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961.
Arthropod phylogeny based on eight molecular loci and morphology 总被引:52,自引:0,他引:52
The interrelationships of major clades within the Arthropoda remain one of the most contentious issues in systematics, which has traditionally been the domain of morphologists. A growing body of DNA sequences and other types of molecular data has revitalized study of arthropod phylogeny and has inspired new considerations of character evolution. Novel hypotheses such as a crustacean-hexapod affinity were based on analyses of single or few genes and limited taxon sampling, but have received recent support from mitochondrial gene order, and eye and brain ultrastructure and neurogenesis. Here we assess relationships within Arthropoda based on a synthesis of all well sampled molecular loci together with a comprehensive data set of morphological, developmental, ultrastructural and gene-order characters. The molecular data include sequences of three nuclear ribosomal genes, three nuclear protein-coding genes, and two mitochondrial genes (one protein coding, one ribosomal). We devised new optimization procedures and constructed a parallel computer cluster with 256 central processing units to analyse molecular data on a scale not previously possible. The optimal 'total evidence' cladogram supports the crustacean-hexapod clade, recognizes pycnogonids as sister to other euarthropods, and indicates monophyly of Myriapoda and Mandibulata. 相似文献
962.
The SH2/SH3 adaptor Grb4 transduces B-ephrin reverse signals 总被引:16,自引:0,他引:16
Bidirectional signals mediated by membrane-anchored ephrins and Eph receptor tyrosine kinases have important functions in cell-cell recognition events, including those that occur during axon pathfinding and hindbrain segmentation. The reverse signal that is transduced into B-ephrin-expressing cells is thought to involve tyrosine phosphorylation of the signal's short, conserved carboxy-terminal cytoplasmic domain. The Src-homology-2 (SH2) domain proteins that associate with activated tyrosine-phosphorylated B-subclass ephrins have not been identified, nor has a defined cellular response to reverse signals been described. Here we show that the SH2/SH3 domain adaptor protein Grb4 binds to the cytoplasmic domain of B ephrins in a phosphotyrosine-dependent manner. In response to B-ephrin reverse signalling, cells increase FAK catalytic activity, redistribute paxillin, lose focal adhesions, round up, and disassemble F-actin-containing stress fibres. These cellular responses can be blocked in a dominant-negative fashion by expression of the isolated Grb4 SH2 domain. The Grb4 SH3 domains bind a unique set of other proteins that are implicated in cytoskeletal regulation, including the Cbl-associated protein (CAP/ponsin), the Abl-interacting protein-1 (Abi-1), dynamin, PAK1, hnRNPK and axin. These data provide a biochemical pathway whereby cytoskeletal regulators are recruited to Eph-ephrin bidirectional signalling complexes. 相似文献
963.
Our understanding of submarine volcanic eruptions has improved substantially in the past decade owing to the recent ability to remotely detect such events and to then respond rapidly with synoptic surveys and sampling at the eruption site. But these data are necessarily limited to observations after the event. In contrast, the 1998 eruption of Axial volcano on the Juan de Fuca ridge was monitored by in situ sea-floor instruments. One of these instruments, which measured bottom pressure as a proxy for vertical deformation of the sea floor, was overrun and entrapped by the 1998 lava flow. The instrument survived-being insulated from the molten lava by the solidified crust-and was later recovered. The data serendipitously recorded by this instrument reveal the duration, character and effusion rate of a sheet flow eruption on a mid-ocean ridge, and document over three metres of lava-flow inflation and subsequent drain-back. After the brief two-hour eruption, the instrument also measured gradual subsidence of 1.4 metres over the next several days, reflecting deflation of the entire volcano summit as magma moved into the adjacent rift zone. These findings are consistent with our understanding of submarine lava effusion, as previously inferred from seafloor observations, terrestrial analogues, and laboratory simulations. 相似文献
964.
Bentley DR Deloukas P Dunham A French L Gregory SG Humphray SJ Mungall AJ Ross MT Carter NP Dunham I Scott CE Ashcroft KJ Atkinson AL Aubin K Beare DM Bethel G Brady N Brook JC Burford DC Burrill WD Burrows C Butler AP Carder C Catanese JJ Clee CM Clegg SM Cobley V Coffey AJ Cole CG Collins JE Conquer JS Cooper RA Culley KM Dawson E Dearden FL Durbin RM de Jong PJ Dhami PD Earthrowl ME Edwards CA Evans RS Gillson CJ Ghori J Green L Gwilliam R Halls KS Hammond S Harper GL Heathcott RW Holden JL 《Nature》2001,409(6822):942-943
We constructed maps for eight chromosomes (1, 6, 9, 10, 13, 20, X and (previously) 22), representing one-third of the genome, by building landmark maps, isolating bacterial clones and assembling contigs. By this approach, we could establish the long-range organization of the maps early in the project, and all contig extension, gap closure and problem-solving was simplified by containment within local regions. The maps currently represent more than 94% of the euchromatic (gene-containing) regions of these chromosomes in 176 contigs, and contain 96% of the chromosome-specific markers in the human gene map. By measuring the remaining gaps, we can assess chromosome length and coverage in sequenced clones. 相似文献
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967.
Kawai J Shinagawa A Shibata K Yoshino M Itoh M Ishii Y Arakawa T Hara A Fukunishi Y Konno H Adachi J Fukuda S Aizawa K Izawa M Nishi K Kiyosawa H Kondo S Yamanaka I Saito T Okazaki Y Gojobori T Bono H Kasukawa T Saito R Kadota K Matsuda H Ashburner M Batalov S Casavant T Fleischmann W Gaasterland T Gissi C King B Kochiwa H Kuehl P Lewis S Matsuo Y Nikaido I Pesole G Quackenbush J Schriml LM Staubli F Suzuki R Tomita M Wagner L Washio T Sakai K Okido T Furuno M Aono H Baldarelli R Barsh G 《Nature》2001,409(6821):685-690
The RIKEN Mouse Gene Encyclopaedia Project, a systematic approach to determining the full coding potential of the mouse genome, involves collection and sequencing of full-length complementary DNAs and physical mapping of the corresponding genes to the mouse genome. We organized an international functional annotation meeting (FANTOM) to annotate the first 21,076 cDNAs to be analysed in this project. Here we describe the first RIKEN clone collection, which is one of the largest described for any organism. Analysis of these cDNAs extends known gene families and identifies new ones. 相似文献
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