Qualitative simulation of the carbon starvation response in Escherichia coli

In case of nutritional stress, like carbon starvation, Escherichia coli cells abandon their exponential-growth state to enter a more resistant, non-growth state called stationary phase. This growth-phase transition is controlled by a genetic regulatory network integrating various environmental signals. Although E. coli is a paradigm of the bacterial world, it is little understood how its response to carbon starvation conditions emerges from the interactions between the different components of the regulatory network. Using a qualitative method that is able to overcome the current lack of quantitative data on kinetic parameters and molecular concentrations, we model the carbon starvation response network and simulate the response of E. coli cells to carbon deprivation. This allows us to identify essential features of the transition between exponential and stationary phase and to make new predictions on the qualitative system behavior following a carbon upshift.     

Characterization and expression profile analysis of a sucrose synthase gene from common bean (Phaseolus vulgaris L.) during seed development

A full-length cDNA encoding common bean (Phaseolus vulgaris L.) sucrose synthase (designated as Pv_BAT93 Sus), which catalyses the synthesis and cleavage of sucrose, was isolated from seeds at 15 days after pollination (DAP) by rapid amplification of cDNA ends (RACE). The full-length cDNA of Pv_BAT93 Sus had a 2,418 bp open reading frame (ORF) encoding a protein of 806 amino acid residues. Sequence comparison analysis showed that Pv_BAT93 Sus was very similar to several members of the sucrose synthase family of other plant species. Tissue expression pattern analysis showed that Pv_BAT93 Sus was expressed in leaves, flowers, stems, roots, cotyledons, and particularly during seed development. Expression studies using in situ hybridization revealed altered spatial and temporal patterns of Sus expression in the EMS mutant relative to wild-type and confirmed Sus expression in common bean developing seeds. The expression and accumulation of Sus mRNA was clearly shown in several tissues, such as the suspensor and embryo, but also in the transfer cells and endothelium. The results highlight the diverse roles that Sus might play during seed development in common bean.     

Characterization of the oligosaccharide moiety of VIP receptor from the human pancreatic cell line BxPC-3

The human pancreatic cell line BxPC-3 displays two classes of binding sites with high and low affinity for VIP. The order of potency of VIP-related peptides in inhibiting either [¹²⁵I]VIP or [¹²⁵I]N-AcPACAP27 binding and in stimulating cAMP production was typical of the human VIP receptor. By combining affinity labeling with glycosidase treatments, we have characterized the VIP receptor as a M_r = 68,200 glycoprotein, consisting of a M_r = 39,300 polypeptide core with at least three N-linked oligosaccharide chains. In addition, our results revealed the presence of a low amount of sialic acid residues in the carbohydrate moiety of receptor.     

Effect of imazaquin on absorption,translocation, and pattern of distribution of chlormequat chloride in winter wheat

The role of imazaquin in the absorption, translocation, and distribution of chlormequat chloride in CYCOCEL^* CL has been studied in winter wheat. Three treatments were applied to the 5th leaf of the main stem at growth stage 5 (Feekes Large scale): (1)¹⁴C-chlormequat chloride, (2) CYCOCEL^* CL containing¹⁴C-chlormequat chloride, and (3) CYCOCEL^* CL containing¹⁴C-imazaquin. Tracing of the radioactivity was followed in the treated leaf, main stem, tillers, and roots. Results showed that more than 85% of the radioactivity absorbed remained in the treated leaf. Ten days after the application of chlormequat chloride alone, 94.4% of the¹⁴C-chlormequat was found in the treated leaf, 2.9% in the main stem, 1.2% in the tillers, and 1.4% in the root system versus 88.2, 8.2, 2.1, and 1.4%, respectively, for the chlormequat chloride plus imazaquin treatment. It was concluded that imazaquin increases the mobility and the pattern of distribution of chlormequat chloride in the plant.     

Variability over time and correlates of cholesterol and blood pressure in systemic lupus erythematosus: a longitudinal cohort study

Introduction  

Total cholesterol (TC) and blood pressure (BP) are likely to take a dynamic course over time in patients with systemic lupus erythematosus (SLE). This would have important implications in terms of using single-point-in-time measurements of these variables to assess coronary artery disease (CAD) risk. The objective of this study was to describe and quantify variability over time of TC and BP among patients with SLE and to determine their correlates.     

Plasticity between MyoC- and MyoA-Glideosomes: An Example of Functional Compensation in Toxoplasma gondii Invasion

The glideosome is an actomyosin-based machinery that powers motility in Apicomplexa and participates in host cell invasion and egress from infected cells. The central component of the glideosome, myosin A (MyoA), is a motor recruited at the pellicle by the acylated gliding-associated protein GAP45. In Toxoplasma gondii, GAP45 also contributes to the cohesion of the pellicle, composed of the inner membrane complex (IMC) and the plasma membrane, during motor traction. GAP70 was previously identified as a paralog of GAP45 that is tailored to recruit MyoA at the apical cap in the coccidian subgroup of the Apicomplexa. A third member of this family, GAP80, is demonstrated here to assemble a new glideosome, which recruits the class XIV myosin C (MyoC) at the basal polar ring. MyoC shares the same myosin light chains as MyoA and also interacts with the integral IMC proteins GAP50 and GAP40. Moreover, a central component of this complex, the IMC-associated protein 1 (IAP1), acts as the key determinant for the restricted localization of MyoC to the posterior pole. Deletion of specific components of the MyoC-glideosome underscores the installation of compensatory mechanisms with components of the MyoA-glideosome. Conversely, removal of MyoA leads to the relocalization of MyoC along the pellicle and at the apical cap that accounts for residual invasion. The two glideosomes exhibit a considerable level of plasticity to ensure parasite survival.     

Biosynthesis of glycoconjugates in mitochondrial outer membranes

The results reported in this paper show two distinct ways for the incorporation ofN-acetylglucosamine into mitochondrial outer membranes. The first one is the glycosylation of dolichol acceptors, which is indicated by the inhibition of the synthesis of these products by the inhibitors of the dolichol intermediates (tunicamycin and GDP). The second one is the incorporation ofN-acetylglucosamine into protein acceptors directly from UDP-N-acetylglucosamine. This second way of glycosylation is only localized in mitochondria outer membranes.The existence of a direct route forN-glycoprotein biosynthesis has been based on the following evidence. First, the synthesis of theN-acetylglucosaminylated protein acceptors was not inhibited by tunicamycin or GDP. Second, the addition of exogenous dolichol-phosphate did not change the rate of biosynthesis of glycosylated protein material. Third, the sequential incorporation ofN-acetylglucosamine and mannose from their nucleotide derivatives in the presence of GDP and tunicamycin led to the synthesis of glycosylated protein material which entirely bound to Concanavalin A-Sepharose. The oligosaccharide moiety of the glycosylated protein material resulting from the direct transfer of sugars from their nucleotide derivatives to the protein acceptor is of theN-glycan type. On sodium dodecylsulphate polyacrylamide gel electrophoresis, this glycosylated material migrated as a marker protein with a molecular weight between 45 000 and 63 000. HPLC chromatofocusing analysis revealed that the fraction studied was anionic. The oligosaccharide moiety of the glycoprotein material can only be elongated by the incorporation ofN-acetylglucosamine and galactose from their nucleotide derivatives.     

In silico and empirical evaluation of twelve metabarcoding primer sets for insectivorous diet analyses

During the most recent decade, environmental DNA metabarcoding approaches have been both developed and improved to minimize the biological and technical biases in these protocols. However, challenges remain, notably those relating to primer design. In the current study, we comprehensively assessed the performance of ten COI and two 16S primer pairs for eDNA metabarcoding, including novel and previously published primers. We used a combined approach of in silico, in vivo‐mock community (33 arthropod taxa from 16 orders), and guano‐based analyses to identify primer sets that would maximize arthropod detection and taxonomic identification, successfully identify the predator (bat) species, and minimize the time and financial costs of the experiment. We focused on two insectivorous bat species that live together in mixed colonies: the greater horseshoe bat (Rhinolophus ferrumequinum) and Geoffroy's bat (Myotis emarginatus). We found that primer degeneracy is the main factor that influences arthropod detection in silico and mock community analyses, while amplicon length is critical for the detection of arthropods from degraded DNA samples. Our guano‐based results highlight the importance of detecting and identifying both predator and prey, as guano samples can be contaminated by other insectivorous species. Moreover, we demonstrate that amplifying bat DNA does not reduce the primers' capacity to detect arthropods. We therefore recommend the simultaneous identification of predator and prey. Finally, our results suggest that up to one‐third of prey occurrences may be unreliable and are probably not of primary interest in diet studies, which may decrease the relevance of combining several primer sets instead of using a single efficient one. In conclusion, this study provides a pragmatic framework for eDNA primer selection with respect to scientific and methodological constraints.