Biomedical subjects

Jinwon Lee

Publications and source records attributed to Jinwon Lee.

13 recordsLinked to original sources

PubMed2006

The rice heterochronic gene SUPERNUMERARY BRACT regulates the transition from spikelet meristem to floral meristem.

Regulating the transition of meristem identity is a critical step in reproductive development. After the shoot apical meristem (SAM) acquires inflorescence meristem identity, it goes through a sequential transition to second- and higher-order meristems that can eventually give rise to floral organs. Despite ample information on the molecular mechanisms that control the transition from SAM to inflorescence meristems, little is known about the mechanism for inflorescence development, especially in monocots. Here, we report the identification of the SUPERNUMERARY BRACT (SNB) gene controlling the transition from spikelet meristem to floral meristem and the floral organ development. This gene encodes a putative transcription factor carrying two AP2 domains. The SNB:GFP fusion protein is localized to the nucleus. SNB is expressed in all the examined tissues, but most strongly in the newly emerging spikelet meristems. In SNB knockout plants, the transition from spikelet meristems to floral meristems is delayed, resulting in the production of multiple rudimentary glumes in an alternative phyllotaxy. The development of additional bracts interferes with subsequent floral architecture. In some spikelets, the empty glumes and lodicules are transformed into lemma/palea-like organs. Occasionally, the number of stamens and carpels is altered and an ectopic floret occurs in the axil of the rachilla. These phenotypes suggest that snb is a heterochronic mutant, affecting the phase transition of spikelet meristems, the pattern formation of floral organs and spikelet meristem determinancy.

Amino Acid Sequence↗

PubMed2006

The rice FON1 gene controls vegetative and reproductive development by regulating shoot apical meristem size.

Most plant organs develop from meristems. Rice FON1, which is an ortholog of Clv1, regulates stem cell proliferation and organ initiation. The point muta-tions, fon1-1 and fon1-2, disrupt meristem balance, resulting in alteration of floral organ numbers and the architecture of primary rachis branches. In this study, we identified two knockout alleles, fon1-3 and fon1-4, generated by T-DNA and Tos17 insertion, respectively. Unlike the previously isolated point mutants, the null mutants have alterations not only of the reproductive organs but also of vegetative tissues, producing fewer tillers and secondary rachis branches. The mutant plants are semi-dwarfs due to delayed leaf emergence, and leaf senescence is delayed. SEM analysis showed that the shoot apical meristems of fon1-3 mutants are enlarged. These results indicate that FON1 controls vegetative as well as reproductive development by regulating meristem size.

Aging↗

PubMed2005

Metabolic engineering of Escherichia coli for enhanced production of succinic acid, based on genome comparison and in silico gene knockout simulation.

Comparative analysis of the genomes of mixed-acid-fermenting Escherichia coli and succinic acid-overproducing Mannheimia succiniciproducens was carried out to identify candidate genes to be manipulated for overproducing succinic acid in E. coli. This resulted in the identification of five genes or operons, including ptsG, pykF, sdhA, mqo, and aceBA, which may drive metabolic fluxes away from succinic acid formation in the central metabolic pathway of E. coli. However, combinatorial disruption of these rationally selected genes did not allow enhanced succinic acid production in E. coli. Therefore, in silico metabolic analysis based on linear programming was carried out to evaluate the correlation between the maximum biomass and succinic acid production for various combinatorial knockout strains. This in silico analysis predicted that disrupting the genes for three pyruvate forming enzymes, ptsG, pykF, and pykA, allows enhanced succinic acid production. Indeed, this triple mutation increased the succinic acid production by more than sevenfold and the ratio of succinic acid to fermentation products by ninefold. It could be concluded that reducing the metabolic flux to pyruvate is crucial to achieve efficient succinic acid production in E. coli. These results suggest that the comparative genome analysis combined with in silico metabolic analysis can be an efficient way of developing strategies for strain improvement.

Base Sequence↗

PubMed2003

Bioremediation of 2,4,6-trinitrotoluene contaminated soil in slurry and column reactors.

The bioremediation of 2,4,6-trinitrotoluene (TNT) contaminated soil was performed on a laboratory scale. To compare bioremediation methods, a soil slurry reactor and a soil column reactor were operated and the effects of supplemental sources were investigated. Optimal conditions for the two bioremediation systems for the removal of TNT were obtained. In the soil slurry reactor, about 60% of the 1000 mg/kg TNT contaminated soil was degraded after 10 d, nearly complete biodegradation (>99%) was achieved within 25 d, and the microorganisms grew and reached a maximum of 9.5 x 10(9) CFU/ml at 15 d. In the soil column reactor, about 50% of the 1000 mg/kg TNT contaminated soil was degraded after 25 d and nearly complete biodegradation (>99%) was achieved within 60 d. Microorganisms grew and reached a maximum of 9.8 x 10(10) CFU/g soil at 40 d. These results should help in determining the best bioremediation method and improving the design and operation of large scale clean up of contaminated sites by bioremediation systems.

Journal Article↗

PubMed2003

Effects of various pretreatments for enhanced anaerobic digestion with waste activated sludge.

The purpose of this study was to enhance the efficiency of anaerobic digestion with waste activated sludge (WAS) by batch experiments. We studied the effects of various pretreatment methods (thermal, chemical, ultrasonic and thermochemical pretreatments) on the biogas production and pollutants reduction owing to solubilization enhancement, particle size reduction, increased soluble protein, and increased soluble COD. The thermochemical pretreatment gave the best results, i.e., the production of methane increased by more than 34.3% and soluble COD (SCOD) removal also increased by more than 67.8% over the control. In this case, the biogas production, methane production and the SCOD removal efficiency were about 5037 l biogas/m3 WAS, 3367 l methane/m3 WAS and 61.4%, respectively. Therefore, it is recognized that higher digestion efficiencies of the WAS were obtained through thermochemical pretreatment of the sludge.

Journal Article↗

PubMed2003

COD reduction and decolorization of textile effluent using a combined process.

This study showed the effectiveness of biological pretreatment involving appropriate microorganisms and suitable support media in a combined process. The combined process consists of biological pretreatment, chemical coagulation and electrochemical oxidation. COD and color were reduced by 95.4% and 98.5% by the combined process, respectively.

Journal Article↗

PubMed2003

Optimization for biodegradation of 2,4,6-trinitrotoluene (TNT) by Pseudomonas putida.

In this study, a strain of Pseudomonas putida KP-T202, isolated from the soil in a contaminated site, degraded 2,4,6-trinitrotoluene (TNT). In order to make this biodegradation process commercially feasible and reduce biodegradation time, optimal environmental factors are determined. At an initial concentration of 100 mg/l, TNT was totally degraded within 15 h under aerobic conditions. The optimal conditions for the biodegradation of TNT were found to be 30 degrees C, pH 7, 1% corn steep liquor (CSL), 0.025% NH,CI and 0.1% Tween 80; the reaction rate constant was 0.348 h(-1) These environmental conditions can be used to improve the efficiency of large-scale reactors for the treatment of TNT-contaminated wastewater and soil. In addition, the intermediates were identified as 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 2,4-dinitrotoluene and 2,6-dinitrotoluene.

Journal Article↗

PubMed2003

Transgene structures in T-DNA-inserted rice plants.

T-DNA is commonly used for delivery of foreign genes and as an insertional mutagen. Although ample information exists regarding T-DNA organization in dicotyledonous plants, little is known about the monocot rice. Here, we investigated the structure of T-DNA in a large number of transgenic rice plants. Analysis of the T-DNA borders revealed that more than half of the right ends were at the cleavage site, whereas the left ends were not conserved and were deleted up to 180 bp from the left border (LB) cleavage site. Three types of junctions were found between T-DNA and genomic DNA. In the first, up to seven nucleotide overlaps were present. The frequency of this type was much higher in the LB region than at the right border (RB). In the second type, which was more frequent in RB, the link was direct, without any overlaps or filler DNA. Finally, the third type showed filler DNA between T-DNA and the plant sequences. Out of 171 samples examined, 77 carried the vector backbone sequence, with the majority caused by the failure of T-strand termination at LB. However, a significant portion also resulted from co-integration of T-DNA and the vector backbone to a single locus. Most linkages between T-DNA and the vector backbone were formed between two 3' ends or two 5' ends of the transferred DNAs. The 3' ends were mostly linked through 3-6 bp of the complementing sequence, whereas the 5' ends were linked through either precise junctions or imprecise junctions with filler DNA.

Base Sequence↗

PubMed2003

CvADH1, a member of short-chain alcohol dehydrogenase family, is inducible by gibberellin and sucrose in developing watermelon seeds.

To understand the molecular mechanisms that control seed formation, we selected a seed-preferential gene (CvADH1) from the ESTs of developing watermelon seeds. RNA blot analysis and in situ localization showed that CvADH1 was preferentially expressed in the nucellar tissue. The CvADH1 protein shared about 50% homology with short-chain alcohol dehydrogenase including ABA2 in Arabidopsis thaliana, stem secoisolariciresinol dehydrogenase in Forsythia intermedia, and 3beta-hydroxysterol dehydrogenase in Digitalis lanata. We investigated gene-expression levels in seeds from both normally pollinated fruits and those made parthenocarpic via N-(2-chloro-4-pyridyl)-N'-phenylurea treatment, the latter of which lack zygotic tissues. Whereas the transcripts of CvADH1 rapidly started to accumulate from about the pre-heart stage in normal seeds, they were not detectable in the parthenocarpic seeds. Treating the parthenogenic fruit with GA(3) strongly induced gene expression, up to the level accumulated in pollinated seeds. These results suggest that the CvADH1 gene is induced in maternal tissues by signals made in the zygotic tissues, and that gibberellin might be one of those signals. We also observed that CvADH1 expression was induced by sucrose in the parthenocarpic seeds. Therefore, we propose that the CvADH1 gene is inducible by gibberellin, and that sucrose plays an important role in the maternal tissues of watermelon during early seed development.

Alcohol Dehydrogenase↗

PubMed2003

Systematic reverse genetic screening of T-DNA tagged genes in rice for functional genomic analyses: MADS-box genes as a test case.

We have generated 47 DNA pools and 235 subpools from 21,049 T-DNA insertion lines of rice. DNA pools of 500-1,000 lines were adequate for screening a T-DNA insertion within a 2-kb region. To examine the efficacy of the DNA pools, we selected MADS-box genes, which play an important role in controlling various aspects of plant development. A total of 34 MIKC-type MADS-box genes have now been identified from rice sequence databases. Our PCR screening for T-DNA insertions within 12 MADS-box genes resulted in the identification of five insertions in four different genes. These DNA pools will be valuable when isolating T-DNA insertional mutants in various rice genes. The DNA pool screening service and the mutant seeds are available upon request to genean@postech.ac.kr.

DNA, Bacterial↗

PubMed2002

Molecular characterization of a GA-inducible gene, Cvsus1, in developing watermelon seeds.

To understand the molecular mechanisms that control seed development, we isolated a seed-preferential gene from ESTs of developing watermelon seeds. The gene Cvsus1 encodes a protein that is 86% identical to the Vicia faba sucrose synthase expressed in developing seeds. RNA blot analysis showed that Cvsus1 was preferentially expressed in watermelon seeds. We also investigated gene expression levels both in pollinated seeds and in parthenocarpic seeds, which lack zygotic tissues. Whereas the transcript level of Cvsus1 was rapidly increased during normal seed development, the expression was not significantly increased in the parthenocarpic seeds. However, treating the parthenocarpic fruits with GA3 strongly induced Cvsus1 expression, up to the level accumulated in pollinated seeds. These results suggest that Cvsus1 is induced in maternal tissues via signals from the zygotic tissues, and that GA may be one of those signals.

Blotting, Southern↗

PubMed2002

Pilot scale treatment of textile wastewater by combined process (fluidized biofilm process-chemical coagulation-electrochemical oxidation).

The performance of pilot scale combined process of fluidized biofilm process, chemical coagulation and electrochemical oxidation for textile wastewater treatment was studied. In order to enhance biological treatment efficiency, two species of microbes, which can degrade textile wastewater pollutants efficiently, were isolated and applied to the system with supporting media. FeCl3 x 6H2O, pH 6 and 3.25 x 10(-3) mol/l were determined as optimal chemical coagulation condition and 25 mM NaCl of electrolyte concentration, 2.1 mA/cm2 of current density and 0.71/min of flow rate were chosen for the most efficient electrochemical oxidation at pilot scale treatment. The fluidized biofilm process showed 68.8% of chemical oxygen demand (COD) and 54.5% of color removal efficiency, even though using relatively low MLSS concentration and short sludge retention time. COD and color removals of 95.4% and 98.5% were achieved by overall combined process. The contribution of fluidized biofilm process to the overall combined process was increased over 25.7% of COD reduction and 20.5% of color reduction by adopting support media in biological treatment. It can be thought that the fluidized biofilm process was effective, and pollutant loading on post-treatment was pretty much decreased by this system. This combined process was highly competitive in comparison to the other similar combined systems. It was concluded that this combined process was successfully employed and much effectively decreased pollutant loading on post-treatment for textile wastewater treatment at pilot scale.

Biofilms↗

PubMed2002

Biokinetic parameter estimation for degradation of 2,4,6-trinitrotoluene (TNT) with Pseudomonas putida KP-T201.

The purpose of this study is to determine the biodegradation kinetics of 2,4,6-trinitrotoluene (TNT) by a newly isolated microorganism. Hundreds of microorganisms were isolated from explosives-contaminated soil in Korea. Examination of culture tests revealed that a few species of microorganisms have good ability to degrade TNT. The most efficient one was selected and identified as Pseudomonas putida KP-T201. Biodegradation of TNT was tested in a batch reactor using a pure culture of P. putida KP-T201. The effect of different concentrations of TNT on the rate of bacterial biodegradation was investigated. The Haldane equation seems to be an adequate expression for the cell growth data, and the kinetic constants obtained were mu(m)=0.65 h(-1), K(S)=0.62 mgl(-1), and K(i)=115 mgl(-1). The dependence of the bacterial specific growth rate on the concentration of TNT could be explained as a conventional model of substrate inhibition.

Journal Article↗