Mechanisms and physiological function of daily haemoglobin oxidation rhythms in red blood cells

Cellular circadian rhythms confer temporal organisation upon physiology that is fundamental to human health. Rhythms are present in red blood cells (RBCs), the most abundant cell type in the body, but their physiological function is poorly understood. Here, we present a novel biochemical assay for haemoglobin (Hb) oxidation status which relies on a redox-sensitive covalent haem-Hb linkage that forms during SDS-mediated cell lysis. Formation of this linkage is lowest when ferrous Hb is oxidised, in the form of ferric metHb. Daily haemoglobin oxidation rhythms are observed in mouse and human RBCs cultured in vitro, or taken from humans in vivo, and are unaffected by mutations that affect circadian rhythms in nucleated cells. These rhythms correlate with daily rhythms in core body temperature, with temperature lowest when metHb levels are highest. Raising metHb levels with dietary sodium nitrite can further decrease daytime core body temperature in mice via nitric oxide (NO) signalling. These results extend our molecular understanding of RBC circadian rhythms and suggest they contribute to the regulation of body temperature

High-Dimensional Coexistence of Temperate Tree Species: Functional Traits, Demographic Rates, Life-History Stages, and Their Physical Context

Theoretical models indicate that trade-offs between growth and survival strategies of tree species can lead to coexistence across life history stages (ontogeny) and physical conditions experienced by individuals. There exist predicted physiological mechanisms regulating these trade-offs, such as an investment in leaf characters that may increase survival in stressful environments at the expense of investment in bole or root growth. Confirming these mechanisms, however, requires that potential environmental, ontogenetic, and trait influences are analyzed together. Here, we infer growth and mortality of tree species given size, site, and light characteristics from forest inventory data from Wisconsin to test hypotheses about growth-survival trade-offs given species functional trait values under different ontogenetic and environmental states. A series of regression analyses including traits and rates their interactions with environmental and ontogenetic stages supported the relationships between traits and vital rates expected from the expectations from tree physiology. A combined model including interactions between all variables indicated that relationships between demographic rates and functional traits supports growth-survival trade-offs and their differences across species in high-dimensional niche space. The combined model explained 65% of the variation in tree growth and supports a concept of community coexistence similar to Hutchinson's n-dimensional hypervolume and not a low-dimensional niche model or neutral model

Impaired Bone Health in Inflammatory Bowel Disease: A Case-Control Study in 80 Pediatric Patients

Peer reviewe

NOF1 Encodes an Arabidopsis Protein Involved in the Control of rRNA Expression

The control of ribosomal RNA biogenesis is essential for the regulation of protein synthesis in eukaryotic cells. Here, we report the characterization of NOF1 that encodes a putative nucleolar protein involved in the control of rRNA expression in Arabidopsis. The gene has been isolated by T-DNA tagging and its function verified by the characterization of a second allele and genetic complementation of the mutants. The nof1 mutants are affected in female gametogenesis and embryo development. This result is consistent with the detection of NOF1 mRNA in all tissues throughout plant life's cycle, and preferentially in differentiating cells. Interestingly, the closely related proteins from zebra fish and yeast are also necessary for cell division and differentiation. We showed that the nof1-1 mutant displays higher rRNA expression and hypomethylation of rRNA promoter. Taken together, the results presented here demonstrated that NOF1 is an Arabidopsis gene involved in the control of rRNA expression, and suggested that it encodes a putative nucleolar protein, the function of which may be conserved in eukaryotes

A LOV Protein Modulates the Physiological Attributes of Xanthomonas axonopodis pv. citri Relevant for Host Plant Colonization

Recent studies have demonstrated that an appropriate light environment is required for the establishment of efficient vegetal resistance responses in several plant-pathogen interactions. The photoreceptors implicated in such responses are mainly those belonging to the phytochrome family. Data obtained from bacterial genome sequences revealed the presence of photosensory proteins of the BLUF (Blue Light sensing Using FAD), LOV (Light, Oxygen, Voltage) and phytochrome families with no known functions. Xanthomonas axonopodis pv. citri is a Gram-negative bacterium responsible for citrus canker. The in silico analysis of the X. axonopodis pv. citri genome sequence revealed the presence of a gene encoding a putative LOV photoreceptor, in addition to two genes encoding BLUF proteins. This suggests that blue light sensing could play a role in X. axonopodis pv. citri physiology. We obtained the recombinant Xac-LOV protein by expression in Escherichia coli and performed a spectroscopic analysis of the purified protein, which demonstrated that it has a canonical LOV photochemistry. We also constructed a mutant strain of X. axonopodis pv. citri lacking the LOV protein and found that the loss of this protein altered bacterial motility, exopolysaccharide production and biofilm formation. Moreover, we observed that the adhesion of the mutant strain to abiotic and biotic surfaces was significantly diminished compared to the wild-type. Finally, inoculation of orange (Citrus sinensis) leaves with the mutant strain of X. axonopodis pv. citri resulted in marked differences in the development of symptoms in plant tissues relative to the wild-type, suggesting a role for the Xac-LOV protein in the pathogenic process. Altogether, these results suggest the novel involvement of a photosensory system in the regulation of physiological attributes of a phytopathogenic bacterium. A functional blue light receptor in Xanthomonas spp. has been described for the first time, showing an important role in virulence during citrus canker disease

Rapid transcriptional plasticity of duplicated gene clusters enables a clonally reproducing aphid to colonise diverse plant species

Background: The prevailing paradigm of host-parasite evolution is that arms races lead to increasing specialisation via genetic adaptation. Insect herbivores are no exception and the majority have evolved to colonise a small number of closely related host species. Remarkably, the green peach aphid, Myzus persicae, colonises plant species across 40 families and single M. persicae clonal lineages can colonise distantly related plants. This remarkable ability makes M. persicae a highly destructive pest of many important crop species. Results: To investigate the exceptional phenotypic plasticity of M. persicae, we sequenced the M. persicae genome and assessed how one clonal lineage responds to host plant species of different families. We show that genetically identical individuals are able to colonise distantly related host species through the differential regulation of genes belonging to aphid-expanded gene families. Multigene clusters collectively upregulate in single aphids within two days upon host switch. Furthermore, we demonstrate the functional significance of this rapid transcriptional change using RNA interference (RNAi)-mediated knock-down of genes belonging to the cathepsin B gene family. Knock-down of cathepsin B genes reduced aphid fitness, but only on the host that induced upregulation of these genes. Conclusions: Previous research has focused on the role of genetic adaptation of parasites to their hosts. Here we show that the generalist aphid pest M. persicae is able to colonise diverse host plant species in the absence of genetic specialisation. This is achieved through rapid transcriptional plasticity of genes that have duplicated during aphid evolution