• Journal of Crop Science and Biotechnology
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• v.11 no.1
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• pp.31-38
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• 2008

Improvement of $N_2$ fixation by symbiotic rhizobia is considered an effective means for enhancing its productivity without high input of nitrogen(N) fertilizer. Several methods to improve $N_2$ fixation have been proposed including the use of supernodulating mutants. The objective of this research was to identify the varietal difference in N and $N_2$-fixation ability among the soybean supernodulating mutants, SS2-2 and Sakukei 4, with different nodulation abilities using $^{15}N$ in field conditions in both Korea and Japan. The dry weight(DW) was higher in wild-type soybeans. The distribution rate of DW in each plant part was high in seeds of supernoduating and wild-type soybeans but high in stems and leaves of non-nodulating mutants. Although the supernodulating mutants had a low DW rate at maturity, they showed a similar $N_2$ fixation ability compared with wild-type. Supernodulating mutant plants mainly obtained N from $N_2$ fixation, while soil N was the main resource for obtaining N in non-nodulating mutants. The percentage of N derived from atmospheric dinitrogen(Ndfa) was higher in supernodulating mutants than in wild-type and relatively high in seeds between plant parts at maturity. In particular, supernodulating mutants showed higher N content in roots than those of wild-type and non-nodulating mutants. It was considered that supernodulating mutants have the advantage of saving nitrate in soil and being beneficial for N absorption of subsequent crops due to their conserving more N in the field and releasing considerable amounts of N from roots and leaves fallen to the soil.

• Korean Journal of Soil Science and Fertilizer
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• v.21 no.4
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• pp.455-461
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• 1988

The pattern of nitrogen fixation by water culture of Sesbania, known as an effective legume plant for nitrogen fixation, in the growth cabinet by Leonard-Jar methods and nitrogen fixation pattern to sesbania are as follows: 1. Dry weight per pot after inoculation of rhizobia to sesbania was by the order for root + stem > root > control and nitrogen contents of plant parts also showed the same tendency as dry weight except leaf. 2. $^{15}N$ value based on natural abundance was by the order of root + stem > root > control, $^{15}N$ value of root nodule and stem nodule among total nitrogen content exhibited positive value but it showed negative value from root, stem and leaf.

• Genomics & Informatics
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• v.10 no.4
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• pp.249-255
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• 2012

In this study, fosmid cloning strategies were used to assess the microbial populations in water from the International Space Station (ISS) drinking water system (henceforth referred to as Prebiocide and Tank A water samples). The goals of this study were: to compare the sensitivity of the fosmid cloning strategy with that of traditional culture-based and 16S rRNA-based approaches and to detect the widest possible spectrum of microbial populations during the water purification process. Initially, microbes could not be cultivated, and conventional PCR failed to amplify 16S rDNA fragments from these low biomass samples. Therefore, randomly primed rolling-circle amplification was used to amplify any DNA that might be present in the samples, followed by size selection by using pulsed-field gel electrophoresis. The amplified high-molecular- weight DNA from both samples was cloned into fosmid vectors. Several hundred clones were randomly selected for sequencing, followed by Blastn/Blastx searches. Sequences encoding specific genes from Burkholderia, a species abundant in the soil and groundwater, were found in both samples. Bradyrhizobium and Mesorhizobium, which belong to rhizobia, a large community of nitrogen fixers often found in association with plant roots, were present in the Prebiocide samples. Ralstonia, which is prevalent in soils with a high heavy metal content, was detected in the Tank A samples. The detection of many unidentified sequences suggests the presence of potentially novel microbial fingerprints. The bacterial diversity detected in this pilot study using a fosmid vector approach was higher than that detected by conventional 16S rRNA gene sequencing.

• Applied Biological Chemistry
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• v.40 no.6
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• pp.551-555
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• 1997

This experiment was carried out to elucidate the biological activity and absorption characteristics of flavonoids in Rhizobium and Bradyrhizobium and to obtain basic information on host specific nodulation by flavonoids in rhizobium-legume symbiosis. The purpose of the present study was to explore the biological activity and the flavonoid absorption indicates that host-specificity is induced by flavonoids in symbiotic nitrogen fixation. Biological activity increased by daidzein and genistein treatment on B. japonicum KCTC 1539 whereas decreased by luteolin treatment but increased by luteolin treatment on R. meliloti whereas decreased by daidzein and genistein treatment. Daidzein and genistein are absorbed by B. japonicum, KCTC 1539 at higher rate than other flavonoids. Especially, luteolin was absorbed at a least rate. Luteolin are absorbed by R. meliloti KCTC 2353 at higher rate than other flavonoids. Especially, daidzein and genistein was absorbed at a least rate.

• Molecules and Cells
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• v.24 no.2
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• pp.185-193
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• 2007

Symbiotic nitrogen fixation with nitrogen-fixing bacteria in the root nodules is a distinctly beneficial metabolic process in legume plants. Legumes control the nodule number and nodulation zone through a systemic negative regulatory system between shoot and root. Mutation in the soybean NTS gene encoding GmNARK, a CLAVATA1-like serine/threonine receptor-like kinase, causes excessive nodule development called hypernodulation. To examine the effect of nts mutation on the gene expression profile in the leaves, suppression subtractive hybridization was performed with the trifoliate leaves of nts mutant 'SS2-2' and the wild-type (WT) parent 'Sinpaldalkong2', and 75 EST clones that were highly expressed in the leaves of the SS2-2 mutant were identified. Interestingly, the expression of jasmonate (JA)-responsive genes such as vspA, vspB, and Lox2 were upregulated, whereas that of a salicylate-responsive gene PR1a was suppressed in the SS2-2 mutant. In addition, the level of JA was about two-fold higher in the leaves of the SS2-2 mutant than in those of the WT under natural growth conditions. Moreover, the JA-responsive gene expression persists in the leaves of SS2-2 mutant without rhizobia infection in the roots. Taken together, our results suggest that the nts mutation increases JA synthesis in mature leaves and consequently leads to constitutive expression of JA-responsive genes which is irrelevant to hypernodulation in the root.

• Applied Biological Chemistry
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• v.28 no.3
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• pp.149-155
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• 1985

590 strains of Rhizobia were isolated from root nodules of the legumes collected at 223 sites in Korea. According to their host specificities they were classified into R. japonicum(218 strains), R. phaseoli(101 strains), R. trifolii(97 strains), R. meliloti(4 strains), R. leguminosarium(1 strain), Rhizobium species(101 strains), and unidentified species(159 strains). 3 potent strains R-138, R-168, and R-214 of R. japonicum have been selected based on the infectivity to soybean cultivar and effeciency of nitrogen fixation. It was observed that the fast-growing strains of R. japonicum contained 1 to 4 plasmids of M.W. of 35-300 Md. However, plasmids were hardly detected for the slow-growing strains.

• Current Research on Agriculture and Life Sciences
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• v.4
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• pp.27-35
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• 1986

This experiment was carried out to elucidate the factor of nitrogenase formation and to establish the nitrogen fixation system in mixed culture of cultured cells and rhizobia through tissue culture technique using three soybean varieties, Hwangkeum, Namcheon and D 68-0099 as host plants. The results obtained were as follows; The callus was induced in embryo and radicle, but not in hypocotyl. The most favorable callus induction was caused by the individual application of 2,4-D and NAA at the concentration of 2mg/1 and 4mg/1, respectively, but in case of treating both 2,4-D and kinetin, that was done at the concentration of 0.2mg(2,4-D)/0.05mg(kinetin)per liter. The growth of cultured cell was good at the concentration of 2.0mg(2,4-D)/1 and 0.2mg(2,4-D)/0.05mg(kinetin)per liter. When cultured cells were inoculated with R. japonicum 019 and 011, their growthes were considerably inhibited. The addition of single amino acid inhibited the growth of cultured cells. Hwangkeum was inhibited considerably by methionine and leucine. The inhibition of growth by single amino acid can be abolished by the addition of certain amino acids. The differentiation of adventitious root was good at the concentration of 2.0mg 2,4-D and 0.2mg 2,4-D/0.05mg kinetin per liter. Of three host plants tested with 25 R. japonicum strains, Hwangkeum had affinity for 10 strains, Namcheon for 7 strains and D68-0099 for none. The nitrogen fixing abilities of Hwangkeum and Namcheon caused by cultured cell-Rhizobium association were high in strain 019, 007, and in 007 mixed with 119, respectively.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.54 no.3
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• pp.299-306
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• 2009

In nitrogen-limited conditions, rhizobia lead to formation of nitrogen-fixing nodules on the roots of leguminous plants. The process of nodulation is autoregulated by pre-existing nodules in the same root system. The altered profile of sap proteins by inoculation with B. japonicum may indicate presence of a signal responsible for autoregulation transferred through stem. The 20 kDa protein enhanced by innoculation significantly decreased in intensity from 2.5 to 7 days after inoculation (DAI). However 6 kDa protein did increase during such a transition period. Western blot analysis showed that both 20 kDa and 6 kDa were cross-reacted with the SKTI antiserum. This suggests that SKTI may be involved in soybean nodulation by specific induction and degradation in stem sap during early stage of nodulation. RNAi technique and Agrobacterium rhizogenes-mediated transformation were applied to investigate the function of SKTI in nodulation. We have found that the number of rhizobium-induced nodule was much less in SKTIi-silenced hairy roots than the non-silenced. Indeed the quantitative RT-PCR showed that the expression level of SKTI gene was reduced over 40% in the transgenic hairy roots compared to the non-transgenic. It appears that the observed early induction of SKTI and degradation into small peptide in a specific time manner may be involved in autoregulation of nodulation in soybean and the specific mechanism of such regulation remains to be investigated.

• Journal of Korean Society of Forest Science
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• v.106 no.2
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• pp.121-129
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• 2017

The soil microbiome plays important roles in material cycling and plant growth in forest ecosystem. Although a lot of researches on forest soil fungi in Korea have been performed, the studies on forest soil bacterial communities have been limited. In this study, we conducted next generation sequencing (NGS) targeting 16S rRNA gene to investigate the soil bacterial communities from natural red pine (Pinus densiflora) forest in Mt. Janggunbong, Bonghwa-gun, Gyeongbuk, Korea. Our results showed that the entire bacterial communities in the study sites include the phyla Proteobacteria, Acidobacteria, Actinobacteria, Planctomycetes, which have been typically observed in forest soils. The composition ratio of Proteobacteria was the highest in the soil bacteria community. The results reflect that Proteobacteria is copiotroph, which generally favors relatively nutrient-rich conditions with abundant organic matter. Some rhizobia species such as Burkholderia, Bradyrhizobium, Rhizobium, which are known to contribute to soil nitrogen-fixation, exist in the study sites. As a result of correlation analysis between soil physicochemical characteristics and bacteria communities, the soil pH was significantly correlated with the soil bacteria compositions.

• Applied Biological Chemistry
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• v.22 no.3
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• pp.166-172
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• 1979

A series of experiments was planned for practical application of rhizobia in grass lands in Korea. This is the report for the studies mainly on the isolation and characterization of alfalfa nodule bacteria, and on the assessment of their nodulation abilities and nitrogen fixation capacities. 1. Total number of 47 strains was isolated from nodules which were taken from alfalfa grown in Daekwanyong, Cheju and other places. 2. Morphological and cultural characteristics of the strains were studied, and attempts. were also made to investigate their antigenic properties and to demonstrate lysogenic strains. The results were; i) the isolates varied in their cultural characteristics on yeast mannitol broth and agar, and in degree of congo red absorption; ii) similarities in their antigenic prorerties were found between the strains: SU 47/M-11, M-13/M-15, and M-3/M-5; iii) no lysogeny was found in the strains. 3. Plant infection test by test tube method in light room were carried out to elucidate the ability of the strains to nodulate Luna alfalfa and of the capacity of such nodules to fix atmospheric nitrogen. The isolates were grouped info non-invasive, ineffective, or effective to the legumes. Those strains which produced effective nodules, supporting similar/higher level of growth as nitrate control were: M-8, 9, 14, 20, 21, 25 and 34.