• Journal of Plant Biotechnology
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• v.32 no.2
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• pp.97-103
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• 2005

Antioxidative responses of transgenic tobacco plants expressing both superoxide dismutase (SOD) and ascorbate peroxidase (APX) in chloroplasts was investigated with several herbicides. In greenhouse test, tolerance of SOD/APX-overexpressed tobacco (CA) to photosystem (PS) I inhibitor paraquat was increased by about 40%. However, any response differences between CA and wild type (WT) tobacco was not observed in a treatment with PS II inhibitors (bromoxynil, diuron and bromacil), chlorophyll biosynthesis inhibitor(oxyfluorfen), carotenoid biosynthesis inhibitor (fluridone) and 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase inhibitor (glyphosate). This tendency was also similar in the growth chamber test of low light intensity, using paraquat and diuron. That is, increased antioxidant activity of CA was shown only in paraquat treatment. When paraquat was foliar-treated to 6 to 9-leaf stage plant, the third to fourth placed leaf from shoot tip showed relatively higher antioxidant activity. Ascorbate supplemented to paraquat solution alleviated the phytotoxicity with a similar range in both CA and WT. In conclusion, CA specifically responded to oxidative stress induced by paraquat among tested herbicides in a whole plant assay.

• Journal of Life Science
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• v.32 no.3
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• pp.249-255
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• 2022

Metabolism is essential for survival and reproduction, and there is a metabolic pathways entry in the clusters of orthologous groups of proteins (COGs) database, updated in 2020. In this study, the metabolic pathways of 1309 prokaryotes were analyzed using COGs. There were 822 COGs associated with 63 metabolic pathways, and the mean for each taxon was between 200.50 (mollicutes) and 527.07 (cyanobacteria) COGs. The metabolic pathway composition ratio (MPCR) was defined as the number of COGs present in one genome in relation to the total number of COGs constituting each metabolic pathway, and the number of pathways with 100% MPCR ranged from 0 to 26 in each prokaryote. Among 1309 species, the 100% MPCR pathways included murein biosynthesis associated with cell wall synthesis (922 species); glycine cleavage (918); and ribosomal 30S subunit synthesis (903). The metabolic pathways with 0% MPCR were those involving photosystem I (1263 species); archaea/vacuolar-type ATP synthase (1028); and Na⁺-translocation NADH dehydrogenase (976). Depending on the prokaryote, three to 49 metabolic pathways could not be performed at all. The sequence of most highly conserved metabolic pathways was ribosome 30S subunit synthesis (96.1% of 1309 species); murein biosynthesis (86.8%); arginine biosynthesis (80.4%); serine biosynthesis (80.3%); and aminoacyl-tRNA synthesis (82.2%). Protein and cell wall synthesis have been shown to be important metabolic pathways in prokaryotes, and the results of this study of COGs related to such pathways can be utilized in, for example, the development of antibiotics and artificial cells.

• Journal of Environmental Science International
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• v.22 no.6
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• pp.705-715
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• 2013

The response of the freshwater microalga Chlorella vulgaris to mercuric ion ($Hg^{2+}$) stress was examined using chlorophyll a fluorescence image analysis and O-J-I-P analysis as a way to monitor the toxic effects of mercury on water ecosystems. The levels of photosynthetic pigments, such as chlorophyll a and b and carotenoids, decreased with increasing $Hg^{2+}$ concentration. The maximum photochemical efficiency of photosystem II(Fv/Fm) changed remarkably with increasing $Hg^{2+}$ concentration and treatment time. In particular, above $200{\mu}M\;Hg^{2+}$, considerable mercury toxicity was seen within 2 h. The chlorophyll a fluorescence transient O-J-I-P was also remarkably affected by $Hg^{2+}$; the fluorescence emission decreased considerably in steps J, I, and P with an increase in $Hg^{2+}$ concentration when treated for 4 h. Subsequently, the JIP-test parameters (Fm, Fv/Fo, RC/CS, TRo/CS, ETo/CS, ${\Phi}_{PO}$, ${\Psi}_O$ and ${\Phi}_{EO}$) decreased with increasing $Hg^{2+}$ concentration, while N, Sm, ABS/RC, DIo/RC and DIo/CS increased. Therefore, a useful biomarker for investigating mercury stress in water ecosystems, and the parameters Fm, ${\Phi}_{PO}$, ${\Psi}_O$, and RC/CS can be used to monitor the environmental stress in water ecosystems quantitatively.

• Journal of Ecology and Environment
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• v.47 no.3
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• pp.85-102
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• 2023

Background: Ecophysiological characteristics of Rosa rugosa were analyzed under different environmental factors from May to October 2022. Photosynthesis, chlorophyll fluorescence, chlorophyll content, leaf water content (LWC), osmolality, carbohydrate content, and total ion content were measured to compare the physiological characteristics of R. rugosa at two study sites (i.e., in large pots and in the Goraebul coastal sand dune area). Results: When R. rugosa was exposed to high temperatures, photosynthetic parameters including net photosynthetic rate (P_N) and stomatal conductance (g_s) in both experiment areas declined. In addition, severe photoinhibition occurs when R. rugosa is continuously exposed to high photosynthetically active radiation (PAR), and because of this, relatively low Y(II) (i.e., the quantum yield of photochemical energy conversion in photosystem II [PSII]) and high Y(NO) (i.e., the quantum yield of non-regulated, non-photochemical energy loss in PSII) in the R. rugosa of the pot were observed. As the high Y(NPQ) (i.e., the quantum yield of regulated non-photochemical energy loss in PSII) of R. rugosa in the coastal sand dune, they dissipated the excessed photon energy through the non-photochemical quenching (NPQ) mechanism when they were exposed to relatively low PAR and low temperature. Rosa rugosa in the coastal sand dune has higher chlorophyll a and carotenoid content. The high chlorophyll a + b and low chlorophyll a/b ratios seemed to optimize light absorption in response to low PAR. High carotenoid content played an important role in NPQ. As a part of the osmotic regulation in response to low LWCs, R. rugosa exposed to high temperatures and continuously high PAR used soluble carbohydrates and ions to maintain high osmolality. Conclusions: We found that F_v/F_m was lower in the potted plants than in the coastal sand dune plants, indicating the vulnerability of R. rugosa to high temperatures and PAR levels. We expect that the suitable habitat range for R. rugosa will shrink and move to north under climate change conditions.

• Journal of Plant Biology
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• v.31 no.4
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• pp.299-307
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• 1988

The electron transport activities of choloroplasts isolated from hte detached rise (Oryza sativa L. cv. Chucheong) leave stored under low temperature(4$^{\circ}C$) with light illumination were investigated to understand the role of light in the low temperature inhibition of photosynthesis in the chilling-sensitive plants. Chlorophyll content of the detached leaves upon incubation at 28$^{\circ}C$ and 4$^{\circ}C$ in the dark was also measured. The rice seedlings were grown with Hoagland medium in the growth chamber of 28$^{\circ}C$ temperature and 400 ft.c fluorescent light with the photoperiod of 16 h. Although chlorophyll content of the detached leaves stored in the dark declined by 61.7% after 28$^{\circ}C$ treatement, there occurred only 5.2% decrease of chlorophyll with 4$^{\circ}C$ treatment. Low temperature treatment(4$^{\circ}C$) for 6 days brought about decreases in total photosystem(PS II＋PS I) activities by 35.2% and 73.6% in te presence and absence of light, respectively, while after 28$^{\circ}C$ treatment of the detached leaves for 6 days in the dark there was only 27.6% decrease in PS II＋PS I activity. PS II activities were also decreased by 35.6% and 72.2% in the light and dark, respectively. PS I activities were decreased slightly, however, by 7.6% and 16.2% in the light and dark, respectively. Investigations into DPClongrightarrowDCPIP and NH2OHlongrightarrowDCPIP activities revealed that low temperature inhibition of PS II activities was not due to the inactivation of the water oxidation capacity at low temperature. It was concluded that light protects the electron transport activities of isolated rice chloroplasts from the inhibitory effect of low temperature in the detached leaves.

• Journal of The Korean Society of Grassland and Forage Science
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• v.20 no.2
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• pp.97-102
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• 2000

To increase thennotolerance of forage crops, transgenic rice plants as a model for transformation of monocots were generated. A cDNA encoding the chloroplast-localized small heat shock protein (small HSP) of rice, Oshsp21, was introduced into rice plants via Agrobacterium-mediated gene transfer system. Calli induced from scutella were co-cultivated with a A. tumefaciens strain EHAlOl canying a plasmid, pIGhsp21. A large number of transgenic plants were regenerated on a medium containing hygromycin. Integration of Oshsp2l gene was confirmed by PCR and Southern blot analyses with genomic DNA. Northern blot and immunoblot analyses revealed that the Oshsp21 gene was constitutively expressed and accumulated as mature protein in transgenic plants. Effects of constitutive expression of the OshspZl on thermotolerance were first probed with the chlorophyll fluorescence. Results indicate that inactivation of electron transport reactions in photosystem I1 (PSII), were mitigated by constitutive expression of the Oshsp21. These results suggest that the chloroplast small HSP plays an important role in protecting photosynthetic machinery during heat stress. (Key words : Thermotolerance, Rice, Transgenic, cDNA)

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.1 no.2
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• pp.69-80
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• 1997

Effects of light on leaf senescence of Phaseolus vulgaris were investigated by measuring the disassembly of chlorophyll-protein complexes in detached leaves which had been kept in the dark or under light. The loss of chlorophyll accompanied by degradation of chlorophyll-protein complexes. PSI (photosystem I) complex containing LHCI (light harvesting complex of PSI) apoproteins was rapidly decreased after the early stage of dark-induced senescence. RC(reaction center)-Core3 was slightly increased until 4 d and slowly decreased thereafter. As disassembly of LHCII trimer progressed after the late stage of senescence, there was a steady increase in the relative amount of SC(small complex)-2 containing LHCII monomer. On the other hand, white and red light adaptation caused the structural stability of chlorophyll-protein complexes during dark-induced senescence. Particularly, red light was more effective in the retardation of LHCII breakdown than white light, whereas white light was slightly effect in protecting the disassembly of PSI complex compared to red light. These results suggest, therefore, that light may be a regulatory factor for stability of chlorophyll-protein complexes in the senescent leaves.

• Journal of Microbiology
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• v.35 no.3
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• pp.206-212
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• 1997

Heliobacillus mobilis is a strictly anaerobic Gram-positive bacterium which contains a primitive Photosystem I-type reaction center. The membrane-bound cytochrome $C_{553}$ from the heliobacterium suggested to be the immediate electron donor to the photooxidized pigment (P798+) has been isolated and characterized. The heme protein was visualized as a major component with an apparent molecular size of 17kDa in TMBZ-staining analysis of the membrane preparation and showed characteristic $\alpha$ (552.5 nm), $\beta$ (522nm), and Soret absorption (416 nm) peaks of a typical reduced c-type cytochrome in the partially purified sample. The internal 43 amino acid sequence of the electron donor was obtained by chemical agent and protease treatments followed by N-terminal sequencing of the resulting fragments. The internal sequence carries lots of lysine residues and a Cys-X-X-Cys-His sequence motif which are the characteristics of typical c-type cytochromes. The analysis of the sequence by FAST or FASTA program, however, did not show any significant similarity to other known heme proteins.

• ALGAE
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• v.21 no.2
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• pp.175-183
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• 2006

Recent phylogenetic studies of scytosiphonacean brown algae show many conflicts with current classification. In order to clearly define the phylogenetic relationships of the family, we newly sequenced the photosystem I coding psaA gene (1488 base pairs) from 13 taxa (15 samples), of the family, and, for comparison, rbcL from four taxa. The psaA region has more informative sites (17.9%) than the rbcL (13.1%) and the number of nodes supported by over 50% bootstrap values is more in the psaA phylogeny (53 /57 nodes; 93%) than in the rbcL (47/63 nodes; 74.6%). The psaA phylogenies are basically congruent with the rbcL trees, recognizing two major groups in the monophyletic Scytosiphonaceae. The first group included Myelophycus, Petalonia, Scytosiphon, and elongate sack-shaped species of Colpomenia, primarily cold temperate elements with unilocular zoidangia on sporophytes. The second group, although not resolved, consisted of Hydroclathrus, Chnoospora, Rosenvingea, and ball-shaped Colpomenia, primarily warm-temperate taxa with both unilocular and plurilocular zoidangia on sporophytes. Chnoospora is not monophyletic, as was previously shown the paraphyly of Colpomenia, Petalonia, and Scytosiphon. Hydroclathrus clathratus from Korea and Japan was not monophyletic. Our studies show that gametophytic characters are the main source of conflict for the present taxonomy of the family. The psaA region is a useful tool for resolution of phylogenetic relationships within the Scytosiphonaceae.

• Journal of Plant Biotechnology
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• v.30 no.4
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• pp.399-403
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• 2003

In order to understand the protection effects of antioxidant enzymes against oxidative stress caused by various environmental stresses, transgenic tobacco (Nicotiana tabacum cv, Xanthi) plants expressing both copper/zinc superoxide dismutase (CuZnSOD) and ascorbate peroxidase (APX) in chloroplasts (referred to as CA plants) were subjected to highlight (1,100$\mu$mol m$^{-2}$ sec$^{-1}$) and chilling at 4$^{\circ}C$. The protection effects of CA plants using leaf discs were compared with those of transgenic plants expressing either CuZnSOD or APX in chloroplasts (SOD plants or APX plants, respectively) and non-transgenic (NT) plants. CA plants showed about 15％ protection in the photosynthetic efficiency (Fv/Fm) of photosystem II relative to NT plants 1 hr after treatment of both highlight and chilling, whereas they showed about 23％ protection in the redox state of P700 in photosystem I at 3 hr after treatment. SOD plants or APX plants showed an intermediate protection effect between CA plants and NT plants. These results demonstrated that the coexpression of CuZnSOD and APX in chloroplasts importantly involves in the protection effects against oxidative stress caused by various environmental stresses.