• Journal of Plant Biology
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• v.36 no.3
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• pp.259-266
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• 1993

In Tris-iso-butanol (TIB; Tris buffer pH 8.8 and 1% iso-butanol)-treated chloroplasts, oxygen evolving activity was more inhibited than Tris-treated chloroplasts, but restored highly by 2,6-dichlorophenol-indophenol (DCPIP) and photoreactivation. To understand the mechanism of this results of TIB in photosynthetic electron transport, system, oxygen consumption and evolution of PS I and PS II were measured and protein of the chloroplasts was analysed. In Tris- and TIB-treated chloroplasts, oxygen evolving activity was increased according to the light intensity. Under 48 W·m-2 light intensity, the oxygen evolving activity in both chloroplasts were similar but as the light intensity was increased, TIB-treated chloroplasts showed higher activity. Under 240 W·m-2 light intensity, TIB-treated chloroplasts showed about 25% higher oxygen evolving activity than Tris-treated chloroplasts. Oxygen evolving activity was increased after photoreactivation in both Tris-treated and TIB-treated chloroplasts. Addition of NH4Cl increased the activity in both chloroplasts but in TIB-treated chloroplasts the increase was 30% higher than that in Tris-treated chloroplasts. In PS I, oxygen evolving activity was not inhibited by both treatments whereas in PS II, significant difference was observed between two treatments. Addition of Mn2+ and Ca2+ enhanced oxygen evolution in both Tris- and TIB-treated chloroplasts. Though enhancement was higher in TIB-treated chloroplasts. No difference was observed n protein analysis of the two thylakoid membrane.

• Journal of Pharmacopuncture
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• v.15 no.1
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• pp.18-22
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• 2012

Panax ginseng is a well-known herbal medicine in traditional Asian medicine. Although wild ginseng is widely accepted to be more active than cultivated ginseng in chemoprevention, little has actually been reported on the difference between wild ginseng and cultivated ginseng. Using suppressive subtraction hybridization, we cloned the p-psbB gene as a candidate target gene for a wild ginseng-specific gene. Here, we report that one of the clones isolated in this screen was the chloroplast p-psbB gene, a chlorophyll a-binding inner antenna protein in the photosystem II complex, located in the lipid matrix of the thylakoid membrane. Real-time results showed that the expression of the p-psbB gene was significantly up-regulated in wild ginseng as compared to cultivated ginseng. Thus, the p-psbB gene may be one of the important markers of wild ginseng.

• Journal of Plant Biology
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• v.37 no.2
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• pp.231-236
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• 1994

The effect of $Cd^{2+}$ on the electron transport rate of PSI and PSII was investigated in isolated spinach chloroplasts. In photosystem II, the rate of electron transport was decreased as the concentration of $Cd^{2+}$ was increased from 1 to $100\;\mu\textrm{M}$. The inhibitory effect of $Cd^{2+}$ was reduced when diphenylcarbazide was added to the reaction medium, indicating that $Cd^{2+}$ affects primarily psn oxygen evolving complexes of thylakoid membrane. The inhibitory effect of $Cd^{2+}$ was reduced when $Mn^{2+}\;and\;Ca^{2+}$ were added to the reaction medium, but the inhibitory effect was not fully relieved. Although the activity of psn was decreased significantly by the treatment of $50\;\mu\textrm{M}\;Cd^{2+}$, Fv/Fm was decreased slightly. However, the treatment of $100\;\mu\textrm{M}\;Cd^{2+}$ resulted in the marked decrease of Fv/Fm. In photosystem I, the rate of electron transport decreased as the concentration of $Cd^{2+}$ was increased from 0.2 to 3.2 mM. The inhibitory effect of $Cd^{2+}$ was decreased when the chloroplast treated with $Cd^{2+}$ was washed by centrifugation.gation.

• Journal of Plant Biology
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• v.35 no.2
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• pp.143-153
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• 1992

Nectar secretion from extrafloral nectary cells of Prunus yedoensis was examined by light and electron microscopy. Nectaries were composed of two or three layers of secretory cells and one layer of subsectretory cells. Vascular bundles in the petioles were connected to those of the subsectretory cell layer. Secretory cells had a number of mitochondria with poorly developed cristae. Plastids had little thylakoids and small vesicles, about 0.2 to 0.3 mm in diameter; however, no plastids had starch grains. Calcium oxalate crystals and plasmodesmata were frequently observed in the subsectretory and secretory cells, respectively. And nectar substances were observed in phloem of petiole, subsectretory, and secretory cells of the secretory gland. These results suggested that the nectar moved by symplastic transport through the plasmodesmata. On the other hand, the nectar droplets were observed in the secretory cell walls. in the cuticular layer just beyond of the former, and on the outer surface of the cuticular layer: such observations indicated that a apoplastic movement was involved in the final step of the nectar secretion. Cellular components related to the nectar transport, such as plasma membrane, cell wall and cuticle were not destroyed but intact: it was interpreted as a eccrine secretion.retion.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.2
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• pp.84-90
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• 2005

The effects of UV-B radiation on the seedling growth, carbohydrate metabolism and antioxidants activities of rice (Oryza sativa L.) were investigated under environmentally controlled chamber. Supplementary UV­B radiation reduced dry matter as well as leaf area, there­fore, relative growth rates (RGR) of seedlings were decreased by up to half compared to control. Photosynthetic products such as soluble sugars and starch were rapidly and significantly reduced by within 1 day of enhanced UV-B radiation due to the inhibition and degradation of photosynthetic processes and thylakoid membrane integrity. In our study, nonstructural carbohydrate levels were proved to be a main indicator on UV-B­induced stress. The behavior of SOD, CAT, APX and POD activities was monitored in the leaves of rice seedlings subjected to UV-B radiation. Under UV-B treatments, SOD activity was initially increased, whereas CAT and POD activities were slowly and slightly increased. However, APX activity showed no presumable results with an increase of UV-B dose. In leaves of rice seedlings, supplementary UV-B radiation caused an increase in free putrescine and spermidine, however spermine remained unaltered, although 24-hrs UV-B treatment slightly increased. This result presumes that an excess UV-B dose may induce ethylene biosynthesis (senescence) rather than polyamine biosynthesis (defense).

• Journal of Plant Biotechnology
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• v.33 no.1
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• pp.1-9
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• 2006

Peroxiredoxins (Prxs) are ubiquitously distributed and play important functions in diverse cellular signaling systems. The proteins are largely classified into three groups, such as typical 2-Cys Prx, atypical 2-Cys Prx, and 1-Cys Prx, that are distinguished by their catalytic mechanisms and number of Cys residues. From the three classes of Prxs, the typical 2-Cys Prx containing the two-conserved Cys residues at its N-terminus and C-terminus catalyzes $H_2O_2$ with the use of thioredoxin (Trx) as an electron donor. During the catalytic cycle, the N-terminal Cys residue undergoes a peroxide-dependent oxidation to sulfenic acid, which can be further oxidized to sulfinic acid at the presence of high concentrations of $H_2O_2$ and a Trx system containing Trx, Trx reductase, and NADPH. The sulfinic acid form of 2-Cys Prx is reduced by the action of sulfiredoxin which requires ATP as an energy source. Under the strong oxidative or heat shock stress conditions, 2-Cys Prx in eukaryotes rapidly switches its protein structure from low-molecular-weight species to high-molecular-weight protein structures. In accordance with its structural changes, the protein concomitantly triggers functional switching from a peroxidase to a molecular chaperone, which can protect its substrate denaturation from external stress. In addition to its N-terminal active site, the C-terminal domain including 'YF-motif' of 2-Cys Prx plays a critical role in the structural changes. Therefore, the C-terminal truncated 2-Cys Prxs are not able to regulate their protein structures and highly resistant to $H_2O_2$-dependent hyperoxidation, suggesting that the reaction is guided by the peroxidatic Cys residue. Based on the results, it may be concluded that the peroxidatic Cys of 2-Cys Prx acts as an '$H_2O_2$-sensor' in the cells. The oxidative stress-dependent regulation of 2-Cys Prx provides a means of defense systems in cells to adapt stress conditions by activating intracellular defense signaling pathways. Particularly, 2-Cys Prxs in plants are localized in chloroplasts with a dynamic protein structure. The protein undergoes conformational changes again oxidative stress. Depending on a redox-potential of the chloroplasts, the plant 2-Cys Prx forms super-molecular weight protein structures, which attach to the thylakoid membranes in a reversible manner.

• Applied Biological Chemistry
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• v.41 no.1
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• pp.42-46
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• 1998

Polymerase chain reaction (PCR) and Southern hybridization analyses were carried out to identify clones of silk worm thorn (Cudraria tricuspidata) and Rose of sharon (Hibiscus syriacus) which look like one tree with two ar three, branches or two or three different trees. For PCR five different PCR primers $(17{\sim}24\;nucleotides)$ are derived from CaMV 35S promoter, nopaline synthase terminator and coding region of thylakoid membrane protein gene. In the case of silk worm thorn, about 500 bp of PCR product was produced from DNAs of one tree or branch in the presence of 35S primer alone. Southern hybridization analysis of genomic DNAs hybridized with $^{32}P$ labeled PCR product showed that the same size of DNA fragments were hybridized with different intensities. In addition, PCR analyses using 20 different primers of OPERON 10-mer kits showed that only OPA01 primer produced PCR products of different size. These results indicate that two different trees of silk worm thorn combined to one tree. In the case of the Rose of Sharon, the same size of PCR products were produced from three different samples but Southern hybridization with the above PCR product as a probe did not show any hybridized bands. PCR analyses in the presence of OPERON 10-mers showed OPA04 and OPA13 produced different products including same sizes of products. These, results indicate that three different trees of the Rose of Sharon seem to be derived from the tree.

• Applied Microscopy
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• v.25 no.4
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• pp.52-61
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• 1995

Ultrastructural characteristics were examined with leaves of three species, O. japonicus A. Berger, O. malacophyllus Fisch., and O. sikokianus Owhi that probably have CAM mode. The mesophyll cells of these Orostachys possessed vacuoles with precipitates, myelin-like figures, and plasmalemmasomes, along with typical chloroplasts, microbodies and darkly stained bodies in their thin peripheral cytoplasm. Separation of the plasmalemma from the cell wall, leaving a space between them, was a common phenomenon in these species. A complex array of small to large vacuoles which contain small, membrane-bounded vesicles or vacuole-like structures were frequently found. A well-developed thylakoid system was observed in the chloroplasts and this indicates that the photosynthetic capacity of these mesophyll cells is probably active. A peculiar configuration of cytoplasm, especially around the chloroplasts, was also encountered. The variety of cytoplasmic constituents and vacuoles suggest the water-storing mesophyll cells may be complex in function. Some cellular features detected in this study strongly suggest the possible occurrence of CAM mode in Orostachys species.

• Journal of Plant Biotechnology
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• v.40 no.3
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• pp.125-134
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• 2013

Lipid droplets called plastoglobules are present in all plastid types. In chloroplasts, they are surrounded by the outer lipid monolayer from and connected to thylakoid membrane. The plastoglobule core contains the neutral lipids, which includes prenylquinones, triacylglycerols, and carotenoids. During stress and various developmental stages such as senescence, the size and number of plastoglobules increase due to the accumulation of lipids. Plastoglobules proteome revealed the presence of metabolic enzymes as well as structural proteins, plastoglobulins/fibrillins. Among the metabolic enzymes, the tocopherol cyclase, VTE1 and the NADPH quinine dehydrogenase, NDC1 have demonstrated that these participate in isoprenoid lipid metabolic pathways at the plastoglobule, notably in the metabolism of prenylquinones (tocopherol, plastoquinol and phylloquinone).

• Applied Biological Chemistry
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• v.40 no.6
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• pp.501-507
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• 1997

Chloroplasts isolated from Stevia rebaudiana Bertoni leaves contained an enzyme activity which catalyzed hydroxylation of ent-kaurenoic acid (ent-kaur-16-en-19-oic acid; ent-KA) to steviol (ent-13-hydroxy kaur-16-en-19-oic acid), the diterpenoid carboxylic alcohol which is the aglycone of sweet stevioside-related glycosides. $[^(14)C]-methylated$ ent-KA was used to localize ent-KA hydroxylase. $[^(14)C]-methyl-KA$ was most actively was transformed into methyl-steviol in chloroplast. The enzymatic activity was found in stroma fraction but not in thylakoid membrane in Stevia rebaudiana Bertoni. However, ent-KA 13-hydroxylase activity was not detected in stroma fraction of either Spinacia oleracea and Solidago altissima. The reaction products using $[^(14)C]-methyl-KA$ were purified and identified on TLC autoradiogram. The hydroxylation of ent-KA from stromal protein to form steviol required NADPH and oxygen. FAD and riboflavin stimulated the enzyme activity 1.5-and 1.7-fold, respectively. It also turned out that the activity of this enzyme using methyl-KA as a substrate was 16.7% that of ent-KA. The purified ent-KA 13-hydroxylase did not act on t-cinnamic acid, 4-hydroxyphenyl acetic acid, choline and resorcinol, known as monooxygenase and hydroxylase substrates.