Cytokinin-dependent secondary growth of the radish root (Raphanus sativus L.)

Geupil Jang,Jung-Hun Lee,Soo-Hyung Park,Ji-Young Lee 한국육종학회 2014 한국육종학회 심포지엄 Vol.2014 No.07

A root serves as an essential organ in plant growth by up-taking nutrients and water from soil and supporting the rest of a plant body. Root apical growth and system architecture have been extensively studied because they strongly affect overall plant growth and yields. Some plant species also utilize roots as storage organs. Many of them, including sweet potatoes (Ipomoea batatas), cassava (Manihot esculenta), and radish (Raphanus sativus) are important crops, however their root development has remained elusive. In this study, we characterized radial root growth in the radish and found that it is very similar to the secondary growth in stems. We identified well established cambium zones in the actively growing radish roots. Cell proliferation activities in the cambium zones positively correlated with root growth rates and final yields. Through a comparative analysis with Arabidopsis root expression data, we selected some putative transcription factors whose expression is highly enriched in the cambia and validated their expression in various stages of radish roots. By comparing their expression in two inbred lines with distinctive radial root growth, we identified transcription factors that are involved in morphological differences. More importantly, our investigation suggests that the differences in the root growth of two radish inbred lines are from changes in cytokinin responses. These findings together highlight that radish could serve as an excellent system for studying root crops and that transcriptional regulation and cytokinin signaling are indispensable for the secondary root growth.

Drought stress promotes xylem differentiation by modulating the interaction between cytokinin and jasmonic acid

Jang, Geupil,Choi, Yang Do Informa UK (TaylorFrancis) 2018 Plant signaling & behavior Vol.13 No.3

Cytokinin-dependent secondary growth determines root biomass in radish ( <i>Raphanus sativus</i> L.)

Jang, Geupil,Lee, Jung-Hun,Rastogi, Khushboo,Park, Suhyoung,Oh, Sang-Hun,Lee, Ji-Young Oxford University Press 2015 Journal of experimental botany Vol.66 No.15

<P>The root serves as an essential organ in plant growth by taking up nutrients and water from the soil and supporting the rest of the plant body. Some plant species utilize roots as storage organs. Sweet potatoes (<I>Ipomoea batatas</I>), cassava (<I>Manihot esculenta</I>), and radish (<I>Raphanus sativus</I>), for example, are important root crops. However, how their root growth is regulated remains unknown. In this study, we characterized the relationship between cambium and radial root growth in radish. Through a comparative analysis with <I>Arabidopsis</I> root expression data, we identified putative cambium-enriched transcription factors in radish and analysed their expression in representative inbred lines featuring distinctive radial growth. We found that cell proliferation activities in the cambium positively correlated with radial growth and final yields of radish roots. Expression analysis of candidate transcription factor genes revealed that some genes are differentially expressed between inbred lines and that the difference is due to the distinct cytokinin response. Taken together, we have demonstrated for the first time, to the best of our knowledge, that cytokinin-dependent radial growth plays a key role in the yields of root crops.</P>

Intercellular trafficking of transcription factors in the vascular tissue patterning

Jang, Geupil,Lee, Ji‐,Young Blackwell Publishing Ltd 2014 Physiologia Plantarum Vol.151 No.2

<P>Throughout life cycles, plants grow in an indeterminate manner by adding new cells and organs with specialized functions. Newly emerging cells acquire their identities depending on their positions relative to the neighboring cells. Exchanging positional signals between cells is critical in this process. Recent studies showed that many transcription factors move between cells or between organs in forms of proteins and messenger RNA (mRNA). Some of these were found to be important positional signals for cell type patterning. Cell type patterning in the vascular system is no exception from this. In this review, we describe recent discoveries of mobile transcription factors that function as positional signals for vascular tissue patterning and propose how these transcription factors integrate with other forms of signals.</P>

Assessing the toxic effects of accumulated arsenic on Arabidopsis thaliana

Jinwoo Jang,Yangwon Jeon,Yeonhong Kim,Geupil Jang,Youngdae Yoon 한국응용생명화학회 2024 Journal of Applied Biological Chemistry (J. Appl. Vol.67 No.-

Previous studies have reported that high pesticide and fertilizer use leads to a gradual accumulation of arsenic in soil environments. To understand the effects of arsenic on plant growth, we aimed to analyze the effect of As(III) on plant growth and development using Arabidopsis thaliana as a model plant. The results revealed that various aspects of plant growth, including seed germination and shoot development, were negatively impacted by As(III) treatment, but the effects were not significant. By contrast, root development was strongly suppressed by As(III) exposure, and the extent of suppression was dependent on the concentration of As(III) used. To gain a deeper understanding of adverse effects on root development, we examined the correlation between As(III) exposure and auxin, a key phytohormone responsible for root growth. Visualizing the auxin response in Arabidopsis roots using DR5::VEUNS and IAA2::GFP revealed that As(III) treatment suppressed auxin response in Arabidopsis roots, and this suppression was tightly correlated with the As(III) concentration. Furthermore, we used As(III)-specific bacterial cell-based biosensors to quantify the accumulation of arsenic in plants and establish a correlation with physiological changes. The inhibition of root growth was observed at 0.5 mg/g of As(III) treatment and it was correlated to 0.063 mg of As(III) per 1 g of dried plant. Although further investigations are required to fully assess the toxic effects of arsenic on the physiological properties of plants, the findings presented in this study provide valuable insights for evaluating the toxic effects of accumulated arsenic on plant growth and development.

Assessing the effects of accumulated Cd(II) on seed germination and root development of Arabidopsis thaliana

Lee Yejin,Jang Jinwoo,Jeon Yangwon,Kim Hyojin,Jang Geupil,Yoon Youngdae 한국응용생명화학회 2021 Applied Biological Chemistry (Appl Biol Chem) Vol.64 No.6

In this study, Arabidopsis thaliana was used as a model system to assess the toxic effects of cadmium on plant development and growth. The germination and growth of A. thaliana was inhibited by Cd(II), and the inhibitory effect was dosage-dependent. The significant decrease of germination rates and root growths of A. thaliana were observed from 50 mg/L and 25 mg/L of CdCl2, respectively. Although both shoot and root growths were suppressed by Cd(II), root developments were more sensitive to Cd(II) than shoot developments, as evidenced by shoot growths observed over 50 mg/L of CdCl2. In the concordance to this result, it was also observed that the expression of DR5::VENUS, a visual marker of auxin response, was dependent on the Cd(II) concentration and was strongly reduced from 5 mg/L of CdCl2. In addition, the E. coli-based biosensors were employed to quantify accumulated Cd(II) in plants to understand the correlation between toxic effects and Cd(II) in plants. As a result, it was revealed that 0.012 mg/g and 0.138 mg/g of Cd(II) in dried plants were corresponded to the concentration inhibiting root developments and root growths, respectively. Although it needs further investigations, the findings play a significant role in assessing the toxic effects of Cd(II) based on the relationship between the toxic effects and accumulated Cd(II) concentrations in plants.

Modulation of the Metal(loid) Specificity of Whole-Cell Bioreporters by Genetic Engineering of ZntR Metal-Binding Loops

( Hyojin Kim ),( Geupil Jang ),( Bong-gyu Kim ),( Youngdae Yoon ) 한국미생물 · 생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.5

Bacterial cell-based biosensors, or whole-cell bioreporters (WCBs), are an alternative tool for the quantification of hazardous materials. Most WCBs share similar working mechanisms. In brief, the recognition of a target by sensing domains induces a biological event, such as changes in protein conformation or gene expression, providing a basis for quantification. WCBs targeting heavy metal(loid)s employ metalloregulators as sensing domains and control the expression of genes in the presence of target metal(loid) ions, but the diversity of targets, specificity, and sensitivity of these WCBs are limited. In this study, we genetically engineered the metal-binding loop (MBL) of ZntR, which controls the znt-operon in Escherichia coli. In the MBL of ZntR, three Cys sites interact with metal ions. Based on the crystal structure of ZntR, MBL sequences were modified by site-directed mutagenesis. As a result, the metal-sensing properties of WCBs differed depending on amino acid sequences and the new selectivity to Cr or Pb was observed. Although there is room for improvement, our results support the use of currently available WCBs as a platform to generate new WCBs to target other environmental pollutants including metal(loid)s.

Regulation of AKT Activity by Inhibition of the Pleckstrin Homology Domain-PtdIns(3,4,5)P₃ Interaction Using Flavonoids

( Yerin Kang ),( Geupil Jang ),( Seunghyun Ahn ),( Youngshim Lee ),( Soon Young Shin ),( Youngdae Yoon ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.8

The serine-threonine kinase AKT plays a pivotal role in tumor progression and is frequently overactivated in cancer cells; this protein is therefore a critical therapeutic target for cancer intervention. We aimed to identify small molecule inhibitors of the pleckstrin homology (PH) domain of AKT to disrupt binding of phosphatidylinositol-3,4,5-trisphosphate (PIP3), thereby downregulating AKT activity. Liposome pulldown assays coupled with fluorescence spectrometry were used to screen flavonoids for inhibition of the AKT PH-PIP3 interaction. Western blotting was used to determine the effects of the inhibitors on AKT activation in cancer cells, and in silico docking was used for structural analysis and optimization of inhibitor structure. Several flavonoids showing up to 50% inhibition of the AKT PH-PIP3 interaction decreased the level of AKT activation at the cellular level. In addition, the modified flavonoid showed increased inhibitory effects and the approach would be applied to develop anticancer drug candidates. In this study, we provide a rationale for targeting the lipidbinding domain of AKT, rather than the catalytic kinase domain, in anticancer drug development.

Modulating the sensing properties of Escherichia coli-based bioreporters for cadmium and mercury

Kang, Yerin,Lee, Woonwoo,Jang, Geupil,Kim, Bong-Gyu,Yoon, Youngdae Springer-Verlag 2018 Applied Microbiology and Biotechnology Vol.102 No.11

Targeted gene suppression through double-stranded RNA application using easy-to-use methods in Arabidopsis thaliana

Park Minsu,Um Tae Young,Jang Geupil,Choi Yang Do,Shin Chanseok 한국응용생명화학회 2022 Applied Biological Chemistry (Appl Biol Chem) Vol.65 No.1

RNA interference (RNAi) is an RNA-dependent gene silencing process that is regulated by the interaction between the RNA-induced silencing complex (RISC) and double-stranded RNA (dsRNA). Exogenous dsRNAs are imported directly into the cytoplasm, where they are cleaved by Dicer into short dsRNA fragments of 20–25 base pairs. These short dsRNA fragments, called small interfering RNAs (siRNAs) have sequence-specific interaction with target genes. The guide strand, onto which siRNAs are incorporated in the RISC interacts with the target mRNA sequence, thereby inducing cleavage and degradation of target messenger RNAs (mRNAs) by ribonucleases. Recent studies have shown that plant dsRNA treatments can induce RNAi. However, the dsRNA application methods and delivery systems involved have not been well examined. In this study, dsRNA was introduced to Arabidopsis thaliana by two methods: dipping and spray. We synthesized two dsRNAs designed to target mRNAs encoding enhanced green fluorescent protein (EGFP). After applying dsRNAs that target EGFP, we found an obvious reduction in GFP expression. This was determined using fluorescence microscopy and quantitative reverse transcription PCR to assess the mRNA levels of the auxin-sensitive reporter DR5-EGFP Arabidopsis thaliana. Our data revealed that applying target gene-specific exogenous dsRNAs can induce suppression of target genes of interest whether the dipping or spray method is used. This study therefore provides a foundation for understanding how to apply and deliver dsRNAs in plants. RNA interference (RNAi) is an RNA-dependent gene silencing process that is regulated by the interaction between the RNA-induced silencing complex (RISC) and double-stranded RNA (dsRNA). Exogenous dsRNAs are imported directly into the cytoplasm, where they are cleaved by Dicer into short dsRNA fragments of 20–25 base pairs. These short dsRNA fragments, called small interfering RNAs (siRNAs) have sequence-specific interaction with target genes. The guide strand, onto which siRNAs are incorporated in the RISC interacts with the target mRNA sequence, thereby inducing cleavage and degradation of target messenger RNAs (mRNAs) by ribonucleases. Recent studies have shown that plant dsRNA treatments can induce RNAi. However, the dsRNA application methods and delivery systems involved have not been well examined. In this study, dsRNA was introduced to Arabidopsis thaliana by two methods: dipping and spray. We synthesized two dsRNAs designed to target mRNAs encoding enhanced green fluorescent protein ( EGFP ). After applying dsRNAs that target EGFP , we found an obvious reduction in GFP expression. This was determined using fluorescence microscopy and quantitative reverse transcription PCR to assess the mRNA levels of the auxin-sensitive reporter DR5-EGFP Arabidopsis thaliana . Our data revealed that applying target gene-specific exogenous dsRNAs can induce suppression of target genes of interest whether the dipping or spray method is used. This study therefore provides a foundation for understanding how to apply and deliver dsRNAs in plants.