Publications by authors named "Dae-Jin Yun"

166 Publications

Redox sensor QSOX1 regulates plant immunity by targeting GSNOR to modulate ROS generation.

Mol Plant 2021 May 4. Epub 2021 May 4.

Division of Applied Life Sciences (BK21) and PMBBRC, Gyeongsang National University, Jinju 52828, Korea; College of Life Sciences, Qingdao Agricultural University, Qingdao 266109, P.R.China. Electronic address:

Reactive oxygen signaling regulates numerous biological processes, including stress responses in plants. Redox sensors transduce reactive oxygen signals into cellular responses. We present biochemical evidence that a plant quiescin sulfhydryl oxidase homolog (QSOX1) is a redox sensor that negatively regulates immunity against a bacterial pathogen. The expression level of QSOX1 is inversely correlated with pathogen-induced ROS accumulation. QSOX1 both senses and regulates ROS levels through interaction with and redox-mediated regulation of S-nitrosoglutathione reductase that, consistent with previous findings, influences reactive nitrogen-mediated regulation of ROS generation. Collectively, our data indicate that QSOX1 is a redox sensor that negatively regulates plant immunity by linking reactive oxygen- and reactive nitrogen-signaling to limit ROS production.
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http://dx.doi.org/10.1016/j.molp.2021.05.004DOI Listing
May 2021

CCoAOMT1 Plays a Role in Drought Stress Response via ROS- and ABA-Dependent Manners.

Plants (Basel) 2021 Apr 21;10(5). Epub 2021 Apr 21.

Institute of Agriculture and Life Science, Gyeongsang National University, Jinju 52828, Korea.

Plants possess adaptive reprogramed modules to prolonged environmental stresses, including adjustment of metabolism and gene expression for physiological and morphological adaptation. encodes a caffeoyl CoA O-methyltransferase and is known to play an important role in adaptation of plants to prolonged saline stress. In this study, we showed that the gene plays a role in drought stress response. Transcript of was induced by salt, dehydration (drought), and methyl viologen (MV), and loss of function mutants of , and exhibit hypersensitive phenotypes to drought and MV stresses. The mutants accumulated higher level of HO in the leaves and expressed lower levels of drought-responsive genes including , , , and as well as and encoding ABA biosynthesis enzymes during drought stress compared to wild-type plants. A seed germination assay of mutants in the presence of ABA also revealed that functions in ABA response. Our data suggests that plays a positive role in response to drought stress response by regulating HO accumulation and ABA signaling.
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http://dx.doi.org/10.3390/plants10050831DOI Listing
April 2021

Characterization of dwarf and narrow leaf () mutant in rice.

Plant Signal Behav 2021 Feb 10;16(2):1849490. Epub 2020 Dec 10.

College of Life Science and Natural Resources, Dong-A University , Busan, Korea.

Height and leaf morphology are important agronomic traits of the major crop plant rice (). In previous studies, the genes ( and ) have identified in rice. Using the / knockout system, we found a new dwarf and narrow leaf (dnl) mutant and identified mutated gene. The mutant showed reduced plant height and leaf blade width compared to the wild type, and increased leaf inclination. The morphological defects of the mutant were caused by the suppressed expression of the gene, which encodes a pfkB carbohydrate kinase protein. These results suggest that expression is involved in modulating plant height and leaf growth. Furthermore, expression also affects productivity in rice: the mutant exhibited reduced panicle length and grain width compared with the wild type. To understand function in rice, we analyzed the expression levels of leaf growth-related genes, such as , and , in the mutant. Expression of and was downregulated in the mutant compared to the wild type. The observation that expression corresponded with that of and is consistent with the narrow leaf phenotype of the mutant. These results suggest that regulates plant height and leaf structure in rice.
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http://dx.doi.org/10.1080/15592324.2020.1849490DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7849693PMC
February 2021

HOS15 is a transcriptional corepressor of NPR1-mediated gene activation of plant immunity.

Proc Natl Acad Sci U S A 2020 12 16;117(48):30805-30815. Epub 2020 Nov 16.

Department of Biomedical Science and Engineering, Konkuk University, 05029 Seoul, South Korea;

Transcriptional regulation is a complex and pivotal process in living cells. HOS15 is a transcriptional corepressor. Although transcriptional repressors generally have been associated with inactive genes, increasing evidence indicates that, through poorly understood mechanisms, transcriptional corepressors also associate with actively transcribed genes. Here, we show that HOS15 is the substrate receptor for an SCF/CUL1 E3 ubiquitin ligase complex (SCF) that negatively regulates plant immunity by destabilizing transcriptional activation complexes containing NPR1 and associated transcriptional activators. In unchallenged conditions, HOS15 continuously eliminates NPR1 to prevent inappropriate defense gene expression. Upon defense activation, HOS15 preferentially associates with phosphorylated NPR1 to stimulate rapid degradation of transcriptionally active NPR1 and thus limit the extent of defense gene expression. Our findings indicate that HOS15-mediated ubiquitination and elimination of NPR1 produce effects contrary to those of CUL3-containing ubiquitin ligase that coactivate defense gene expression. Thus, HOS15 plays a key role in the dynamic regulation of pre- and postactivation host defense.
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http://dx.doi.org/10.1073/pnas.2016049117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7720166PMC
December 2020

Chromatin remodeling complex HDA9-PWR-ABI4 epigenetically regulates drought stress response in plants.

Plant Signal Behav 2020 10 4;15(10):1803568. Epub 2020 Aug 4.

Department of Biomedical Science & Engineering, Konkuk University , Seoul, South Korea.

Among all the major environmental challenges, drought stress causes considerable damage to plant growth and agricultural productivity. Drought stress directly promotes the accumulation of abscisic acid (ABA) via the activation of genes that encode enzymes involved in ABA biosynthesis, which protect the plant against water-limiting conditions. At the same time, the expression of genes that encode ABA-hydroxylases that inactivate the newly synthesized ABA, is repressed by drought stress. These phenomena occur through epigenetic modifications via the reversible processes of histone acetylation and deacetylation, also known as chromatin remodeling, which is an important regulatory mechanism that responds to various environmental stresses. Recently, we had reported that the chromatin remodeling complex HDA9-PWR-ABI4 promotes the development of drought tolerance through the deacetylation of genes that encode the major enzymes involved in ABA catabolism. Here, we discuss the role of HDA9 and PWR in regulating drought stress by modulating the acetylation status of the genes.
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http://dx.doi.org/10.1080/15592324.2020.1803568DOI Listing
October 2020

ABAting the Response: A Novel ABA Signal Terminator that Disrupts the Hormone Co-receptor Complex.

Mol Plant 2020 09 24;13(9):1241-1243. Epub 2020 Jul 24.

Department of Biomedical Science & Engineering, Konkuk University, Seoul 05029, South Korea. Electronic address:

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http://dx.doi.org/10.1016/j.molp.2020.07.017DOI Listing
September 2020

The GIGANTEA-ENHANCED EM LEVEL Complex Enhances Drought Tolerance via Regulation of Abscisic Acid Synthesis.

Plant Physiol 2020 09 20;184(1):443-458. Epub 2020 Jul 20.

Department of Biomedical Science and Engineering, Konkuk University, Seoul 05029, Korea

Drought is one of the most critical environmental stresses limiting plant growth and crop productivity. The synthesis and signaling of abscisic acid (ABA), a key phytohormone in the drought stress response, is under photoperiodic control. GIGANTEA (GI), a key regulator of photoperiod-dependent flowering and the circadian rhythm, is also involved in the signaling pathways for various abiotic stresses. In this study, we isolated ENHANCED EM LEVEL (EEL)/basic Leu zipper 12, a transcription factor involved in ABA signal responses, as a GI interactor in Arabidopsis (). The diurnal expression of (), a rate-limiting ABA biosynthetic enzyme, was reduced in the , , and mutants under normal growth conditions. Chromatin immunoprecipitation and electrophoretic mobility shift assays revealed that EEL and GI bind directly to the ABA-responsive element motif in the promoter. Furthermore, the , , and mutants were hypersensitive to drought stress due to uncontrolled water loss. The transcript of , endogenous ABA levels, and stomatal closure were all reduced in the , , and mutants under drought stress. Our results suggest that the EEL-GI complex positively regulates diurnal ABA synthesis by affecting the expression of , and contributes to the drought tolerance of Arabidopsis.
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http://dx.doi.org/10.1104/pp.20.00779DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7479899PMC
September 2020

HKT sodium and potassium transporters in Arabidopsis thaliana and related halophyte species.

Physiol Plant 2021 Apr 23;171(4):546-558. Epub 2020 Jul 23.

Department of Biomedical Science & Engineering, Konkuk University, Seoul, 05029, South Korea.

High salinity induces osmotic stress and often leads to sodium ion-specific toxicity, with inhibitory effects on physiological, biochemical and developmental pathways. To cope with increased Na in soil water, plants restrict influx, compartmentalize ions into vacuoles, export excess Na from the cell, and distribute ions between the aerial and root organs. In this review, we discuss our current understanding of how high-affinity K transporters (HKT) contribute to salinity tolerance, focusing on HKT1-like family members primarily involved in long-distance transport, and in the recent research in the model plant Arabidopsis and its halophytic counterparts of the Eutrema genus. Functional characterization of the salt overly sensitive (SOS) pathway and HKT1-type transporters in these species indicate that they utilize similar approaches to deal with salinity, regardless of their tolerance.
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http://dx.doi.org/10.1111/ppl.13166DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8048799PMC
April 2021

PWR/HDA9/ABI4 Complex Epigenetically Regulates ABA Dependent Drought Stress Tolerance in .

Front Plant Sci 2020 26;11:623. Epub 2020 May 26.

Department of Biomedical Science and Engineering, Konkuk University, Seoul, South Korea.

Drought stress adversely affects plant growth and development and significantly reduces crop productivity and yields. The phytohormone abscisic acid (ABA) rapidly accumulates in response to drought stress and mediates the expression of stress-responsive genes that help the plant to survive dehydration. The protein Powerdress (PWR), which interacts with Histone Deacetylase 9 (HDA9), has been identified as a critical component regulating plant growth and development, flowering time, floral determinacy, and leaf senescence. However, the role and function of PWR and HDA9 in abiotic stress response had remained elusive. Here we report that a complex of PWR and HDA9 interacts with ABI4 and epigenetically regulates drought signaling in plants. T-DNA insertion mutants of and are insensitive to ABA and hypersensitive to dehydration. Furthermore, the expression of ABA-responsive genes (, , and ) is also downregulated in and mutants. Yeast two-hybrid assays showed that PWR and HDA9 interact with ABI4. Transcript levels of genes that are normally repressed by ABI4, such as , and , are increased in . More importantly, during dehydration stress, PWR and HDA9 regulate the acetylation status of the , which encodes a major enzyme of ABA catabolism. Taken together, our results indicate that PWR, in association with HDA9 and ABI4, regulates the chromatin modification of genes responsible for regulation of both the ABA-signaling and ABA-catabolism pathways in response to ABA and drought stress.
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http://dx.doi.org/10.3389/fpls.2020.00623DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7266079PMC
May 2020

HOS15: A missing link that fine-tunes ABA signaling and drought tolerance in .

Plant Signal Behav 2020 07 19;15(7):1770964. Epub 2020 May 19.

Department of Biomedical Science & Engineering, Konkuk University , Seoul, South Korea.

Among the phytohormones, abscisic acid (ABA) specifically regulates plant adaptation to osmotic stresses, such as drought and high salinity, by controlling the internal water status in plants. A significant accumulation of ABA occurs in response to conditions of water deficit; this is followed by a sophisticated signaling relay, known as the ABA signaling pathway, which decreases the rate of transpiration through stomatal closure, thereby suppressing photosynthetic activity. Snf1-related kinases (SnRK2s) are the major components regulating the ABA signaling pathway. Of these, SnRK2.6 (OST1) and SnRK2.3 are negatively regulated by HOS15 (IGH EXPRESSION OF MOTICALLY RESPONSIVE15), in an ABA-dependent manner, to cease the signaling relay. HOS15 is a WD40-repeat protein that regulates several physiological processes, including plant growth and development, freezing stress responses, and ABA signaling. Here, we provide a brief overview of the functional importance of HOS15 in the regulation of ABA signaling and drought stress.
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http://dx.doi.org/10.1080/15592324.2020.1770964DOI Listing
July 2020

Desensitization of ABA-Signaling: The Swing From Activation to Degradation.

Front Plant Sci 2020 22;11:379. Epub 2020 Apr 22.

Department of Biomedical Science and Engineering, Konkuk University, Seoul, South Korea.

Abscisic acid (ABA) is a key plant stress-signaling hormone that accumulates upon osmotic stresses such as drought and high salinity. Several proteins have been identified that constitute the ABA-signaling pathway. Among them ABA receptors (PYR/PYL/RCAR), co-receptor PP2Cs (protein phosphatases), SnRK2 kinases (SNF1-related protein kinases) and ABI5/ABFs (transcription factors) are the major components. Upon ABA signal, PYR/PYL receptors interact with and recruit PP2Cs, releasing SnRK2s kinases from sequestration with PP2Cs. This allows SnKR2s to promote the activation of downstream transcription factors of ABA pathway. However, apart from activation, ubiquitination and degradation of core proteins in the ABA pathway by the ubiquitin proteasome system is less explored. In this review we will focus on the recent findings about feedback regulation of ABA signaling core proteins through degradation, which is emerging as a critical step that modulates and eventually ceases the signal relay. Additionally, we also discuss the importance of the recently identified effector protein HOS15, which negatively regulate ABA-signaling through degradation of OST1.
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http://dx.doi.org/10.3389/fpls.2020.00379DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7188955PMC
April 2020

Histone Deacetylase HDA9 With ABI4 Contributes to Abscisic Acid Homeostasis in Drought Stress Response.

Front Plant Sci 2020 25;11:143. Epub 2020 Feb 25.

Department of Biomedical Science and Engineering, Konkuk University, Seoul, South Korea.

Drought stress, a major environmental factor, significantly affects plant growth and reproduction. Plants have evolved complex molecular mechanisms to tolerate drought stress. In this study, we investigated the function of the RPD3-type HISTONE DEACETYLASE 9 (HDA9) in response to drought stress. The loss-of-function mutants and were insensitive to abscisic acid (ABA) and sensitive to drought stress. The ABA content in the mutant was reduced in wild type (WT) plant. Most histone deacetylases in animals and plants form complexes with other chromatin-remodeling components, such as transcription factors. In this study, we found that HDA9 interacts with the ABA INSENSITIVE 4 (ABI4) transcription factor using a yeast two-hybrid assay and coimmunoprecipitation. The expression of and , which encode (+)-ABA 8'-hydroxylases, key enzymes in ABA catabolic pathways, was highly induced in , , , and mutants upon drought stress. Chromatin immunoprecipitation and quantitative PCR showed that the HDA9 and ABI4 complex repressed the expression of and by directly binding to their promoters in response to drought stress. Taken together, these data suggest that HDA9 and ABI4 form a repressive complex to regulate the expression of and in response to drought stress in .
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http://dx.doi.org/10.3389/fpls.2020.00143DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7052305PMC
February 2020

The Auxin Signaling Repressor IAA8 Promotes Seed Germination Through Down-Regulation of Transcription in .

Front Plant Sci 2020 20;11:111. Epub 2020 Feb 20.

Division of Applied Life Science (BK21 Plus program), Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju, South Korea.

Seed germination is a complex biological process controlled by various regulators, including phytohormones. Among these, abscisic acid and gibberellic acid inhibit and promote seed germination, respectively. Many studies have addressed the biological roles of auxin in plant growth and development, but very few have considered its role in seed germination. Here, we identified a novel function of the auxin signaling repressor Aux/IAA8 during seed germination. The loss-of-function mutant exhibited delayed seed germination. The phenotype of was restored by ectopic expression of . Interestingly, IAA8 accumulated to high levels during seed germination, which was achieved not only by increased protein synthesis but also by the stabilization of IAA8 protein. We also showed that IAA8 down-regulates the transcription of (), a negative regulator of seed germination. Our study, thus strongly suggest that the auxin signaling repressor IAA8 acts as a positive regulator of seed germination in .
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http://dx.doi.org/10.3389/fpls.2020.00111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7045070PMC
February 2020

Plant-Growth Promoting YC7007 Modulates Stress-Response Gene Expression and Provides Protection From Salt Stress.

Front Plant Sci 2019 9;10:1646. Epub 2020 Jan 9.

Division of Applied Life Science (BK21plus program), Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju, South Korea.

High salt stress caused by ionic and osmotic stressors eventually results in the suppression of plant growth and a reduction in crop productivity. In our previous reports, we isolated the endophytic bacterium YC7007 from the rhizosphere of rice ( L.), which promoted plant growth and development and suppressed bacterial disease in rice by inducing systemic resistance and antibiotic production. In this study, seedlings under salt stress that were bacterized with YC7007 displayed an increase in the number of lateral roots and greater fresh weight relative to that of the control seedlings. The chlorophyll content of the bacterized seedlings was increased when compared with that of untreated seedlings. The accumulation of salt-induced malondialdehyde and Na in seedlings was inhibited by their co-cultivation with YC7007. The expression of stress-related genes in the shoots and roots of seedlings was induced by YC7007 inoculation under salt stress conditions. Interestingly, YC7007-mediated salt tolerance requires SOS1, a plasma membrane-localized Na/H antiporter, given that plant growth in and mutants was promoted under salt-stress conditions, whereas that of mutants was not. In addition, inoculation with YC7007 in upland-crops, such as radish and cabbage, increased the number of lateral roots and the fresh weight of seedlings under salt-stress conditions. Our results suggest that YC7007 enhanced plant tolerance to salt stress via the SOS1-dependent salt signaling pathway, resulting in the normal growth of salt-stressed plants.
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http://dx.doi.org/10.3389/fpls.2019.01646DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6962239PMC
January 2020

STCH4/REIL2 Confers Cold Stress Tolerance in Arabidopsis by Promoting rRNA Processing and CBF Protein Translation.

Cell Rep 2020 01;30(1):229-242.e5

Shanghai Center for Plant Stress Biology, Center of Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, People's Republic of China; Institute of Plant Physiology and Ecology, Center of Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, People's Republic of China; Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA. Electronic address:

Plants respond to cold stress by inducing the expression of transcription factors that regulate downstream genes to confer tolerance to freezing. We screened an Arabidopsis transfer DNA (T-DNA) insertion library and identified a cold-hypersensitive mutant, which we named stch4 (sensitive to chilling 4). STCH4/REIL2 encodes a ribosomal biogenesis factor that is upregulated upon cold stress. Overexpression of STCH4 confers chilling and freezing tolerance in Arabidopsis. The stch4 mutation reduces CBF protein levels and thus delayed the induction of C-repeat-binding factor (CBF) regulon genes. Ribosomal RNA processing is reduced in stch4 mutants, especially under cold stress. STCH4 associates with multiple ribosomal proteins, and these interactions are modulated by cold stress. These results suggest that the ribosome is a regulatory node for cold stress responses and that STCH4 promotes an altered ribosomal composition and functions in low temperatures to facilitate the translation of proteins important for plant growth and survival under cold stress.
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http://dx.doi.org/10.1016/j.celrep.2019.12.012DOI Listing
January 2020

Expression of Arabidopsis thaliana Thioredoxin-h2 in Brassica napus enhances antioxidant defenses and improves salt tolerance.

Plant Physiol Biochem 2020 Feb 28;147:313-321. Epub 2019 Dec 28.

Division of Applied Life Science (BK21 Plus), Gyeongsang National University, Jinju, 52828, Republic of Korea; PMBBRC, IALS & RILS, Gyeongsang National University, Jinju, 52828, Republic of Korea. Electronic address:

Salt stress limits crop productivity worldwide, particularly in arid and heavily irrigated regions. Salt stress causes oxidative stress, in which plant cells accumulate harmful levels of reactive oxygen species (ROS). Thioredoxins (Trxs; EC 1.8.4.8) are antioxidant proteins encoded by a ubiquitous multigene family. Arabidopsis thaliana Trx h-type proteins localize in the cytoplasm and other subcellular organelles, and function in plant responses to abiotic stresses and pathogen attack. Here, we isolated the Arabidopsis genes encoding two cytosolic h-type Trx proteins, AtTrx-h2 and AtTrx-h3 and generated transgenic oilseed rape (Brassica napus) plants overexpressing AtTrx-h2 or AtTrx-h3. Heterologous expression of AtTrx-h2 in B. napus conferred salt tolerance with plants grown on 50 mM NaCl having higher fresh weight and chlorophyll contents compared with controls in hydroponic growth system. By contrast, expression of AtTrx-h3 or the empty vector control did not improve salt tolerance. In addition, AtTrx-h2-overexpressing transgenic plants exhibited lower levels of hydrogen peroxide and higher activities of antioxidant enzymes including peroxidase, catalase, and superoxide dismutase, compared with the plants expressing the empty vector control or AtTrx-h3. These results suggest that AtTrx-h2 is a promising candidate for engineering or breeding crops with enhanced salt stress tolerance.
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http://dx.doi.org/10.1016/j.plaphy.2019.12.032DOI Listing
February 2020

AtPR5K2, a PR5-Like Receptor Kinase, Modulates Plant Responses to Drought Stress by Phosphorylating Protein Phosphatase 2Cs.

Front Plant Sci 2019 11;10:1146. Epub 2019 Oct 11.

Department of Biomedical Science and Engineering, Konkuk University, Seoul, South Korea.

Cell surface receptors perceive signals from the environment and transfer them to the interior of the cell. The PR5 receptor-like kinase (AtPR5K) subfamily consists of three members with extracellular domains that share sequence similarity with the PR5 proteins. In this study, we characterized the role of AtPR5K2 in plant drought-stress signaling. is predominantly expressed in leaves and localized to the plasma membrane. The mutant showed tolerance to dehydration stress, while -overexpressing plants was hypersensitive to drought. Bimolecular fluorescence complementation assays showed that AtPR5K2 physically interacted with the type 2C protein phosphatases ABA-insensitive 1 (ABI1) and ABI2 and the SNF1-related protein kinase 2 (SnRK2.6) proteins, all of which are involved in the initiation of abscisic acid (ABA) signaling; however, these interactions were inhibited by treatments of exogenous ABA. Moreover, AtPR5K2 was found to phosphorylate ABI1 and ABI2, but not SnRK2.6. Taken together, these results suggest that AtPR5K2 participates in ABA-dependent drought-stress signaling through the phosphorylation of ABI1 and ABI2.
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http://dx.doi.org/10.3389/fpls.2019.01146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6822995PMC
October 2019

Rheostatic Control of ABA Signaling through HOS15-Mediated OST1 Degradation.

Mol Plant 2019 11 3;12(11):1447-1462. Epub 2019 Sep 3.

Department of Biomedical Science & Engineering, Konkuk University, Seoul 05029, South Korea. Electronic address:

Dehydrating stresses trigger the accumulation of abscisic acid (ABA), a key plant stress-signaling hormone that activates Snf1-Related Kinases (SnRK2s) to mount adaptive responses. However, the regulatory circuits that terminate the SnRK2s signal relay after acclimation or post-stress conditions remain to be defined. Here, we show that the desensitization of the ABA signal is achieved by the regulation of OST1 (SnRK2.6) protein stability via the E3-ubiquitin ligase HOS15. Upon ABA signal, HOS15-induced degradation of OST1 is inhibited and stabilized OST1 promotes the stress response. When the ABA signal terminates, protein phosphatases ABI1/2 promote rapid degradation of OST1 via HOS15. Notably, we found that even in the presence of ABA, OST1 levels are also depleted within hours of ABA signal onset. The unexpected dynamics of OST1 abundance are then resolved by systematic mathematical modeling, demonstrating a desensitizing feedback loop by which OST1-induced upregulation of ABI1/2 leads to the degradation of OST1. This model illustrates the complex rheostat dynamics underlying the ABA-induced stress response and desensitization.
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http://dx.doi.org/10.1016/j.molp.2019.08.005DOI Listing
November 2019

The Physiological Functions of Universal Stress Proteins and Their Molecular Mechanism to Protect Plants From Environmental Stresses.

Front Plant Sci 2019 5;10:750. Epub 2019 Jun 5.

Division of Applied Life Science (BK21Plus), Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju, South Korea.

Since the original discovery of a Universal Stress Protein (USP) in , a number of USPs have been identified from diverse sources including archaea, bacteria, plants, and metazoans. As their name implies, these proteins participate in a broad range of cellular responses to biotic and abiotic stresses. Their physiological functions are associated with ion scavenging, hypoxia responses, cellular mobility, and regulation of cell growth and development. Consistent with their roles in resistance to multiple stresses, USPs show a wide range of structural diversity that results from the diverse range of other functional motifs fused with the USP domain. As well as providing structural diversity, these catalytic motifs are responsible for the diverse biochemical properties of USPs and enable them to act in a number of cellular signaling transducers and metabolic regulators. Despite the importance of USP function in many organisms, the molecular mechanisms by which USPs protect cells and provide stress resistance remain largely unknown. This review addresses the diverse roles of USPs in plants and how the proteins enable plants to resist against multiple stresses in ever-changing environment. Bioinformatic tools used for the collection of a set of USPs from various plant species provide more than 2,100 USPs and their functional diversity in plant physiology. Data from previous studies are used to understand how the biochemical activity of plant USPs modulates biotic and abiotic stress signaling. As USPs interact with the redox protein, thioredoxin, in Arabidopsis and reactive oxygen species (ROS) regulates the activity of USPs, the involvement of USPs in redox-mediated defense signaling is also considered. Finally, this review discusses the biotechnological application of USPs in an agricultural context by considering the development of novel stress-resistant crops through manipulating the expression of genes.
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http://dx.doi.org/10.3389/fpls.2019.00750DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6560075PMC
June 2019

Lignin biosynthesis genes play critical roles in the adaptation of plants to high-salt stress.

Plant Signal Behav 2019 3;14(8):1625697. Epub 2019 Jun 3.

a Institute of Agriculture & Life Science , Gyeongsang National University , Jinju , Korea.

Salinity is a major abiotic stressor that limits the growth, development, and reproduction of plants. Our previous metabolic analysis of high salt-adapted callus suspension cell cultures from roots indicated that physical reinforcement of the cell wall is an important step in adaptation to saline conditions. Compared to normal cells, salt-adapted cells exhibit an increased lignin content and thickened cell wall. In this study, we investigated not only the lignin biosynthesis gene expression patterns in salt-adapted cells, but also the effects of a loss-of-function of CCoAOMT1, which plays a critical role in the lignin biosynthesis pathway, on plant responses to high-salt stress. Quantitative real-time PCR analysis revealed higher mRNA levels of genes involved in lignin biosynthesis, including , and , in salt-adapted cells relative to normal cells, which suggests activation of the lignin biosynthesis pathway in salt-adapted cells. Moreover, plants harboring the mutants, and , were phenotypically hypersensitive to salt stress. Our study has provided molecular and genetic evidence indicating the importance of enhanced lignin accumulation in the plant cell wall during the responses to salt stress.
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http://dx.doi.org/10.1080/15592324.2019.1625697DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6619940PMC
May 2020

A Critical Role of Sodium Flux via the Plasma Membrane Na/H Exchanger SOS1 in the Salt Tolerance of Rice.

Plant Physiol 2019 06 16;180(2):1046-1065. Epub 2019 Apr 16.

Instituto de Bioquimica Vegetal y Fotosintesis (IBVF), Consejo Superior de Investigaciones Científicas (CSIC) and University of Seville, 41092 Seville, Spain

Rice () stands among the world's most important crop species. Rice is salt sensitive, and the undue accumulation of sodium ions (Na) in shoots has the strongest negative correlation with rice productivity under long-term salinity. The plasma membrane Na/H exchanger protein Salt Overly Sensitive 1 (SOS1) is the sole Na efflux transporter that has been genetically characterized to date. Here, the importance of SOS1-facilitated Na flux in the salt tolerance of rice was analyzed in a reverse-genetics approach. A loss-of-function mutant displayed exceptional salt sensitivity that was correlated with excessive Na intake and impaired Na loading into the xylem, thus indicating that SOS1 controls net root Na uptake and long-distance Na transport to shoots. The acute Na sensitivity of plants at low NaCl concentrations allowed analysis of the transcriptional response to sodicity stress without effects of the osmotic stress intrinsic to high-salinity treatments. In contrast with that in the wild type, mutant roots displayed preferential down-regulation of stress-related genes in response to salt treatment, despite the greater intensity of stress experienced by the mutant. These results suggest there is impaired stress detection or an inability to mount a comprehensive response to salinity in In summary, the plasma membrane Na/H exchanger SOS1 plays a major role in the salt tolerance of rice by controlling Na homeostasis and possibly contributing to the sensing of sodicity stress.
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http://dx.doi.org/10.1104/pp.19.00324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6548274PMC
June 2019

Role and Functional Differences of HKT1-Type Transporters in Plants under Salt Stress.

Int J Mol Sci 2019 Mar 1;20(5). Epub 2019 Mar 1.

Department of Biomedical Science & Engineering, Konkuk University, Seoul 05029, Korea.

Abiotic stresses generally cause a series of morphological, biochemical and molecular changes that unfavorably affect plant growth and productivity. Among these stresses, soil salinity is a major threat that can seriously impair crop yield. To cope with the effects of high salinity on plants, it is important to understand the mechanisms that plants use to deal with it, including those activated in response to disturbed Na⁺ and K⁺ homeostasis at cellular and molecular levels. HKT1-type transporters are key determinants of Na⁺ and K⁺ homeostasis under salt stress and they contribute to reduce Na⁺-specific toxicity in plants. In this review, we provide a brief overview of the function of HKT1-type transporters and their importance in different plant species under salt stress. Comparison between HKT1 homologs in different plant species will shed light on different approaches plants may use to cope with salinity.
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http://dx.doi.org/10.3390/ijms20051059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6429402PMC
March 2019

HOS15 Interacts with the Histone Deacetylase HDA9 and the Evening Complex to Epigenetically Regulate the Floral Activator .

Plant Cell 2019 01 3;31(1):37-51. Epub 2019 Jan 3.

Division of Applied Life Science (BK21Plus), Plant Molecular Biology and Biotechnology Research Center, Research Institute of Life Sciences, Gyeongsang National University, Jinju 52828, Republic of Korea

In plants, seasonal inputs such as photoperiod and temperature modulate the plant's internal genetic program to regulate the timing of the developmental transition from vegetative to reproductive growth. This regulation of the floral transition involves chromatin remodeling, including covalent modification of histones. Here, we report that HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE 15 (HOS15), a WD40 repeat protein, associates with a histone deacetylase complex to repress transcription of the ()-mediated photoperiodic flowering pathway in Arabidopsis (). Loss of function of HOS15 confers early flowering under long-day conditions because elevated expression. LUX ARRHYTHMO (LUX), a DNA binding transcription factor and component of the Evening Complex (EC), is important for the binding of HOS15 to the promoter. In wild type, HOS15 associates with the EC components LUX, EARLY FLOWERING 3 (ELF3), and ELF4 and the histone deacetylase HDA9 at the promoter, resulting in histone deacetylation and reduced expression. In the mutant, the levels of histone acetylation are elevated at the promoter, resulting in increased expression. Our data suggest that the HOS15-EC-HDA9 histone-modifying complex regulates photoperiodic flowering via the transcriptional repression of .
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http://dx.doi.org/10.1105/tpc.18.00721DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6391688PMC
January 2019

Post-translational and transcriptional regulation of phenylpropanoid biosynthesis pathway by Kelch repeat F-box protein SAGL1.

Plant Mol Biol 2019 Jan 12;99(1-2):135-148. Epub 2018 Dec 12.

Department of Life Science, Sogang University, Seoul, 04107, Republic of Korea.

Key Message: A Kelch repeat F-box containing protein, SMALL AND GLOSSY LEAVES1 (SAGL1) regulates phenylpropanoid biosynthesis as a post-translational regulator for PAL1 (phenylalanine ammonia-lyase) and an indirect transcriptional regulator for ANTHOCYANIDIN SYNTHASE. Phenylpropanoid biosynthesis in plants produces diverse aromatic metabolites with important biological functions. Phenylalanine ammonia-lyase (PAL) catalyzes the first step in phenylpropanoid biosynthesis by converting L-phenylalanine to trans-cinnamic acid. Here, we report that SMALL AND GLOSSY LEAVES1 (SAGL1), a Kelch repeat F-box protein, interacts with PAL1 protein for proteasome-mediated degradation to regulate phenylpropanoid biosynthesis in Arabidopsis. Mutations in SAGL1 caused high accumulation of anthocyanins and lignin derived from the phenylpropanoid biosynthesis pathway. We found that PAL enzyme activity increased in SAGL1-defective mutants, sagl1, but decreased in SAGL1-overexpressing Arabidopsis (SAGL1OE) without changes in the transcript levels of PAL genes, suggesting protein-level regulation by SAGL1. Indeed, the levels of PAL1-GFP fusion protein were reduced when both SAGL1 and PAL1-GFP were transiently co-expressed in leaves of Nicotiana benthamiana. In addition, bimolecular fluorescence complementation analysis suggested an interaction between SAGL1 and PAL1. We also found that the transcript levels of ANTHOCYANIDIN SYNTHASE (ANS) increased in the sagl1 mutants but decreased in SAGL1OE. Our results suggest that SAGL1 regulates phenylpropanoid biosynthesis post-translationally at PAL1 and transcriptionally at ANS.
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http://dx.doi.org/10.1007/s11103-018-0808-8DOI Listing
January 2019

Metabolic Adjustment of Arabidopsis Root Suspension Cells During Adaptation to Salt Stress and Mitotic Stress Memory.

Plant Cell Physiol 2019 Mar;60(3):612-625

Institute of Agriculture & Life Science, Gyeongsang National University, Jinju, Korea.

Sessile plants reprogram their metabolic and developmental processes during adaptation to prolonged environmental stresses. To understand the molecular mechanisms underlying adaptation of plant cells to saline stress, we established callus suspension cell cultures from Arabidopsis roots adapted to high salt for an extended period of time. Adapted cells exhibit enhanced salt tolerance compared with control cells. Moreover, acquired salt tolerance is maintained even after the stress is relieved, indicating the existence of a memory of acquired salt tolerance during mitotic cell divisions, known as mitotic stress memory. Metabolite profiling using 1H-nuclear magnetic resonance (NMR) spectroscopy revealed metabolic discrimination between control, salt-adapted and stress-memory cells. Compared with control cells, salt-adapted cells accumulated higher levels of sugars, amino acids and intermediary metabolites in the shikimate pathway, such as coniferin. Moreover, adapted cells acquired thicker cell walls with higher lignin contents, suggesting the importance of adjustments of physical properties during adaptation to elevated saline conditions. When stress-memory cells were reverted to normal growth conditions, the levels of metabolites again readjusted. Whereas most of the metabolic changes reverted to levels intermediate between salt-adapted and control cells, the amounts of sugars, alanine, γ-aminobutyric acid and acetate further increased in stress-memory cells, supporting a view of their roles in mitotic stress memory. Our results provide insights into the metabolic adjustment of plant root cells during adaptation to saline conditions as well as pointing to the function of mitotic memory in acquired salt tolerance.
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http://dx.doi.org/10.1093/pcp/pcy231DOI Listing
March 2019

It's Hard to Avoid Avoidance: Uncoupling the Evolutionary Connection between Plant Growth, Productivity and Stress "Tolerance".

Int J Mol Sci 2018 Nov 20;19(11). Epub 2018 Nov 20.

Department of Biomedical Science and Engineering Konkuk University, Seoul 05029, Korea.

In the last 100 years, agricultural developments have favoured selection for highly productive crops, a fact that has been commonly associated with loss of key traits for environmental stress tolerance. We argue here that this is not exactly the case. We reason that high yield under near optimal environments came along with of plant stress perception and consequently of stress avoidance mechanisms, such as slow growth, which were originally needed for survival over long evolutionary time periods. Therefore, mechanisms employed by plants to cope with a stressful environment during evolution were overwhelmingly geared to avoid detrimental effects so as to ensure survival and that plant stress "tolerance" is fundamentally and evolutionarily based on "avoidance" of injury and death which may be referred to as evolutionary avoidance (EVOL-Avoidance). As a consequence, slow growth results from being exposed to stress because genes and genetic programs to adjust growth rates to external circumstances have evolved as a survival but not productivity strategy that has allowed extant plants to avoid extinction. To improve productivity under moderate stressful conditions, the evolution-oriented plant stress response circuits must be changed from a survival mode to a continued productivity mode or to the evolutionary avoidance response, as it were. This may be referred to as Agricultural (AGRI-Avoidance). Clearly, highly productive crops have kept the slow, reduced growth response to stress that they evolved to ensure survival. Breeding programs and genetic engineering have not succeeded to genetically remove these responses because they are polygenic and redundantly programmed. From the beginning of modern plant breeding, we have not fully appreciated that our crop plants react overly-cautiously to stress conditions. They over-reduce growth to be able to survive stresses for a period of time much longer than a cropping season. If we are able to remove this polygenic redundant survival safety net we may improve yield in moderately stressful environments, yet we will face the requirement to replace it with either an emergency slow or no growth (dormancy) response to extreme stress or use resource management to rescue crops under extreme stress (or both).
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http://dx.doi.org/10.3390/ijms19113671DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6274854PMC
November 2018

Tomato PEPR1 ORTHOLOG RECEPTOR-LIKE KINASE1 Regulates Responses to Systemin, Necrotrophic Fungi, and Insect Herbivory.

Plant Cell 2018 09 21;30(9):2214-2229. Epub 2018 Aug 21.

Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907

Endogenous peptides regulate plant immunity and growth. Systemin, a peptide specific to the Solanaceae, is known for its functions in plant responses to insect herbivory and pathogen infections. Here, we describe the identification of the tomato () PEPR1/2 ORTHOLOG RECEPTOR-LIKE KINASE1 (PORK1) as the TOMATO PROTEIN KINASE1b (TPK1b) interacting protein and demonstrate its biological functions in systemin signaling and tomato immune responses. Tomato RNA interference (RNAi) plants with significantly reduced expression showed increased susceptibility to tobacco hornworm (), reduced seedling growth sensitivity to the systemin peptide, and compromised systemin-mediated resistance to Systemin-induced expression of (), a classical marker for systemin signaling, was abrogated in RNAi plants. Similarly, in response to systemin and wounding, the expression of jasmonate pathway genes was attenuated in RNAi plants. TPK1b, a key regulator of tomato defense against and , was phosphorylated by PORK1. Interestingly, wounding- and systemin-induced phosphorylation of TPK1b was attenuated when expression was suppressed. Our data suggest that resistance to and is dependent on PORK1-mediated responses to systemin and subsequent phosphorylation of TPK1b. Altogether, PORK1 regulates tomato systemin, wounding, and immune responses.
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http://dx.doi.org/10.1105/tpc.17.00908DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6181013PMC
September 2018

The High-Affinity Potassium Transporter EpHKT1;2 From the Extremophile Mediates Salt Tolerance.

Front Plant Sci 2018 30;9:1108. Epub 2018 Jul 30.

Department of Biomedical Science and Engineering, Konkuk University, Seoul, South Korea.

To survive salt stress, plants must maintain a balance between sodium and potassium ions. High-affinity potassium transporters (HKTs) play a key role in reducing Na toxicity through K uptake. (formerly known as ), a halophyte closely related to , has two genes that encode EpHKT1;1 and EpHKT1;2. In response to high salinity, the transcript level increased rapidly; by contrast, the transcript increased more slowly in response to salt treatment. Yeast cells expressing EpHKT1;2 were able to tolerate high concentrations of NaCl, whereas EpHKT1;1-expressing yeast cells remained sensitive to NaCl. Amino acid sequence alignment with other plant HKTs showed that EpHKT1;1 contains an asparagine residue (Asn-213) in the second pore-loop domain, but EpHKT1;2 contains an aspartic acid residue (Asp-205) at the same position. Yeast cells expressing EpHKT1;1, in which Asn-213 was substituted with Asp, were able to tolerate high concentrations of NaCl. In contrast, substitution of Asp-205 by Asn in EpHKT1;2 did not enhance salt tolerance and rather resulted in a similar function to that of AtHKT1 (Na influx but no K influx), indicating that the presence of Asn or Asp determines the mode of cation selectivity of the HKT1-type transporters. Moreover, plants (Col-) overexpressing showed significantly higher tolerance to salt stress and accumulated less Na and more K compared to those overexpressing or . Taken together, these results suggest that EpHKT1;2 mediates tolerance to Na ion toxicity in and is a major contributor to its halophytic nature.
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http://dx.doi.org/10.3389/fpls.2018.01108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6077265PMC
July 2018

EMR, a cytosolic-abundant ring finger E3 ligase, mediates ER-associated protein degradation in Arabidopsis.

New Phytol 2018 10 22;220(1):163-177. Epub 2018 Jun 22.

Division of Applied Life Sciences (BK21+) and Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju, 52828, Korea.

Investigation of the endoplasmic reticulum-associated degradation (ERAD) system in plants led to the identification of ERAD-mediating RING finger protein (EMR) as a plant-specific ERAD E3 ligase from Arabidopsis. EMR was significantly up-regulated under endoplasmic reticulum (ER) stress conditions. The EMR protein purified from bacteria displayed high E3 ligase activity, and tobacco leaf-produced EMR mediated mildew resistance locus O-12 (MLO12) degradation in a proteasome-dependent manner. Subcellular localization and coimmunoprecipitation analyses showed that EMR forms a complex with ubiquitin-conjugating enzyme 32 (UBC32) as a cytosolic interaction partner. Mutation of EMR and RNA interference (RNAi) increased the tolerance of plants to ER stress. EMR RNAi in the bri1-5 background led to partial recovery of the brassinosteroid (BR)-insensitive phenotypes as compared with the original mutant plants and increased ER stress tolerance. The presented results suggest that EMR is involved in the plant ERAD system that affects BR signaling under ER stress conditions as a novel Arabidopsis ring finger E3 ligase mainly present in cytosol while the previously identified ERAD E3 components are typically membrane-bound proteins.
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http://dx.doi.org/10.1111/nph.15279DOI Listing
October 2018

Epigenetic switch from repressive to permissive chromatin in response to cold stress.

Proc Natl Acad Sci U S A 2018 06 21;115(23):E5400-E5409. Epub 2018 May 21.

Department of Biomedical Science and Engineering, Konkuk University, 05029 Seoul, South Korea;

Switching from repressed to active status in chromatin regulation is part of the critical responses that plants deploy to survive in an ever-changing environment. We previously reported that HOS15, a WD40-repeat protein, is involved in histone deacetylation and cold tolerance in However, it remained unknown how HOS15 regulates cold responsive genes to affect cold tolerance. Here, we show that HOS15 interacts with histone deacetylase 2C (HD2C) and both proteins together associate with the promoters of cold-responsive genes, and Cold induced HD2C degradation is mediated by the CULLIN4 (CUL4)-based E3 ubiquitin ligase complex in which HOS15 acts as a substrate receptor. Interference with the association of HD2C and the gene promoters by HOS15 correlates with increased acetylation levels of histone H3. HOS15 also interacts with CBF transcription factors to modulate cold-induced binding to the gene promoters. Our results here demonstrate that cold induces HOS15-mediated chromatin modifications by degrading HD2C. This switches the chromatin structure status and facilitates recruitment of CBFs to the gene promoters. This is an apparent requirement to acquire cold tolerance.
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http://dx.doi.org/10.1073/pnas.1721241115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6003311PMC
June 2018