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71.
Molecular characterization of Ph1 as a major chromosome pairing locus in polyploid wheat 总被引:1,自引:0,他引:1
Griffiths S Sharp R Foote TN Bertin I Wanous M Reader S Colas I Moore G 《Nature》2006,439(7077):749-752
The foundation of western civilization owes much to the high fertility of bread wheat, which results from the stability of its polyploid genome. Despite possessing multiple sets of related chromosomes, hexaploid (bread) and tetraploid (pasta) wheat both behave as diploids at meiosis. Correct pairing of homologous chromosomes is controlled by the Ph1 locus. In wheat hybrids, Ph1 prevents pairing between related chromosomes. Lack of Ph1 activity in diploid relatives of wheat suggests that Ph1 arose on polyploidization. Absence of phenotypic variation, apart from dosage effects, and the failure of ethylmethane sulphonate treatment to yield mutants, indicates that Ph1 has a complex structure. Here we have localized Ph1 to a 2.5-megabase interstitial region of wheat chromosome 5B containing a structure consisting of a segment of subtelomeric heterochromatin that inserted into a cluster of cdc2-related genes after polyploidization. The correlation of the presence of this structure with Ph1 activity in related species, and the involvement of heterochromatin with Ph1 (ref. 6) and cdc2 genes with meiosis, makes the structure a good candidate for the Ph1 locus. 相似文献
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Reboul J Vaglio P Rual JF Lamesch P Martinez M Armstrong CM Li S Jacotot L Bertin N Janky R Moore T Hudson JR Hartley JL Brasch MA Vandenhaute J Boulton S Endress GA Jenna S Chevet E Papasotiropoulos V Tolias PP Ptacek J Snyder M Huang R Chance MR Lee H Doucette-Stamm L Hill DE Vidal M 《Nature genetics》2003,34(1):35-41
To verify the genome annotation and to create a resource to functionally characterize the proteome, we attempted to Gateway-clone all predicted protein-encoding open reading frames (ORFs), or the 'ORFeome,' of Caenorhabditis elegans. We successfully cloned approximately 12,000 ORFs (ORFeome 1.1), of which roughly 4,000 correspond to genes that are untouched by any cDNA or expressed-sequence tag (EST). More than 50% of predicted genes needed corrections in their intron-exon structures. Notably, approximately 11,000 C. elegans proteins can now be expressed under many conditions and characterized using various high-throughput strategies, including large-scale interactome mapping. We suggest that similar ORFeome projects will be valuable for other organisms, including humans. 相似文献
75.
Selective gating of visual signals by microstimulation of frontal cortex 总被引:21,自引:0,他引:21
Several decades of psychophysical and neurophysiological studies have established that visual signals are enhanced at the locus of attention. What remains a mystery is the mechanism that initiates biases in the strength of visual representations. Recent evidence argues that, during spatial attention, these biases reflect nascent saccadic eye movement commands. We examined the functional interaction of saccade preparation and visual coding by electrically stimulating sites within the frontal eye fields (FEF) and measuring its effect on the activity of neurons in extrastriate visual cortex. Here we show that visual responses in area V4 could be enhanced after brief stimulation of retinotopically corresponding sites within the FEF using currents below that needed to evoke saccades. The magnitude of the enhancement depended on the effectiveness of receptive field stimuli as well as on the presence of competing stimuli outside the receptive field. Stimulation of non-corresponding FEF representations could suppress V4 responses. The results suggest that the gain of visual signals is modified according to the strength of spatially corresponding eye movement commands. 相似文献
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Differentiation potential of subsets of CD4-8- thymocytes 总被引:2,自引:0,他引:2
Precursor T cells in the thymus are contained within a subpopulation of thymocytes that lack the markers CD4 and CD8. We have examined the heterogeneity of these cells by flow cytometric analysis, and defined four subpopulations using the cell surface markers Thy-1, J11d and the IL-2 receptor (IL-2R). The J11d+ subset of CD4-8- cells all bear the antigen Thy-1, and some express the IL-2R. Staining and RNA analysis of J11d+ cells suggest that some express receptors of the CD3 gamma delta type, but none express CD3 alpha beta receptors. In fetal thymus organ culture, the J11d+ cells diversify to form 'cortical type' CD4+8+ cells and 'medullary type' cells expressing either CD4 or CD8; in vivo they repopulate the thymus of an irradiated host and seed the periphery with T cells. In contrast, the J11d- subset of CD4-8- thymocytes do not all bear Thy-1 and none express the IL-2R, but some express antigen receptors of the CD3 alpha beta type. They have more limited diversification potential in organ culture, and in vivo fail to recolonize the irradiated host in a homing-independent assay. We conclude that they are not precursor T cells, but rather a side-branch from the main line of T cell differentiation. 相似文献
80.
Molecular mechanisms of spider silk 总被引:2,自引:0,他引:2
Hu X Vasanthavada K Kohler K McNary S Moore AM Vierra CA 《Cellular and molecular life sciences : CMLS》2006,63(17):1986-1999
Spiders spin high-performance silks through the expression and assembly of tissue-restricted fibroin proteins. Spider silks
are composite protein biopolymers that have complex microstructures. Retrieval of cDNAs and genomic DNAs encoding silk fibroins
has revealed an association between the protein sequences and structure-property relationships. However, before spider silks
can be subject to genetic engineering for commercial applications, the complete protein sequences and their functions, as
well as the details of the spinning mechanism, will require additional progress and collaborative efforts in the areas of
biochemistry, molecular biology and material science. Novel approaches to reveal additional molecular constituents embedded
in the spider fibers, as well as cloning strategies to manipulate the genes for expression, will continue to be important
aspects of spider biology research. Here we summarize the molecular characteristics of the different spider fibroins, the
mechanical properties and assembly process of spidroins and the advances in protein expression systems used for recombinant
silk production. We also highlight different technical approaches being used to elucidate the molecular constituents of silk
fibers.
Received 28 February 2006; received after revision 14 April 2006; accepted 22 May 2006
X. Hu and K. Vasanthavada contributed equally to this work. 相似文献