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Donald R. McCarty Christian B. Carson Mark Lazar S. Caprice Simonds 《Genesis (New York, N.Y. : 2000)》1989,10(6):473-481
The viviparous-1 (vp1) locus in maize is a developmental gene that controls diverse aspects of the maturation phase of seed development. Mutations of vp1 alter embryo sensitivity to the hormone abscisic acid and block formation of anthocyanin pigment. Molecular cloning of a Robertson Mutator-induced mutant allele, vp1-mum-1, by transposable element tagging has allowed analysis of several transposon-induced vp1 mutants. In the vp1-Mc mutation, the gene is disrupted by 4.0 kbp insertion, which results in expression of a 3′ truncated mRNA. Phenotypically, this allele is at least partially functional in causing embryo dormancy, but is ineffective in controlling anthocyanin expression. This result suggests that disruption of the C-terminal domain of the Vp1 protein specifically affects regulation of the anthocyanin pathway. A second Mutator- derived allele, vp1-mum2, exhibits an unusual form of somatic mutability in which endosperm cells revert from wild-type vp1 expression to a mutant condition. The vp1-mum2 allele contains a 1.5 kbp Insertion that has no detectable homology to known Mu elements. This element is retained In wild-type germinal revertants derived from vp1-mum2 An apparent DNA modification affecting cleavage at an internal Sstl restriction site in the element correlates with vp1-mum2 states that exhibit wild-type Vp1 expression. A model involving mitotic assortment of modified and unmodified DNA strands during development is proposed for vp1-mum2 somatic mutation. 相似文献
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To analyze the sexual behavior of male black-legged deer ticks Ixodes dammini,we collected ticks infesting 202 white-tailed deer. On average, 17.7 males and 8.8 females infested each deer. Field-collected males copulated with a mean of 2.25 females, and virgin males mated with 2.4 females. On experimental hosts, males established sexual contact with feeding females and repelled other males, and about half remained paired after their mate detached. Engorged females continue to be receptive, and males mate more readily with them than with nonfed females. We conclude that male I. damminiare endowed with a repertoire of behaviors which favor an opportunistic mating before seeking a host and a preference for mating with feeding females on the host accompanied by tenacious mate guarding. 相似文献
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Ligand-induced endocytosis of the EGF receptor is blocked by mutational inactivation and by microinjection of anti-phosphotyrosine antibodies 总被引:29,自引:0,他引:29
Early events in ligand-induced endocytosis of the EGF receptor have been examined. A mutant EGF receptor devoid of intrinsic protein-tyrosine kinase activity bound EGF and dimerized normally yet failed to undergo ligand-induced internalization. Immunofluorescence microscopy revealed that receptors lacking kinase activity failed to undergo the ligand-induced internalization characteristic of receptors with kinase activity. Monoclonal anti-phosphotyrosine antibodies effectively inhibited phosphorylation of exogenous substrates in vitro and, when microinjected into cells containing active EGF receptors, prevented internalization of the receptor when cells were subsequently challenged with EGF. These results point to a crucial role for the kinase activity of the EGF receptor in the process of ligand-induced endocytosis of receptors, and imply that a phosphorylated substrate(s) is required. 相似文献
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Role of fructose 2,6-bisphosphate in the regulation of glycolysis and gluconeogenesis in chicken liver 总被引:3,自引:0,他引:3
O K Chaekal J C Boaz T Sugano R A Harris 《Archives of biochemistry and biophysics》1983,225(2):771-778
Glucagon and dibutyryl cyclic AMP inhibited glucose utilization and lowered fructose 2,6-bisphosphate levels of hepatocytes prepared from fed chickens. Partially purified preparations of chicken liver 6-phosphofructo-1-kinase and fructose 1,6-bisphosphatase were activated and inhibited by fructose 2,6-bisphosphate, respectively. The sensitivities of these enzymes and the changes observed in fructose 2,6-bisphosphate levels are consistent with an important role for this allosteric effector in hormonal regulation of carbohydrate metabolism in chicken liver. In contrast, oleate inhibition of glucose utilization by chicken hepatocytes occurred without change in fructose, 2,6-bisphosphate levels. Likewise, pyruvate inhibition of lactate gluconeogenesis in chicken hepatocytes cannot be explained by changes in fructose 2,6-bisphosphate levels. Exogenous glucose caused a marked increase in fructose 2,6-bisphosphate content of hepatocytes from fasted but not fed birds. Both glucagon and lactate prevented this glucose effect. Fasted chicken hepatocytes responded to lower glucose concentrations than fasted rat hepatocytes, perhaps reflecting the species difference in hexokinase isozymes. 相似文献
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