Diacylglycerol is required for the formation of COPI vesicles in the Golgi-to-ER transport pathway

Diacylglycerol is necessary for trans-Golgi network (TGN) to cell surface transport, but its functional relevance in the early secretory pathway is unclear. Although depletion of diacylglycerol did not affect ER-to-Golgi transport, it led to a redistribution of the KDEL receptor to the Golgi, indicating that Golgi-to-ER transport was perturbed. Electron microscopy revealed an accumulation of COPI-coated membrane profiles close to the Golgi cisternae. Electron tomography showed that the majority of these membrane profiles originate from coated buds, indicating a block in membrane fission. Under these conditions the Golgi-associated pool of ARFGAP1 was reduced, but there was no effect on the binding of coatomer or the membrane fission protein CtBP3/BARS to the Golgi. The addition of 1,2-dioctanoyl-sn-glycerol or the diacylglycerol analogue phorbol 12,13-dibutyrate reversed the effects of endogenous diacylglycerol depletion. Our findings implicate diacylglycerol in the retrograde transport of proteins from Golgi to the ER and suggest that it plays a critical role at a late stage of COPI vesicle formation.     

Phylogeny of the reptilian Eimeria: are Choleoeimeria and Acroeimeria valid generic names?

Reptiles are the animals with the most described coccidian species among all vertebrates. However, the co‐evolutionary relationships in this host–parasite system have been scarcely studied. Paperna & Landsberg (South African Journal of Zoology, 24, 1989, 345) proposed the independent evolutionary origin of the Eimeria‐like species isolated from reptiles based on morphological and developmental characteristics of their oocysts. Accordingly, they suggested the reclassification of these parasites in two new genera, Choleoeimeria and Acroeimeria. The validity of the genera proposed to classify reptilian Eimeria species remained unresolved due to the lack of species genetically characterized. In this study, we included 18S rRNA gene sequences from seven Eimeria‐like species isolated from five different lizard host families. The phylogenetic analyses confirmed the independent evolutionary origin of the Eimeria‐like species infecting lizards. Within this group, most species were placed into two monophyletic clades. One of them included the species with ellipsoidal oocysts (i.e. Choleoeimeria‐like oocysts), whereas the species with more spheroidal oocysts (i.e. Acroeimeria‐like oocysts) were included in the second one. This result supports the taxonomic validity of the genera Acroeimeria and Choleoeimeria.     

Estimating and interpreting migration of Amazonian forests using spatially implicit and semi‐explicit neutral models

With many sophisticated methods available for estimating migration, ecologists face the difficult decision of choosing for their specific line of work. Here we test and compare several methods, performing sanity and robustness tests, applying to large‐scale data and discussing the results and interpretation. Five methods were selected to compare for their ability to estimate migration from spatially implicit and semi‐explicit simulations based on three large‐scale field datasets from South America (Guyana, Suriname, French Guiana and Ecuador). Space was incorporated semi‐explicitly by a discrete probability mass function for local recruitment, migration from adjacent plots or from a metacommunity. Most methods were able to accurately estimate migration from spatially implicit simulations. For spatially semi‐explicit simulations, estimation was shown to be the additive effect of migration from adjacent plots and the metacommunity. It was only accurate when migration from the metacommunity outweighed that of adjacent plots, discrimination, however, proved to be impossible. We show that migration should be considered more an approximation of the resemblance between communities and the summed regional species pool. Application of migration estimates to simulate field datasets did show reasonably good fits and indicated consistent differences between sets in comparison with earlier studies. We conclude that estimates of migration using these methods are more an approximation of the homogenization among local communities over time rather than a direct measurement of migration and hence have a direct relationship with beta diversity. As betadiversity is the result of many (non)‐neutral processes, we have to admit that migration as estimated in a spatial explicit world encompasses not only direct migration but is an ecological aggregate of these processes. The parameter m of neutral models then appears more as an emerging property revealed by neutral theory instead of being an effective mechanistic parameter and spatially implicit models should be rejected as an approximation of forest dynamics.     

Involvement of EupR,a response regulator of the NarL/FixJ family,in the control of the uptake of the compatible solutes ectoines by the halophilic bacterium <Emphasis Type="Italic">Chromohalobacter salexigens</Emphasis>

Background  

Osmosensing and associated signal transduction pathways have not yet been described in obligately halophilic bacteria. Chromohalobacter salexigens is a halophilic bacterium with a broad range of salt tolerance. In response to osmotic stress, it synthesizes and accumulates large amounts of the compatible solutes ectoine and hydroxyectoine. In a previous work, we showed that ectoines can be also accumulated upon transport from the external medium, and that they can be used as carbon sources at optimal, but not at low salinity. This was related to an insufficient ectoine(s) transport under these conditions.     

Leptin and adiponectin, but not IL18, are related with insulin resistance in treated HIV-1-infected patients with lipodystrophy

Leptin, adiponectin and IL18 are adipokines related with obesity, insulin resistance and dyslipidemia in the general population. Treated HIV-1-infected patients with lipodystrophy may develop insulin resistance and proatherogenic dyslipidemia. We assessed the relationship between plasma adipokine levels, adipokine genetics, lipodystrophy and metabolic disturbances. Plasma leptin, adiponectin and IL18 levels were assessed in 446 individuals: 282 HIV-1-infected patients treated with antiretroviral drugs (132 with lipodystrophy and 150 without) and 164 uninfected controls (UC). The LEP2410A>G, LEPRQ223R, ADIPQ276G>T, ADIPOR2-Intron5A>G and IL18-607C>A polymorphisms were validated by sequencing. Leptin levels were higher in UC than in HIV-1-infected, either with or without lipodystrophy (p<0.001 for both comparisons) and were lower in patients with lipodystrophy compared with those without lipodystrophy (p=0.006). In patients with lipodystrophy, leptin had a positive correlation with insulin and with HOMA-IR. Adiponectin levels were non-significantly different in UC and HIV-1-infected patients. Patients with lipodystrophy had lower adiponectin levels than non-lipodystrophy subjects (p<0.001). In patients with lipodystrophy, adiponectin was negatively correlated with insulin, HOMA-IR and triglycerides. Plasma IL18 levels were higher in HIV-1-infected patients compared with UC (p<0.001), and no differences were found according to the presence of lipodystrophy. In patients with lipodystrophy there was a negative correlation between IL18 levels and LDLc. Genetic analyses indicated no significant associations with lipodystrophy nor with insulin resistance or with lipid abnormalities. In conclusion, HIV-1-infected patients have reduced plasma leptin levels. This reduction is magnified in patients with lipodystrophy whose adiponectin levels were lower than that of non-lipodystrophy subjects. Plasma IL18 levels are increased in infected patients irrespective of the presence of lipodystrophy. The polymorphisms assessed are not associated with lipodystrophy or metabolic disturbances in treated HIV-1-infected patients.     

Deciphering the interleukin 28B variants that better predict response to pegylated interferon-α and ribavirin therapy in HCV/HIV-1 coinfected patients

Previous works have documented the contribution of different IL28B-associated SNPs to spontaneous HCV clearance. This study investigated the effect of different interleukin (IL) 28B genetic variants on interferon (IFN)-based therapy response. We genotyped eight IL28B single-nucleotide polymorphisms (SNPs) in a cohort of 197 hepatitis C virus (HCV)/human immunodeficiency virus type 1 (HIV-1) coinfected patients from our clinic unit who received combined pegylated (peg)-IFN-α and ribavirin (RBV) therapy. This analysis included the two strongest tag predictors for HCV clearance, rs8099917 and rs12979860, and four causal variants (rs4803219, rs28416813, rs8103142, and rs4803217) located in the IL28B promoter, coding, and 3′-untranslated regions. Haplotypes carrying the major alleles at IL28B SNPs were highly associated with sustained virological responses (SVRs) after treatment with peg-IFN-α and RBV [odds ratio (OR) = 2.5, 95% confidence interval (CI) = 1.6–4.0, 4.0×10⁻⁵]. Three causal SNP genotypes (rs28416813, rs8103142, and rs4803217) displayed the highest association with SVRs (OR = 3.7, 95% CI = 2.0–6.7, p = 1.3×10⁻⁵). All four causal variants were in high linkage disequilibrium, both among themselves (r²≥0.94) and with the rs12979860 variant (r²≥0.92). In contrast, rs8099917 was in low linkage disequilibrium with the four causal variants (r²≤0.45) and with the rs12979860 variant (r² = 0.45). These results demonstrate that rs12979860, compared to rs8099917, may be a better predictor of response to the peg-IFN/RBV treatment among HCV/HIV-1 coinfected patients. Moreover, causal IL28B variants are strongly associated with treatment SVRs.     

Costly signaling,ritual and cooperation: evidence from Candomblé, an Afro-Brazilian religion

The apparent wastefulness of religious ritual represents a puzzle for rational choice theorists and evolutionary scholars. In recent years, it has been proposed that such rituals represent costly signals that promote intragroup cooperation precisely because of the effort and resources they require. This hypothesis was tested over the course of a 14-month long ethnographic study in the northeast of Brazil. The research focused on adherents of Candomblé, an African diasporic religion organized in autonomous congregations primarily located in low-income urban areas. Individuals who reported higher levels of religious commitment behaved more generously in a public goods economic game and revealed more instances of provided and received cooperation within their religious community. This suggests that ritual as a costly signaling may effectively predict willingness to cooperate with other group members and that the signaler may accrue benefits in the form of received cooperation. Socioeconomic variables are also shown to mediate religious signaling. This raises the possibility that signalers strategically alter their expressions of commitment as their needs and circumstances change.     

MAPK phosphatase MKP2 mediates disease responses in Arabidopsis and functionally interacts with MPK3 and MPK6

Mitogen‐activated protein kinase (MAPK) cascades have important functions in plant stress responses and development and are key players in reactive oxygen species (ROS) signalling and in innate immunity. In Arabidopsis, the transmission of ROS and pathogen signalling by MAPKs involves the coordinated activation of MPK6 and MPK3; however, the specificity of their negative regulation by phosphatases is not fully known. Here, we present genetic analyses showing that MAPK phosphatase 2 (MKP2) regulates oxidative stress and pathogen defence responses and functionally interacts with MPK3 and MPK6. We show that plants lacking a functional MKP2 gene exhibit delayed wilting symptoms in response to Ralstonia solanacearum and, by contrast, acceleration of disease progression during Botrytis cinerea infection, suggesting that this phosphatase plays differential functions in biotrophic versus necrotrophic pathogen‐induced responses. MKP2 function appears to be linked to MPK3 and MPK6 regulation, as indicated by BiFC experiments showing that MKP2 associates with MPK3 and MPK6 in vivo and that in response to fungal elicitors MKP2 exerts differential affinity versus both kinases. We also found that MKP2 interacts with MPK6 in HR‐like responses triggered by fungal elicitors, suggesting that MPK3 and MPK6 are subject to differential regulation by MKP2 in this process. We propose that MKP2 is a key regulator of MPK3 and MPK6 networks controlling both abiotic and specific pathogen responses in plants.