• Journal of Ginseng Research
• /
• v.41 no.4
• /
• pp.463-468
• /
• 2017

Background: Both Panax ginseng Meyer and Panax quinquefolius are obligate shade-loving plants whose natural habitats are broadleaved forests of Eastern Asia and North America. Panax species are easily damaged by photoinhibition when they are exposed to high temperatures or insufficient shade. In this study, a cytohistological study of the leaf structures of two of the most well-known Panax species was performed to better understand the physiological processes that limit photosynthesis. Methods: Leaves of ginseng plants grown in soil and hydroponic culture were sectioned for analysis. Leaf structures of both Panax species were observed using a light microscope, scanning electron microscope, and transmission electron microscope. Results: The mesostructure of both P. ginseng and P. quinquefolius frequently had one layer of non-cylindrical palisade cells and three or four layers of spongy parenchymal cells. P. quinquefolius contained a similar number of stomata in the abaxial leaf surface but more tightly appressed enlarged grana stacks than P. ginseng contained. The adaxial surface of the epidermis in P. quinquefolius showed cuticle ridges with a pattern similar to that of P. ginseng. Conclusion: The anatomical leaf structure of both P. ginseng and P. quinquefolius shows that they are typical shade-loving sciophytes. Slight differences in chloroplast structure suggests that the two different species can be authenticated using transmission electron microscopy images, and light-resistant cultivar breeding can be performed via controlling photosynthesis efficiency.

• Journal of Environmental Science International
• /
• v.11 no.10
• /
• pp.1023-1030
• /
• 2002

The effects on photosynthesis of NaCl(0, 0.2, 0.4, 0.6, 0.8 or 1.0 M) were examined in etiolated barley seedlings. Chlorophyll(Chl) a, Chl b and carotenoid contents, Chl a fluorescence and quenching coefficients of Chl fluorescence have been determined in the primary leaves of etiolated barley seedlings cultivated under low light(60 $\mu$㏖ $m^{-2}\;s^{-1}$). Chl a, b, and carotenoid contents were decreased remarkably in comparison with the control at 0.4 M NaCl. However, the value of Fo and Fv were decreased at 0.6 M NaCl and the ratio of Fv/Fm were deceased at 1.0 M NaCl. Chlorophyll synthesis was seriously inhibited from 0.4 M NaCl, and the photosynthetic electron transport system was inhibited from 0.6 M NaCl. Quantum of photosystem II reaction center was inhibited at 1.0 M NaCl. The effects of NaCl on the Chl content were raised in a 6 hrs, but the effects of NaCl on the value of Fo, Fv and Fv/Fm were raised in 30 hrs. The value of qP was decreased in comparison with the control at all concentrations, but there was a small change in the value qE. These results provide evidence that NaCl inhibited effects of various concentration of NaCl were inhibited quinone redox, however, proton gradient between thylakoid membranes was little damaged.

• Journal of Photoscience
• /
• v.12 no.1
• /
• pp.33-39
• /
• 2005

Plants possess the ability to dissipate the excitation energy for the protection of photosynthetic apparatus from absorbed excess light. Heat dissipation is regulated by xanthophyll cycle in thylakoid membranes of chloroplasts. We investigated the mechanistic aspects of xanthophyll cycle-dependent photoprotection against low-temperature photoinhibition in plants. Using barley and rice as chilling-resistant species and sensitive ones, respectively, chilling-induced chlorophyll fluorescence quenching, composition of xanthophyll cycle pigments and mRNA expression of the zeaxanthin epoxidase were examined. Chilled barley plants exhibited little changes in chlorophyll fluorescence quenching either of photochemical or non-photochemical nature and in the photosynthetic electron transport, indicating low reduction state of PS II primary electron acceptor. In contrast to the barley, chilled rice showed a marked decline in those parameters mentioned above, indicating the increased reduction state of PS II primary electron acceptor. In addition, barley plants were shown to have a higher capacity to elevate the pool size of xanthophyll cycle pigments in response to cold stress compared to rice plants. Such species-dependent regulation of xanthophyll cycle activity was correlated with the gene expression level of cold-induced zeaxanthin epoxidase. Chilled rice plants depressed the gene expression of zeaxanthin epoxidase, whereas barley increased its expression in response to cold stress. We suggest that chilling-induced alterations in the pool size of xanthophyll cycle pigments related to its capacity would play an important role in regulating plant's sensitivity to chilling stress.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2022.10a
• /
• pp.187-187
• /
• 2022

Purple-discoloration of the uppermost leaves has been observed in some soybean cultivars in recent years. The purpose of this study was to characterize the novel phenotypic changes between the uppermost and middle leaves via multiple approaches. First, quantitative trait loci mapping was conducted to detect loci associated with the novel phenotype using 85 recombinant inbred lines (RILs) of the 'Daepung' × PI 96983 population. 180K SNP data, a major quantitative trait locus (QTL) was identified at around 60 cM of chromosome 6, which accounts for 56% of total phenotypic variance. The genomic interval is about ~700kb, and a list of annotated genes includes the T-gene which is known to control pubescence and seed coat color and is presumed to encode flavonoid 35-hydroxylase (F3'H). Based on Hyperspectral imaging, the reflectance at 528-554 nm wavelength band was extremely reduced in the uppermost leaves compared to the middle (green leaves), which is presumed die to the accumulation of anthocyanins. In addition, purple-discolored leaf tissues were observed and compared to normal leaves using a transmission electronic microscope (TEM). Base on observations of the cell organelles, the purple-discolored uppermost leaves had many pigments formed in the epidermal cells unlike the normal middle leaves, and the cell wall thickness was twice as thick in the discolored leaves. The thickness of the thylakoid layer in the chloroplast the number of starch grains, the size of starch all decreased in the discolored leaves, while the number of plastoglobule and mitochondria increased.

• Journal of Plant Biotechnology
• /
• v.33 no.1
• /
• pp.1-9
• /
• 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
• /
• v.41 no.1
• /
• pp.42-46
• /
• 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
• /
• v.25 no.4
• /
• pp.52-61
• /
• 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
• /
• v.40 no.3
• /
• pp.125-134
• /
• 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
• /
• v.40 no.6
• /
• pp.501-507
• /
• 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.

• Journal of Photoscience
• /
• v.11 no.3
• /
• pp.115-120
• /
• 2004

For the expression study of antioxidant isoenzyme genes in rice (Oryza sativa L.) plants, extensive searches for genes of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) isoforms were performed through the GenBank database. The genes for two cytosolic and one plastidic CuZn-SOD, one Fe-SOD, two Mn-SOD, two cytosolic and two chloroplastic (stromal and thylakoid) APX, and three CAT isoforms were available in japonica-type rice. These isoforms were named as cCuZn-SOD1, cCuZn-SOD2, pCuZn-SOD, Fe-SOD, Mn-SOD1, Mn-SOD2, cAPXa, cAPXb, Chl_sAPX, Chl_tAPX, CATa, CATb, and CATc, respectively. Since they shared a high degree of homology in the nucleotide and amino acid sequences, the gene-specific primers for the genes were designed directly from their full-length cDNAs found in the database except for the CATa gene. These primers were used in the RT-PCR analysis to investigate the differential expression of antioxidant isoenzyme genes in rice plants from the seeds irradiated with low doses (2, 4, 8, and 16 Gy) of gamma-radiation. The gammairradiation slightly increased the transcripts of pCuZn-SOD, while those of Fe-SOD, cAPXb, and CATb decreased. However, no substantial differences were observed in the expression of all the isoenzyme genes between the control and irradiated groups. In this study, gene specific primers for thirteen SOD, APX and CAT isoenzymes were constructed from the full-length cDNAs. The results of RT-PCR analysis obtained by using these primers suggests that the expression levels of SOD, APX, and CAT isoenzyme genes in rice seedlings were hardly affected by gamma-irradiation at the seed stage.