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Choonkyun Jung,심재성,Jun Sung Seo,이한용,김정호,Yang Do Choi,정종주 한국분자세포생물학회 2010 Molecules and cells Vol.29 No.1
The Arabidopsis thaliana transcription factor gene At-MYB44 was induced within 10 min by treatment with methyl jasmonate (MeJA). Wound-induced expression of the gene was observed in local leaves, but not in distal leaves, illustrating jasmonate-independent induction at wound sites. AtMYB44 expression was not abolished in Arabidopsis mutants insensitive to jasmonate (coi1), eth-ylene (etr1), or abscisic acid (abi3-1) when treated with the corresponding hormones. Moreover, various growth hor-mones and sugars also induced rapid AtMYB44 transcript accumulation. Thus, AtMYB44 gene activation appears to not be induced by any specific hormone. MeJA-induced activation of jasmonate-responsive genes such as JR2, VSP, LOXII, and AOS was attenuated in transgenic Arabi-dopsis plants overexpressing the gene (35S:AtMYB44), but significantly enhanced in atmyb44 knockout mutants. The 35S:MYB44 and atmyb44 plants did not show defec-tiveness in MeJA-induced primary root growth inhibition, indicating that the differences in jasmonate-responsive gene expression observed was not due to alterations in the jasmonate signaling pathway. 35S:AtMYB44 seedlings exhibited slightly elevated chlorophyll levels and less jas-monate-induced anthocyanin accumulation, demonstrat-ing suppression of jasmonate-mediated responses and enhancement of ABA-mediated responses. These obser-vations support the hypothesis of mutual antagonistic actions between jasmonate- and abscisic acid-mediated signaling pathways.
Jung, Choonkyun,Seo, Jun Sung,Han, Sang Won,Koo, Yeon Jong,Kim, Chung Ho,Song, Sang Ik,Nahm, Baek Hie,Choi, Yang Do,Cheong, Jong-Joo American Society of Plant Physiologists 2008 Plant Physiology Vol.146 No.2
<P>AtMYB44 belongs to the R2R3 MYB subgroup 22 transcription factor family in Arabidopsis (Arabidopsis thaliana). Treatment with abscisic acid (ABA) induced AtMYB44 transcript accumulation within 30 min. The gene was also activated under various abiotic stresses, such as dehydration, low temperature, and salinity. In transgenic Arabidopsis carrying an AtMYB44 promoter-driven beta-glucuronidase (GUS) construct, strong GUS activity was observed in the vasculature and leaf epidermal guard cells. Transgenic Arabidopsis overexpressing AtMYB44 is more sensitive to ABA and has a more rapid ABA-induced stomatal closure response than wild-type and atmyb44 knockout plants. Transgenic plants exhibited a reduced rate of water loss, as measured by the fresh-weight loss of detached shoots, and remarkably enhanced tolerance to drought and salt stress compared to wild-type plants. Microarray analysis and northern blots revealed that salt-induced activation of the genes that encode a group of serine/threonine protein phosphatases 2C (PP2Cs), such as ABI1, ABI2, AtPP2CA, HAB1, and HAB2, was diminished in transgenic plants overexpressing AtMYB44. By contrast, the atmyb44 knockout mutant line exhibited enhanced salt-induced expression of PP2C-encoding genes and reduced drought/salt stress tolerance compared to wild-type plants. Therefore, enhanced abiotic stress tolerance of transgenic Arabidopsis overexpressing AtMYB44 was conferred by reduced expression of genes encoding PP2Cs, which have been described as negative regulators of ABA signaling.</P>
The Deubiquitinating Enzymes UBP12 and UBP13 Positively Regulate MYC2 Levels in Jasmonate Responses
Jeong, Jin Seo,Jung, Choonkyun,Seo, Jun Sung,Kim, Ju-Kon,Chua, Nam-Hai American Society of Plant Biologists 2017 The Plant cell Vol.29 No.6
<P>The transcription factor MYC2 has emerged as a master regulator of jasmonate (JA)-mediated responses as well as crosstalk among different signaling pathways. The instability of MYC2 is in part due to the action of PUB10 E3 ligase, which can polyubiquitinate this protein. Here, we show that polyubiquitinated MYC2 can be deubiquitinated by UBP12 and UBP13 in vitro, suggesting that the two deubiquitinating enzymes can counteract the effect of PUB10 in vivo. Consistent with this view, UBP12 and UBP13 associate with MYC2 in the nucleus. Transgenic Arabidopsis thaliana plants deficient in UBP12 and UBP13 show accelerated decay of MYC2 and are hyposensitive to JA, whereas plants overexpressing UBP12 or UBP13 have prolonged MYC2 half-life and are hypersensitive to JA. Our results suggest that there is a genetic link between UBP12, UBP13, and MYC2. Our results identify UBP12 and UBP13 as additional positive regulators of JA responses and suggest that these enzymes likely act by stabilizing MYC2.</P>
Seoung Hyun Lyou,Hyon Jin Park,Choonkyun Jung,Hwang Bae Sohn,이가람,김정호,김민균,최양도,정종주 한국분자세포생물학회 2009 Molecules and cells Vol.27 No.1
The Arabidopsis gene AtLEC (At3g15356) gene encodes a putative 30-kDa protein with a legume lectin-like domain. Likely to classic legume lectin family of genes, AtLEC is expressed in rosette leaves, primary inflorescences, and roots, as observed in Northern blot analysis. The accumulation of AtLEC transcript is induced very rapidly, within 30 min, by chitin, a fungal wall-derived oligosaccharide elictor of the plant defense response. Transgenic Arabidopsis carrying an AtLEC promoter-driven -glucuronidase (GUS) construct exhibited GUS activity in the leaf veins, secondary inflorescences, carpel heads, and silique receptacles, in which no expression could be seen in Northern blot analysis. This observation suggests that AtLEC expression is induced transiently and locally during developmental processes in the absence of an external signal such as chitin. In addition, mechanically wounded sites showed strong GUS activity, indicating that the AtLEC promoter responds to jasmonate. Indeed, methyl jasmonate and ethylene exposure induced AtLEC expression within 3-6 h. Thus, the gene appears to play a role in the jasmonate-/ethylene-responsive, in addition to the chitin-elicited, defense responses. However, chitin-induced AtLEC expression was also observed in jasmonate-insensitive (coi1) and ethylene-insensitive (etr1-1) Arabidopsis mutants. Thus, it appears that chitin promotes AtLEC expression via a jasmonate- and/or ethylene-independent pathway.
Yean Joo Seo,박종범,Yeon-Jeong Cho,Choonkyun Jung,서학수,박순기,남백희,송종태 한국분자세포생물학회 2010 Molecules and cells Vol.30 No.3
Ethylene-responsive factors (ERFs), within a subgroup of the AP2/ERF transcription factor family, are involved in diverse plant reactions to biotic or abiotic stresses. Here, we report that overexpression of an ERF gene from Bras-sica rapa ssp. pekinensis (BrERF4) led to improved toler-ance to salt and drought stresses in Arabidopsis. It also significantly affected the growth and development of transgenic plants. We detected that salt-induced expres-sions of a transcriptional repressor gene, AtERF4, and some Ser/Thr protein phosphatase2C genes, ABI1, ABI2 and AtPP2CA, were suppressed in BrERF4-overexpres-sing Arabidopsis plants. Furthermore, BrERF4 was in-duced by treatment with ethylene or methyljasmonate, but not by abscisic acid or NaCl in B. rapa. These results sug-gest that BrERF4 is activated through a network of differ-ent signaling pathways in response to salinity and drought.
Floral Nectary-specific Gene NTR1 Encodes a Jasmonic Acid Carboxyl Methyltransferase
Seo, Hak Soo,Song, Jong Tae,Koo, Yeon Jong,Jung, Choonkyun,Yeu, Song Yion,Kim, Minkyun,Song, Sang Ik,Lee, Jong Seob,Hwang, Ingyu,Cheong, Jong-Joo,Choi, Yang Do 한국응용생명화학회 2001 Journal of Applied Biological Chemistry (J. Appl. Vol.44 No.3
NTR1 gene of Brassica campestris L. ssp. perkinensis encodes a floral nectary-specific methyltransferase. In this study, the NTR1 cDNA was expressed in E. coli to examine the enzymatic characteristics of the protein product. The GST-NTR1 fusion protein was purified to near homogeneity, showing that the size of NTR1 was 44 kDa. The protein reacted specifically with jasmonic acid (JA), consuming methyl group from S-adenosyl-L-methionine (SAM). GC-MS analysis revealed that the compound produced was authentic methyl jasmonate (MeJA), suggesting that NTR1 is an S-adenosyl-L-methionine: jasmonic acid carboxyl methyltransferase. Km values of NTR1 for JA and SAM were 38.0 and $6.4{\mu}M$, respectively. Optimal activity of the NTR1 was observed at $20^{\circ}C$, pH 7.5, in the presence of 100-150 mM KCl. Thus, kinetic properties, thermal characteristics, optimal pH, and ion-dependency of the NTR1 activity were almost identical to those of Arabidopsis JA methyltransferase JMT, indicating that these two proteins are orthologues of each other.
AtMYB44 suppresses transcription of the late embryogenesis abundant protein gene <i>AtLEA4-5</i>
Nguyen, Nguyen Hoai,Nguyen, Chau Thi Thu,Jung, Choonkyun,Cheong, Jong-Joo Elsevier 2019 Biochemical and biophysical research communication Vol.511 No.4
<P><B>Abstract</B></P> <P>AtLEA4-5 is a member of the group 4 late embryogenesis abundant (LEA) proteins, which are involved in the tolerance of water deficit in <I>Arabidopsis thaliana</I>. Chromatin immunoprecipitation assays revealed that the transcription factor AtMYB44 bound directly to the <I>AtLEA4-5</I> gene promoter region under normal conditions, but was eliminated in response to osmotic stress (mannitol treatment). A quantitative reverse transcription PCR assay revealed that transcription of the <I>AtLEA4-5</I> gene was induced in response to either salt (salinity) or mannitol (osmosis) treatment. The abiotic stress-induced increase in <I>AtLEA4-5</I> transcripts was reduced in <I>35S:AtMYB44</I> transgenic plants, indicating that the transcription factor AtMYB44 represses gene transcription. More RNA polymerase II stalled at the transcription start site (TSS) of the <I>AtLEA4-5</I> gene loci under osmotic stress, but the increment was reduced in the <I>35S:AtMYB44</I> plants. Histones are evicted from the promoter region under osmotic stress; however, histone eviction was hampered in the <I>35S:AtMYB44</I> plants. Under osmotic stress, the acetylated histones remaining at the TSS region was significantly lower in the <I>35S:AtMYB44</I> plants compared with wild-type plants. These results indicate that AtMYB44 suppresses polymerase-mediated transcription of the <I>AtLEA4-5</I>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> AtMYB44 binds to the <I>AtLEA4-5</I> gene promoter region under normal conditions. </LI> <LI> Osmotic stress eliminates AtMYB44 from the <I>AtLEA4-5</I> gene promoter. </LI> <LI> AtMYB44 suppresses polymerase-mediated transcription of <I>AtLEA4-5.</I> </LI> <LI> AtMYB44 reduces nucleosome acetylation in the <I>AtLEA4-5</I> TSS proximal region. </LI> </UL> </P>
Application of CRISPR-Based C-to-G Base editing in rice protoplasts
Lee Jimin,Oh Nuri,Yun Jae-Young,Choi Hee Soon,Seo Jang-Kyun,Kang Jin-Ho,Jung Choonkyun 한국응용생명화학회 2023 Applied Biological Chemistry (Appl Biol Chem) Vol.66 No.-
Recently, new types of base editors, C-to-G base editors (CGBEs), that enable cytosine transversions that are unachievable with cytosine base editors (CBEs) and adenosine base editors (ABEs), have been developed in human cells. However, despite their importance in crop genome editing, the efficacy of CGBEs has not yet been extensively evaluated. In our study, based on the previously reported plant-compatible CBE and human CGBE, we demonstrated that our monocot plant-compatible CGBEs (PcCGBEs) enable cytosine transversions (C-to-G) in rice protoplasts. For all targets tested, PcCGBEs (monocot plant-compatible CGBEs) appeared to have substantial levels of C-to-G editing activity. PcCGBE showed a much higher C-to-G base editing activity and C-to-G specificity among C-to-D conversions than the mini-version of PcCGBE. Our demonstration of PcCGBE could provide a platform for the further development of enhanced CGBEs for reliable application as a new crop breeding technology.