• Korean Journal of Organic Agriculture
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• v.14 no.2
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• pp.179-189
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• 2006

After examining the difference in the photosynthesis rate of corn according to the planting distance, the distance of $40{\times}40cm$ showed the lowest rate by 23 days after transplanting (May 31); however, there was no significant difference in the photosynthesis rate due to increased salt tolerance in the plant as time went by. As for the difference in growth features of a plant, the planting distance of $40{\times}40cm$ showed a growing disorder due to the influence of salt by 23 days after trans-plantation (May 31); however, there was a desirable growth as time went by. For the difference in the salt content within a plant, the planting distance of $40{\times}40cm$ tended to be higher than other planting distances, and the K+ content is much higher than other kinds of salt after examining the difference in salt absorption. As for the correlation between saline components within a plant, there was a significant negative correlation among $K^{+},\;Ca^{2+},\;and\;Na^{+}$ while there was a significant positive correlation among $Mg^{2+},\;Ca^{2+}$, and Na+. After examining the effectiveness of salt removal from soil according to com cultivation, the planting distance of $30{\times}30cm$ showed a remarkable decrease by 37 days, compared with 23 days, after transplantation in $K^{+}$ by 28%, $Ca^{2+}$ by 36.6%, $Mg^{2+}$ by 30.6%, and $Na^{+}$ by 22.9%. And the salt content is higher in surface soil than in subsoil.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.238-238
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• 2017

Salt stress is one of the deteriorating abiotic stresses due to the climate change, which causes over-accumulation of $Na^+$ and $Cl^-$ ions in plants and inhibits the growth and yield of rice especially in coastal Southeastern Asia. The yield components of rice plant (panicle number, spikelet number per panicle, 1000-grain weight, % of ripened grains) that are majorly affected by salt stress vary with growth stages at which the plant is subjected to the stress. In addition, the salt sensitivity of each yield component differs among rice varieties even when the salt-affected growth stage was same, which indicates that the physiological mechanism to maintain each yield component is different from each other. Therefore, we hypothesized that rice plant has different genes/QTLs that contribute to the maintenance of each yield component. Using a Japanese leading rice cultivar, Koshihikari, and salt-tolerant Nona bokra's chromosome segment substitution lines (CSSLs) with the genetic background of Koshihikari (44 lines in total) (Takai et al. 2007), we screened higher yielding CSSLs under salinity in comparison to Koshihikari and identified the yield components that were improved by the introgression of chromosome segment(s) of Nona bokra. The experiment was conducted in a salinized paddy field. One-month-old seedlings were transplanted into a paddy field without salinity. These were allowed to establish for one month, and then the field was salinized by introducing saline water to maintain the surface water at 0.4% salinity until harvest. The experiments were done twice in 2015 and 2016. Although all the CSSLs and Koshihikari decreased their yield under salinity, some CSSLs showed relatively higher yield compared with Koshihikari. In Koshihikari, all the yield components except panicle number were decreased by salinity and % of ripened grains was mostly reduced, followed by spikelet number per panicle and 1000-grain weight. When compared with Koshihikari, keeping a higher % of ripened grains under salinity attributed to the significantly greater yield in one CSSL. This indicated that the % of ripened grains is the most sensitive to salt stress among the yield components of Koshihikari and that the Nona bokra chromosome segments that maintained it contributed to increased yield under salt stress. In addition, growth analyses showed that maintaining relative growth rate in the late grain filling stage led to the increased yield under salt stress but not in earlier stages.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.20-20
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• 2017

Plant genomes include heterochromatic loci that consist of repetitive sequences and transposable elements. LTR retrotransposon is the major class of transposons in advanced plants in terms of proportion in plant genome. The elements contribute not only to genome size but also to genome stability and gene expression. A number of cases have been reported transposon insertions near genic regions affect crop traits such as fruit pigments, stress tolerance, and yields. Functional LTR retrotransposons produce extrachromosomal DNA from genomic RNA by reverse transcription that takes place within virus-like-particles (VLPs). DECREASED DNA METHYLATION 1 (DDM1) plays important roles in maintaining DNA methylation of heterochromatin affecting all sequence contexts, CG, CHG, and CHH. Previous studies showed that ddm1 mutant exhibits massive transcription of retrotransposons in Arabidopsis, but only few of them were able to create new insertions into the genome. RNA-dependent RNA POLYMERASE 6 (RDR6) is known to function in restricting accumulation of transposon RNA by processing the transcripts into 21-22 nt epigenetically activated small interfering RNA (easiRNA). We purified VLPs and sequence cDNA to identify functional LTR retrotransposons in Arabidopsis ddm1 and ddm1rdr6 plants. Over 20 LTR copia and gypsy families were detected in ddm1 and ddm1rdr6 sequencing libraries and most of them were not reported for mobility. In ddm1rdr6, short fragments of ATHILA gypsy elements were detected. It suggests easiRNAs might regulate reverse transcription steps. The highest enriched element among transposon loci was previously characterized EVADE element. It has been reported that active EVADE element is more efficiently silenced through female germline than male germline. By genetic analyses, we found ddm1 and rdr6 mutation affect maternal silencing of active EVADE elements. DDM1-GFP protein accumulated in megaspore mother cell but was not found in mature egg cell. The fusion protein was also found in early embryo and maternal DDM1-GFP allele was more dominantly expressed in the embryo. We observed localization of DDM1-GFP in Arabidopsis and DDM1-YFP in maize and found the proteins accumulated in dividing zone of root tips. Currently we are looking at cell cycle dependency of DDM1 expression using maize system. Among 10 AGO proteins in Arabidopsis, AGO9 is specifically expressed in egg cell and shoot meristematic cells. In addition, mutation of AGO9 and RDR6 caused failure in maternal silencing, implying 21-22 nt easiRNA pathway is important for retrotransposon silencing in female gametophyte or/and early embryo. On the other hand, canonical 24 nt sRNA-directed DNA methylation (RdDM) pathways did not contribute to maternal silencing as confirmed by this study. Heat-activated LTR retrotransposon, ONSEN, was not silenced by DDM1 but the silencing mechanisms require RdDM pathways in somatic cells. We will propose distinct mechanisms of LTR retrotransposons in germline and somatic stages.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.97-97
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• 2017

Plant genomes include heterochromatic loci that consist of repetitive sequences and transposable elements. LTR retrotransposon is the major class of transposons in advanced plants in terms of proportion in plant genome. The elements contribute not only to genome size but also to genome stability and gene expression. A number of cases have been reported transposon insertions near genic regions affect crop traits such as fruit pigments, stress tolerance, and yields. Functional LTR retrotransposons produce extrachromosomal DNA from genomic RNA by reverse transcription that takes place within virus-like-particles (VLPs). DECREASED DNA METHYLATION 1 (DDM1) plays important roles in maintaining DNA methylation of heterochromatin affecting all sequence contexts, CG, CHG, and CHH. Previous studies showed that ddm1 mutant exhibits massive transcription of retrotransposons in Arabidopsis, but only few of them were able to create new insertions into the genome. RNA-dependent RNA POLYMERASE 6 (RDR6) is known to function in restricting accumulation of transposon RNA by processing the transcripts into 21-22 nt epigenetically activated small interfering RNA (easiRNA). We purified VLPs and sequence cDNA to identify functional LTR retrotransposons in Arabidopsis ddm1 and ddm1rdr6 plants. Over 20 LTR copia and gypsy families were detected in ddm1 and ddm1rdr6 sequencing libraries and most of them were not reported for mobility. In ddm1rdr6, short fragments of ATHILA gypsy elements were detected. It suggests easiRNAs might regulate reverse transcription steps. The highest enriched element among transposon loci was previously characterized EVADE element. It has been reported that active EVADE element is more efficiently silenced through female germline than male germline. By genetic analyses, we found ddm1 and rdr6 mutation affect maternal silencing of active EVADE elements. DDM1-GFP protein accumulated in megaspore mother cell but was not found in mature egg cell. The fusion protein was also found in early embryo and maternal DDM1-GFP allele was more dominantly expressed in the embryo. We observed localization of DDM1-GFP in Arabidopsis and DDM1-YFP in maize and found the proteins accumulated in dividing zone of root tips. Currently we are looking at cell cycle dependency of DDM1 expression using maize system. Among 10 AGO proteins in Arabidopsis, AGO9 is specifically expressed in egg cell and shoot meristematic cells. In addition, mutation of AGO9 and RDR6 caused failure in maternal silencing, implying 21-22 nt easiRNA pathway is important for retrotransposon silencing in female gametophyte or/and early embryo. On the other hand, canonical 24 nt sRNA-directed DNA methylation (RdDM) pathways did not contribute to maternal silencing as confirmed by this study. Heat-activated LTR retrotransposon, ONSEN, was not silenced by DDM1 but the silencing mechanisms require RdDM pathways in somatic cells. We will propose distinct mechanisms of LTR retrotransposons in germline and somatic stages.

• Korean Journal of Environmental Agriculture
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• v.33 no.3
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• pp.220-230
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• 2014

BACKGROUND: Excessive metals in the soil have become one of the most significant environmental problems. Phytoremediation has received considerable attention as a method for restoring the contaminated soils. The microbes having remarkable metal tolerance and plant growth-promoting abilities could also play a significant role in remediation of metal-contaminated soils, because bioaugmentation with such microbes could promote phytoextraction of metals. Therefore, the present study was focused on evaluating the phytoextraction of heavy metals (Co, Pb and Zn) in Helianthus annuus (sunflower) induced by bioaugmentation of a phosphate solubilizing bacterium. METHODS AND RESULTS: A phosphate solubilizing bacterium was isolated from metal-contaminated soils based on the greater halo size (>3 mm) with solid NBRIP agar medium containing 10 g glucose, 5 g $Ca_3(PO_4)_2$, 5 g $MgCl_2{\cdot}6H_2O$, 0.25 g $MgSO_4.7H_2O$, 0.2 g KCl, 0.1 g $(NH_4)_2SO_4$ in 1 L distilled water. Isolated bacterial strain was assessed for their resistance to heavy metals; $CoCl_2.6H_2O$, $2PbCO_3.Pb(OH)_2$, and $ZnCl_2$ at various concentrations ranging from $100-400{\mu}g/mL$ (Co, Pb and Zn) using the agar dilution method. A pot experiment was conducted with aqueous solutions of different heavy metals (Co, Pb and Zn) to assess the effect of bacterial strain on growth and metal uptake by Helianthus annuus (sunflower). The impact of bacterial inoculation on the mobility of metals in soil was investigated under laboratory conditions with 50 mL scaled polypropylene centrifuge tubes. The metal contents in the filtrate of plant extracts were determined using an atomic absorption spectrophotometer (Perkinelmer, Aanalyst 800, USA). CONCLUSION: Inoculation with Enterobacter ludwigii PSB 28 resulted in increased shoot and root biomass and enhanced accumulation of Co, Pb and Zn in Helianthus annuus plants. The strain was found to be capable of promoting metal translocation from the roots to the shoots of H. annuus. Therefore, Enterobacter ludwigii PSB 28 could be identified as an effective promoter of phytoextraction of Co, Pb and Zn from metal-contaminated soils.

• Journal of Plant Biotechnology
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• v.38 no.1
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• pp.54-61
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• 2011

Antisense construct of cDNA for senescencerelated ACC oxidase (CAO) cDNA isolated from carnation flowers were introduced into tobacco by Agrobacteriummediated transformation. The decreasing expression of NtACO and the reduction of ethylene production were observed in these transgenic lines. In contrast, the SAMDC transcripts and spermidine content were increased. The findings that higher content of spermidine in the ethylene suppressed transgenic plants compared with wild-type should be directly resulted in the enhancement of SAMDC activity followed by the increased accumulation of SAMDC transcript. To investigate the pathogenic response in these transgenic plants, wild-type and transgenic plants were inoculated with Phytophthora parasitica pv. nicotianae. Transgenic plants suppressing ethylene production showed the increased resistance against fungal pathogen, comparing with wild-type plant. PR-protein genes expression in CAO-AS-2 and CAOAS-4 were also higher at the normal growth condition and pathogenic response than in wild-type plants. The results of higher spermidine content and SAMDC activity in transgenic plants, CAO-AS-2 and CAO-AS-4, support the possibility that an increase in spermidine content might induce the higher transcripts of PR-protein genes. This results agreed with the phenomena that spermidine promoted the expression of PR1a and a SAMDC inhibitor, MGBG, decreased the expression of PR1a in leaf discs. These results suggest that the resistance against fungal pathogen in transgenic tobacco impaired in ethylene production might be caused by increasing in polyamine, especially spermidine, biosynthesis.

• Journal of Plant Biotechnology
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• v.38 no.1
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• pp.22-29
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• 2011

Although reactive oxygen species (ROS) are inevitable by-products of many redox reactions in eukaryotic cells, they play a crucial role as signaling molecules in many cellular processes for development and defense response to abiotic stresses. The biphasic ROS production which was peaked twice in a first transient phase and a second massive phase was occurred after treatment of abiotic stress such as oxidative stress, high salinity. This biphasic generation of ROS was followed by the biphasic production of stress hormone, ethylene. The mechanism of interactions between ROS and ethylene biosynthesis is studied in tobacco (Nicotiana tabaccum L.) plants under the abiotic stresses. The stress-induced ethylene production was significantly inhibited in RbohD-AS and RbohF-AS, in which antisense expression of NADPH oxidase genes was performed. The accumulation of ROS, which was determined by DAB and DCFH-DA staining, was significantly decreased after abiotic stresses in transgenic plants. The suppression of signaling with ethylene and ROS induced more tolerance in response to abiotic stress. The transgenic plants were more tolerant in MS medium supplemented with salinity stress in contrast with wild-type. Stress-induced cell damage determined by DNA fragmentation was decreased at phase II in those transgenic plants. Therefore, the first burst of ROS is more responsible for making a role as a signaling molecule during stress-induced response. These results suggested that ethylene and ROS act in a positive feedback cycle that results in mutual enhancement of ethylene and ROS production during stress-induced cell death.

• Applied Biological Chemistry
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• v.25 no.3
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• pp.135-141
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• 1982

Two rice cultivars, Jinju and Iri 348, were used to compare the changes in the contents of some organic metabolites and ions and in some enzyme levels under water-and salt-stressed conditions. The water loss and proline accumulation under water and salt stresses were accelerated more in the salt-sensitive cultivar Iri 348 than in the salt-tolerant Jinju. The contents of crude protein, total free amino acids, proline and polyphenols increased under water-or salt-stressed rice, but that of reducing sugar increased under water stress only. The water-and salt-stresses induced the high ratio of low molecular organic solutes to crude protein in Jinju but not in Iri 348. The ratio of total free amino acids to crude protein increased under the stressed conditions was likely due to high protease activity. The contents of $Na^+$ and $Cl^-$ were higher in Iri 348 than in Jinju. Iri 348 had higher values of $Na^+/Ca^{2+}$ and monovalent/divalent of cations, but lower of $K^+/Na^+$ than Jinju Rice. The further studies should emphasize to set the correlations between these ratios and tolerance to water and salt stresses among rice cultivars.

• Journal of Acupuncture Research
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• v.23 no.2
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• pp.1-19
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• 2006

Objectives : The aim of this study was to investigate the hypoglycemic and hypolipidemic activities and mechanisms of Acanthopanax senticosus (AS) herbal acupuncture. Methods : Anti-diabetic and anti-steatotic activity of the AS herbal acupuncture was investigated on C57BL/6J ob/ob mice. After random grouping at the age of 9 weeks, the herbal acupuncture groups were injected subcutaneously at the left and right Gansu (BL18) corresponding acupuncture points alternately on exactly the same time every day with 0.1ml of either 400 mg/kg or 800 mg/kg of AS (AS400 and AS800) for 8-week period. As a positive control, metformin was administrated at a dose of 300 mg/kg (MT300). Body weights were measured weekly, and on every other week blood was collected for blood glucose analysis. At the end of study, blood was also collected for determination of plasma insulin and lipid levels, after which they were killed and periepidydimal fat, liver, muscle, and pancreas were immediately removed. The removed tissues were instantly soaked in liquid nitrogen and stored at $-70^{\circ}C$ for morphological examination and mRNA analysis. Results : The AS herbal acupuncture significantly prevented weight gain on C57BL/6J ob/ob mice. The AS herbal acupuncture lowered blood glucose and improved glucose tolerance in C57BL/6J ob/ob mice. The increase of insulin response during the OGTT was inhibited by the AS herbal acupuncture. Insulin sensitivity of skeletal tissue was enhanced. Plasma lipid levels were significantly improved in the AS herbal acupuncture groups. The AS herbal acupuncture decreased hepatic lipogenesis and hepatic triglyceride production, and increased fatty acid (FA) transporter that involves in FA uptake. The AS herbal acupuncture inhibited the increase of liver mass by prevention of the accumulation of TG but did not inhibit weight gain of fat tissue on C57BL/6J ob/ob mice. Conclusion : In summary, we have demonstrated several unique properties of the AS herbal acupuncture in decreasing body weight, and reversing insulin resistance and hepatic steatosis in ob/ob mice. This AS herbal acupuncture acts as an insulin sensitizer and specifically decreases circulating glucose and lipids, and suppresses hepatic lipogenesis.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.427-434
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• 2009

Indigenous bacterium which shows a tolerance to high metal toxicity was isolated from soil concomitantly contaminated with oil and heavy metals. The characteristics of the bacterium for Pb and Cd biosorption was investigated under the various experimental conditions such as bacterial growth phase, the initial metal concentration, the input biomass amount, temperature and pH. The Langmuir adsorption isotherm modeling was described to know the capacity and intensity of biosorption. The low initial concentration of heavy metals and high biomass has a maximum heavy metal removal efficiency, but biosorption capacity of Pb and Cd has different values. Biosorption efficiency was highest in the end of the microbial growth stage and under pH 5~9 condition, but was less affected by temperature variation of 25~$35^{\circ}C$. The maximum biosorption capacity for Pb and Cd was 62.11 and 192.31 mg/g, respectively and each $R^2$ was calculated as 0.71 and 0.98 by applying Langmuir isothermal adsorption equation. Biosorption for Cd was considered as monomolecular adsorption to single layer on the surface of cells, whereas biosorption for Pb was considered as accumulation process into the cell by the microbial metabolism and precipitation reaction with anion of bacteria.