• Korean Journal of Weed Science
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• v.31 no.4
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• pp.323-329
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• 2011

We investigated photodynamic stress-induced antioxidant responses in transgenic rice overexpressing Bradyrhizobium japonicum 5-aminolevulinic acid synthase (ALA-S) coding sequence lacking plastidal transit sequence. High light of $350{\mu}mol\;m^{-2}\;s^{-1}$ decreased the quantum yield in the transgenic lines, C4 and C5, compared to that of wild-type line. By contrast, non-photochemical quenching (NPQ) levels of C4 and C5 under high light were higher than those of the transgenic lines under low light of $150{\mu}mol\;m^{-2}\;s^{-1}$ as well as wild-type line under low and high light. Greater levels of NPQ in the transgenic lines exposed to high light were in a close correlation with increases in the xanthophyll pigment, zeaxanthin. Under high light, levels of neoxanthin, violaxanthin, lutein, and ${\beta}$-carotene in the transgenic lines were lower than those in wild-type line. Taken together, nonphotochemical energy dissipation and photoprotectant xanthophyll pigments play a critical role to deal with the severe photodynamic damage in the transgenic rice plants, although they could not overcome the photodynamic stress, leading to severe photobleaching symptoms.

• ALGAE
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• v.20 no.2
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• pp.121-125
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• 2005

The modern integrated fish-seaweed mariculture has been tested to reduce the environmental impacts of an intensive fed culture. To obtain the best seaweed bioremediation performance, the effects of therapeutants used for fish disease control on the selected seaweed species should be considered. As a selected seaweed, Porphyra yezoensis was tested with six commercial antibiotics including erythromycin thiocyanate_A, erythromycin thiocyanate_B, oxytetracycline, doxycycline, pefloxacin, and amoxicillin trihydrate under the batch incubation at a photon flux density of 10 $\mu$mol ${\cdot}m^{-2}\;{\cdot}\;s^{-1}$ at 15$^{\circ}C$. Among the tested commercial antibiotics, erythromycin thiocyanate_A, erythromycin thiocyanate_B, oxytetracycline, and doxycycline showed decreases in Fv/Fm, the photochemical efficiency of photosystem II, with a dose-dependant and time-dependant manner. From the quenching analysis of chlorophyll fluorescence, three differential patterns were observed in the antibiotics-treated Porphyra: (1) high nonphotochemical quenching (NPQ) and low photochemical quenching (qP) in the cases of Erythromycin thiocyanate_B and amoxicillin trihydrate, (2) high NPQ and high qP in the case of pefloxacin and (3) low NPQ and low qP in the case of oxytetracycline. These results indicated that antibiotics affected in various ways on the photosynthetic apparatus, reflecting differential lesion sites of antibiotics. In addition, the rates of ammonium uptake also decreased with a decrease of Fv/Fm in P. yezoensis thalli treated with erythromycin thiocyanate_B and oxytetracycline. Therefore, the four antibiotics mentioned could affect the bioremediation capacity of the selected seaweed species in the integrated fish-seaweed mariculture system due to the decrease of photosynthetic activity and the simultaneous decrease of ammonium uptake.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.676-682
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• 2012

The objectives of this study focused on measuring chlorophyll fluorescence related to drought stress comparing some parameters. Almost parameters were declined although they were not significant on the basis of mean values of fluorescence of total leaf area. While the ratio of fluorescence intensity variable chlorophyll ($F_V$) to fluorescence intensity maximal chlorophyll ($F_M$) was not changed, the effective quantum yield of photochemical energy conversion in photosystemII (${\Phi}PSII$) and chlorophyll fluorescence decrease ratio ($R_{fd}$) were slightly reduced, indicating inhibition of the electron transport from quinone bind protein A ($Q_A$) to quinone bind protein B ($Q_B$). Some parameters such as non-photochemical quenching rate ($NPQ_{_-LSS}$) and coefficients of non-photochemical quenching of variable fluorescence (qN) in mid-zone of leaf and near petiole zone leaf were significantly enhanced within 4 days after drought stress, which can be used as physiological stress parameters. Decrease in ${\Phi}PSII$ could was significantly measured in all leaf zones. In conclusion, three parametric evidences for chlorophyll fluorescence responses such as ${\Phi}PSII$, NPQ, and qN insinuated the possibility of photophysiological indices under drought stress.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1479-1484
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• 2010

Photosynthesis uses light energy to drive the oxidation of water at an oxygen-evolving catalytic site within photosystem II (PSII). Chlorophyll binding by the photosystem II subunit S protein, PsbS, was found to be necessary for energy-dependent quenching (qE), the major energy-dependent component of non-photochemical quenching (NPQ) in Arabidopsis thaliana. It is proposed that PsbS acts as a trigger of the conformational change that leads to the establishment of nonphotochemical quenching. However, the exact structure and function of PsbS in PSII are still unknown. Here, we clone and express the recombinant PsbS gene from Arabidopsis thaliana in E. coli and purify the resulting homogeneous protein. We used various biochemical and biophysical techniques to elucidate PsbS structure and function, including circular dichroism (CD), fluorescence, and DSC. The protein shows optimal stability at $4^{\circ}C$ and pH 7.5. The CD spectra of PsbS show that the conformational changes of the protein were strongly dependent on pH conditions. The CD curve for PsbS at pH 10.5 curve had the deepest negative peak and the peak of PsbS at pH 4.5 was the least negative. The fluorescence emission spectrum of the purified PsbS protein was also measured, and the ${\lambda}_{max}$ was found to be at 328 nm. PsbS revealed some structural changes under varying temperature and oxygen gas condition.