The zebrafish mutant vps18 as a model for vesicle-traffic related hypopigmentation diseases

Hypopigmentation is a characteristic of several diseases associated with vesicle traffic defects, like the Hermansky-Pudlak, Chediak-Higashi, and Griscelli syndromes. Hypopigmentation is also a characteristic of the zebrafish mutant vps18(hi2499A), which is affected in the gene vps18, a component of the homotypic fusion and protein sorting complex that is involved in tethering during vesicular traffic. Vps18, as part of this complex, participates in the formation of early endosomes, late endosomes, and lysosomes. Here, we show that Vps18 is also involved in the formation of melanosomes. In the zebrafish mutant vps18(hi2499A) the retroviral insertion located at exon 4 of vps18, leads to the formation of two abnormal splicing variants lacking the coding sequence for the clathrin repeat and the RING finger conserved domains. A deficiency of Vps18 in zebrafish larvae results in hepatomegaly and skin hypopigmentation. We also observed a drastic reduction in the number of melanosomes in the eye's retinal pigmented epithelium along with the accumulation of immature melanosomes. A significant reduction in the vps18(hi2499A) larvae visual system capacity was found using the optokinetic response assay. We propose that the insertional mutant vps18(hi2499A) can be used as a model for studying hypopigmentation diseases in which vesicle traffic problems exist.     

Can landscape ecology untangle the complexity of antibiotic resistance?

Bacterial resistance to antibiotics continues to pose a serious threat to human and animal health. Given the considerable spatial and temporal heterogeneity in the distribution of resistance and the factors that affect its evolution, dissemination and persistence, we argue that antibiotic resistance must be viewed as an ecological problem. A fundamental difficulty in assessing the causal relationship between antibiotic use and resistance is the confounding influence of geography: the co-localization of resistant bacterial species with antibiotic use does not necessarily imply causation and could represent the presence of environmental conditions and factors that have independently contributed to the occurrence of resistance. Here, we show how landscape ecology, which links the biotic and abiotic factors of an ecosystem, might help to untangle the complexity of antibiotic resistance and improve the interpretation of ecological studies.     

Plant proteome analysis: a 2004-2006 update

Since the appearance of the review entitled "Plant Proteome Analysis" in Proteomics in February 2004 (Cánovas, F. M., Dumas-Gaudot, E., Recorbert, G., Jorrín, J. et al., Proteomics 2004, 4, 285-298), about 200 original articles focusing on plant proteomics have been published. Although this represents less than 1% of the global proteomics output during this period, it nevertheless reflects an increase in activity over the period 1999-2004. These papers concern the proteome of at least 35 plant species but have concentrated mainly on thale cress (Arabidopsis thaliana) and rice (Oryza sativa). The scientific objectives have ranged from a proteomic analysis of organs, tissues, cell suspensions, or subcellular fractions to the study of plant development and response to various stresses. A number of contributions have covered PTMs and protein interactions. The dominant analytical platform has been 2-DE coupled to MS, but "second generation" techniques such as DIGE, multidimensional protein identification technology, isotope-coded affinity tags, and stable isotope labeling by amino acids in cell culture have begun to make an impact. This review aims to provide an update of the contribution of proteomics to plant biology during the period 2004-2006, and is divided into six sections: introduction, subcellular proteomes, plant development, responses to biotic and abiotic stresses, PTMs, and protein interactions. The conclusions summarize a view of the major pitfalls and challenges of plant proteomics.     

A new tris(2-furyl) substituted pyrazolylborate ligand and its zinc complex chemistry

The new ligand hydrotris(3-(2′-furyl)-5-methylpyrazolyl)borate (Tp^Fu,Me) was prepared by the usual procedure. With zinc salts, it forms the Tp^Fu,MeZn-X complexes (X = Cl, Br, I, NCS, CH₃COO, CF₃COO). With zinc perchlorate, the bis-ligand complex Zn(Tp^Fu,Me)₂ is formed preferrably, but by carefully controlling the reaction conditions, the “enzyme model” Tp^Fu,MeZn-OH could be obtained. The latter models carbonic anhydrase by inserting CO₂ and CS₂ in methanol producing Tp^Fu,MeZn-OCOOMe and Tp^Fu,MeZn-SCSOMe. It models hydrolases by the hydrolytic cleavage of tris(p-nitrophenyl)phosphate and γ-thiobutyrolactone. It does not hydrolyse trifluoroacetamide, but instead deprotonates it, yielding Tp^Fu,MeZn-NHCOCF₃.     

Blue light activates the sigmaB-dependent stress response of Bacillus subtilis via YtvA

Here we present evidence for a physiologically relevant light response mediated by the LOV domain-containing protein YtvA in the soil bacterium Bacillus subtilis. The loss and overproduction of YtvA abolish and enhance, respectively, the increase in sigma(B)-controlled ctc promoter activity at moderate light intensities. These effects were absent in the dark and in red light but present under blue-light illumination. Thus, activation of the general stress response in B. subtilis is modulated by blue light.     

MR1-restricted V alpha 19i mucosal-associated invariant T cells are innate T cells in the gut lamina propria that provide a rapid and diverse cytokine response

Mucosal-associated invariant T (MAIT) cells reside primarily in the gut lamina propria and require commensal flora for selection/expansion. They are restricted by the highly conserved MHC class I-related molecule MR1 and, like most NK T cells, express an invariant TCRalpha chain. Although they probably contribute to gut immunity, MAIT cells have not been functionally characterized because they are so rare. To create a model in which they are more abundant, we generated transgenic mice expressing only the TCRalpha chain (Valpha19i) that defines MAIT cells. By directly comparing Valpha19i transgenic mice on MR1+/+ and MR1-/- backgrounds, we were able to distinguish and characterize a population of Valpha19i T cells dependent on MR1 for development. MR1-restricted Valpha19i transgenic T cells recapitulate what is known about MAIT cell development. Furthermore, a relatively high proportion of transgenic MAIT cells express NK1.1, and most have a cell surface phenotype similar to that of Valpha14i NK T cells. Finally, MR1-restricted Valpha19i T cells secrete IFN-gamma, IL-4, IL-5, and IL-10 following TCR ligation, and we provide evidence for what may be two functionally distinct MAIT cell populations. These data strongly support the idea that MAIT cells contribute to the innate immune response in the gut mucosa.     

The influence of temperature and host availability on the host exploitation strategies of sexual and asexual parasitic wasps of the same species

In the hymenopteran parasitoid Venturia canescens, asexual (obligate thelytoky not induced by Wolbachia bacteria) and sexual (arrhenotokous) wasps coexist in field conditions despite the demographic cost incurred due to the production of males by sexual females. Arrhenotoky predominates in field conditions, whereas populations in indoor conditions (mills, granaries) are exclusively thelytokous. These differences in the relative abundance of the two modes of reproduction between environments suggest that the individuals of each reproductive mode may have developed strategies adapted to the conditions prevailing in each kind of habitat. The two environments contrast in temperature variability and in the spatial heterogeneity of host availability. In this study, we considered the combined effect of temperature and host availability on host patch exploitation by thelytokous and arrhenotokous V. canescens. As expected, arrhenotokous females were more sensitive to temperature changes. If the temperature decreased before foraging, they remained longer and exploited patches more thoroughly. This is consistent with the expected behaviour of parasitoids in response to signs of unfavourable conditions that entail increasing risk of time limitation or a reduced probability of attaining further patches. Both arrhenotokous and thelytokous females increased patch exploitation with host availability. However, unexpectedly, we found no difference in the way the two types of wasp responded to differences in host availability. Differences in the strategies adopted under different environmental conditions may indicate divergence of niche-specific life history traits between the two modes of reproduction. Niche displacement may partly account for the coexistence of these two modes of reproduction at a geographical scale.     

The relationship of sex and ectoparasite infestation in the water rat Scapteromys aquaticus (Rodentia: Cricetidae) in La Plata, Argentina

I studied the relationship between sex and infestation with ectoparasites in the water rat Scapteromys aquaticus from La Plata river marshland, Argentina. The Relative Density's Index (RDI) for males was 3.90% (females 3.60%). A total of 2653 ectoparasites were collected on 33 male hosts, and 1945 on 31 females. Ectoparasite specific richness (S) and diversity (H) were S = 14, H = 1.17 on males, and S = 10, H = 1.52 on females. The similarity between male and female rodents according to their ectoparasites was 75.00%. Although no ectoparasite species showed significant mean abundance (MA) differences between host sexes (p < 0.05), and only Laelaps manguinhosi prevalence was significantly higher on male hosts (N = 2.01, p < 0.05) in this study, there are reasons to think that the sex of the water rat affects ectoparasite burden and specific richness. This information has epidemiological potential because the closely related Scapteromys tumidus is involved in the transmission of Rickettsia coronii, which causes Marsella fever in humans.