Crystal Structure and Pathophysiological Role of the Pneumococcal Nucleoside-binding Protein PnrA

Nucleotides are important for RNA and DNA synthesis and, despite a de novo synthesis by bacteria, uptake systems are crucial. Streptococcus pneumoniae, a facultative human pathogen, produces a surface-exposed nucleoside-binding protein, PnrA, as part of an ABC transporter system. Here we demonstrate the binding affinity of PnrA to nucleosides adenosine, guanosine, cytidine, thymidine and uridine by microscale thermophoresis and indicate the consumption of adenosine and guanosine by ¹H NMR spectroscopy. In a series of five crystal structures we revealed the PnrA structure and provide insights into how PnrA can bind purine and pyrimidine ribonucleosides but with preference for purine ribonucleosides. Crystal structures of PnrA:nucleoside complexes unveil a clear pattern of interactions in which both the N- and C- domains of PnrA contribute. The ribose moiety is strongly recognized through a conserved network of H-bond interactions, while plasticity in loop 27–36 is essential to bind purine- or pyrimidine-based nucleosides.Further, we deciphered the role of PnrA in pneumococcal fitness in infection experiments. Phagocytosis experiments did not show a clear difference in phagocytosis between PnrA-deficient and wild-type pneumococci. In the acute pneumonia infection model the deficiency of PnrA attenuated moderately virulence of the mutant, which is indicated by a delay in the development of severe lung infections. Importantly, we confirmed the loss of fitness in co-infections, where the wild-type out-competed the pnrA-mutant. In conclusion, we present the PnrA structure in complex with individual nucleosides and show that the consumption of adenosine and guanosine under infection conditions is required for virulence.     

Trypanocidal Activity of Dysphania ambrosioides,Lippia alba,and Tetradenia riparia Essential Oils against Trypanosoma cruzi

Despite the current treatments against Chagas Disease (CD), this vector-borne parasitic disease remains a serious public health concern. In this study, we have explored the in vitro and/or in vivo trypanocidal and cytotoxic activities of the essential oils (EOs) obtained from Dysphania ambrosioides (L.) Mosyakin & Clemants (Amaranthaceae) (DA-EO), Lippia alba (Mill.) N.E. Brown (Verbenaceae) (LA-EO), and Tetradenia riparia (Hochst.) Codd (Lamiaceae) (TR-EO) grown in Brazil Southeast. DA-EO was the most active against the trypomastigote and amastigote forms in vitro; the IC₅₀ values were 8.7 and 12.2 μg mL⁻¹, respectively. The EOs displayed moderate toxicity against LLCMK2 cells, but the DA-EO showed high selectivity index (SI) for trypomastigote (SI=33.2) and amastigote (SI=11.7) forms. Treatment with 20 mg/kg DA-EO, LA-EO, or TR-EO for 20 days by intraperitoneal administration reduced parasitemia by 6.36 %, 4.74 %, and 32.68 % on day 7 and by 12.04 %, 27.96 %, and 65.5 % on day 9. These results indicated that DA-EO, LA-EO, and TR-EO have promising trypanocidal potential in vitro, whereas TR-EO has also potential trypanocidal effects in vivo.     

Assessment of Environmental Hazards to Public Health in Temperate Urban Argentina

EcoHealth - Human health risk in urban areas depends on multiple environmental features. We performed a year-round survey in a highly urbanized district located in temperate Argentina (General San...     

Better alone? A demographic case study of the hemiparasite Castilleja tenuiflora (Orobanchaceae): A first approximation

Castilleja tenuiflora is a facultative root hemiparasitic plant that has colonized a disturbed lava field in central Mexico. To determine the effects of hemiparasitism on the population dynamics of the parasite, we identified a set of potential hosts and quantified their effects on the vital rates of C. tenuiflora during 2016–2018. Connections between the roots of the hemiparasite and the hosts were confirmed with a scanning electron microscope. Annual matrices considering two conditions (with and without potential hosts) were built based on vital rates for each year, and annual stochastic finite rate growth rates (λ_s) were calculated. Plants produced more reproductive structures with hosts than without hosts. A Life Table Response Experiment (LTRE) was performed to compare the contributions of vital rates between conditions. We identified 19 species of potential hosts for this generalist hemiparasite. Stochastic lambda with hosts λ_s = 1.02 (CI = 0.9999, 1.1) tended to be higher than without them λ_s = 0.9503 (CI = 0.9055, 0.9981). The highest elasticity values correspond to survival. LTRE indicated that the most important parameters are survival and fecundity; the total contribution of fecundity (0.0192) to the difference in growth was three times lower than that of survival (0.0603). Piqueria trinervia was the most abundant host, and C. tenuiflora had a higher lambda with it than with other species. Individuals can grow alone, but hosts can have a positive effect on the vital parameters of C. tenuiflora and on λ.     

Alendronate inhibits triglyceride accumulation and oxidative stress in adipocytes and the inflammatory response of macrophages which are associated with adipose tissue dysfunction

Journal of Physiology and Biochemistry - Alendronate, a bisphosphonate used to prevent osteoporosis, stimulates osteogenesis but impairs adipogenesis. Different clinical trials suggest that the...     

Ancient saltern metagenomics: tracking changes in microbes and their viruses from the underground to the surface

Microbial communities in hypersaline underground waters derive from ancient organisms trapped within the evaporitic salt crystals and are part of the poorly known subterranean biosphere. Here, we characterized the viral and prokaryotic assemblages present in the hypersaline springs that dissolve Triassic-Keuper evaporite rocks and feed the Añana Salt Valley (Araba/Alava, Basque Country, Spain). Four underground water samples (around 23% total salinity) with different levels of exposure to the open air were analysed by means of microscopy and metagenomics. Cells and viruses in the spring water had lower concentrations than what are normally found in hypersaline environments and seemed to be mostly inactive. Upon exposure to the open air, there was an increase in activity of both cells and viruses as well as a selection of phylotypes. The underground water was inhabited by a rich community harbouring a diverse set of genes coding for retinal binding proteins. A total of 35 viral contigs from 15 to 104 kb, representing partial or total viral genomes, were assembled and their evolutionary changes through the spring system were followed by SNP analysis and metagenomic island tracking. Overall, both the viral and the prokaryotic assemblages changed quickly upon exposure to the open air conditions.     

Disentangling Two QTL on Porcine Chromosome 12 for Backfat Fatty Acid Composition

A previous study allowed the identification of two QTL regions at positions 11–34 cM (QTL1) and 68–76 cM (QTL2) on porcine chromosome SSC12 affecting several backfat fatty acids in an Iberian x Landrace F2 intercross. In the current study, different approaches were performed in order to better delimit the quoted QTL regions and analyze candidate genes. A new chromosome scan, using 81 SNPs selected from the Porcine 60KBeadChip and six previously genotyped microsatellites have refined the QTL positions. Three new functional candidate genes (ACOX1, ACLY, and SREBF1) have been characterized. Moreover, two putative promoters of porcine ACACA gene have also been investigated. New isoforms and 24 SNPs were detected in the four candidate genes, 19 of which were genotyped in the population. ACOX1 and ACLY SNPs failed to explain the effects of QTL1 on palmitic and gadoleic fatty acids. QTL2, affecting palmitoleic, stearic, and vaccenic fatty acids, maps close to the ACACA gene location. The most significant associations have been detected between one intronic (g.53840T > C) and one synonymous (c.5634T > C) ACACA SNPs and these fatty acids. Complementary analyses including ACACA gene expression quantification and association studies in other porcine genetic types do not support the expected causal effect of ACACA SNPs.     

The Phosphorylated Pathway of Serine Biosynthesis Is Essential Both for Male Gametophyte and Embryo Development and for Root Growth in Arabidopsis

This study characterizes the phosphorylated pathway of Ser biosynthesis (PPSB) in Arabidopsis thaliana by targeting phosphoserine phosphatase (PSP1), the last enzyme of the pathway. Lack of PSP1 activity delayed embryo development, leading to aborted embryos that could be classified as early curled cotyledons. The embryo-lethal phenotype of psp1 mutants could be complemented with PSP1 cDNA under the control of Pro35S (Pro35S:PSP1). However, this construct, which was poorly expressed in the anther tapetum, did not complement mutant fertility. Microspore development in psp1.1/psp1.1 Pro35S:PSP1 arrested at the polarized stage. The tapetum from these lines displayed delayed and irregular development. The expression of PSP1 in the tapetum at critical stages of microspore development suggests that PSP1 activity in this cell layer is essential in pollen development. In addition to embryo death and male sterility, conditional psp1 mutants displayed a short-root phenotype, which was reverted in the presence of Ser. A metabolomic study demonstrated that the PPSB plays a crucial role in plant metabolism by affecting glycolysis, the tricarboxylic acid cycle, and the biosynthesis of amino acids. We provide evidence of the crucial role of the PPSB in embryo, pollen, and root development and suggest that this pathway is an important link connecting primary metabolism with development.     

oiwa,a Female Gametophytic Mutant Impaired in a Mitochondrial Manganese-Superoxide Dismutase,Reveals Crucial Roles for Reactive Oxygen Species during Embryo Sac Development and Fertilization in Arabidopsis

Reactive oxygen species (ROS) can function as signaling molecules, regulating key aspects of plant development, or as toxic compounds leading to oxidative damage. In this article, we show that the regulation of ROS production during megagametogenesis is largely dependent on MSD1, a mitochondrial Mn-superoxide dismutase. Wild-type mature embryo sacs show ROS exclusively in the central cell, which appears to be the main source of ROS before pollination. Accordingly, MSD1 shows a complementary expression pattern. MSD1 expression is elevated in the egg apparatus at maturity but is downregulated in the central cell. The oiwa mutants are characterized by high levels of ROS detectable in both the central cell and the micropylar cells. Remarkably, egg apparatus cells in oiwa show central cell features, indicating that high levels of ROS result in the expression of central cell characteristic genes. Notably, ROS are detected in synergid cells after pollination. This ROS burst depends on stigma pollination but precedes fertilization, suggesting that embryo sacs sense the imminent arrival of pollen tubes and respond by generating an oxidative environment. Altogether, we show that ROS play a crucial role during female gametogenesis and fertilization. MSD1 activity seems critical for maintaining ROS localization and important for embryo sac patterning.