• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.76.1-76
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• 2003

The coat protein (CP) of Turnip crinkle virus (TCV) is organized into 3 distinct domains, R domain (RNA-binding) connected by an arm, 5 domain and P domain. We have previously shown that the CP of TCV strongly suppresses RNA silencing, and have mapped N-terminal R domain of which is also the elicitor of resistance response in the Arabidopsis ecotype Di-17 carrying the HRT resistance gene. In order to map the region in the TCV CP that is responsible for silencing suppression, a series of CP mutants were constructed, transformed into Agrobacterium, coinfiltrated either with HC-Pro (the helper component proteinase of tobacco etch potyvirus) known as a suppressor of PTGS or GFP constructs into leaves of Nicotiana benthmiana expressing GFP transgenically. In the presence of HC-Pro, all CP mutants were well protected, accumulating mutant CP mRNAs and their proteins even 5 days post-infiltration (DPI). In the presence of GFP, some mutant constructs which showed the accumulation of CP mutants and GFP mRNAs at early stage but eventually degraded at 5 DPI. Only a mutant which carrying 4 amino acid deletion of R domain was tolerable to maintain suppressing activity, suggesting that the suppressing activity is not directly related with the eliciting activity. A transient assay also revealed that the mutants synthesized their proteins, suggesting that a full length of CP sequences and its intact structure are required to stabilize CP, which suppresses the RNA silencing.

• Molecules and Cells
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• v.41 no.4
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• pp.351-361
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• 2018

Sucrose is a crucial compound for the growth and development of plants, and the regulation of multiple genes depends on the amount of soluble sugars present. Sucrose acts as a signaling molecule that regulates a proton-sucrose symporter, with its sensor being the sucrose transporter. Flavonoid and anthocyanin biosynthesis are regulated by sucrose, and sucrose signaling can affect flavonoid and anthocyanin accumulation. In the present study, we found a Myb transcription factor affecting accumulation of anthocyanin. AtMyb56 showed an increase in its expression in response to sucrose treatment. Under normal conditions, anthocyanin accumulation was similar between Col-0 (wild type) and atmyb56 mutant seedlings; however, under sucrose treatment, the level of anthocyanin accumulation was lower in the atmyb56 mutant plants than in Col-0 plants. Preliminary microarray analysis led to the investigation of the expression of one candidate gene, AtGPT2, in the atmyb56 mutant. The phosphate translocator, which is a plastidial phosphate antiporter family, catalyzes the import of glucose-6-phosphate (G-6-P) into the chloroplast. AtGPT2 gene expression was altered in atmyb56 seedlings in a sucrose-dependent manner in response to circadian cycle. Furthermore, the lack of AtMyb56 resulted in altered accumulation of maltose in a sucrose-dependent manner. Therefore, the sucrose responsive AtMyb56 regulates AtGPT2 gene expression in a sucrose-dependent manner to modulate maltose and anthocyanin accumulations in response to the circadian cycle.

• Journal of Plant Biotechnology
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• v.37 no.4
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• pp.483-493
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• 2010

Knock-out of a gene by insertional mutagenesis is a direct way to address its function through the mutant phenotype. Among ca. 15,000 gene-trapped Ds insertion lines of rice, we identified one line from selected sensitive lines in highly salt stress. We conducted gene tagging by TAIL-PCR, and DNA gel blot analysis from salt sensitive mutant. A gene encoding an oligopeptide transporter (OPT family) homologue was disrupted by the insertion of a Ds transposon into the OsOPT10 gene that was located shot arm of chromosome 8. The OsOPT10 gene (NP_001062118.) has 6 exons and encodes a protein (752 aa) containing the OPT family domain. RT-PCR analysis showed that the expression of OsOPT10 gene was rapidly and strongly induced by stresses such as high-salinity (250 mM), osmotic, drought, $100\;{\mu}M$ ABA. The subcellular localization assay indicated that OsOPT10 was localized specifically in the plasma membrane. Overexpression of OsOPT10 in Arabidopsis thaliana and rice conferred tolerance of transgenic plants to salt stress. Further we found expression levels of some stress related genes were inhibited in OsOPT10 transgenic plants. These results suggested that OsOPT10 might play crucial but differential roles in plant responses to various abiotic stresses.

• Journal of Life Science
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• v.17 no.5 s.85
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• pp.641-645
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• 2007

We conducted a seed germination screening under saline conditions to identify salt tolerance(sto) mutants with ethyl methane sulfonate(EMS) mutagenesis seed pool. During the screening, we identified three mutant lines that seemed to confer elevated salt tolerance in high concentrations of NaCl. At 175 mM NaCl, germination rate of sto42-14 mutant(one of the EMS salt tolerance mutants) was 7-fold higher than that of wild-type plants. Interestingly, sto42-14 mutant exhibited insensitivity to high glucose concentration and growth inhibition to gibberellin. Our results suggest that sto42-14 is involved in salt stress tolerance as well as in glucose and gibberellin response in Arabidopsis.

• BMB Reports
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• v.53 no.3
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• pp.160-165
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• 2020

The root meristem of Arabidopsis thaliana is protected by the root cap, the size of which is tightly regulated by the balance between the formative cell divisions and the dispersal of the outermost cells. We isolated an enhancer-tagged dominant mutant displaying the short and twisted root by the overexpression of ZINC-FINGER OF ARABIDOPSIS THALIANA1 (ZAT1) encoding an EAR motif-containing zinc-finger protein. The growth inhibition by ZAT1 was shared by ZAT4 and ZAT9, the ZAT1 homologues. The ZAT1 promoter was specifically active in the outermost cells of the root cap, in which ZAT1-GFP was localized when expressed by the ZAT1 promoter. The outermost cell-specific expression pattern of ZAT1 was not altered in the sombrero (smb) or smb bearskin1 (brn1) brn2 accumulating additional root-cap layers. In contrast, ZAT4-GFP and ZAT9-GFP fusion proteins were distributed to the inner root-cap cells in addition to the outermost cells where ZAT4 and ZAT9 promoters were active. Overexpression of ZAT1 induced the ectopic expression of PUTATIVE ASPARTIC PROTEASE3 involved in the programmed cell death. The EAR motif was essential for the growth inhibition by ZAT1. These results suggest that the three related ZATs might regulate the maturation of the outermost cells of the root cap.

• Journal of Photoscience
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• v.9 no.2
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• pp.90-93
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• 2002

Phytochrome A (phyA) and phytochrome B (phyB) perceive light and adapt to fluctuating circumstances by different manners in terms of effective wavelengths, required fluence and photoreversibility. Action spectra for induction of seed germination and inhibition of hypocotyl elongation using phytochrome mutants of Arabidopsis showed major difference. PhyA is the principal photoreceptor for the very low fluence responses and the far-red light-induced high irradiance responses, while phyB controls low fluence response in a red/far-red reversible mode. The structural requirement of their bilin chromophores for photosensory specificity of phyA and phyB was investigated by reconstituting holophytochromes through feeding various synthetic bilins to the following chromophore-deficient mutants: hy1, hyl/phyA and hyl/phyB mutants of Arabidopsis. We found that the vinyl side-chain of the D-ring in phytochromobilin interacts with phyA apoprotein. This interaction plays a direct role in mediating the specific photosensory function of phyA. The ethyl side-chain of the D-ring in phycocyanobilin fails to interact with phyA apoprotein, therefore, phyA specific photosensory function is not observed. In contrast, both phytochromobilin and phycocyanobilin interact with phyB apoprotein and induce phyB specific photosensory functions. Structural requirements of the apoproteins and the chromophores for the specific photoperception of phyA and phyB are discussed.

• BMB Reports
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• v.40 no.3
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• pp.396-403
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• 2007

Proline accumulation has been shown to correlate with tolerance to drought and salt stresses in plants. We attempt to introduce the wild-type, mutant, and fusion proBA genes derived from Bacillus subtilis into Arabidopsis thaliana under the control of a strong promoter cauliflower mosaic virus 35S (CaMV35S). The transgenic plants produced higher level of free proline than control and the overproduction of proline resulted in the increased tolerance to osmotic stress in transgenic plants. Besides, the mutation in proBA genes, which were proved to lead $\alpha$-glutamyl kinase ($\alpha$-GK) reduces sensitivity to the end-product inhibition and the fusion of proB and proA also result in increasing proline production and confer osmotolerance in transgenic lines.

• Molecules and Cells
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• v.25 no.3
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• pp.438-445
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• 2008

Leaf senescence is a highly regulated genetic process that constitutes the last stage of plant development and provides adaptive fitness by relocating metabolites from senescing leaves to reproducing seeds. Characterization of various senescence mutants, mostly in Arabidopsis, and genome-wide analyses of gene expression, have identified a wide array of regulatory components, including transcription factors and enzymes as well as signaling molecules mediating growth hormones and environmental stress responses. In this work we demonstrate that a membrane-associated NAC transcription factor, NTL9, mediates osmotic stress signaling in leaf senescence. The NTL9 gene is induced by osmotic stress. Furthermore, activation of the dormant, membrane-associated NTL9 is elevated under the same conditions. A series of senescence-associated genes (SAGs) were upregulated in transgenic plants overexpressing an activated form of NTL9, and some of them were slightly but reproducibly downregulated in a T-DNA insertional NTL9 knockout mutant. These observations indicate that NTL9 mediates osmotic stress responses that affect leaf senescence, providing a genetic link between intrinsic genetic programs and external signals in the control of leaf senescence.

• Journal of Applied Biological Chemistry
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• v.42 no.4
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• pp.169-174
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• 1999

Arabidopsis AHL gene contains 4 exons encoding a putative protein highly homologous to the yeast salt-sensitive enzyme HAL2, a 3'(2'),5'-bisphosphate nucleotidase involving in reductive sulfate assimilation. AHL cDNA complemented yeast met22 (hal2) mutant. AHL fusion protein expressed in E. coli exhibited $Mg^{2+}$-dependent, 3'-phosphoadenosine 5'-phosphate (PAP)-specific phosphatase activity. $Li^+,\;Na^+,\;K^+$ and $Ca^{2+}$ ions inhibit the enzyme activity by competing with $Mg^{2+}$ for the active site of the enzyme. The enzyme activity was also sensitive to ${\mu}M$ concentrations of toxic heavy metal ions such as $Cd^{2+},\;Cu^{2+}$ and $Zn^{2+}$, but was not recovered by addition of more $Mg^{2+}$ ions, suggesting that these ions inactivate the enzyme with a mechanism other than competition with $Mg^{2+}$ ions. Inhibition of the AHL enzyme activity may result in accumulation of PAP, which is highly toxic to the cell. Thus, the AHL enzyme could be one of the intial targets of heavy metal toxicity in plants.

• Molecules and Cells
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• v.44 no.10
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• pp.746-757
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• 2021

Plant somatic cells can be reprogrammed into a pluripotent cell mass, called callus, which can be subsequently used for de novo shoot regeneration through a two-step in vitro tissue culture method. MET1-dependent CG methylation has been implicated in plant regeneration in Arabidopsis, because the met1-3 mutant exhibits increased shoot regeneration compared with the wild-type. To understand the role of MET1 in de novo shoot regeneration, we compared the genome-wide DNA methylomes and transcriptomes of wildtype and met1-3 callus and leaf. The CG methylation patterns were largely unchanged during leaf-to-callus transition, suggesting that the altered regeneration phenotype of met1-3 was caused by the constitutively hypomethylated genes, independent of the tissue type. In particular, MET1-dependent CG methylation was observed at the blue light receptor genes, CRYPTOCHROME 1 (CRY1) and CRY2, which reduced their expression. Coexpression network analysis revealed that the CRY1 gene was closely linked to cytokinin signaling genes. Consistently, functional enrichment analysis of differentially expressed genes in met1-3 showed that gene ontology terms related to light and hormone signaling were overrepresented. Overall, our findings indicate that MET1-dependent repression of light and cytokinin signaling influences plant regeneration capacity and shoot identity establishment.