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201.
Armelle Coeur d’acier Giuseppe Cocuzza Emmanuelle Jousselin Vincenzo Cavalieri Sebastiano Barbagallo 《Zoologica scripta》2008,37(2):175-193
Phylogenetic relationships among members of the Aphid genus Brachycaudus (Homoptera: Aphididae) were inferred from partial sequences of mitochondrial cytochrome B oxidase (CytB), two partial fragments of mitochondrial cytochrome C oxidase subunit I (COI) and the internal transcribed spacer II (ITS2) of ribosomal DNA. Twenty-nine species, with several specimens per species, were included, representing all the historically recognized species-groups and subgenera used in the genus except the monospecific subgenus Mordvilkomemor. Results indicate that the genus Brachycaudus is a well-supported monophyletic group. While our results validate the monophyly of subgenera Thuleaphis , Appelia and Brachycaudus s. str. , they reveal two discrepancies in the classical taxonomy. First, the monotypic subgenus Nevskyaphis does not appear valid. Second, the traditionally defined Acaudus subgenus is not monophyletic. On the other hand, our phylogenetic trees corroborate Andreev's recent definition of Acaudus and Brachycaudina. However, they clearly show that the subgenera Prunaphis , Nevskyaphis and Scrophulaphis as defined by this author do not form monophyletic groups. Our results also highlight a highly supported clade that has not been discussed by previous authors; this clade could form a new subgenus, the subgenus Nevskyaphis . Finally, our study shows that molecular data and morphology meet the same limits in delimiting species groups and species themselves. Species groups in which taxonomic treatment is difficult are polytomous. Furthermore, except for one node clustering Brachycaudus s. str . and Appelia, intersubgeneric relationships remain poorly resolved even when several genes are added to the phylogenetic analysis. These results, together with previous studies in other aphid groups suggest that diversification might have been a rapid process in aphids. 相似文献
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Sara Planamente Samuel Mondy Florence Hommais Armelle Vigouroux Solange Moréra Denis Faure 《Molecular microbiology》2012,86(5):1085-1099
GABA acts as an intercellular signal in eukaryotes and as an interspecies signal in host–microbe interactions. Structural characteristics of selective eukaryotic GABA receptors and bacterial GABA sensors are unknown. Here, we identified the selective GABA‐binding protein, called Atu4243, in the plant pathogen Agrobacterium tumefaciens. A constructed atu4243 mutant was affected in GABA transport and in expression of the GABA‐regulated functions, including aggressiveness on two plant hosts and degradation of the quorum‐sensing signal. The GABA‐bound Atu4243 structure at 1.28 Å reveals that GABA adopts a conformation never observed so far and interacts with two key residues, Arg203 and Asp226 of which the role in GABA binding and GABA signalling in Agrobacterium has been validated using appropriate mutants. The conformational GABA‐analogue trans‐4‐aminocrotonic acid (TACA) antagonizes GABA activity, suggesting structural similarities between the binding sites of the bacterial sensor Atu4243 and mammalian GABAC receptors. Exploration of genomic databases reveals Atu4243 orthologues in several pathogenic and symbiotic proteobacteria, such as Rhizobium, Azospirillum, Burkholderia and Pseudomonas. Thus, this study establishes a structural basis for selective GABA sensors and offers opportunities for deciphering the role of the GABA‐mediated communication in several host–pathogen interactions. 相似文献
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Sampaio C Dance M Montagner A Edouard T Malet N Perret B Yart A Salles JP Raynal P 《Molecular and cellular biology》2008,28(2):587-600
Phosphoinositide 3-kinase (PI3K) participates in extracellular signal-regulated kinase 1 and 2 (ERK1-2) activation according to signal strength, through unknown mechanisms. We report herein that Gab1/Shp2 constitutes a PI3K-dependent checkpoint of ERK1-2 activation regulated according to signal intensity. Indeed, by up- and down-regulation of signal strength in different cell lines and through different methods, we observed that Gab1/Shp2 and Ras/ERK1-2 in concert become independent of PI3K upon strong epidermal growth factor receptor (EGFR) stimulation and dependent on PI3K upon limited EGFR activation. Using Gab1 mutants, we observed that this conditional role of PI3K is dictated by the EGFR capability of recruiting Gab1 through Grb2 or through the PI3K lipid product PIP3, according to a high or weak level of receptor stimulation, respectively. In agreement, Grb2 siRNA generates, in cells with maximal EGFR stimulation, a strong dependence on PI3K for both Gab1/Shp2 and ERK1-2 activation. Therefore, Ras/ERK1-2 depends on PI3K only when PIP3 is required to recruit Gab1/Shp2, which occurs only under weak EGFR mobilization. Finally, we show that, in glioblastoma cells displaying residual EGFR activation, this compensatory mechanism becomes necessary to efficiently activate ERK1-2, which could probably contribute to tumor resistance to EGFR inhibitors. 相似文献
209.
The sedimentary layer deposited at the surface of stormwater infiltration basins is highly organic and multicontaminated.
It undergoes considerable moisture content fluctuations due to the drying and inundation cycles (called hydric dynamics) of
these basins. Little is known about the microflora of the sediments and its dynamics; hence, the purpose of this study is
to describe the physicochemical and biological characteristics of the sediments at different hydric statuses of the infiltration
basin. Sediments were sampled at five time points following rain events and dry periods. They were characterized by physical
(aggregation), chemical (nutrients and heavy metals), and biological (total, bacterial and fungal biomasses, and genotypic
fingerprints of total bacterial and fungal communities) parameters. Data were processed using statistical analyses which indicated
that heavy metal (1,841 μg/g dry weight (DW)) and organic matter (11%) remained stable through time. By contrast, aggregation,
nutrient content (NH4+, 53–717 μg/g DW), pH (6.9–7.4), and biological parameters were shown to vary with sediment water content and sediment biomass,
and were higher consecutive to stormwater flows into the basin (up to 7 mg C/g DW) than during dry periods (0.6 mg C/g DW).
Coinertia analysis revealed that the structure of the bacterial communities is driven by the hydric dynamics of the infiltration
basin, although no such trend was found for fungal communities. Hydric dynamics more than rain events appear to be more relevant
for explaining variations of aggregation, microbial biomass, and shift in the microbial community composition. We concluded
that the hydric dynamics of stormwater infiltration basins greatly affects the structural stability of the sedimentary layer,
the biomass of the microbial community living in it and its dynamics. The decrease in aggregation consecutive to rewetting
probably enhances access to organic matter (OM), explaining the consecutive release of NH4+, the bloom of the microbial biomass, and the change in structure of the bacterial community. These results open new perspectives
for basin management since the risk of OM and pollutant transfer to the aquifer is greatly affected by alternating dry and
flood periods. 相似文献
210.
Marshall G Howard Z Dry J Fenton S Heathcote D Gray N Keen H Logie A Holt S Smith P Guichard SM 《Biochemical Society transactions》2011,39(2):456-459
AZD8055 is a small-molecule inhibitor of mTOR (mammalian target of rapamycin) kinase activity. The present review highlights molecular and phenotypic differences between AZD8055 and allosteric inhibitors of mTOR such as rapamycin. Biomarkers, some of which are applicable to clinical studies, as well as biological effects such as autophagy, growth inhibition and cell death are compared between AZD8055 and rapamycin. Potential ways to develop rational combinations with mTOR kinase inhibitors are also discussed. Overall, AZD8055 may provide a better therapeutic strategy than rapamycin and analogues. 相似文献