Circadian control of ORE1 by PRR9 positively regulates leaf senescence in Arabidopsis

The circadian clock coordinates the daily cyclic rhythm of numerous biological processes by regulating a large portion of the transcriptome. In animals, the circadian clock is involved in aging and senescence, and circadian disruption by mutations in clock genes frequently accelerates aging. Conversely, aging alters circadian rhythmicity, which causes age-associated physiological alterations. However, interactions between the circadian clock and aging have been rarely studied in plants. Here, we investigated potential roles for the circadian clock in the regulation of leaf senescence in plants. Members of the evening complex in Arabidopsis circadian clock, EARLY FLOWERING 3 (ELF3), EARLY FLOWERING 4 (ELF4), and LUX ARRHYTHMO (LUX), as well as the morning component PSEUDO-RESPONSE REGULATOR 9 (PRR9), affect both age-dependent and dark-induced leaf senescence. The circadian clock regulates the expression of several senescence-related transcription factors. In particular, PRR9 binds directly to the promoter of the positive aging regulator ORESARA1 (ORE1) gene to promote its expression. PRR9 also represses miR164, a posttranscriptional repressor of ORE1. Consistently, genetic analysis revealed that delayed leaf senescence of a prr9 mutant was rescued by ORE1 overexpression. Thus, PRR9, a core circadian component, is a key regulator of leaf senescence via positive regulation of ORE1 through a feed-forward pathway involving posttranscriptional regulation by miR164 and direct transcriptional regulation. Our results indicate that, in plants, the circadian clock and leaf senescence are intimately interwoven as are the clock and aging in animals. (c) 2018 National Academy of Sciences. All rights reseve

Differential Protein Expression in Human Dental Pulp: Comparison of Healthy, Inflamed, and Traumatic Pulp

Trauma or injury to the dental pulp causes inflammation. This study compared the proteome of healthy pulp with inflamed pulp and traumatic pulp to identify the differentially expressed proteins in the diseased state. Five participants were grouped based on the pulpal status of the teeth: healthy, inflamed, or traumatic pulp. Pulp was extirpated and stored immediately in liquid nitrogen. Pulp tissues were subjected to 2-dimensional gel electrophoresis, and spot selection was performed. The selected spots were analyzed using liquid chromatography-tandem mass spectrometry and identified by correlating mass spectra to the proteomic databases. Fifteen spots showed increased expression in the inflamed and traumatic pulp. Annexin V, type II keratin, and hemoglobin levels were increased two-fold in the inflamed and traumatic pulp group and annexin V, mutant beta-actin, and hemoglobin were increased by ten-fold in the inflamed or traumatic pulp group, compared to levels in the healthy pulp group. Annexin V constituted two out of fifteen protein spots, and seemed to play a critical role in inhibiting inflammation and promoting the immune reaction. Further studies on this protein concerning its role in pulp repair are necessary to elucidate the underlying mechanisms

Antagonistic Roles of PhyA and PhyB in Far-Red Light-Dependent Leaf Senescence in Arabidopsis thaliana

Leaf senescence is regulated by diverse developmental and environmental factors to maximize plant fitness. The red to far-red light ratio (R:FR) detected by plant phytochromes is reduced under vegetation shade, thus initiating leaf senescence. However, the role of phytochromes in promoting leaf senescence under FR-enriched conditions is not fully understood. In this study, we investigated the role of phyA and phyB in regulating leaf senescence under FR in Arabidopsis thaliana (Arabidopsis). FR enrichment and intermittent FR pulses promoted the senescence of Arabidopsis leaves. Additionally, phyA and phyB mutants showed enhanced and repressed senescence phenotypes in FR, respectively, indicating that phyA and phyB antagonistically regulate FR-dependent leaf senescence. Transcriptomic analysis using phyA and phyB mutants in FR identified differentially expressed genes (DEGs) involved in leaf senescence-related processes, such as responses to light, phytohormones, temperature, photosynthesis and defense, showing opposite expression patterns in phyA and phyB mutants. These contrasting expression profiles of DEGs support the antagonism between phyA and phyB in FR-dependent leaf senescence. Among the genes showing antagonistic regulation, we confirmed that the expression of WRKY6, which encodes a senescence-associated transcription factor, was negatively and positively regulated by phyA and phyB, respectively. The wrky6 mutant showed a repressed senescence phenotype compared with the wild type in FR, indicating that WRKY6 plays a positive role in FR-dependent leaf senescence. Our results imply that antagonism between phyA and phyB is involved in fine-tuning leaf senescence under varying FR conditions in Arabidopsis.(c) The Author(s) 2018

Biological Function and Potential Applications of Garcinol in Human Dental Pulp Stem Cells

IntroductionThe regeneration of pulp tissue is crucial for true regenerative endodontic treatment, which requires a reduction in osteogenic differentiation. Garcinol, a histone acetyltransferase inhibitor, is a natural regulator that is known to suppress the osteogenic differentiation of dental pulp stem cells. In this study, the inhibitory effect of garcinol on the osteogenic differentiation of human dental pulp stem cells (hDPSCs) was evaluated using three-dimensional culture under in vitro and in vivo conditions.MethodshDPSCs were obtained from caries-free third molars and cultured with 10 μM garcinol for 7 days in an ultra-low attachment plate. The cell stemness and expression of osteogenic differentiation-related genes were analyzed using reverse transcription-polymerase chain reaction and single-cell analysis. A transplantation experiment was performed in mice to investigate whether garcinol-treated hDPSCs showed restrained osteogenic differentiation.ResultshDPSCs cultured in the U-shaped ultra-low attachment plate showed the highest expression of stemness-related genes. Garcinol-treated hDPSCs demonstrated downregulation of osteogenic differentiation, with lower expression of bone sialoprotein, which is related to bone formation, and higher expression of dentin sialophosphoprotein, which is related to dentin formation. However, the garcinol-treated hDPSCs did not show any alterations in their stemness. Consistent results were observed in the transplantation experiment in mice.ConclusionsGarcinol reduced the osteogenic differentiation of hDPSCs, which can contribute to true regenerative endodontic treatment

Comparison of Biocompatibility of Calcium Silicate-Based Sealers and Epoxy Resin-Based Sealer on Human Periodontal Ligament Stem Cells

The aim of this study was to evaluate the biocompatibility of calcium silicate-based sealers (CeraSeal and EndoSeal TCS) and epoxy resin-based sealer (AH-Plus) in terms of cell viability, inflammatory response, expression of mesenchymal phenotype, osteogenic potential, cell attachment, and morphology, of human periodontal ligament stem cells (hPDLSCs). hPDLSCs were acquired from the premolars (n = 4) of four subjects, whose ages extended from 16 to 24 years of age. Flow cytometry analysis showed stemness of hPDLSCs was maintained in all materials. In cell viability test, AH-Plus showed the lowest cell viability, and CeraSeal showed significantly higher cell viability than others. In ELISA test, AH-Plus showed higher expression of IL-6 and IL-8 than calcium silicate-based sealers. In an osteogenic potential test, AH-Plus showed a lower expression level than other material; however, EndoSeal TCS showed a better expression level than others. All experiments were repeated at least three times per cell line. Scanning electronic microscopy studies showed low degree of cell proliferation on AH-Plus, and high degree of cell proliferation on calcium silicate-based sealers. In this study, calcium silicate-based sealers appear to be more biocompatible and less cytotoxic than epoxy-resin based sealers

ZnO/CuO/M (M = Ag, Au) Hierarchical Nanostructure by Successive Photoreduction Process for Solar Hydrogen Generation

To date, solar energy generation devices have been widely studied to meet a clean and sustainable energy source. Among them, water splitting photoelectrochemical cell is regarded as a promising energy generation way for splitting water molecules and generating hydrogen by sunlight. While many nanostructured metal oxides are considered as a candidate, most of them have an improper bandgap structure lowering energy transition efficiency. Herein, we introduce a novel wet-based, successive photoreduction process that can improve charge transfer efficiency by surface plasmon effect for a solar-driven water splitting device. The proposed process enables to fabricate ZnO/CuO/Ag or ZnO/CuO/Au hierarchical nanostructure, having an enhanced electrical, optical, photoelectrochemical property. The fabricated hierarchical nanostructures are demonstrated as a photocathode in the photoelectrochemical cell and characterized by using various analytic tools

High-Throughput and Computational Study of Leaf Senescence through a Phenomic Approach

Leaf senescence is influenced by its life history, comprising a series of developmental and physiological experiences. Exploration of the biological principles underlying leaf lifespan and senescence requires a schema to trace leaf phenotypes, based on the interaction of genetic and environmental factors. We developed a new approach and concept that will facilitate systemic biological understanding of leaf lifespan and senescence, utilizing the phenome high-throughput investigator (PHI) with a single-leaf-basis phenotyping platform. Our pilot tests showed empirical evidence for the feasibility of PHI for quantitative measurement of leaf senescence responses and improved performance in order to dissect the progression of senescence triggered by different senescence-inducing factors as well as genetic mutations. Such an establishment enables new perspectives to be proposed, which will be challenged for enhancing our fundamental understanding on the complex process of leaf senescence. We further envision that integration of phenomic data with other multi-omics data obtained from transcriptomic, proteomic, and metabolic studies will enable us to address the underlying principles of senescence, passing through different layers of information from molecule to organism. © 2017 Lyu, Baek, Jung, Chu, Nam, Kim and Lim. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. © 2017 Lyu, Baek, Jung, Chu, Nam, Kim and Lim. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. © 2017 Lyu, Baek, Jung, Chu, Nam, Kim and Lim. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.2