and supplementary exercises (three times a week for 20 min). Compared to the pre values cycling O2peak [11.9 (SD 2.9) vs 14.0 (SD 2.3) ml · kg–1 · min–1], maximal self paced walking speed [0.68 (SD 0.33) vs 1.16 (SD 0.30) m · s–1], and net walking power [2.16 (SD 0.89) vs 2.73 (SD 0.91) W · kg–1] had increased (P < 0.01) while net energy cost [3.31 (SD 0.66) vs 2.33 (SD 0.38) J · kg–1 · m–1] had decreased (P < 0.001) after the training period. Approximately 42% of the increase of walking speed resulted from a higher walking power
output, whereas approximately 58% corresponded to a positive effect on walking economy. The improvement in walking economy
was a function of an increase in walking velocity itself and a result of a more efficient walking technique. These results
would indicate that in patients with marked exercise intolerance, adequate exercise training programmes could contribute to
favourable metabolic changes with positive effects on the economy of motion.
Accepted: 29 August 1996 相似文献
9.
D. A. Mullin D. L. Zies A. H. Mullin N. Caballera B. Ely 《Molecular & general genetics : MGG》1997,254(4):456-463
IS511 is an endogenous insertion sequence (IS) of the bacterium Caulobactercrescentus strain CB15 and it is the first Caulobacter IS to be characterized at the molecular level. We determined the 1266-bp nucleotide sequence of IS511 and investigated its genetic organization, relationship to other ISs, and transposition properties. IS511 belongs to a distinct branch of the IS3 family that includes ISRI, IS476, and IS1222, based on nucleotide sequence similarity. The nucleotide sequence of IS511 encodes open reading frames (orfs) designated here as orfA and orfB, and their relative organization and amino acid sequences of the predicted protein products are very similar to those of
orfAs and orfBs of other IS3 family members. Nuclease S1 protection assays identified an IS511 RNA, and its 5′ end maps approximately 16 nucleotides upstream of orfA and about six nucleotides downstream of a sequence that is similar to the consensus sequence of C. crescentus housekeeping promoters. Evidence is presented that IS511 is capable of precise excision from the chromosome, and transposition from the chromosome to a plasmid. Transpositional insertions
of IS511 occurred within sequences with a relatively high G + C content, and they were usually, but not always, flanked by a 4-bp
direct repeat that matches a sequence at the site of insertion. We also determined the nucleotide sequence flanking the four
endogenous IS511 elements that reside in the chromosome of C. crescentus. Our findings demonstrate that IS511 is a transposable IS that belongs to a branch of the IS3 family.
Received: 18 August 1996 / Accepted: 17 September 1996 相似文献
10.
Light response characteristics of a morphologically diverse group of southern hemisphere conifers as measured by chlorophyll fluorescence 总被引:5,自引:0,他引:5
Unlike northern hemisphere conifer families, the southern family, Podocarpaceae, produces a great variety of foliage forms
ranging from functionally broad-, to needle-leaved. The production of broad photosynthetic surfaces in podocarps has been
linked qualitatively to low-light-environments, and we undertook to assess the validity of this assumption by measuring the
light response of a morphologically diverse group of podocarps. The light response, as apparent photochemical electron transport
rate (ETR), was measured by modulated fluorescence in ten species of this family and six associated species (including five
Cupressaceae and one functionally needle-leaved angiosperm) all grown under identical glasshouse conditions. In all species,
ETR was found to increase as light intensity increased, reaching a peak value (ETRmax) at saturating quantum flux (PPFDsat), and decreasing thereafter. ETRmax ranged from 217 μmol electrons · m−2 · s−1 at a PPFDsat of 1725 μmol photons · m−2 · s−1 in Actinostrobus acuminatus to an ETR of 60 μmol electrons · m−2 · s−1 at a PPFDsat of 745 μmol electrons · m−2 · s−1 in Podocarpus dispermis. Good correlations were observed between ETRmax and both PPFDsat and maximum assimilation rate measured by gas-exchange analysis. The effective quantum yield at light saturation remained
constant in all species with an average value of 0.278 ± 0.0035 determined for all 16 species. Differences in the shapes of
light response curves were related to differences in the response of non-photochemical quenching (q
n), with q
n saturating faster in species with low PPFDsat. Amongst the species of Podocarpaceae, the log of average shoot width was well correlated with PPFDsat, wider leaves saturating at lower light intensities. This suggests that broadly flattened shoots in the Podocarpaceae are
an adaptation to low light intensity.
Received: 15 April 1996 / Accepted: 30 September 1996 相似文献
11.
H. Adelsberger J. Dudel 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1996,180(1):53-61
Whereas the inhibitory innervation of the deep extensor abdominal muscle in crayfish is mediated by a weakly acting common
inhibitor, the opener muscle exhibits a stronger inhibition. In the present study the most abundant γ-aminobutyric acid-activated
chloride channel on distal fibers of crayfish opener muscle was characterized by measuring the current responses after applying
pulses of γ-aminobutyric acid to outside-out patches. The results were compared to those obtained earlier with the chloride
channel on the deep extensor abdominal muscle of the same species. The double logarithmic plot of the dose-response relationship
had a slope of n
H = 2.2 in contrast to n
H = 5.3 for the channel on the deep extensor abdominal muscle. The rise time of the current response declined to 1 ms at a
γ-aminobutyric acid concentration of 50 mmol · l−1. With lower concentrations the rise time increased to a maximal value of 280 ms. No peak of the rise time at low γ-aminobutyric
acid concentrations, as observed for the channel on the deep extensor abdominal muscle, was obvious. The open and closed times
were similar to those of the channel of the deep extensor abdominal muscle. Different reaction schemes were discussed to describe
the kinetics of the chloride channel of the opener muscle.
Accepted: 12 August 1996 相似文献
12.
We have used the polymerase chain reaction (PCR) method to monitor meiotic recombination in the basidiomycete Coprinus cinereus. We used DNA-mediated transformation to recover strains with modifications of the trp1 locus. The modifications were designed to introduce unique PCR priming sites separated by a homologous 2.4 kb region in which
crossing over could occur. We showed that exchange occurred in this region at the frequency expected for a typical region
of this genome (2.4 kb should correspond to a genetic length of 0.08 cM). We also detected products resulting from crossing
over in DNAs extracted from cells in meiotic prophase. The assay should be useful for monitoring exchange in mutants that
cannot complete meiosis.
Received: 5 September 1996 / Accepted: 1 December 1996 相似文献
13.
To isolate genes that negatively regulate cell growth, we constructed a galactose-inducible expression library with partially
digested Saccharomyces cerevisiae genomic DNA fragments inserted downstream of the GAL10 promoter. In all, 240 000 yeast transformants were screened for lethality on galactose medium. From 17 such transformants
identified, 16 nonoverlapping DNA sequences were obtained. Restriction mapping and determination of DNA sequences adjacent
to the GAL10 promoter indicated that the inserts encoded part or all of the URA2, RBP1, TPK3, SAC7, BOI1, and BNI1 genes, and also open reading frames (ORFs) from chromosomes IV, V, IX, XI, and XIII. Some of the identified sequences lacked
the amino-terminal sequences of the ORFs, suggesting that truncated forms of the proteins might be necessary for growth inhibition.
The sequence of the pGA108 insert was highly homologous to the telomeric X-element and contained an ARS consensus sequence, suggesting a possible growth inhibitory effect of an RNA molecule. Overexpression of the BNI1ΔN and BOI1ΔN genes, which lacked amino-terminal sequences, was associated with phenotypes similar to those of mutants defective in bud
formation. Overexpression of the GIN4 and GIN12 sequences induced elongated buds and a G2/M arrest-like phenotype, respectively.
The phenotypes induced by the overexpression of our cloned sequences could result from either a dominant-positive or a dominant-negative
effect and, unexpectedly, in one case from an effect of an RNA.
Received: 3 June 1996 / Accepted: 1 October 1996 相似文献
14.
R. N. Z. A. Rahman S. Fujiwara M. Takagi T. Imanaka 《Molecular & general genetics : MGG》1998,257(3):338-347
The gdhA gene encoding glutamate dehydrogenase (GDH) from the hyperthermophilic archaeon Pyrococcus sp. KOD1 was cloned and sequenced. Phylogenetic analysis was performed on an alignment of 25 GDH sequences including KOD1-GDH,
and two protein families were distinguished, as previously reported. KOD1-GDH was classified as new member of the hexameric
GDH Family II. The gdhA gene was expressed in Escherichia coli, and recombinant KOD1-GDH was purified. Its enzymatic characteristics were compared with those of the native KOD1-GDH. Both
enzymes had a molecular mass of 47 300 Da and were shown to be functional in a hexameric form (284 kDa). The N-terminal amino
acid sequences of native KOD1-GDH and the recombinant GDH were VEIDPFEMAV and MVEIDPFEMA, respectively, indicating that native
KOD1-GDH does not retain the initial methionine at the N-terminus. The recombinant GDH displayed enzyme characteristics similar
to those of the native GDH, except for a lower level of thermostability, with a half-life of 2 h at 100° C, compared to 4 h
for the native enzyme purified from KOD1. Kinetic studies suggested that the reaction is biased towards glutamate production.
KOD1-GDH utilized both coenzymes NADH and NADPH, as do most eukaryal GDHs.
Received: 6 May 1997 / Accepted: 23 September 1997 相似文献
15.
Evidence for NO-dependent vasodilation in the trout (Oncorhynchus mykiss ) coronary system 总被引:1,自引:0,他引:1
T. Mustafa C. Agnisola J. K. Hansen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):98-104
The effects of l-arginine, and its analogues N
ω-nitro-l-arginine methyl ester and N
ω-nitro-l-arginine on vascular resistance were investigated in the intact coronary system of an isolated non-working trout heart preparation.
l-Arginine, at 10–8 mol · l–1induced a slight vasodilatory effect (max 10%). N
ω-nitro-l-arginine methyl ester and N
ω-Nitro-l-arginine in the range 10–8–10–4 mol · l–1 caused dose-dependent increases in coronary resistance. The vasodilatory action of l-arginine was abolished when the preparation was pretreated with 10–4 mol · l–1
N
ω-nitro-l-arginine or N
ω-nitro-l-arginine methyl ester. Nitroprusside alone at 1 mmol · l–1 induced a maximum vasodilation (30%) of the coronary system. Methylene blue a known inhibitor of guanylate cyclase, induced
a strong vasoconstriction (already significant at 10–5 mol · l–1) and was able to overcome the vasodilative effect of nitroprusside. The endothelial nitric oxide agonists acetylcholine and
serotonin, established in mammalian vessels, also mediate vasodilation in trout coronary system. In 50% of preparations, acetylcholine
induced a biphasic response with vasodilation at low concentration (max 15% at 10–8 mol · l–1). Serotonin displayed a dose-response vasodilation in the range 10–8–10–4 mol · l–1 (max 20%). These vasodilative effects were reduced or abolished by 10–4 mol · l–1
l-NA. These data support the existence of NO-mediated vasodilation mechanisms in the trout coronary system.
Accepted: 1 July 1996 相似文献
16.
J.-P. Cassart J. ?stling H. Ronne J. Vandenhaute 《Molecular & general genetics : MGG》1997,255(1):9-18
The Mig1 repressor is a key effector in glucose repression in the yeast Saccharomyces cerevisiae. To gain further insights into structure-function relationships, we have now cloned the MIG1 homologue from the yeast Kluyveromyces marxianus. The amino acid sequence deduced from KmMIG1 differs significantly from ScMig1p outside the highly conserved zinc fingers. However, 12 discrete conserved motifs could
be identified in a multiple alignment that also included the K. lactis Mig1p sequence. We further found that KmMig1p is fully functional when expressed in S. cerevisiae. First, it represses the SUC2 promoter almost as well as ScMig1p. This repression requires the Cyc8 and Tup1 proteins and is dependent on a C-terminal
region comprising several conserved leucine-proline repeats. Second, KmMig1p is regulated by glucose in S. cerevisiae, and a KmMig1-VP16 hybrid activator is inhibited by the ScSnf1p kinase in the absence of glucose. This suggests that KmMig1p
has retained the ability to interact with several S. cerevisiae proteins, and reinforces the notion that the conserved motifs are functionally important. Finally, we found that the physiological
role of Mig1p also is conserved in K. marxianus, since KmMig1p represses INU1, the counterpart of SUC2 in this organism.
Received: 16 October 1996 / Accepted: 19 February 1997 相似文献
17.
P. Meier J. Zettel 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):297-304
In the Swiss Prealps Entomobrya nivalis hibernates in an inactive state, hidden under bark flakes on spruce. For freeze avoidance it relies on thermal hysteresis
proteins (THPs) and polyols (mainly ribitol, with small amounts arabitol and threitol). Polyols are present only during the
inactive state, THPs additionally protect during the transition phase in spring and autumn, when animals are still active
but frosts may occur. Peak values were recorded in February/March for THPs (3.5 °C hysteresis between melting and freezing
point) and for polyols (26 μg mg−1 FW; hemolymph osmolality 680 mosmol l−1). E. nivalis is able to control its hemolymph osmolality independently of body water content. Mean osmolality in summer was 350– 440 mosmol l−1, in winter it was elevated to 650 mosmol l−1, due to a synthesis mainly of ribitol. Body water content varied between 1.8 and 3.3 mg H2O mg−1 DW, depending on humidity conditions. Experiments on triggering of antifreeze synthesis showed the action of temperature
and photoperiod as cues, but there was also evidence for an endogenous rhythm. No clear correlation between antifreeze concentration
and supercooling ability could be established, suggesting that gut content or other parameters also play an inportant role.
Accepted: 18 November 1995 相似文献
18.
Identification of transposon-like elements in non-coding regions of tomato ACC oxidase genes 总被引:4,自引:0,他引:4
B. Blume C. S. Barry A. J. Hamilton M. Bouzayen D. Grierson 《Molecular & general genetics : MGG》1997,254(3):297-303
1-aminocyclopropane-1-carboxylate (ACC) oxidase, which catalyses the terminal step in ethylene biosynthesis, is encoded by
a small multigene family in tomato that is differentially expressed in response to developmental and environmental cues. In
this study we report the isolation and sequencing of approximately 2 kb of 5′-flanking sequence of three tomato ACC oxidase
genes (LEACO1, LEACO2, LEACO3) and the occurrence of class I and class II mobile element-like insertions in promoter and intron regions of two of them.
The LEACO1 upstream region contains a 420-bp direct repeat which is present in multiple copies in the tomato genome and is very similar
to sequences in the promoters of the tomato E4 and 2A11 genes. The region covering the repeats resembles the remnant of a retrotransposon. Two copies of a small transposable element,
belonging to the Stowaway inverted repeat element family, have been found in the 5′-flanking sequence and the third intron of LEACO3.
Received: 8 August 1996 / Accepted: 4 November 1996 相似文献
19.
M. Kato A. Aoyama F. Naruse T. Kobayashi N. Tsukagoshi 《Molecular & general genetics : MGG》1997,254(2):119-126
Using AnCP (Aspergillus nidulans CCAAT-binding protein) as a CCAAT-specific binding factor model, the possibility that one factor is able to recognize CCAAT
sequences in several different genes in A.␣nidulans was examined. DNase I protection analysis showed that AnCP specifically bound to CCAAT sequence-containing regions comprising
21 to 36 bp of the taa, amdS and gatA genes. Furthermore, replacement of the CCAAT sequence with CGTAA was found to abolish the binding of AnCP and to have an
inhibitory effect on taa promoter activity. This clearly demonstrates a positive function of the CCAAT element. However, amylase was induced by starch
and repressed by glucose in a CCAAT-box disruptant, as in wild-type cells.
Received: 28 June 1996 / Accepted: 7 October 1996 相似文献
20.
Stem respiration of ponderosa pines grown in contrasting climates: implications for global climate change 总被引:7,自引:0,他引:7
We examined the effects of climate and allocation patterns on stem respiration in ponderosa pine (Pinus ponderosa) growing on identical substrate in the cool, moist Sierra Nevada mountains and the warm, dry, Great Basin Desert. These environments
are representative of current climatic conditions and those predicted to accompany a doubling of atmospheric CO2, respectively, throughout the range of many western north American conifers. A previous study found that trees growing in
the desert allocate proportionally more biomass to sapwood and less to leaf area than montane trees. We tested the hypothesis
that respiration rates of sapwood are lower in desert trees than in montane trees due to reduced stem maintenance respiration
(physiological acclimation) or reduced construction cost of stem tissue (structural acclimation). Maintenance respiration
per unit sapwood volume at 15°C did not differ between populations (desert: 6.39 ± 1.14 SE μmol m−3 s−1, montane: 6.54 ± 1.13 SE μmol m−3 s−1, P = 0.71) and declined with increasing stem diameter (P = 0.001). The temperature coefficient of respiration (Q
10) varied seasonally within both environments (P = 0.05). Construction cost of stem sapwood was the same in both environments (desert: 1.46 ± 0.009 SE g glucose g−1 sapwood, montane: 1.48 ± 0.009 SE glucose g−1 sapwood, P = 0.14). Annual construction respiration calculated from construction cost, percent carbon and relative growth rate was greater
in montane populations due to higher growth rates. These data provide no evidence of respiratory acclimation by desert trees.
Estimated yearly stem maintenance respiration was greater in large desert trees than in large montane trees because of higher
temperatures in the desert and because of increased allocation of biomass to sapwood. By analogy, these data suggest that
under predicted increases in temperature and aridity, potential increases in aboveground carbon gain due to enhanced photosynthetic
rates may be partially offset by increases in maintenance respiration in large trees growing in CO2-enriched atmospheres.
Received: 4 November 1996 / Accepted: 23 January 1997 相似文献