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담배 현탁배양 세포에 있어 Polyamine 과 Ethylene 생합성시 중간산물로서 S - Adenosylmethionine 의 역할
박기영(Ky Young Park),이순희(Sun Hi Lee) 한국식물학회 1990 Journal of Plant Biology Vol.33 No.2
The role of S-adenosylmethionine(SAM) as an intermediate in interrelation between polyamine and ethylene biosynthesis was studied in suspension cultures of Nicotiana tabacum L. Exogenous SAM stimulated the polyamine and ethylene biosynthesis in 4 days-cultured cells, which were in active cell divisions, and 10 day cultured cells, which went on with active cell elongation and senescence. SAM-induced ethylene production was more effective in 10 day-cultured cells than in 4 day-cultured cells, but SAM-induced polyamine biosynthesis was more effective in 4 day-cultured cells than in 10 day-cultured cells. Polyamine contents were increased by the blockage of ethylene biosynthetic pathway in the conversion of SAM to ethylene via 1-aminocyclopropane-1-carboxylic acid(ACC) with aminooxyacetic acid (AOA). Also, ethylene production was increased by the inhibitors of polyamine biosynthesis such as methylglyoxal bis-(guanylhydrazone) (MGBG), dicyclohexylamine (DCHA), α-difluorome-trylarginine (DFMA) and α-difluoromethylornithine (DFMO). These results suggest that there may be interrelations between polyamine and ethylene biosynthesis for the competition of SAM and the inherent mechanism of switch on-off in polyamine and ethylene biosynthetic activity with the progress of cell growth and senescence.
담배 현탁 배양세포에서 Ethylene 생합성에 미치는 Polyamine 의 작용기작 (作用機作)
이순희(Sun Hi Lee),박기영(Ky Young Park) 한국식물학회 1988 Journal of Plant Biology Vol.31 No.4
We investigated the activities of choline kinase, CTP: phosphorylcholine cytidyltransferase, and phosphatase during the greening of etiolated barley seedlings. Activities of choline kinase in leaves increasd until 6 hours after illumination and decreased considerably after 6 hours, while activities of CTP: phosphorylcholine cytidyltransferase increased after illumination. On the contrary, changes of these two enzymatic activities showed reverse pattern in roots. The activities of phosphatase which hydrolyze phosphorylcholine decreased in leaves but changed little in roots during greening. The concentration of phosphorylcholine increased in xylem exudate and in roots during greening, while decreased in leaves. These results suggested that more phosphorylcholine arrive in leaves from roots as greening of etiolated barley seedlings.
담배 ( Nicotiana tabacum L. ) 현탁배양 세포에서 DNA 합성에 미치는 Polyamine 의 효과
남경희(Kyoung Hee Nam),박기영(Ky Young Park),이순희(Sun Hi Lee) 한국식물학회 1993 Journal of Plant Biology Vol.36 No.1
Effects of polyamines on DNA synthesis were studied in synchronized culture of Nicotiana tabacum L. When DFMO and DFMA, inhibitors of ornithine decarboxylase and arginine decarboxylase, respectively were initially applied to the cells, the polyamine contents were rapidly drooped and [methyl-^3H] thymidine incorporation into DNA was markedly reduced during the early stage of culture period. Inhibition of DNA synthesis, however, was partially reversed when these inhibitors were applied simultaneously with putrescine. In addition, exogenous administration of putrescine also increased the DNA syntheses during the all over the culture period. In vitro activity of DNA polymerase from Nicotiana tabacum L. was promoted by increasing concentrations of polyamines in the reaction mixture. Maximal activity was shown at 5 mM putrescine, 0.5 mM spermidine and spermine, respectively. Lack of Mg^2+ ion in the reaction buffer resulted in an inhibition of the enzyme activity by about 30%. The inhibition could not be completely reversed by application of polyamines at optimal concentrations. These results suggest that polyamines promote the DNA synthesis in vivo and in vitro by stabilizing the DNA-helix upon binding to negatively charged groups on DNA or increasing the activity of DNA polymerase in Nicotiana tabacum L.
Chlamydomonas 에서 분리한 DNA Methylase 와 엽록체 DNA Methylation
김남곤(Nam Gon Kim),김재윤(Jae Yoon Kim),이순희(Sun Hi Lee),이강오(Kang Oh Lee),김영민(Young Min Kim),박기영(Ky Young Park) 한국식물학회 1992 Journal of Plant Biology Vol.35 No.4
Two kinds of DNA methylases were purified from Chlamydomonas 21 gr(mt^+) gametic cells to determine the DNA methylases related to chloroplast DNA methylation and to examine their affinities for various DNAs. Two DNA methylases had distinct physical properties under the same condition of pH and ionic strength, and had different molecular weights as determined on a nondenatured gradient polyacrylamide gel electrophoresis. As the two enzymes had similar enzymatic activities on λ phage DNA and non-methylated λ DNA, it is suspected that they may act on cytosine methylation. In contrast with DNA methylase Ⅰ, DNA methylase Ⅱ showed a higher methyl-incorporation rate into poly(dG-dC)·poly(dG-dC) than poly(dA-dC)·poly(dG-dT). Therefore, it may have a greater affinity for (G-C) sequence than (A-C). When chloroplast DNA was isolated from Chlamydomonas in the vegetative and gametic stages and the activities of DNA methylase Ⅰ and Ⅱ were examined on these DNAs, they revealed 20% and 10% lower rates, respectively, of methyl-incorporation into the gametic chloroplast DNA than into the vegetative DNA.