Light and flow regimes regulate the metabolism of rivers

Mean annual temperature and mean annual precipitation drive much of the variation in productivity across Earth's terrestrial ecosystems but do not explain variation in gross primary productivity (GPP) or ecosystem respiration (ER) in flowing waters. We document substantial variation in the magnitude and seasonality of GPP and ER across 222 US rivers. In contrast to their terrestrial counterparts, most river ecosystems respire far more carbon than they fix and have less pronounced and consistent seasonality in their metabolic rates. We find that variation in annual solar energy inputs and stability of flows are the primary drivers of GPP and ER across rivers. A classification schema based on these drivers advances river science and informs management.We thank Ted Stets, Jordan Read, Tom Battin, Sophia Bonjour, Marina Palta, and members of the Duke River Center for their help in developing these ideas. This work was supported by grants from the NSF 1442439 (to E.S.B. and J.W.H.), 1834679 (to R.O.H.), 1442451 (to R.O.H.), 2019528 (to R.O.H. and J.R.B.), 1442140 (to M.C.), 1442451 (to A.M.H.), 1442467 (to E.H.S.), 1442522 (to N.B.G.), 1624807 (to N.B.G.), and US Geological Survey funding for the working group was supported by the John Wesley Power Center for Analysis and Synthesis. Phil Savoy contributed as a postdoc- toral associate at Duke University and as a postdoctoral associate (contractor) at the US Geological Survey

The role of epigenetics in renal ageing

An ability to separate natural ageing processes from processes specific to morbidities is required to understand the heterogeneity of age-related organ dysfunction. Mechanistic insight into how epigenetic factors regulate ageing throughout the life course, linked to a decline in renal function with ageing, is already proving to be of value in the analyses of clinical and epidemiological cohorts. Noncoding RNAs provide epigenetic regulatory circuits within the kidney, which reciprocally interact with DNA methylation processes, histone modification and chromatin. These interactions have been demonstrated to reflect the biological age and function of renal allografts. Epigenetic factors control gene expression and activity in response to environmental perturbations. They also have roles in highly conserved signalling pathways that modulate ageing, including the mTOR and insulin/insulin-like growth factor signalling pathways, and regulation of sirtuin activity. Nutrition, the gut microbiota, inflammation and environmental factors, including psychosocial and lifestyle stresses, provide potential mechanistic links between the epigenetic landscape of ageing and renal dysfunction. Approaches to modify the renal epigenome via nutritional intervention, targeting the methylome or targeting chromatin seem eminently feasible, although caution is merited owing to the potential for intergenerational and transgenerational effects

Biosynthesis of S-adenosylmethionine in a recombinant yeast strain

The present invention makes use of a chimeric gene that, when incorporated into an appropriate host, results in the overproduction of S-adenosylmethionine without the need to supply the host with a source of untransformed methionine. The need for the methionine source is eliminated because the appropriately chosen host manufactures the amino acid on its own, and when the host is modified by the inclusion of a chimeric gene of the present invention, it transforms the methionine that is produced into S-adenosylmethionine. In addition, the same chimeric gene causes accumulation of methionine and increase in folate content in the same host. One form of the present invention is a fused gene encoding for methylene tetrahydrofolate reductase (MTHFR) made up of an N-terminal domain from a yeast organism and a C-terminal domain from a plant species. An example of a suitable plant species is Arabidopsis thaliana. An example of a suitable yeast organism is Saccharomyces cerevisiae.Board of Regents, University of Texas Syste

AN EXAMINATION OF THE RESONANT MULTIPHOTON IONIZATION OF CF3ICF_{3}I

Author Institution: Department of Chemistry, University of Cincinnati; Department of Chemistry, University of KentuckyResonant $(2+1)$ multiphoton ionization (MPI) has been observed in the 300--306 nm excitation region for both cold molecular beam and room temperature samples of $CF_{3}I$. Excitation spectra with mass-selected ion detection will be presented and discussed. MPI/photoelectron spectra of $CF_{3}I$ will be used to demonstrate that parent $CF_{3}I^{+}$ ions are produced predominantely in their ground $\tilde{X} ^{2}E_{1/2}$ state. Tentative spectral assignments based on the photoion and photoelectron data have been made

Metabolic engineering in yeast demonstrates that S-adenosylmethionine controls flux through the methylenetetrahydrofolate reductase reaction in vivo

One-carbon flux into methionine and S-adenosylmethionine (AdoMet) is thought to be controlled at the methylenetetrahydrofolate reductase (MTHFR) step. Mammalian MTHFRs are inhibited by AdoMet in vitro, and it has been proposed that methyl group biogenesis is regulated in vivo by this feedback loop. In this work, we used metabolic engineering in the yeast Saccharomyces cerevisiae to test this hypothesis. Like mammalian MTHFRs, the yeast MTHFR encoded by the MET13 gene is NADPH-dependent and is inhibited by AdoMet in vitro. This contrasts with plant MTHFRs, which are NADH-dependent and AdoMet-insensitive. To manipulate flux through the MTHFR reaction in yeast, the chromosomal copy of MET13 was replaced by an Arabidopsis MTHFR cDNA (AtMTHFR-1) or by a chimeric sequence (Chimera-1) comprising the yeast N-terminal domain and the AtMTHFR-1 C-terminal domain. Chimera-1 used both NADH and NADPH and was insensitive to AdoMet, supporting the view that the C-terminal domain is responsible for AdoMet inhibition. Engineered yeast expressing Chimera-1 accumulated 140-fold more AdoMet and 7-fold more methionine than did the wild-type and grew normally. Yeast expressing AtMTHFR-1 accumulated 8-fold more AdoMet. This is the first in vivo evidence that the AdoMet sensitivity and pyridine nucleotide preference of MTHFR control methylneogenesis. (13)C labeling data indicated that glycine cleavage becomes a more prominent source of one-carbon units when Chimera-1 is expressed. Possibly related to this shift in one-carbon fluxes, total folate levels are doubled in yeast cells expressing Chimera-1