Dual Role of Mitochondrial Porin in Metabolite Transport across the Outer Membrane and Protein Transfer to the Inner Membrane

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Community assembly processes along a sub-Mediterranean elevation gradient: analyzing the interdependence of trait community weighted mean and functional diversity

Plant Ecology - Community-weighted mean (CWM) and functional diversity (FD) describe the two aspects of plant communities’ functional structure. While they have been often used separately to...     

Precise Gene Editing Preserves Hematopoietic Stem Cell Function following Transient p53-Mediated DNA Damage Response

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Leishmania amazonensis: Anionic currents expressed in oocytes upon microinjection of mRNA from the parasite

Transport mechanisms involved in pH homeostasis are relevant for the survival of Leishmania parasites. The presence of chloride conductive pathways in Leishmania has been anticipated since anion channel inhibitors limit the proton extrusion mediated by the H+ATPase, which is the major regulator of intracellular pH in amastigotes. In this study, we used Xenopus laevis oocytes as a heterologous expression system in which to study the expression of ion channels upon microinjection of polyA mRNA from Leishmania amazonensis. After injection of polyA mRNA into the oocytes, we measured three different types of currents. We discuss the possible origin of each, and propose that Type 3 currents could be the result of the heterologous expression of proteins from Leishmania since they show different pharmacological and biophysical properties as compared to endogenous oocyte currents.     

Pregnant female lizards Iberolacerta cyreni adjust refuge use to decrease thermal costs for their body condition and cell-mediated immune response

Lizards often respond to increased predation risk by increasing refuge use, but this strategy may entail a loss of thermoregulatory opportunities, which may lead to a loss of body condition. This may be especially important for pregnant oviparous female lizards, because they need to maintain optimal body temperatures as long as possible to maximize developmental embryos rate until laying. However, little is known about how increased time spent at low temperatures in refuges affects body condition and health state of pregnant female lizards. Furthermore, it is not clear how initial body condition affects refuge use. Female Iberian rock lizards forced to increase time spent at low temperatures showed lower body condition and tended to show lower cell-mediated immune responses than control females. Therefore, the loss of thermoregulatory opportunities seems to be an important cost for pregnant females. Nevertheless, thereafter, when we simulated two repeated predatory attacks, females modified refuge use in relation to their body condition, with females with worse condition decreasing time hidden after attacks. In conclusion, female lizards seemed able to compensate increased predation risk with flexible antipredatory strategies, thus minimizing costs for body condition and health state.     

Association between the ACCN1 gene and multiple sclerosis in Central East Sardinia

Multiple genome screens have been performed to identify regions in linkage or association with Multiple Sclerosis (MS, OMIM 126200), but little overlap has been found among them. This may be, in part, due to a low statistical power to detect small genetic effects and to genetic heterogeneity within and among the studied populations. Motivated by these considerations, we studied a very special population, namely that of Nuoro, Sardinia, Italy. This is an isolated, old, and genetically homogeneous population with high prevalence of MS. Our study sample includes both nuclear families and unrelated cases and controls. A multi-stage study design was adopted. In the first stage, microsatellites were typed in the 17q11.2 region, previously independently found to be in linkage with MS. One significant association was found at microsatellite D17S798. Next, a bioinformatic screening of the region surrounding this marker highlighted an interesting candidate MS susceptibility gene: the Amiloride-sensitive Cation Channel Neuronal 1 (ACCN1) gene. In the second stage of the study, we resequenced the exons and the 3' untranslated (UTR) region of ACCN1, and investigated the MS association of Single Nucleotide Polymorphisms (SNPs) identified in that region. For this purpose, we developed a method of analysis where complete, phase-solved, posterior-weighted haplotype assignments are imputed for each study individual from incomplete, multi-locus, genotyping data. The imputed assignments provide an input to a number of proposed procedures for testing association at a microsatellite level or of a sequence of SNPs. These include a Mantel-Haenszel type test based on expected frequencies of pseudocase/pseudocontrol haplotypes, as well as permutation based tests, including a combination of permutation and weighted logistic regression analysis. Application of these methods allowed us to find a significant association between MS and the SNP rs28936 located in the 3' UTR segment of ACCN1 with p = 0.0004 (p = 0.002, after adjusting for multiple testing). This result is in tune with several recent experimental findings which suggest that ACCN1 may play an important role in the pathogenesis of MS.     

Coronavirus non-structural protein 1 is a major pathogenicity factor: implications for the rational design of coronavirus vaccines

Attenuated viral vaccines can be generated by targeting essential pathogenicity factors. We report here the rational design of an attenuated recombinant coronavirus vaccine based on a deletion in the coding sequence of the non-structural protein 1 (nsp1). In cell culture, nsp1 of mouse hepatitis virus (MHV), like its SARS-coronavirus homolog, strongly reduced cellular gene expression. The effect of nsp1 on MHV replication in vitro and in vivo was analyzed using a recombinant MHV encoding a deletion in the nsp1-coding sequence. The recombinant MHV nsp1 mutant grew normally in tissue culture, but was severely attenuated in vivo. Replication and spread of the nsp1 mutant virus was restored almost to wild-type levels in type I interferon (IFN) receptor-deficient mice, indicating that nsp1 interferes efficiently with the type I IFN system. Importantly, replication of nsp1 mutant virus in professional antigen-presenting cells such as conventional dendritic cells and macrophages, and induction of type I IFN in plasmacytoid dendritic cells, was not impaired. Furthermore, even low doses of nsp1 mutant MHV elicited potent cytotoxic T cell responses and protected mice against homologous and heterologous virus challenge. Taken together, the presented attenuation strategy provides a paradigm for the development of highly efficient coronavirus vaccines.     

Allelochemical Stress Can Trigger Oxidative Damage in Receptor Plants: Mode of Action of Phytotoxicity

Plants can interact with other plants through the release of chemical compounds or allelochemicals. These compounds released by donor plants influence germination, growth, development, and establishment of receptor plants; having an important role on the pattern of vegetation, i.e as invasive strategy, and on crop productivity. This phytotoxic or negative effect of the released allelochemicals (allelochemical stress) is caused by modifying or altering diverse metabolic processes, having many molecular targets in the receptor plants. Recently, using an aggressive and allelopathic plant Sicyos deppei as the donor plant, and Lycopersicon esculentum as the receptor plant, we showed that the allelochemicals released by S. deppei caused oxidative damage through an increase in reactive oxygen species (ROS) and activation or modification of antioxidant enzymes. Based on this study, we proposed that oxidative stress is one of the mechanisms, among others, by which an allelopathic plant causes phytotoxicity to other plants.Key Words: allelochemical stress, Sicyos deppei, Lycopersicon esculentum, plant allelochemicals, phytotoxicity, ROS, lipid peroxidationIt is well known that plants interact with many organisms, including co-habitation with other plants. Among these relations are the ones referred to as allelochemical interactions. Allelopathy can be defined as a mechanism of interference in plant growth and development mediated by the addition of plant-produced secondary products (allelochemicals) to the soil rhizosphere. Allelochemicals are present in all types of plants and tissues and are released into the soil rhizosphere by a variety of mechanisms, including decomposition of residues, volatilization, and root exudation.^1–3 These released allelochemicals become stressful only when they are toxic or when they affect the growth and development of surrounding plants (phytotoxicity). Studies on allelochemical stress have been expanding; recently the phenomenon has taken on increased importance, since it can help explain plant growth inhibition in interspecies interactions and in structuring the plant community. It appears to be one mechanism or strategy used by invasive plants to become successful and replace other native ones.^4–6On the other hand, the chemical diversity of the organic compounds that mediate these allelochemical interactions is as diverse as their modes of action. Many studies have shown that allelochemicals interfere with several physiological processes in the receptor organism.^3,7,8 The physiological effects on receptor plants or other organisms are useful in determining the role of the allelochemicals in the system. Recently, it has been proposed that allelochemicals can cause oxidative stress in target plants and therefore activate the antioxidant mechanism.^3,8–12 In particular; our studies have been focused on knowing the physiological targets of the phytotoxic compounds released by a noxious and endemic weed Sicyos deppei G. Don (Cucurbitaceae). We have taken as the model the receptor or damaged plant Lycopersicon esculentum Mill (Solanaceae), since in Mexican crop-fields, it is common to find both plants. We have observed the strong allelopathic potential of S. deppei and are exploring the potential metabolic target that could be involved in the strong phytotoxic effect of this weed.^13–16 We recently documented the oxidative damage that an aqueous leachate of S. deppei caused in the target plant L. esculentum.¹⁶ In this work we explored in seeds and in primary roots the antioxidant mechanism of tomato to determine whether or not the inhibitory effect of S. deppei was due to oxidative damage. We analyzed the activity and expression of some antioxidant enzymes involved in the detoxification of ROS, and found an imbalance in its activity as well as an increase in the levels of H₂O₂ at 24 h of treatment. Additional studies on the levels of ROS, including hydrogen peroxide, were monitored in primary roots from germinating seeds under allelochemical stress by imaging the ROS-sensitive fluorescent dye dichlorofluorescein (_H2DCFDA, carboxy-2′, 7′-diclhlorofluorescein diacetate) in a confocal microscope (BIORAD 1024, 488 nm dichroic and 510–560 nm emission). DCFDA fluorescence increases as the dye is oxidized by ROS to dichlorofluorescein (DCF). Figure 1 shows a marked increase in fluorescence at 48 h and 72 h of treatment (Fig. 1A–C) compared with the same treatment at 24 h, and with the corresponding control. This fluorescence was more evident at the root cap and at the zone of root hairs in treated seeds.Open in a separate windowFigure 1Allelochemical stress caused by S. deppei elicits ROS generation in tomato germinating seeds. Panels show control (left) and treatment (right) at 24 h (A), 48 h (B), and 72 h (C). Lower panels show higher magnification (40X) of the corresponding time. Seedlings with primary roots were stained for 10–15 minutes with 25 µM DCFDA in distilled water.Clearly, allelochemical stress caused by S. deppei is producing an oxidative imbalance as evidenced by generation of ROS and alteration of activity of antioxidant enzymes. Another result that supports this observation is the high level of lipid peroxidation that we observed at 48 and 72 h, which correlates with the inhibition of two membrane-associated enzymes, H⁺-ATPase¹⁵ and NADPH oxidase.¹⁶ We believe, however, that the oxidative damage we observed is not solely responsible for the phytotoxic effect of S. deppei on tomato growth. In other words, we suggest that its inhibitory effect represents the sum of many metabolic processes affected at different times. Currently we are studying the dynamics of carbohydrate mobilization, cell wall loosing of the endosperm to allow the protrusion of the radicle, and ABA content. Preliminary results have shown that there is a delay in expression of some enzyme activities and a high content of ABA.     

Notch expression patterns in the retina: An eye on receptor-ligand distribution during angiogenesis

The critical contribution of the Notch signaling pathway to vascular morphogenesis has been underscored by loss-of-function studies in mouse and zebrafish. Nonetheless, a comprehensive understanding as to how this signaling system influences the formation of blood vessels at the cellular and molecular level is far from reached. Here, we provide a detailed analysis of the distribution of active Notch1 in relation to its DSL (Delta, Serrate, Lag2) ligands, Jagged1, Delta-like1, and Delta-like4, during progressive stages of vascular morphogenesis and maturation. Important differences in the cellular distribution of Notch ligands were found. Jagged1 (Jag1) was detected in "stalk cells" of the leading vasculature and at arterial branch points, a site where Delta-like4 (Dll4) was clearly absent. Dll4 was the only ligand expressed in "tip cells" at the end of the growing vascular sprouts. It was also present in stalk cells, capillaries, arterial endothelium, and in mural cells of mature arteries in a homogenous manner. Delta-like1 (Dll1) was observed in both arteries and veins of the developing network, but was also excluded from mature arterial branch points. These findings support alternative and distinct roles for Notch ligands during the angiogenic process.