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Mitogen-Activated Protein Kinase Kinase 3 Is Required for Regulation during Dark-Light Transition
Lee, Horim Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.7
Plant growth and development are coordinately orchestrated by environmental cues and phytohormones. Light acts as a key environmental factor for fundamental plant growth and physiology through photosensory phytochromes and underlying molecular mechanisms. Although phytochromes are known to possess serine/threonine protein kinase activities, whether they trigger a signal transduction pathway via an intracellular protein kinase network remains unknown. In analyses of mitogen-activated protein kinase kinase (MAPKK, also called MKK) mutants, the mkk3 mutant has shown both a hypersensitive response in plant hormone gibberellin (GA) and a less sensitive response in red light signaling. Surprisingly, light-induced MAPK activation in wild-type (WT) seedlings and constitutive MAPK phosphorylation in dark-grown mkk3 mutant seedlings have also been found, respectively. Therefore, this study suggests that MKK3 acts in negative regulation in darkness and in light-induced MAPK activation during dark-light transition.
Horim Lee 한국식물학회 2018 Journal of Plant Biology Vol.61 No.6
The shoot apical meristem (SAM) serves as anon-drying reservoir of pluripotent stem cells to supply newdaughter cells forming above-ground tissues and organs suchas leaves, stems, flowers and fruits throughout the life cycleof plants. Accordingly, the homeostasis control of stem celldivision and differentiation must be an essential core mechanismfor harmonic growth and development of plants as multicellularhigher eukaryotes. Unlike animals, plants are sessile organismsand thus constantly face environmental factors, includingabiotic stresses. Therefore, post-embryonic developmentderived from stem cells in the SAM likely interacts withsurrounding abiotic stresses for plant adaptation and plasticdevelopment. For this reason, this review provides the mostrecent findings regarding comprehensive signaling networksinvolved in stem cell maintenance in the SAM, and thendescribes how stem cell signaling is related with abioticstress response through involvement of phytohormones andreactive oxygen species in the SAM.
Co-sensitization of metal free organic dyes in flexible dye sensitized solar cells
Lee, Horim,Kim, Jihun,Kim, Dong Young,Seo, Yongsok Elsevier 2018 ORGANIC ELECTRONICS Vol.52 No.-
<P><B>Abstract</B></P> <P>A metal-free organic dye (JH-1) and an unsymmetrical squaraine dye (SQ2) were used for co-sensitization of a flexible TiO<SUB>2</SUB> electrode in order to obtain a broad spectral response in the visible light regions. Because of enhanced light absorption, the performance of the flexible plastic dye-sensitized solar cells (DSSCs) was enhanced. The dye concentration of co-sensitized TiO<SUB>2</SUB> film was higher than that of individual dye-sensitized TiO<SUB>2</SUB> film, leading to improved photovoltaic performance with the panchromatic light harvesting of JH-1 and SQ2 (350–720 nm). Optimum molar ratio of individual dye, dye concentration and adsorption kinetics onto the TiO<SUB>2</SUB> photoelectrode, and ideal thickness of HS-TiO<SUB>2</SUB> layer have been investigated. A flexible DSSC co-sensitized with the molar ratio of 60:40 (JH-1:SQ2) and TiO<SUB>2</SUB> film thickness of 6 μm yielded a high photocurrent density of 12.32 mA cm<SUP>−2</SUP>, an open circuit voltage of 0.754 V, a fill factor of 0.68, and a power conversion efficiency of 6.31% under 1 sun illumination (100 mW cm<SUP>−2</SUP>). Interestingly, the co-sensitizers did not compete with each other for the absorption. Both the open circuit photovoltage and the photocurrent density were unexpectedly increased with co-sensitization which means that enhancement in photocurrents can be achieved without sacrificing the open circuit photovoltage for the co-sensitized solar cells, once the electron recombination and dye aggregation are retarded by the co-sensitization.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An organic dye (JH-1) and a squaraine dye (SQ2) were used for co-sensitization of a flexible TiO2 electrode. </LI> <LI> Because of enhanced light absorption, the performance of the flexible DSSCs was enhanced. </LI> <LI> A DSSC with a molar ratio of 60:40 (JH-1:SQ2) yielded a power conversion efficiency of 6.31%. </LI> <LI> Both V<SUB>OC</SUB> and J<SUB>SC</SUB> were unexpectedly increased with co-sensitization. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Lee, Horim,Hwang, Daesub,Jo, Seong Mu,Kim, Dongho,Seo, Yongsok,Kim, Dong Young American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.6
<P>Hierarchically structured TiO<SUB>2</SUB> (HS-TiO<SUB>2</SUB>) was prepared on a flexible ITO-PEN (polyethylene naphthalate) substrate via electrospray deposition using a commercially available TiO<SUB>2</SUB> nanocrystalline powder in order to fabricate flexible DSSCs under low-temperature (<150 °C) conditions. The cell efficiency increased when using flexible ITO-PEN substrates post-treated by either a mechanical compression treatment or a chemical sintering treatment using titanium n-tetrabutoxide (TTB). The mechanical compression treatment reduced the surface area and porosity of the HS-TiO<SUB>2</SUB>; however, this treatment improved the interparticle connectivity and physical adhesion between the HS-TiO<SUB>2</SUB> and ITO-PEN substrate, which increased the photocurrent density of the as-pressed HS-TiO<SUB>2</SUB> cells. The electron diffusion coefficients of the as-pressed HS-TiO<SUB>2</SUB> improved upon compression treatment, whereas the recombination lifetimes remained unchanged. An additional chemical sintering post-treatment involving TTB was tested for its effects on DSSC efficiency. The freshly coated TiO<SUB>2</SUB> submitted to TTB hydrolysis in water at 100 °C yielded an anatase phase. TTB treatment of the HS-TiO<SUB>2</SUB> cell after compression treatment yielded faster electron diffusion, providing an efficiency of 5.57% under 100 mW cm<SUP>–2</SUP>, AM 1.5 global illumination.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-6/am3007164/production/images/medium/am-2012-007164_0008.gif'></P>
Lee, Jungeun,He, Kun,Stolc, Viktor,Lee, Horim,Figueroa, Pablo,Gao, Ying,Tongprasit, Waraporn,Zhao, Hongyu,Lee, Ilha,Deng, Xing Wang American Society of Plant Physiologists 2007 The Plant cell Vol.19 No.3
<P>The transcription factor LONG HYPOCOTYL5 (HY5) acts downstream of multiple families of the photoreceptors and promotes photomorphogenesis. Although it is well accepted that HY5 acts to regulate target gene expression, in vivo binding of HY5 to any of its target gene promoters has yet to be demonstrated. Here, we used a chromatin immunoprecipitation procedure to verify suspected in vivo HY5 binding sites. We demonstrated that in vivo association of HY5 with promoter targets is not altered under distinct light qualities or during light-to-dark transition. Coupled with DNA chip hybridization using a high-density 60-nucleotide oligomer microarray that contains one probe for every 500 nucleotides over the entire Arabidopsis thaliana genome, we mapped genome-wide in vivo HY5 binding sites. This analysis showed that HY5 binds preferentially to promoter regions in vivo and revealed >3000 chromosomal sites as putative HY5 binding targets. HY5 binding targets tend to be enriched in the early light-responsive genes and transcription factor genes. Our data thus support a model in which HY5 is a high hierarchical regulator of the transcriptional cascades for photomorphogenesis.</P>
Lee, Horim,Choi, Dongwhi,Kim, Dong Sung,Lim, Geunbae Springer Berlin Heidelberg 2015 Nano-micro letters Vol.7 No.4
<P>The spontaneously generated electrical charge of a droplet dispensed from conventional pipetting is undesirable and unpredictable for most experiments that use pipetting. Hence, a method for controlling and removing the electrical charge needs to be developed. In this study, by using the electrode-deposited pipet tip (E-pipet tip), the charge-controlling system is newly developed and the electrical charge of a droplet is precisely controlled. The effect of electrolyte concentration and volume of the transferred solution to the electrical charge of a dispensed droplet is theoretically and experimentally investigated by using the equivalent capacitor model. Furthermore, a proof-of-concept example of the self-alignment and self-assembly of sequentially dispensed multiple droplets is demonstrated as one of the potential applications. Given that the electrical charge of the various aqueous droplets can be precisely and simply controlled, the fabricated E-pipet tip can be broadly utilized not only as a general charge-controlling platform of aqueous droplets but also as a powerful tool to explore fundamental scientific research regarding electrical charge of a droplet, such as the surface oscillation and evaporation of charged droplets.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1007/s40820-015-0048-2) contains supplementary material, which is available to authorized users.</P>