排序方式: 共有8条查询结果,搜索用时 31 毫秒
1
1.
The effects of light intensity, pH, temperature, and UV irradiation on the photosynthetic rate of Prochloron isolated from the ascidian host Lissoclinum patella, collected from Palau, were examined. Photosynthesis increased with light intensity with saturation at 500 μmol/m2 per second. It was maximum at pH 8 to 9 but almost completely suppressed below pH 7. The optimum temperature was 35° to 40°C,
but the photosynthesis was absent at ≤20°C and at 45°C. It was recovered when the symbiont was transferred from 1 hour of
incubation at ≤20°C to 35°C but not when transferred from incubation at 45°C. Ultraviolet irradiation severely inhibited the
photosynthesis of Prochloron in isolation but not in vivo. This protection was brought about by the tunic covering the ascidian colony, which contains
UV-absorbing mycosporine-like amino acids. These results indicate that the characteristic condition of the tropical marine
environment largely determines the ecological distribution of Prochloron, and the ascidian tunic protects the organism from UV radiation.
Received February 17, 2000; accepted August 8, 2000. 相似文献
2.
Maribel L. Dionisio-Sese Atsuhiro Shimada Tadashi Maruyama Shigetoh Miyachi 《Archives of microbiology》1993,159(1):1-5
The prokaryotic algal symbiont of ascidians, Prochloron sp., was found to exhibit carbonic anhydrase activity which is largely associated with the cell surface. This extracellular carbonic anhydrase activity was inhibited, while the intracellular activity was not affected, by chloride or bromide. Acetazolamide and ethoxyzolamide inhibited carbonic anhydrase activity with I50 values of 7×10-4 and 3×10-4M, respectively. These I50 values are similar to those observed for intracellular carbonic anhydrases of Synechococcus sp. PCC7942, Chlamydomonas reinhardii and spinach.Abbreviations AZA
acetazolamide
- CA
carbonic anhydrase
- chl
chlorophyll
- EZA
ethozyzolamide
- I50
concentration of an inhibitor required to cause 50% inhibition
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- U
unit 相似文献
3.
The effects of NaCl on the internal and external carbonic anhydrase (CA) activity of several marine microalgae were studied. Unlike freshwater microalgae in which CA activity is generally inhibited by NaCl, marine microalgae exhibited considerable species-dependent variation when exposed to NaCl. CA activity in Phaeodactylum tricornutum, a diatom, was inhibited, whereas it was activated in the coccolithophorid Pleurochrysis carterae. CA activity in the chlorophyte Dunaliella primolecta was not significantly affected by NaCl. In Dunaliella salina and Dunaliella parva, NaCl inhibited external CA without affecting the internal activity, whereas in Chlorella vulgaris C-133 and Dunaliella peircei only the internal CA was inhibited. Internal CA of Dunaliella tertiolecta was not affected by NaCl, but the external enzyme was significantly enhanced. Salt substitution experiments revealed that chloride (Cl-) is the ion affecting CA activity; the effect of Cl- can be replaced by bromide ion. Cl- affects external CA activity while also affecting the apparent affinity for inorganic carbon during photosynthesis. Microalgae whose internal CA activity was enhanced by Cl- showed higher intracellular Cl- concentrations than those species that were inhibited. 相似文献
4.
Pesheva Iskra; Kodama Minoru; Dionisio-Sese Maribel L.; Miyachi Shigetoh 《Plant & cell physiology》1994,35(3):379-387
When air-grown cells of Chlorococcum littorale was enrichedwith CO2, growth was enhanced after a lag period of one to twodays at 20% CO2, and 3 to 6 days at 40% CO2. Changes in therate of photosynthesis measured as oxygen evolution and CO2fixation, were similar to those observed for growth. Duringthe initial inhibition of photosynthesis in 40% CO2, the activityof PSII was suppressed. In contrast, PSI activity was greatlyenhanced. Air-grown cells of C. littorale possessed comparatively highcarbonic anhydrase (CA) activity which was localized insidethe cells and on the cell surface. Under high CO2 concentrationsextracellular CA activity was greatly suppressed and intracellularactivity almost completely abolished. Phosphoenol pyruvate carboxylaseactivity was also suppressed in high CO2-grown cells. Ribulose-l,5-bisphosphatecarboxylase activity was higher in high-CO2 grown cells thanin air-grown cells. The above results indicated that the lagphase induced by 40% CO2 was due to suppression of PSII activity.
1Part of this work was reported in the International PhotosynthesisCongress, Nagoya, 1992. 相似文献
5.
6.
Bouly JP Schleicher E Dionisio-Sese M Vandenbussche F Van Der Straeten D Bakrim N Meier S Batschauer A Galland P Bittl R Ahmad M 《The Journal of biological chemistry》2007,282(13):9383-9391
Cryptochromes are blue light-sensing photoreceptors found in plants, animals, and humans. They are known to play key roles in the regulation of the circadian clock and in development. However, despite striking structural similarities to photolyase DNA repair enzymes, cryptochromes do not repair double-stranded DNA, and their mechanism of action is unknown. Recently, a blue light-dependent intramolecular electron transfer to the excited state flavin was characterized and proposed as the primary mechanism of light activation. The resulting formation of a stable neutral flavin semiquinone intermediate enables the photoreceptor to absorb green/yellow light (500-630 nm) in addition to blue light in vitro. Here, we demonstrate that Arabidopsis cryptochrome activation by blue light can be inhibited by green light in vivo consistent with a change of the cofactor redox state. We further characterize light-dependent changes in the cryptochrome1 (cry1) protein in living cells, which match photoreduction of the purified cry1 in vitro. These experiments were performed using fluorescence absorption/emission and EPR on whole cells and thereby represent one of the few examples of the active state of a known photoreceptor being monitored in vivo. These results indicate that cry1 activation via blue light initiates formation of a flavosemiquinone signaling state that can be converted by green light to an inactive form. In summary, cryptochrome activation via flavin photoreduction is a reversible mechanism novel to blue light photoreceptors. This photocycle may have adaptive significance for sensing the quality of the light environment in multiple organisms. 相似文献
7.
Activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) in heated crude extracts from seedlings of the rice cultivars Hitomebore and IR28 was investigated in the presence of proline and betaine. Both solutes retarded the inactivation of the enzyme extracted from the leaves of both cultivars at temperature-stress from 35 to 45 °C. At 50 °C, however, betaine was effective in both cultivars. Stabilization of RuBPCO activity was independent of the added solute from 1 to 2 M concentration. 相似文献
8.
Activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) in heated crude extracts from seedlings of the rice cultivars
Hitomebore and IR28 was investigated in the presence of proline and betaine. Both solutes retarded the inactivation of the
enzyme extracted from the leaves of both cultivars at temperature-stress from 35 to 45 °C. At 50 °C, however, betaine was
effective in both cultivars. Stabilization of RuBPCO activity was independent of the added solute from 1 to 2 M concentration.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
1