Browsing by Issue Date, starting with "2014-02"
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- History of the invasive African olive tree in Australia and Hawaii: evidence for sequential bottlenecks and hybridization with the Mediterranean olivePublication . Besnard, Guillaume; Dupuy, Jérémy; Larter, Maximilien; Cuneo, Peter; Cooke, David; Chikhi, LounesHumans have introduced plants and animals into new continents and islands with negative effects on local species. This has been the case of the olive that was introduced in Australia, New Zealand and Pacific islands where it became invasive. Two subspecies were introduced in Australia, and each successfully invaded a specific area: the African olive in New South Wales (NSW) and the Mediterranean olive in South Australia. Here, we examine their origins and spread and analyse a large sample of native and invasive accessions with chloroplast and nuclear microsatellites. African olive populations from the invaded range exhibit two South African chlorotypes hence supporting an introduction from South Africa, while populations from South Australia exhibit chlorotypes of Mediterranean cultivars. Congruently, nuclear markers support the occurrence of two lineages in Australia but demonstrate that admixture took place, attesting that they hybridized early after introduction. Furthermore, using an approximate Bayesian computation framework, we found strong support for the serial introduction of the African olive from South Africa to NSW and then from NSW to Hawaii. The taxon experienced successive bottlenecks that did not preclude invasion, meaning that rapid decisions need to be taken to avoid naturalization where it has not established a large population yet.
- Mapping molecules to structure: unveiling secrets of centriole and cilia assembly with near-atomic resolutionPublication . Jana, Swadhin Chandra; Marteil, Gaëlle; Bettencourt-Dias, MónicaCentrioles are microtubule (MT)-based cylinders that form centrosomes and can be modified into basal bodies that template the axoneme, the ciliary MT skeleton. These MT-based structures are present in all branches of the eukaryotic tree of life, where they have important sensing, motility and cellular architecture-organizing functions. Moreover, they are altered in several human conditions and diseases, including sterility, ciliopathies and cancer. Although the ultrastructure of centrioles and derived organelles has been known for over 50 years, the molecular basis of their remarkably conserved properties, such as their 9-fold symmetry, has only now started to be unveiled. Recent advances in imaging, proteomics and crystallography, allowed the building of 3D models of centrioles and derived structures with unprecedented molecular details, leading to a much better understanding of their assembly and function. Here, we cover progress in this field, focusing on the mechanisms of centriole and cilia assembly.
- The developmental control of size in insectsPublication . Nijhout, H. Frederik; Riddiford, Lynn M.; Mirth, Christen; Shingleton, Alexander W.; Suzuki, Yuichiro; Callier, VivianeThe mechanisms that control the sizes of a body and its many parts remain among the great puzzles in developmental biology. Why do animals grow to a species-specific body size, and how is the relative growth of their body parts controlled to so they grow to the right size, and in the correct proportion with body size, giving an animal its species-characteristic shape? Control of size must involve mechanisms that somehow assess some aspect of size and are upstream of mechanisms that regulate growth. These mechanisms are now beginning to be understood in the insects, in particular in Manduca sexta and Drosophila melanogaster. The control of size requires control of the rate of growth and control of the cessation of growth. Growth is controlled by genetic and environmental factors. Insulin and ecdysone, their receptors, and intracellular signaling pathways are the principal genetic regulators of growth. The secretion of these growth hormones, in turn, is controlled by complex interactions of other endocrine and molecular mechanisms, by environmental factors such as nutrition, and by the physiological mechanisms that sense body size. Although the general mechanisms of growth regulation appear to be widely shared, the mechanisms that regulate final size can be quite diverse.
- Modeling Malaria Infection and Immunity against Variant Surface Antigens in Príncipe Island, West AfricaPublication . Trovoada, Maria Jesus; Gonçalves, Lígia A.; Marinho, Cláudio R. F.; Turner, Louise; Hviid, Lars; Penha-Gonçalves, Carlos; Gomes, M. Gabriela M.After remarkable success of vector control campaigns worldwide, concerns about loss of immunity against Plasmodium falciparum due to lack of exposure to the parasite are relevant since an increase of severe cases in less immune individuals is expected. We present a mathematical model to investigate the impact of reducing exposure to the parasite on the immune repertoire against P. falciparum erythrocyte membrane protein 1 (PfEMP1) variants. The model was parameterized with data from Príncipe Island, West Africa, and applied to simulate two alternative transmission scenarios: one where control measures are continued to eventually drive the system to elimination; and another where the effort is interrupted after 6 years of its initiation and the system returns to the initial transmission potential. Population dynamics of parasite prevalence predict that in a few years infection levels return to the pre-control values, while the re-acquisition of the immune repertoire against PfEMP1 is slower, creating a window for increased severity. The model illustrates the consequences of loss of immune repertoire against PfEMP1 in a given setting and can be applied to other regions where similar data may be available.
- Androgen responsiveness to competition in humans: the role of cognitive variablesPublication . Oliveira, Rui; Oliveira, GonçaloAlthough androgens are commonly seen as male sex hormones, it has been established over the years that in both sexes, androgens also respond to social challenges. To explain the socially driven changes in androgens, two theoretical models have been proposed: the biosocial model and the challenge hypothesis. These models are typically seen as partly overlapping; however, they generate different predictions that are clarified here. In humans, sports competition and nonmetabolic competitive tasks have been used in the laboratory setting, as a proxy for agonistic interactions in animals. The results reviewed here show that the testosterone (T) response to competition in humans is highly variable – the studies present postcompetition T levels and changes in T that depend on the contest outcome and that cannot be predicted by the current theoretical models. These conflicting results bring to the foreground the importance of considering cognitive factors that could moderate the androgen response to competition. Among these variables, we elect cognitive appraisal and its components as a key candidate modulating factor. It is known that T also modulates the cognitive processes that are relevant to performance in competition. In this article, we reviewed the evidence arising from studies investigating the effect of administering exogenous T and compare those results with the findings from studies that measured endogenous T levels. Finally, we summarized the importance of also considering the interaction between androgens and other hormones, such as cortisol, when investigating the social modulation of T, as proposed by the dual-hormone hypothesis.
- Association of BANK1 and cytokine gene polymorphisms with type 1 diabetes in TunisiaPublication . Zouidi, Ferjani; Stayoussef, Mouna; Bouzid, Dorra; Fourati, Hajer; Abida, Olfa; João, Costa; Ayed, Mourad Ben; Fakhfakh, Raouia; Thouraya, Kammoun; Monjia, Hachicha; Carlos, Penha-Gonçalves; Masmoudi, HatemType 1 diabetes (T1D) is an autoimmune disease (AID) with both genetic and environmental components. We aimed to investigate the genetic association of polymorphisms in genes previously linked with other AIDs, namely BANK1, IL15 and IL2/IL21 region. A total of 76 T1D patients and 162 controls from Southern Tunisia were recruited for a case-control association study investigating the relationship between sixteen SNPs of the BANK1, IL15 and IL2/IL21 gene region and T1D. In the BANK1 gene, G allele and GG genotype of rs3733197 were significantly increased in the group of T1D patients compared to controls. In addition, in the IL15 gene, the minor allele A of rs10519613 polymorphism was significantly higher in patients than in controls. No significant association was found for SNPS in IL2/IL21 gene region. The analysis of the haplotype structure revealed the G-C-A-C-T haplotype of the IL15 gene as associated with a reduction in the risk of developing T1D, while A-T-A-C-T haplotype increased the risk of developing the disease. Furthermore, in the IL2/IL21 region, only one haplotype consisting of eight SNPs was markedly associated with T1D susceptibility. Moreover, G-C combination of the BANK1/IL15 was significantly increased in T1D patients, compared to controls. Our results establish BANK1 and IL15 as new T1D genetic susceptibility factors and replicate the association of the 4q27 region with T1D. Our data agree with the effect previously observed for other autoimmune conditions and delineate a shared underlying mechanism.