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Galactic Archeology with the AEGIS Survey: The Evolution of Carbon and Iron in the Galactic Halo
Yoon, Jinmi,Beers, Timothy C.,Dietz, Sarah,Lee, Young Sun,Placco, Vinicius M.,Costa, Gary Da,Keller, Stefan,Owen, Christopher I.,Sharma, Mahavir American Astronomical Society 2018 The Astrophysical journal Vol.861 No.2
<P>Understanding the evolution of carbon and iron in the Milky Way's halo is of importance because these two elements play crucial roles in constraining star formation, Galactic assembly, and chemical evolution in the early universe. Here we explore the spatial distributions of the carbonicity, [C/Fe], and metallicity, [Fe/H], of the halo system based on medium-resolution (R similar to 1300)spectroscopy of similar to 58,000 stars in the southern hemisphere from the AAOmega Evolution of Galactic Structure (AEGIS) survey. The AEGIS carbonicity map exhibits a positive gradient with distance, as similarly found for the Sloan Digital Sky Survey carbonicity map of Lee et al. The metallicity map confirms that [Fe/H] decreases with distance from the inner halo to the outer halo. We also explore the formation and chemical evolution history of the halo by considering the populations of carbon-enhanced metalpoor (CEMP) stars present in the AEGIS sample. The cumulative and differential frequency of CEMP-no stars (as classified by their characteristically lower levels of absolute carbon abundance, A(C) <= 7.1, for subgiants and giants) increases with decreasing metallicity and is substantially higher than previous determinations for CEMP stars as a whole. In contrast, that of CEMP-s stars (with higher A(C)) remains almost flat, at a value of similar to 10% in the range -4.0 less than or similar to [Fe/H] less than or similar to -2.0. The distinctly different behaviors of the CEMP-no and CEMP-s stars relieve the tension with population synthesis models assuming a binary mass-transfer origin, which previously struggled to account for the higher reported frequencies of CEMP stars, taken as a whole, at low metallicity.</P>
Roles of lignin biosynthesis and regulatory genes in plant development
Yoon, Jinmi,Choi, Heebak,An, Gynheung John Wiley and Sons Inc. 2015 Journal of integrative plant biology Vol.57 No.11
<P><B>Abstract</B></P><P>Lignin is an important factor affecting agricultural traits, biofuel production, and the pulping industry. Most lignin biosynthesis genes and their regulatory genes are expressed mainly in the vascular bundles of stems and leaves, preferentially in tissues undergoing lignification. Other genes are poorly expressed during normal stages of development, but are strongly induced by abiotic or biotic stresses. Some are expressed in non‐lignifying tissues such as the shoot apical meristem. Alterations in lignin levels affect plant development. Suppression of lignin biosynthesis genes causes abnormal phenotypes such as collapsed xylem, bending stems, and growth retardation. The loss of expression by genes that function early in the lignin biosynthesis pathway results in more severe developmental phenotypes when compared with plants that have mutations in later genes. Defective lignin deposition is also associated with phenotypes of seed shattering or brittle culm. MYB and NAC transcriptional factors function as switches, and some homeobox proteins negatively control lignin biosynthesis genes. Ectopic deposition caused by overexpression of lignin biosynthesis genes or master switch genes induces curly leaf formation and dwarfism.</P>
Chromatin Interacting Factor OsVIL2 Is Required for Outgrowth of Axillary Buds in Rice
Yoon, Jinmi,Cho, Lae-Hyeon,Lee, Sichul,Pasriga, Richa,Tun, Win,Yang, Jungil,Yoon, Hyeryung,Jeong, Hee Joong,Jeon, Jong-Seong,An, Gynheung Korean Society for Molecular and Cellular Biology 2019 Molecules and cells Vol.42 No.12
Shoot branching is an essential agronomic trait that impacts on plant architecture and yield. Shoot branching is determined by two independent steps: axillary meristem formation and axillary bud outgrowth. Although several genes and regulatory mechanism have been studied with respect to shoot branching, the roles of chromatin-remodeling factors in the developmental process have not been reported in rice. We previously identified a chromatin-remodeling factor OsVIL2 that controls the trimethylation of histone H3 lysine 27 (H3K27me3) at target genes. In this study, we report that loss-of-function mutants in OsVIL2 showed a phenotype of reduced tiller number in rice. The reduction was due to a defect in axillary bud (tiller) outgrowth rather than axillary meristem initiation. Analysis of the expression patterns of the tiller-related genes revealed that expression of OsTB1, which is a negative regulator of bud outgrowth, was increased in osvil2 mutants. Chromatin immunoprecipitation assays showed that OsVIL2 binds to the promoter region of OsTB1 chromatin in wild-type rice, but the binding was not observed in osvil2 mutants. Tiller number of double mutant osvil2 ostb1 was similar to that of ostb1, suggesting that osvil2 is epistatic to ostb1. These observations indicate that OsVIL2 suppresses OsTB1 expression by chromatin modification, thereby inducing bud outgrowth.
KNOX Protein OSH15 Induces Grain Shattering by Repressing Lignin Biosynthesis Genes
Yoon, Jinmi,Cho, Lae-Hyeon,Antt, Htet Wai,Koh, Hee-Jong,An, Gynheung American Society of Plant Biologists 2017 Plant Physiology Vol.174 No.1
<P>Seed shattering is an agronomically important trait. Two major domestication factors are responsible for this: qSH1 and SH5. Whereas qSH1 functions in cell differentiation in the abscission zone (AZ), a major role of SH5 is the repression of lignin deposition. We have determined that a KNOX protein, OSH15, also controls seed shattering. Knockdown mutations of OSH15 showed reduced seed-shattering phenotypes. Coimmunoprecipitation experiments revealed that OSH15 interacts with SH5 and qSH1, two proteins in the BELL homeobox family. In transgenic plants carrying the OSH15 promoter-GUS reporter construct, the reporter gene was preferentially expressed in the AZ during young spikelet development. The RNA in situ hybridization experiment also showed that OSH15 messenger RNAs were abundant in the AZ during spikelet development. Analyses of osh15 SH5-D double mutants showed that SH5 could not increase the degree of seed shattering when OSH15 was absent, indicating that SH5 functions together with OSH15. In addition to the seed-shattering phenotype, osh15 mutants displayed dwarfism and accumulated a higher amount of lignin in internodes due to increased expression of the genes involved in lignin biosynthesis. Knockout mutations of CAD2, which encodes an enzyme for the last step in the monolignol biosynthesis pathway, caused an easy seed-shattering phenotype by reducing lignin deposition in the AZ. This indicated that the lignin level is an important determinant of seed shattering in rice (Oryza sativa). Chromatin immunoprecipitation assays demonstrated that both OSH15 and SH5 interact directly with CAD2 chromatin. We conclude that OSH15 and SH5 form a dimer that enhances seed shattering by directly inhibiting lignin biosynthesis genes.</P>
Functional group effects on a metal-organic framework catalyst for CO<sub>2</sub> cycloaddition
Noh, Jinmi,Kim, Youngik,Park, Hyojin,Lee, Jihyun,Yoon, Minyoung,Park, Myung Hwan,Kim, Youngjo,Kim, Min THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.64 No.-
<P><B>Abstract</B></P> <P>A variety of metal-organic frameworks (MOFs) have been reported as efficient catalysts for CO<SUB>2</SUB> fixation reactions, such as cycloaddition to cyclic carbonates. The permanent porosity of the frameworks and the Lewis acidity of the MOF metal sites have been considered as the major contributors to the catalytic activity in the cycloaddition of CO<SUB>2</SUB>. In this study, we have, instead, focused on the effects of the organic functional groups for effective catalytic ability. A total of eight different functionalized Zr-based MOFs were tested. It was revealed that the non-functionalized pristine UiO-66 MOF (UiO=University of Oslo) showed the best conversion at low temperature (77% at 50°C), whereas the hydroxy-functionalized UiO-66-OH MOF displayed the best conversion at high temperature (91% at 140°C). The Zr-MOF could be recycled up to four times without a significant decrease in the reactivity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The organic functional group effects on MOF-catalyzed CO<SUB>2</SUB> cycloaddition have been examined. </LI> <LI> Non-functionalized Zr-based MOF, UiO-66 showed the best catalytic activity at 50°C. </LI> <LI> The hydroxy-functionalized UiO-66-OH performed cyclic organic carbonate synthesis efficiently at 140°C. </LI> <LI> Various epoxides were successfully converted to cyclic organic carbonates, and the Zr-MOF catalyst could be recycled by simple centrifugation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>