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Genomic structure and comparison of mouse tissue-specific alkaline phosphatase genes 总被引:6,自引:0,他引:6
A full-length human placental alkaline phosphatase (AP) cDNA was used to identify and clone related genes from mouse genomic libraries. We report the cloning, sequence, and structural comparison of the mouse embryonic and intestinal AP genes and a putative AP pseudogene. All three mouse genes are composed of 11 exons interrupted by 10 small introns (70-261 bp) with an organization analogous to that of the three human tissue-specific AP genes. Introns interrupt the coding sequences at identical positions in all three mouse and human tissue-specific AP genes. The deduced amino acid sequence of the isozymes predicts proproteins of 529, 559, and 466 amino acids for embryonic AP, intestinal AP, and pseudo-AP, respectively. A repetitive sequence inserted in exon XI of the mouse intestinal AP gene codes for a unique stretch of 41 amino acids, 20 of which are threonines. This insertion has disrupted a region recognized as being responsible for phosphatidylinositol anchorage of human placental AP to the cytoplasmic membrane. Phylogenetic analysis indicates that the three mouse AP isozymes form a distinct group separate from the human tissue-specific AP isozymes, suggesting the taxon-specific evolution of the AP genes as opposed to independent evolution of AP genes expressed in specific tissues. 相似文献
214.
Conceptual models of drought‐adaptive traits have been used in breeding to accumulate complementary physiological traits (PT) in selected progeny, resulting in distribution of advanced lines to rain‐fed environments worldwide by the International Maize and Wheat Improvement Center (CIMMYT). Key steps in PT breeding at CIMMYT include characterisation of crossing block lines for stress adaptive mechanisms, strategic crossing among parents that encompass as many target traits as possible and early generation selection (EGS) of bulks for canopy temperature (CT). The approach has been successful using both elite × elite crosses as well as three way crosses involving stress adapted landraces. Other EGS techniques that are amenable to high throughput include measurement of spectral reflectance indices and stomatal aperture‐related traits. Their genetic‐ and cost‐effectiveness are supported by realisation of genetic yield gains in response to trait selection, and by economic analysis, respectively. Continual reselection within restricted gene pools is likely to lead to diminishing returns, however, exotic parents can be used to introduce new allelic diversity. Examples include landraces from the primary gene pool, and products of inter‐specific hybridisation with the secondary gene pool consisting of closely related wheat genomes. Both approaches have been successful in introducing stress‐adaptive traits. The main problem with knowing which genetic resource to use in wide‐crossing is the uncertainty with which phenotypic expression can be extrapolated from one genome/genepool to another because of their unimproved or undomesticated genetic backgrounds. Nonetheless, their PT expression can be measured and used as a basis for investing in crossing or wide crossing. Discovering the genetic basis of PT is highly complex because putative QTLs may interact with environment and genetic background, including genes of major effect. Detection of QTLs was improved in mapping populations where flowering time was controlled, while new mapping populations have been designed by screening potential parents that do not contrast in the Rht, Ppd and Vrn alleles. Association genetics mapping is another approach that can be employed for gene discovery using exclusively agronomically improved material, thereby minimising the probability of identifying yield QTLs whose alleles have been already improved by conventional breeding. 相似文献
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Dorso-marginal epithelium, a distinct crescent-shaped region in the early gastrula of Bufo arenarum, appears after involution as a narrow dorso-median strip of archenteric endoderm close to the notochord. In explant cultures,
this layer showed an extreme dorsalizing activity, promoting the formation of notochordal structures from ventro-mesodermal
cells. In the presence of ectoderm, this inductive activity was expanded resulting in a wide range of dorso-lateral components
such as notochord, muscle, nephric tubules, mesothelium and mesenchyme. The mesodermal origin of these derivatives was confirmed
by the use of FDA (fluorescein-dextran-amine)-labelled explants. Extensive mesodermal development in cultures seems to require
cell contacts between the inner aspect of the dorso-marginal epithelium and mesodermal cells. When such contacts were prevented,
cultures would only differentiate erythrocytes as a result of a purely ectodermal stimulus. Bisection of the dorso-marginal
epithelium in whole embryos resulted in the development of a duplicated set of axial structures, clearly showing the role
of the epithelium as a dorsal organizer.
Received: 30 July 1996 / Accepted: 20 February 1997 相似文献