Determining novel functions of Arabidopsis 14-3-3 proteins in central metabolic processes

<p>Abstract</p> <p>Background</p> <p>14-3-3 proteins are considered master regulators of many signal transduction cascades in eukaryotes. In plants, 14-3-3 proteins have major roles as regulators of nitrogen and carbon metabolism, conclusions based on the studies of a few specific 14-3-3 targets.</p> <p>Results</p> <p>In this study, extensive novel roles of 14-3-3 proteins in plant metabolism were determined through combining the parallel analyses of metabolites and enzyme activities in 14-3-3 overexpression and knockout plants with studies of protein-protein interactions. Decreases in the levels of sugars and nitrogen-containing-compounds and in the activities of known 14-3-3-interacting-enzymes were observed in 14-3-3 overexpression plants. Plants overexpressing 14-3-3 proteins also contained decreased levels of malate and citrate, which are intermediate compounds of the tricarboxylic acid (TCA) cycle. These modifications were related to the reduced activities of isocitrate dehydrogenase and malate dehydrogenase, which are key enzymes of TCA cycle. In addition, we demonstrated that 14-3-3 proteins interacted with one isocitrate dehydrogenase and two malate dehydrogenases. There were also changes in the levels of aromatic compounds and the activities of shikimate dehydrogenase, which participates in the biosynthesis of aromatic compounds.</p> <p>Conclusion</p> <p>Taken together, our findings indicate that 14-3-3 proteins play roles as crucial tuners of multiple primary metabolic processes including TCA cycle and the shikimate pathway.</p

Nucleon-nucleon effective potential in dense matter including rho-meson exchange

We obtain the RPA summed one-meson exchange potential between nucleons in symmetric nuclear matter at zero temperature, from a model which includes rho, sigma, omega and pi mesons. The behavior of rho mesons inside the medium is first discussed using different schemes to extract a finite contribution from the vacuum polarization. These schemes give qualitatively different results for the in-medium rho mass. The results are discussed in connection with the nourenormalizability of the model. We next study the modified potential as density increases. In the intermediate-distance range, it is qualitatively modified by matter and vacuum effects. In the long-distance range (r > 2 fm), one observes the presence of oscillations, which are not present in free space. Features on this distance range arc insensitive to the renormalization scheme

NADPH-dependent extracellular superoxide production is vital to photophysiology in the marine diatom Thalassiosira oceanica

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Diaz, J. M., Plummer, S., Hansel, C. M., Andeer, P. F., Saito, M. A., & McIlvin, M. R. NADPH-dependent extracellular superoxide production is vital to photophysiology in the marine diatom Thalassiosira oceanica. Proceedings of the National Academy of Sciences of the United States of America, 116 (33), (2019): 16448-16453, doi: 10.1073/pnas.1821233116.Reactive oxygen species (ROS) like superoxide drive rapid transformations of carbon and metals in aquatic systems and play dynamic roles in biological health, signaling, and defense across a diversity of cell types. In phytoplankton, however, the ecophysiological role(s) of extracellular superoxide production has remained elusive. Here, the mechanism and function of extracellular superoxide production by the marine diatom Thalassiosira oceanica are described. Extracellular superoxide production in T. oceanica exudates was coupled to the oxidation of NADPH. A putative NADPH-oxidizing flavoenzyme with predicted transmembrane domains and high sequence similarity to glutathione reductase (GR) was implicated in this process. GR was also linked to extracellular superoxide production by whole cells via quenching by the flavoenzyme inhibitor diphenylene iodonium (DPI) and oxidized glutathione, the preferred electron acceptor of GR. Extracellular superoxide production followed a typical photosynthesis-irradiance curve and increased by 30% above the saturation irradiance of photosynthesis, while DPI significantly impaired the efficiency of photosystem II under a wide range of light levels. Together, these results suggest that extracellular superoxide production is a byproduct of a transplasma membrane electron transport system that serves to balance the cellular redox state through the recycling of photosynthetic NADPH. This photoprotective function may be widespread, consistent with the presence of putative homologs to T. oceanica GR in other representative marine phytoplankton and ocean metagenomes. Given predicted climate-driven shifts in global surface ocean light regimes and phytoplankton community-level photoacclimation, these results provide implications for future ocean redox balance, ecological functioning, and coupled biogeochemical transformations of carbon and metals.This work was supported by a postdoctoral fellowship from the Ford Foundation (to J.M.D.), the National Science Foundation (NSF) under grants OCE 1225801 (to J.M.D.) and OCE 1246174 (to C.M.H.), a Junior Faculty Seed Grant from the University of Georgia Research Foundation (to J.M.D.), and a National Science Foundation Graduate Research Fellowship (to S.P.). The FIRe was purchased through a NSF equipment improvement grant (1624593).The authors thank Melissa Soule for assistance with LC/MS/MS analysis of peptide samples

Revised ephemeris and orbital period derivative of the supersoft X-ray source CAL 87 based on 34 years of observations

In this study, we present an analysis of over 34 years of observational data from CAL 87, an eclipsing supersoft X-ray source. The primary aim of our study, which combines previously analysed measurements as well as unexplored publicly available datasets, is to examine the orbital period evolution of CAL 87. After meticulously and consistently determining the eclipse timings, we constructed an O$-$C (observed minus calculated) diagram using a total of 38 data points. Our results provide confirmation of a positive derivative in the system's orbital period, with a determined value of $\dot{P}=+ 8.18\pm1.46\times10^{-11}$ s/s. We observe a noticeable jitter in the eclipse timings and additionally identify a systematic delay in the X-ray eclipses compared to those observed in longer wavelengths. We discuss the interplay of the pertinent factors that could contribute to a positive period derivative and the inherent variability in the eclipses.Comment: 5 pages, 4 figures. Accepted to MNRA

Derivation and Characterization of Induced Pluripotent Stem Cells from Equine Fibroblasts

Pluripotent stem cells offer unprecedented potential not only for human medicine but also for veterinary medicine, particularly in relation to the horse. Induced pluripotent stem cells (iPSCs) are particularly promising, as they are functionally similar to embryonic stem cells and can be generated in vitro in a patient-specific manner. In this study, we report the generation of equine iPSCs from skin fibroblasts obtained from a foal and reprogrammed using viral vectors coding for murine Oct4, Sox2, c-Myc, and Klf4 sequences. The reprogrammed cell lines were morphologically similar to iPSCs reported from other species and could be stably maintained over more than 30 passages. Immunostaining and polymerase chain reaction analyses revealed that these cell lines expressed an array of endogenous markers associated with pluripotency, including OCT4, SOX2, NANOG, REX1, LIN28, SSEA1, SSEA4, and TRA1-60. Furthermore, under the appropriate conditions, the equine iPSCs readily formed embryoid bodies and differentiated in vitro into cells expressing markers of ectoderm, mesoderm, and endoderm, and when injected into immunodeficient mice, gave raise to tumors containing differentiated derivatives of the 3 germ layers. Finally, we also reprogrammed fibroblasts from a 2-year-old horse. The reprogrammed cells were similar to iPSCs derived from neonatal fibroblasts in terms of morphology, expression of pluripotency markers, and differentiation ability. The generation of these novel cell lines constitutes an important step toward the understanding of pluripotency in the horse, and paves the way for iPSC technology to potentially become a powerful research and clinical tool in veterinary biomedicine