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991.
Ghassen Abid Yordan Muhovski Jean-Marie Jacquemin Dominique Mingeot Khaled Sassi André Toussaint Jean-Pierre Baudoin 《Plant Cell, Tissue and Organ Culture》2011,107(2):341-353
Two genotypes of common bean (Phaseolus vulgaris L.) were studied to determine the structural cause of seed abortion in this species. In the non-abortive control (wild-type,
cultivar BAT93), the histological analysis revealed a classical pattern of seed development and showed coordinated differentiation
of the embryo proper, suspensor, endosperm tissue and seed coat. In contrast, the ethyl methanesulfonate (EMS) mutant (cultivar
BAT93) showed disruption in the normal seed development leading to embryo abortion. Aborted embryos from these degenerate
seeds showed abnormalities in suspensor and cotyledons at the globular, heart, torpedo and cotyledon stages. Exploring the
feasibility of incorporating the available online bioinformatics databases, we identified 22 genes revealing high homology
with genes involved in Arabidopsis
thaliana embryo development and expressed in common bean immature seeds. The expression patterns of these genes were confirmed by
RT–PCR. All genes were highly expressed in seed tissues. To study the expression profiles of isolated genes during Phaseolus embryogenesis, six selected genes were examined by quantitative RT–PCR analysis on the developing embryos of wild-type and
EMS mutant plants. All selected genes were expressed differentially at different stages of embryo development. These results
could help to improve understanding of the mechanism of common bean embryogenesis. 相似文献
992.
Baud'huin M Ruiz-Velasco C Jego G Charrier C Gasiunas N Gallagher J Maillasson M Naggi A Padrines M Redini F Duplomb L Heymann D 《European journal of cell biology》2011,90(1):49-57
The bone microenvironment (e.g. glycosaminoglycans (GAGs), growth factors) plays a major role in bone resorption, especially in the formation of osteoclasts which differentiate from the hematopoietic lineage in the presence of RANKL. Previous studies revealed that GAGs may influence osteoclastogenesis, but data are very controversial, some studies showing an inhibitory effect of GAGs on osteoclastic differentiation whereas others demonstrated a stimulatory effect. To clarify their activities, we investigated the effect of 5 families of GAGs in three different models of human/mouse osteoclastogenesis. The present data revealed that heparin inhibited osteoclastogenesis in these three models, which was confirmed by a decrease in mRNA expression of osteoclastic markers and by an inhibition of the bone resorption capacity. We also demonstrated in RAW 264.7 cells that other families of GAGs different from heparin inhibited RANKL-induced osteoclastogenesis, and that this inhibition was dependent on the length and the level of sulfation of GAGs. In the present work, heparin did not bind to RANKL and did not modulate RANKL signaling. Heparin acted at 2 distinct steps of osteoclastogenesis from human CD14(+) cells: first, heparin strongly decreased the adherence of osteoclast precursors, and secondly inhibited osteoclasts to spread and to be active. Furthermore, the second action of heparin was reversible as the removal of heparin at the end of the culture time allowed the condensed cells to spread out and showed the formation of morphological active osteoclasts. The present work clearly evidences that GAGs inhibit osteoclastogenesis in vitro and strengthens the therapeutic interest of defined GAGs in osteolytic diseases. 相似文献
993.
Migration of B cells within lymphoid follicles is controlled by the chemokine receptors CXCR5 and CCR7 and the G-protein-coupled receptor EBI2 (GPR183). Whereas CXCR5 and CCR7 are known to mediate migration toward their respective chemokine ligands, it is unclear whether EBI2 acts by modulating these processes or by directly mediating chemotaxis toward its own spatially restricted ligand. It is also unknown how signals from these three receptors are integrated to control B cell localization. To answer these questions, we generated compound knockout mice deficient in expression of EBI2, CXCR5, or CCR7. Analysis of these mice revealed that EBI2 mediates B cell migration toward the outer areas of follicles and to bridging channels of the spleen independent of both CXCR5 and CCR7. Migratory signals delivered by EBI2 were shown to control B cell organization within the spleen and to be particularly important for positioning activated B cells in the early stages of Ab responses. An additional minor role for EBI2 was identified in the organization and affinity maturation of B cells in germinal centers. Thus, EBI2-mediated chemotaxis provides a third dimension to B cell migration that balances and integrates with the inputs from CXCR5 and CCR7 to determine B cell positioning. 相似文献
994.
Graff L Obrdlik P Yuan L Loqué D Frommer WB von Wirén N 《Journal of experimental botany》2011,62(4):1361-1373
AMMONIUM TRANSPORTER (AMT) proteins are conserved in all domains of life and mediate the transport of ammonium or ammonia across cell membranes. AMTs form trimers and use intermolecular interaction between subunits to regulate activity. So far, binding forces that stabilize AMT protein complexes are not well characterized. High temperature or reducing agents released mono- and dimeric forms from trimeric complexes formed by AMT1;1 from Arabidopsis and tomato. However, in the paralogue LeAMT1;3, trimeric complexes were not detected. LeAMT1;3 differs from the other AMTs by an unusually short N-terminus, suggesting a role for the N-terminus in oligomer stability. Truncation of the N-terminus in LeAMT1;1 destabilized the trimer and led to loss of functionality when expressed in yeast. Swapping of the N-terminus between LeAMT1;1 and LeAMT1;3 showed that sequences in the N-terminus of LeAMT1;1 are necessary and sufficient for stabilization of the interaction among the subunits. Two N-terminal cysteine residues are highly conserved among AMT1 transporters in plants but are lacking in LeAMT1;3. C3S or C27S variants of LeAMT1;1 showed reduced complex stability, which coincided with lower transport capacity for the substrate analogue methylammonium. Both cysteine-substituted LeAMT1;1 variants showed weaker interactions with the wildtype as determined by a quantitative analysis of the complex stability using the mating-based split-ubiquitin assay. These data indicate that the binding affinity of AMT1 subunits is stabilized by cysteines in the N-terminus and suggest a role for disulphide bridge formation via apoplastic N-terminal cysteine residues. 相似文献
995.
Gaffé J McKenzie C Maharjan RP Coursange E Ferenci T Schneider D 《Journal of molecular evolution》2011,72(4):398-412
Insertion sequence (IS) elements are present in almost all bacterial genomes and are mobile enough to provide genomic tools
to differentiate closely related isolates. They can be used to estimate genetic diversity and identify fitness-enhancing mutations
during evolution experiments. Here, we determined the genomic distribution of eight IS elements in 120 genomes sampled from
Escherichia coli populations that evolved in glucose- and phosphate-limited chemostats by comparison to the ancestral pattern. No significant
differential transposition of the various IS types was detected across the environments. The phylogenies revealed substantial
diversity amongst clones sampled from each chemostat, consistent with the phenotypic diversity within populations. Two IS-related
changes were common to independent chemostats, suggesting parallel evolution. One of them corresponded to insertions of IS1 elements within rpoS encoding the master regulator of stress conditions. The other parallel event was an IS5-dependent deletion including mutY involved in DNA repair, thereby providing the molecular mechanism of generation of mutator clones in these evolving populations.
These deletions occurred in different co-existing genotypes within single populations and were of various sizes. Moreover,
differential locations of IS elements combined with their transpositional activity provided evolved clones with different
phenotypic landscapes. Therefore, IS elements strongly influenced the evolutionary processes in continuous E. coli cultures by providing a way to modify both the global regulatory network and the mutation rates of evolving cells. 相似文献
996.
997.
998.
Alaux C Folschweiller M McDonnell C Beslay D Cousin M Dussaubat C Brunet JL Le Conte Y 《Journal of invertebrate pathology》2011,106(3):380-385
Nosema ceranae, a microsporidian parasite originally described in the Asian honey bee Apis cerana, has recently been found to be cross-infective and to also parasitize the European honey bee Apis mellifera. Since this discovery, many studies have attempted to characterize the impact of this parasite in A. mellifera honey bees. Nosema species can infect all colony members, workers, drones and queens, but the pathological effects of this microsporidium has been mainly investigated in workers, despite the prime importance of the queen, who monopolizes the reproduction and regulates the cohesion of the society via pheromones. We therefore analyzed the impact of N. ceranae on queen physiology. We found that infection by N. ceranae did not affect the fat body content (an indicator of energy stores) but did alter the vitellogenin titer (an indicator of fertility and longevity), the total antioxidant capacity and the queen mandibular pheromones, which surprisingly were all significantly increased in Nosema-infected queens. Thus, such physiological changes may impact queen health, leading to changes in pheromone production, that could explain Nosema-induced supersedure (queen replacement). 相似文献
999.
Somatic hybridization for citrus rootstock breeding: an effective tool to solve some important issues of the Mediterranean citrus industry 总被引:2,自引:0,他引:2
Dambier D Benyahia H Pensabene-Bellavia G Aka Kaçar Y Froelicher Y Belfalah Z Lhou B Handaji N Printz B Morillon R Yesiloglu T Navarro L Ollitrault P 《Plant cell reports》2011,30(5):883-900
The prevalence of sour orange rootstock in the southern and eastern part of the Mediterranean Basin is presently threatened by the spread of Citrus Tristeza Virus (CTV) and its main vector Toxoptera citricida, combined with abiotic constraints such as drought, salinity and alkalinity. The search for alternative CTV-resistant rootstocks that also withstand the other constraints is now considered an urgent priority for a sustainable citrus industry in the area. Complementary progenitors can be found in citrus germplasm to combine the desired traits, particularly between Poncirus and Citrus genera. The production of somatic hybrids allows cumulating all dominant traits irrespective of their heterozygosity level, and would appear to be an effective way to solve the rootstock challenge facing the Mediterranean citrus industry. This paper presents the results obtained during a regional collaborative effort between five countries, to develop new rootstocks by somatic hybridization. New embryogenic callus lines to be used for somatic hybridization have been created. Protoplast fusions have been performed at CIRAD and IVIA laboratories, focusing on intergeneric combinations. Analysis of ploidy level by flow cytometry and molecular markers confirmed the acquisition of new interesting tetraploid somatic hybrids for six combinations. Diploid cybrids with intergeneric (Citrus?×?Poncirus) nucleus and C. reticulata or C. aurantifolia mitochondria were also identified for four combinations. The agronomical performance of a pre-existing somatic hybrid between Poncirus trifoliata and Citrus reticulata was validated in calcareous soils in Morocco. Somatic hybridization is now integrated into the breeding programs of the five Mediterranean countries. 相似文献
1000.