Biomedical subjects

Xian-De Liu

Publications and source records attributed to Xian-De Liu.

5 recordsLinked to original sources

PubMed2006

Transient decrease of light-harvesting complex II phosphorylation level by hypoosmotic shock in dark-adapted Dunaliella salina.

This study investigated the regulation of major light harvesting chlorophyll a/b protein (LHCII) phosphorylation by hypoosmotic shock in dark-adapted Dunaliella salina cells. When the external NaCl concentration decreased in darkness, D. salina LHCII phosphorylation levels transiently dropped within 20 min and then restored gradually to basal levels. The transient decrease in LHCII phosphorylation levels was insensitive to NaF, a phosphatase inhibitor. Inhibition of intracellular ATP production by addition of an uncoupler or an ATP synthase inhibitor increased LHCII phosphorylation levels in D. salina cells exposed to hypoosmotic shock. Taken together, these results indicate that hypoosmotic shock inhibits the LHCII phosphorylation process. The related mechanism and physiological significance are discussed.

Adenosine Triphosphate↗

PubMed2006

[State transition of the photosynthetic apparatus in plant].

State transition of the photosynthetic apparatus in plants is a short-term adaptation mediated mainly by the reversible phosphorylation of the main light-harvesting complex protein (LHCII) and its migration between photosystem I (PSI) and photosystem II (PSII). In higher plants and Chlamydomonas, LHCII phosphorylation is mainly controlled by the redox state of plastoquinone pool and cytochrome b(6)f complex, while salt could induce a redox-independent LHCII phosphorylation via transient changes in ion concentrations in Dunaliella. State transition can balance the distribution of excitation energy between PSII and PSI by changes in light absorption cross section and excitation energy spillover between the two photosystems. The preliminary results got in the studies of green algae reveal that state transition can also balance the ATP supply and demand.

Adenosine Triphosphate↗

PubMed2005

Salt-induced redox-independent phosphorylation of light harvesting chlorophyll a/b proteins in Dunaliella salina thylakoid membranes.

This study investigated the regulation of the major light harvesting chlorophyll a/b protein (LHCII) phosphorylation in Dunaliella salina thylakoid membranes. We found that both light and NaCl could induce LHCII phosphorylation in D. salina thylakoid membranes. Treatments with oxidants (ferredoxin and NADP) or photosynthetic electron flow inhibitors (DCMU, DBMIB, and stigmatellin) inhibited LHCII phosphorylation induced by light but not that induced by NaCl. Furthermore, neither addition of CuCl(2), an inhibitor of cytochrome b(6)f complex reduction, nor oxidizing treatment with ferricyanide inhibited light- or NaCl-induced LHCII phosphorylation, and both salts even induced LHCII phosphorylation in dark-adapted D. salina thylakoid membranes as other salts did. Together, these results indicate that the redox state of the cytochrome b(6)f complex is likely involved in light- but not salt-induced LHCII phosphorylation in D. salina thylakoid membranes.

Chlorophyta↗

PubMed2005

[Changes in trans-thylakoid membrane proton motive force induced by treatments with red and far-red light in Dunaliella salina].

The changes in trans-thylakoid membrane proton motive force caused by red light and caused by far-red light in the halotolerant green alga, Dunaliella salina are investigated. Irradiation with red light decreased the intensity of the fast phase of millisecond delayed light emission (ms-DLE) in D. salina, and far-red light led to the opposite effects. Under low temperature conditions (4 degrees C), red light still decreased ms-DLE fast phase intensity, however, far-red light did not enhance the ms-DLE fast phase intensity as it did at room temperature. In the presence of the uncoupler, nigericin, which eliminates the proton gradient across the thylakoid membrane, there was still a decrease in ms-DLE after red light irradiation, while far-red light had no stimulatory effects anymore. The far-red light-induced increase in ms-DLE fast phase is thus suggested to be due to the proton gradient formed by water oxidation in photosystem II. Previous studies with higher plants revealed that far red light increased ms-DLE fast phase intensity slightly, while red light caused a transient increase in ms-DLE fast phase intensity followed by a gradual decrease. Taken together, green algae differ from higher plants with respect to red light- and far red light-induced changes in ms-DLE. The possible reason is discussed.

Chlorophyta↗

PubMed2004

NaCl-induced phosphorylation of light harvesting chlorophyll a/b proteins in thylakoid membranes from the halotolerant green alga, Dunaliella salina.

Light could induce phosphorylation of light harvesting chlorophyll a/b binding proteins (LHCII) in Dunaliella salina and spinach thylakoid membranes. We found that neither phosphorylation was affected by glycerol, whereas treatment with NaCl significantly enhanced light-induced LHCII phosphorylation in D. salina thylakoid membranes and inhibited that in spinach. Furthermore, even in the absence of light, NaCl and several other salts induced LHCII phosphorylation in D. salina thylakoid membranes, but not in spinach thylakoid membranes. In addition, hypertonic shock induced LHCII phosphorylation in intact D. salina under dark conditions and cells adapted to different NaCl concentrations exhibited similar LHCII phosphorylation levels. Taken together, these results show for the first time that while LHCII phosphorylation of D. salina thylakoid membranes resembles that of spinach thylakoid membranes in terms of light-mediated control, the two differ with respect to NaCl sensitivity under light and dark conditions.

Chlorophyta↗