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Dive into the research topics where Jun Hyeok Kim is active.

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Featured researches published by Jun Hyeok Kim.


Plant Molecular Biology | 2011

A dual role for MYB60 in stomatal regulation and root growth of Arabidopsis thaliana under drought stress.

Jee Eun Oh; Yerim Kwon; Jun Hyeok Kim; Hana Noh; Suk Whan Hong; Hojoung Lee

In response to environmental challenges, plant cells activate several signaling pathways that trigger the expression of transcription factors. Arabidopsis MYB60 was reported to be involved in stomatal regulation under drought conditions. Here, two splice variants of the MYB60 gene are shown to play a crucial role in stomatal movement. This role was demonstrated by over-expressing each variant, resulting in enhanced sensitivity to water deficit stress. The MYB60 splice variants, despite the fact that one of which lacks the first two exons encoding the first MYB DNA binding domain, both localize to the nucleus and promote guard cell deflation in response to water deficit. Moreover, MYB60 expression is increased in response to a low level of ABA and decreased in response to high level of ABA. At initial stage of drought stress, the plant system may modulate the root growth behavior by regulating MYB60 expression, thus promotes root growth for increased water uptake. In contrast, severe drought stress inhibits the expression of the MYB60 gene, resulting in stomatal closure and root growth inhibition. Taken together, these data indicate that MYB60 plays a dual role in abiotic stress responses in Arabidopsis through its involvement in stomatal regulation and root growth.


Journal of Plant Physiology | 2013

Loss of the R2R3 MYB, AtMyb73, causes hyper-induction of the SOS1 and SOS3 genes in response to high salinity in Arabidopsis

Jun Hyeok Kim; Nguyen Hoai Nguyen; Chan Young Jeong; Ngoc Trinh Nguyen; Suk Whan Hong; Hojoung Lee

Environmental stressors, including high salt, drought, and low or high temperatures, are often associated with significant losses in agricultural productivity. Plants have evolved a diverse array of signaling pathways to modulate their development in response to various environmental challenges. Here, we report the characterization of a member of the R2R3-MYB transcription factor family, AtMyb73. The expression of AtMyb73 was up-regulated by salt stress but not by other stresses. The maximum level of AtMyb73 expression occurred at 6h of 300mM NaCl treatment. Under salt stress, atmyb73 ko mutant plants exhibited higher survival rates compare to wild type (Col-0) plants. Using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis, we determined that the accumulation of salt overly sensitive (SOS) transcripts, SOS1 and SOS3, was higher in atmyb73 ko and atmyb73 eko plants than in wild type plants in response to 300mM NaCl treatment. These results indicate that AtMyb73 is a negative regulator of SOS induction in response to salt stress in Arabidopsis thaliana.


Journal of Experimental Botany | 2013

A novel Arabidopsis MYB-like transcription factor, MYBH, regulates hypocotyl elongation by enhancing auxin accumulation

Yerim Kwon; Jun Hyeok Kim; Hoai Nguyen Nguyen; Yusuke Jikumaru; Yuji Kamiya; Suk Whan Hong; Hojoung Lee

Critical responses to developmental or environmental stimuli are mediated by different transcription factors, including members of the ERF, bZIP, MYB, MYC, and WRKY families. Of these, MYB genes play roles in many developmental processes. The overexpression of one MYB gene, MYBH, significantly increased hypocotyl elongation in Arabidopsis thaliana plants grown in the light, and the expression of this gene increased markedly in the dark. The MYBH protein contains a conserved motif, R/KLFGV, which was implicated in transcriptional repression. Interestingly, the gibberellin biosynthesis inhibitor paclobutrazol blocked the increase in hypocotyl elongation in seedlings that overexpressed MYBH. Moreover, the function of MYBH was dependent on phytochrome-interacting factor (PIF) proteins. Taken together, these results suggest that hypocotyl elongation is regulated by a delicate and efficient mechanism in which MYBH expression is triggered by challenging environmental conditions such as darkness, leading to an increase in PIF accumulation and subsequent enhanced auxin biosynthesis. These results indicate that MYBH is one of the molecular components that regulate hypocotyl elongation in response to darkness.


Plant Cell Reports | 2013

Loss of all three calreticulins, CRT1, CRT2 and CRT3, causes enhanced sensitivity to water stress in Arabidopsis

Jun Hyeok Kim; Nguyen Hoai Nguyen; Ngoc Trinh Nguyen; Suk Whan Hong; Hojoung Lee

Key messageThe calreticulin triple knockout mutant shows growth defects in response to abiotic stress.AbstractThe endoplasmic reticulum (ER) is an essential organelle that is responsible for the folding and maturation of proteins. During ER stress, unfolded protein aggregates accumulate in the cell, leading to the unfolded protein response (UPR). The UPR up-regulates the expression of ER-stress-responsive genes encoding calreticulin (CRT), an ER-localized Ca2+-binding protein. To understand the function of plant CRTs, we generated a triple knockout mutant, t123, which lacks CRT1, CRT2 and CRT3 and examined the roles of calreticulins in abiotic stress tolerance. A triple knockout mutant increased sensitivity to water stress which implies that calreticulins are involved in the Arabidopsis response to water stress. We identified that the cyclophilin AtCYP21-2, which is located in the ER, was specifically enhanced in the t123 mutants. Seed germination of the atcyp21-1 mutant was retarded by water stress. Taken together, these results suggest that regulatory proteins that serve to protect plants from water stress are folded properly in part with the help of calreticulins. The AtCYP21-2 may also participate in this protein-folding process in association with calreticulins.


Plant Cell and Environment | 2015

AtMyb7, a subgroup 4 R2R3 Myb, negatively regulates ABA-induced inhibition of seed germination by blocking the expression of the bZIP transcription factor ABI5

Jun Hyeok Kim; Woo Young Hyun; Hoai Nguyen Nguyen; Chan Young Jeong; Liming Xiong; Suk Whan Hong; Hojoung Lee

Various Myb proteins have been shown to play crucial roles in plants, including primary and secondary metabolism, determination of cell fate and identity, regulation of development and involvement in responses to biotic and abiotic stresses. The 126 R2R3 Myb proteins (with two Myb repeats) have been found in Arabidopsis; however, the functions of most of these proteins remain to be fully elucidated. In the present study, we characterized the function of AtMyb7 using molecular biological and genetic analyses. We used qRT-PCR to determine the levels of stress-response gene transcripts in wild-type and atmyb7 plants. We showed that Arabidopsis AtMyb7 plays a critical role in seed germination. Under abscisic acid (ABA) and high-salt stress conditions, atmyb7 plants showed a lower germination rate than did wild-type plants. Furthermore, AtMyb7 promoter:GUS seeds exhibited different expression patterns in response to variations in the seed imbibition period. AtMyb7 negatively controls the expression of the gene encoding bZIP transcription factor, ABI5, which is a key transcription factor in ABA signalling and serves as a crucial regulator of germination inhibition in Arabidopsis.


Plant Cell Reports | 2013

TTG1-mediated flavonols biosynthesis alleviates root growth inhibition in response to ABA

Hoai Nguyen Nguyen; Jun Hyeok Kim; Woo Young Hyun; Ngoc Trinh Nguyen; Suk Whan Hong; Hojoung Lee

Key messageOur results demonstrate that the flavonoids biosynthetic pathway can be effectively manipulated to confer enhanced plant root growth under water-stress conditions.AbstractAbscisic acid (ABA) is one of most important phytohormones. It functions in various processes during the plant lifecycle. Previous studies indicate that ABA has a negative effect on root growth and branching. Auxin is another key plant growth regulator that plays an essential role in plant growth and development. In contrast to ABA, auxin is a positive regulator of root growth and development at low concentrations. This study was performed to help understand whether flavonoids can suppress the effect of ABA on lateral root growth. The recessive TRANSPARENT TESTA GLABRA 1 (ttg1) mutant was characterized on ABA and sucrose treatments. It was determined that auxin mobilization could be altered by modifying flavonoids biosynthesis, which resulted in alterations of root architecture in response to ABA treatment. Moreover, transgenic TTG1-overexpression (TTG1-OX) seedlings exhibited enhanced root length and lateral root number compared to wild-type seedlings grown under normal or stress conditions. Genetic manipulation of the flavonoids biosynthetic pathway could therefore be employed successfully for the improvement of plant root systems by overcoming the inhibition of ABA and some abiotic stresses.


Plant Physiology and Biochemistry | 2016

Characterization of Arabidopsis thaliana FLAVONOL SYNTHASE 1 (FLS1) -overexpression plants in response to abiotic stress

Nguyen Hoai Nguyen; Jun Hyeok Kim; Jaeyoung Kwon; Chan Young Jeong; Won Je Lee; Dongho Lee; Suk Whan Hong; Hojoung Lee

Flavonoids are an important group of secondary metabolites that are involved in plant growth and contribute to human health. Many studies have focused on the biosynthesis pathway, biochemical characters, and biological functions of flavonoids. In this report, we showed that overexpression of FLS1 (FLS1-OX) not only altered seed coat color (resulting in a light brown color), but also affected flavonoid accumulation. Whereas fls1-3 mutants accumulated higher anthocyanin levels, FLS1-OX seedlings had lower levels than those of the wild-type. Besides, shoot tissues of FLS1-OX plants exhibited lower flavonol levels than those of the wild-type. However, growth performance and abiotic stress tolerance of FLS1-OX, fls1-3, and wild-type plants were not significantly different. Taken together, FLS1 can be manipulated (i.e., silenced or overexpressed) to redirect the flavonoid biosynthetic pathway toward anthocyanin production without negative effects on plant growth and development.


Journal of The Korean Society for Applied Biological Chemistry | 2013

Induction of oxidative stress by overexpression of α-zein cDNA with mutation in signal peptide in Arabidopsis

Jun Hyeok Kim; Ngoc Trinh Nguyen; Vu van Kien; Nguyen Hoai Nguyen; Young Seok Jang; Hojoung Lee; Suk Whan Hong

Defective endosperm (De*)-B30 is a dominant maize mutation in the gene that encodes the storage protein, α-zein protein. The De*-B30 mutation results in a defective signal peptide in a 19-kD α-zein protein, which triggers endoplasmic reticulum (ER) stress, leading to up-regulation of genes associated with the unfolded protein response. To extend our knowledge of the physiological responses to constitutive ER stress in plants, transgenic Arabidopsis plants were constructed, in which De*-B30 transcripts were constitutively expressed under the control of the CaMV 35S promoter. Transgenic plants exhibited pale green leaves and growth retardation during the early vegetative stage. In addition, the growth rate of hypocotyl elongation was depressed in dark-grown transgenic seedlings. However, RNA blot analyses revealed no induction of the ER stress-inducible genes, including AtBiP1, AtCNX1, and AtCRT1 in transgenic Arabidopsis plants. Even though transgenic plants also were revealed to retain wild-type level of tunicamycin sensitivity, they showed an increase in hydrogen peroxide production. Higher levels of AtGST1 gene expression in transgenic plants were revealed. These findings suggest that reactive oxygen species are involved in the response to constitutive ER stress in Arabidopsis.


Journal of The Korean Society for Applied Biological Chemistry | 2011

Enhanced level of anthocyanin leads to increased salt tolerance in arabidopsis PAP1-D plants upon sucrose treatment

Jee Eun Oh; Young Hye Kim; Jun Hyeok Kim; Ye Rim Kwon; Hojoung Lee


Plant Cell Reports | 2002

Isolation and characterization of lipid transfer protein (LTP) genes from a wheat-rye translocation line

Cheol Seong Jang; Dong Sub Kim; S. Bu; Jun Hyeok Kim; S. Lee; Jerry W. Johnson; Yong Weon Seo

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Suk Whan Hong

Chonnam National University

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Ngoc Trinh Nguyen

Chonnam National University

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Hana Noh

Chonnam National University

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