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81.
Christophe Sola Ingrid Filliol Eric Legrand Igor Mokrousov Nalin Rastogi 《Journal of molecular evolution》2001,53(6):680-689
This paper deals with phylogenetic relationships among a set of 90 clinical strains representative of the worldwide diversity
of the Mycobacterium tuberculosis complex (Kremer et al. 1999) using eight independent genetic markers: IS6110, IS1081, the direct repeat (DR) locus, and five variable number of tandem DNA repeat loci (VNTR). In a preliminary experiment, phylogenetic
trees based on single markers were constructed that led to the detection of some similarities between the VNTR-based and the
spoligotyping-based phylogenetic trees. In the second step, a more global phenetic approach based on pairwise comparison of
strains within each typing system was used, followed by calculations of mean genetic distances based on all the eight loci
and the use of the neighbor-joining algorithm for tree reconstruction. This analysis confirmed our preliminary observations
and suggested the existence of at least two new phylogeographical clades of M. tuberculosis, one defined as the ``East African–Indian family' (EA-I), which may find its origin on the African or Asian continents, and
the other as the ``Latin American and Mediterranean' (LA-M) family. The existence of these two families was also validated
by an independent phylogenetic analysis of spoligotyping on a larger set of shared types (n= 252) and further corroborated by VNTR and katG–gyrA results. The potential origin of these families of bacilli is discussed based on cattle domestication and human migration
history. In conclusion, the information contained in insertion sequence and repetitive DNAs may serve as a model for the phylogenetic
reconstruction of the M. tuberculosis complex. 相似文献
82.
Lou Brossette Joël Meunier Simon Dupont Anne‐Genevive Bagnres Christophe Lucas 《Ecology and evolution》2019,9(1):192-200
Parental care is a major component of reproduction in social organisms, particularly during the foundation steps. Because investment into parental care is often costly, each parent is predicted to maximize its fitness by providing less care than its partner. However, this sexual conflict is expected to be low in species with lifelong monogamy, because the fitness of each parent is typically tied to the other's input. Somewhat surprisingly, the outcomes of this tug‐of‐war between maternal and paternal investments have received important attention in vertebrate species, but remain less known in invertebrates. In this study, we investigated how queens and kings share their investment into parental care and other social interactions during colony foundation in two termites with lifelong monogamy: the invasive species Reticulitermes flavipes and the native species R. grassei. Behaviors of royal pairs were recorded during six months using a non‐invasive approach. Our results showed that queens and kings exhibit unbalanced investment in terms of grooming, antennation, trophallaxis, and vibration behavior. Moreover, both parents show behavioral differences toward their partner or their descendants. Our results also revealed differences among species, with R. flavipes exhibiting shorter periods of grooming and antennation toward eggs or partners. They also did more stomodeal trophallaxis and less vibration behavior. Overall, this study emphasizes that despite lifelong monogamy, the two parents are not equally involved in the measured forms of parental care and suggests that kings might be specialized in other tasks. It also indicates that males could play a central, yet poorly studied role in the evolution and maintenance of the eusocial organization. 相似文献
83.
Soil–plant–atmosphere conditions regulating convective cloud formation above southeastern US pine plantations 下载免费PDF全文
Gabriele Manoli Jean‐Christophe Domec Kimberly Novick Andrew Christopher Oishi Asko Noormets Marco Marani Gabriel Katul 《Global Change Biology》2016,22(6):2238-2254
Loblolly pine trees (Pinus taeda L.) occupy more than 20% of the forested area in the southern United States, represent more than 50% of the standing pine volume in this region, and remove from the atmosphere about 500 g C m per year through net ecosystem exchange. Hence, their significance as a major regional carbon sink can hardly be disputed. What is disputed is whether the proliferation of young plantations replacing old forest in the southern United States will alter key aspects of the hydrologic cycle, including convective rainfall, which is the focus of the present work. Ecosystem fluxes of sensible () and latent heat (LE) and large‐scale, slowly evolving free atmospheric temperature and water vapor content are known to be first‐order controls on the formation of convective clouds in the atmospheric boundary layer. These controlling processes are here described by a zero‐order analytical model aimed at assessing how plantations of different ages may regulate the persistence and transition of the atmospheric system between cloudy and cloudless conditions. Using the analytical model together with field observations, the roles of ecosystem and LE on convective cloud formation are explored relative to the entrainment of heat and moisture from the free atmosphere. Our results demonstrate that cloudy–cloudless regimes at the land surface are regulated by a nonlinear relation between the Bowen ratio and root‐zone soil water content, suggesting that young/mature pines ecosystems have the ability to recirculate available water (through rainfall predisposition mechanisms). Such nonlinearity was not detected in a much older pine stand, suggesting a higher tolerance to drought but a limited control on boundary layer dynamics. These results enable the generation of hypotheses about the impacts on convective cloud formation driven by afforestation/deforestation and groundwater depletion projected to increase following increased human population in the southeastern United States. 相似文献
84.
Andrea Gloria‐Soria Diego Ayala Ambicadutt Bheecarry Olger Calderon‐Arguedas Dave D. Chadee Marina Chiappero Maureen Coetzee Khouaildi Bin Elahee Ildefonso Fernandez‐Salas Hany A. Kamal Basile Kamgang Emad I. M. Khater Laura D. Kramer Vicki Kramer Alma Lopez‐Solis Joel Lutomiah Ademir Martins Jr Maria Victoria Micieli Christophe Paupy Alongkot Ponlawat Nil Rahola Syed Basit Rasheed Joshua B. Richardson Amag A. Saleh Rosa Maria Sanchez‐Casas Gonçalo Seixas Carla A. Sousa Walter J. Tabachnick Adriana Troyo Jeffrey R. Powell 《Molecular ecology》2016,25(21):5377-5395
Mosquitoes, especially Aedes aegypti, are becoming important models for studying invasion biology. We characterized genetic variation at 12 microsatellite loci in 79 populations of Ae. aegypti from 30 countries in six continents, and used them to infer historical and modern patterns of invasion. Our results support the two subspecies Ae. aegypti formosus and Ae. aegypti aegypti as genetically distinct units. Ae. aegypti aegypti populations outside Africa are derived from ancestral African populations and are monophyletic. The two subspecies co‐occur in both East Africa (Kenya) and West Africa (Senegal). In rural/forest settings (Rabai District of Kenya), the two subspecies remain genetically distinct, whereas in urban settings, they introgress freely. Populations outside Africa are highly genetically structured likely due to a combination of recent founder effects, discrete discontinuous habitats and low migration rates. Ancestral populations in sub‐Saharan Africa are less genetically structured, as are the populations in Asia. Introduction of Ae. aegypti to the New World coinciding with trans‐Atlantic shipping in the 16th to 18th centuries was followed by its introduction to Asia in the late 19th century from the New World or from now extinct populations in the Mediterranean Basin. Aedes mascarensis is a genetically distinct sister species to Ae. aegypti s.l. This study provides a reference database of genetic diversity that can be used to determine the likely origin of new introductions that occur regularly for this invasive species. The genetic uniqueness of many populations and regions has important implications for attempts to control Ae. aegypti, especially for the methods using genetic modification of populations. 相似文献
85.
M Deschodt-Lanckman P Robberecht J Christophe 《Archives of biochemistry and biophysics》1981,208(1):1-10
Heparin inhibited the adenylate cyclase activity of semipurified rat pancreatic plasma membranes stimulated by hormones and by Gpp(NH)p but not by fluoride or when in the persistently active state. When observed, the inhibition was rapid and sustained. It was of a noncompetitive type and never exceeded 20% for secretin. The inhibition of Gpp(NH)p-stimulated activity was more pronounced (48% inhibition at a heparin concentration of 50 μg/ml). For the C-terminal octapeptide of pancreozymin (CCK-8)-stimulated adenylate cyclase, the inhibition amounted to 93% at 50 μg/ml. This inhibition was competitive at low heparin concentration and of a mixed type above 10 μg/ml. Besides, heparin inhibited (I50 = 6 μg/ml) the binding of peptides of the CCK family to their specific receptors without affecting the apparent Kd value of binding. Taken together, these relatively specific effects of heparin gave evidence in favor of the existence of CCK spare receptors. Dextran sulfate was more potent than heparin as an inhibitor of adenylate cyclase activation while chondroitin-4-sulfate and chondroitin-6-sulfate were ineffective. Dansylated pancreatic plasma membranes exhibited characteristics of adenylate cyclase activation by CCK-8 which were similar to those found for untreated membranes exposed to heparin. 相似文献
86.
Konka Veeranjaneyulu Denis Charlebois Christophe N. N'soukpoé-Kossi Roger M. Leblanc 《Photosynthesis research》1992,34(2):271-278
Sulfite treatment of pea leaf disks in light caused a significant decrease in the relative quantum yield of photosynthetic oxygen evolution and energy storage (ES) as measured by photoacoustic (PA) spectroscopy. The inhibition was concentration dependent and was less in darkness than in light, indicating light-dependent inhibitory site(s) on the photosynthetic electron transport chain. Further, in darksulfite-treated leaves, the energy storage was more affected than the relative quantum yield of oxygen evolution, suggesting that photophosphorylation and/or cyclic electron transport around PS I are sites of sulfite action in darkness. The Rfd values, the ratio of fluorescence decrease (fd) to the steady-state fluorescence (fs), decreased significantly in leaves treated with sulfite in light but were not affected in dark-treated ones, confirming the photoacoustic observations. Similarly, the ratio of variable fluorescence (Fv) to maximum fluorescence (Fm), a measure of PS II photochemical efficiency, was affected by sulfite treatment in light and not changed by treatment in darkness. An attempt was made to explain the mechanism of sulfite action on photosynthetic electron transport in light and in darkness.Abbreviations APT
amplitude of photothermal signal
- Aox
amplitude of oxygen signal
- ES
energy storage
- fd
fluorescence decrease
- fs
steady-state fluorescence
- Fm
maximum fluorescence
- Fv
variable fluorescence
- PA
photoacoustic(s) 相似文献
87.
In the presence of the I-Ealpha protein, transgenic (Tg) mice expressing the 1H3.1 alphabeta TCR that is specific for the Ealpha52-68:I-A(b) complex display drastic intrathymic deletion. Although peripheral T cells from these mice remained unresponsive to the Ealpha52-68:I-A(b) complex, they contained a subpopulation able to specifically react to this complex in the presence of exogenous IL-2, indicating that some 1H3.1 alphabeta TCR Tg T cells have escaped clonal deletion and efficiently populated the periphery. IL-2-dependent, Ealpha52-68:I-A(b) complex-responsive T cells were CD4-CD8- and expressed the 1H3.1 alphabeta TCR. Such T cells could develop intrathymically, did not show sign of regulatory/suppressor activity, displayed a typical naive phenotype, and seemed to persist in vivo over time. CD4-CD8- TCR Tg T cells were also detected when the surface density of the deleting ligand was increased on MHC class II+ cells. In addition, the development of CD4-CD8- 1H3.1 alphabeta TCR Tg T cells could be supported by I-A(b) molecules. These observations indicate that CD4 surface expression neither specifies, nor is required for, the thymic export of mature thymocytes expressing a MHC class II-restricted alphabeta TCR. The data also show that, although the avidity of the interaction involved in intrathymic deletion is significantly lower than that involved in mature T cell activation, its range can be large enough to be influenced by the presence or absence of coreceptors. Finally, the margin created by the absence of CD4 coreceptor was substantial because it could accommodate various amounts of the deleting ligand on thymic stromal cells. 相似文献
88.
Plant myxodiasporous species have the ability to release a polysaccharidic mucilage upon imbibition of the seed (myxospermy) or the fruit (myxocarpy). This is a widespread capacity in angiosperms providing multiple ecological functions including higher germination efficiency under environmental stresses. It is unclear whether myxodiaspory has one or multiple evolutionary origins and why it was supposedly lost in several species. Here, we summarize recent advances on three main aspects of myxodiaspory. (a) It represents a combination of highly diverse traits at different levels of observation, ranging from the dual tissular origin of mucilage secretory cells to diverse mucilage polysaccharidic composition and ultrastructural organization. (b) An asymmetrical selection pressure is exerted on myxospermy-related genes that were first identified in Arabidopsis thaliana. The A. thaliana and the flax intra-species mucilage variants show that myxospermy is a fast-evolving trait due to high polymorphism in a few genes directly acting on mucilage establishment. In A. thaliana, these actors are downstream of a master regulatory complex and an original phylogenetic overview provided here illustrates that this complex has sequentially evolved after the common ancestor of seed plants and was fully established in the common ancestor of the rosid clade. (c) Newly identified myxodiaspory ecological functions indicate new perspectives such as soil microorganism control and plant establishment support. 相似文献
89.
Diploid/polyploid syntenic shuttle mapping and haplotype-specific chromosome walking toward a rust resistance gene (Bru1) in highly polyploid sugarcane (2n approximately 12x approximately 115) 下载免费PDF全文
Le Cunff L Garsmeur O Raboin LM Pauquet J Telismart H Selvi A Grivet L Philippe R Begum D Deu M Costet L Wing R Glaszmann JC D'Hont A 《Genetics》2008,180(1):649-660
The genome of modern sugarcane cultivars is highly polyploid ( approximately 12x), aneuploid, of interspecific origin, and contains 10 Gb of DNA. Its size and complexity represent a major challenge for the isolation of agronomically important genes. Here we report on the first attempt to isolate a gene from sugarcane by map-based cloning, targeting a durable major rust resistance gene (Bru1). We describe the genomic strategies that we have developed to overcome constraints associated with high polyploidy in the successive steps of map-based cloning approaches, including diploid/polyploid syntenic shuttle mapping with two model diploid species (sorghum and rice) and haplotype-specific chromosome walking. Their applications allowed us (i) to develop a high-resolution map including markers at 0.28 and 0.14 cM on both sides and 13 markers cosegregating with Bru1 and (ii) to develop a physical map of the target haplotype that still includes two gaps at this stage due to the discovery of an insertion specific to this haplotype. These approaches will pave the way for the development of future map-based cloning approaches for sugarcane and other complex polyploid species. 相似文献
90.
H2AX: functional roles and potential applications 总被引:1,自引:0,他引:1
Jennifer S. Dickey Christophe E. Redon Asako J. Nakamura Brandon J. Baird Olga A. Sedelnikova William M. Bonner 《Chromosoma》2009,118(6):683-692
Upon DNA double-strand break (DSB) induction in mammals, the histone H2A variant, H2AX, becomes rapidly phosphorylated at
serine 139. This modified form, termed γ-H2AX, is easily identified with antibodies and serves as a sensitive indicator of
DNA DSB formation. This review focuses on the potential clinical applications of γ-H2AX detection in cancer and in response
to other cellular stresses. In addition, the role of H2AX in homeostasis and disease will be discussed. Recent work indicates
that γ-H2AX detection may become a powerful tool for monitoring genotoxic events associated with cancer development and tumor
progression. 相似文献