• Journal of The Korean Society of Grassland and Forage Science
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• v.27 no.4
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• pp.241-248
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• 2007

Cytokinins are essential plant hormones that play crucial roles in various aspects of plant growth and development. By using mRNA differential display, we isolated a cytokinine-inducible cDNA encoding pathogenesis-related (PR) 4 from Arabidopsis amp1 mutant. The full-length PR4 cDNA, designated AtPR4, contains an open reading frame of 212 amino acids with calculated molecular mass of 22,900 Da and isoelectric point (pI) of 7.89. Genomic DNA blotting showed that the Arabidopsis genome has one copy of AtPR4. AtPR4 mRNA was induced by cytokinin and NaCl, but decreased by SA or JA treatment. PR proteins are induced in response to pathogen attack. Thus the AtPR4 gene isolated in this study may be a useful candidate for genetic engineering of forage crops for increased tolerance against pathogen.

• Journal of Life Science
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• v.15 no.6 s.73
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• pp.889-894
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• 2005

This experiment was carried out to investigate the effects of simulated acid rain (SAR) in the shoot growth and internal structure of Arabidopsis thaliana. In the shoot growth, the plants treated with SAR (pH 3.0) for 15 days showed no morphological change compared to the control plants. Some change was observed in the internal structure of the stems: the epidermis and cortex tissues of the stems treated with SAR were partly damaged. The plants treated with SAR showed no noticeable difference compared to the control plants, but morphological changes were observed in the leaf. The leaves of the plants treated with SAR showed many white necrotic spots on the part of upper epidermis. A light microscopic examination of the leaves with necrotic spots showed that the upper epidermis was severely compressed with the damaged cuticle layer and the mesophyll cells were also damaged and compressed. However, noticeable structural change of vascular bundle cells was not observed.

• Journal of Life Science
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• v.22 no.8
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• pp.999-1008
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• 2012

The circadian clock is a self-sustaining 24-hour timekeeper that allows organisms to anticipate daily-changing environmental time cues. Circadian clock genes are regulated by a transcriptional-translational feedback loop. In Arabidopsis, LATE ELONGATED HYPOCOTYL (LHY) and CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) transcripts are highly expressed in the morning. Translated LHY and CCA1 proteins repress the expression of the TIMING OF CAB EXPRESSION 1 (TOC1) transcripts, which peaks in the evening. The TOC1 protein elevates the expression of the LHY and CCA1 transcripts, forming a negative feedback loop that is believed to constitute the oscillatory mechanism of the clock. In mammals, the transcription factor protein CLOCK, which is a central component of the circadian clock, was reported to have an intrinsic histone acetyltransferase (HAT) activity, suggesting that histone acetylation is important for core clock mechanisms. However, little is known about the components necessary for the histone acetylation of the Arabidopsis clock-related genes. Here, I report that DET1 (De-Etiolated1) functions as a negative regulator of a key component of the Arabidopsis circadian clock gene LHY in constant dark phases (DD) and is required for the down-regulation of LHY expression through the acetylation of histone 3 (H3Ac). However, the HATs directly responsible for the acetylation of H3 within LHY chromatin need to be identified, and a link connecting the HATs and DET1 protein is still absent.

• Journal of Life Science
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• v.17 no.2 s.82
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• pp.235-240
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• 2007

AvrRpt2 protein triggers hypersensitive response (HR) and strong disease resistance when it is translocated from a bacterial pathogen Pseudomonas sp. to host plant cells containing a cognate RPS2 resistance protein through Type III Secretion System (TTSS). However, AvrRpt2 protein can function as the effector that suppresses a basal defense and enhances the disease symptom when functional RPS2 resistance protein is absent in the infected plant cells. Using Affymetrix Arabidopsis DNA chip, we found that many genes were specifically regulated by AvrRpt2 protein in the rps2 Arabidopsis mutant. Here, we showed that expression of AtERF11 that is known as a member of B1a subcluster of AP2/ERF transcription factor family was down regulated specifically by AvrRpt2. To determine its function in plant resistance, we also generated the Arabidopsis thaliana transgenic plants constitutively overexpressing AtERF11 under CaMV 355 promoter, which conferred an enhanced resistance against a bacterial pathogen, Pseudomonas syringae pv. tomato DC3000. Thus, these results collectively suggest that AtERF11 plays a role as a positive regulator for disease resistance against biotrophic bacterial pathogen in plant.

• Journal of Life Science
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• v.12 no.4
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• pp.399-406
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• 2002

The Arabidopsis mutants involved in chloroplast development were induced by seed treatment of diepoxybutane which was rarely known mutagenic compound in plant mutagenesis. Three kinds of mutants designated as iml, gev, and yev were represented by the characteristics of variegated leaves, green vein with yellow leaves, and yellow green vein with green leaves respectively. We investigated the ultrastructure of chloroplast in mutated regions using transmission electron microscopy. The ultrastructure of chroloplast in wildtype showed regularly stacked grana thylakoid and stroma thylakoid while iml, gev and yev mutants displayed different shapes of grana stacking and stroma stacking of chloroplasts. Genetic analysis of three chloroplast mutants exhibit that divergent traits were ruled by a single recessive nuclear gene.

• Journal of Life Science
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• v.16 no.3 s.76
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• pp.447-453
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• 2006

Histidine kinase plays important roles in signal transduction in plant. We characterized the function of Arabidopsis histidine kinase 3 (AHK3) and analyzed the expression patterns of genes and proteins in its mutant ahk3 by trans-zeatin (t-zeatin). The ahk3 exhibited decreased sensitivity to t-zeatin during callus formation, seedling growth, and leaf senescence. From proteomic analysis of ahk3, eukaryotic translation initiation factor 5A-2, auxin binding glutathione S-transferase, and NDPK1 were identified not to be induced by t-zeatin, when compared to the wild-type. In addition, the expression levels of ARR4 and ARR16 among A-type response regulators (ARRs) markedly decreased in ahk3 by t-zeatin treatment. These results suggest that AHK3 plays an important role in cytokinin signaling and the proteins identified from proteomic analysis and specific ARRs, ARR4 and ARR16 may be directly or indirectly associated in AHK3-mediated cytokinin signaling.

• Korean Journal of Plant Tissue Culture
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• v.26 no.4
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• pp.259-264
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• 1999

In order to study the role of ethylene on the formation of adventitious roots, trichomes and calli, the effects of 1-aminocyclopropane-l-carboxylic acid (ACC), ethephon, $CoCl_2$ and $AgNO_3$ were investigated in the leaf segments from ecotype Columbia of Arabidopsis thaliana. When the leaf segments were cultured on the media for forming adventitious roots (0.1 mg/L NAA), trichomes (2.0 mg/L NAA) and calli (10.0 mg/L NAA), and then each cultures was treated with 1-100 mg/L of ACC and ethephon, respectively. On the adventitious root-forming medium adventitious root formation was decreased, and trichomes were induced. And on the trichome-forming medium trichome formation was decreased, and calli were induced. In order hand each culture was treated with 1-100 mg/L of $CoCl_2$ and $AgNO_3$, respectively. On the adventitious root-forming medium adventitious roots was increased without trichome formation, and on the trichome-forming medium trichome formation was decreased, and adventitious roots were induced. However on the callus-forming medium treated with ACC, ethephon, $CoCl_2$ and $AgNO_3$, respectively, callus formation was inhibited and trichomes were induced in all cultures.

• Journal of Life Science
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• v.17 no.10
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• pp.1414-1418
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• 2007

This study was to examine the accumulated concentration of lead in the organ of Arabidopsis thaliana grown in the soil added three different concentrations of lead. The accumulated concentrations of lead in the stem of plant grown in the soil added official standard concentration of lead of pollutant exhaust notified by the Ministry of Environment (1 mg/l), concentration ten times higher than the official standard concentration (10 mg/l) and concentration fifty times higher (50 mg/l) were similar to the rate of increase between three different concentrations, and increased average 24% compared with normal plant stem. The accumulated concentrations of lead in the leaf of plant grown in the soil added three different concentrations of lead were increased average 57% compared with normal plant leaf. And accumulated concentrations of lead in the leaf was no significant difference according to increase of lead concentration added in the soil as stem, the rate of increase was similar to between three different concentrations. The accumulated concentrations of lead in the root of plant grown in the soil added official standard concentration of lead of pollutant exhaust and concentration ten times higher were increased average 114% compared with normal plant root, but increased about 861% in the concentration fifty times higher than the official standard concentration. This result contrast with the data of stem and leaf. The accumulated concentration of lead in the plant body of Arabidopsis thaliana was increased according to increase of lead concentration added in the soil. Especially, the accumulated concentration of lead in the plant body grown in the concentration fifty times higher than the official standard concentration was increased about 2.6 times than normal plant. These results show that lead contaminated within the soil was more accumulated in the root than the stem or leaf, and accumulated concentrations of lead in the stem and leaf were not increased in proportion to the concentration of lead in the soil, but very increased in proportion to the concentration in the root.

• Horticultural Science & Technology
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• v.31 no.1
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• pp.95-102
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• 2013

Binary trans-activation (pOp/LhG4) system is one of the regulatory systems of transgene expression. The target gene expression is achieved by crossing the reporter plants with an activator in this system. In this study, we used the features of this system in Chinese cabbage as a way to protect genetic resources and new varieties. To establish pOp/LhG4 system in Chinese cabbage, we designed an activator (35SLhG41300), and reporter constructs (pOpGUSBart) and co-transformed using Agrobacterium. The transgenic plants were selected by antibiotics and the functional activity of pOp/LhG4 system was confirmed by GUS expression. To induce the tissue-specific function, we constructed pOp/LhG4 system (795LhGBart) using female tissue specific promoter (ProAt1g26795) of Arabidopsis. Co-transformed transgenic plants clearly showed tissue specific expression in Arabidopsis. The results suggest the possibility of the system's application of $F_1$ generation can be restricted by expressing the target gene to protect a new variety and genetic resource in Chinese cabbages.

• Journal of Life Science
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• v.31 no.2
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• pp.109-114
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• 2021

Oryzalin is a dinitroaniline herbicide that has been known to disrupt microtubules. Microtubules and microfilaments are components of cytoskeletons that are implicated in plant cell growth, which requires the synthesis of cellulose when cell walls elongate. In addition, microtubules are also involved in the sedimentation of statoliths, which regulate the perception of gravity in the columella cells of root tips. In this study, we investigated the effect of oryzalin on the growth and gravitropic response of Arabidopsis roots. The role of ethylene in oryzalin's effect was also examined using these roots. Treatment of oryzalin at a concentration of 10-4 M completely inhibited the roots' growth and gravitropic response. At a concentration of 10-6 M oryzalin, root growth was inhibited by 47% at 8 hr when compared to control. Gravitropic response was inhibited by about 38% compared to control in roots treated with 10-6 M oryzalin for 4 hr. To understand the role of oryzalin in the regulation of root growth and gravitropic response, we measured ethylene production in root segments treated with oryzalin. It was found that the addition of oryzalin stimulated ethylene production through the activation of ACC oxidase and ACC synthase genes, which are key components in the synthesis of ethylene. From these findings, it can be inferred that oryzalin inhibits the growth and gravitropic response of Arabidopsis roots by stimulating ethylene production. The increased ethylene alters the arrangement of the microtubules, which eventually interferes with the growth of the cell wall.