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Control of photoreceptor cell fate by the sevenless protein requires a functional tyrosine kinase domain 总被引:29,自引:0,他引:29
The sevenless (sev) gene determines the fate of a single photoreceptor cell type in the eye of Drosophila. It encodes a putative cell-surface protein with homology to tyrosine kinases. Here we have determined the complete structure of the sev gene and have demonstrated that the role of the sev protein in this developmental decision is critically dependent on the tyrosine kinase function. In comparison with other known tyrosine kinases, the sev gene product is unique in size and structure. It is a polypeptide of 2554 amino acids with two putative transmembrane segments. A single amino acid substitution in the ATP-binding site of the putative kinase domain results in the synthesis of an inactive sev protein unable to determine cell fate. 相似文献
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We use the Dpp morphogen gradient in the Drosophila wing disc as a model to address the fundamental question of how a gradient of a growth factor can produce uniform growth. We first show that proper expression and subcellular localization of components in the Fat tumor-suppressor pathway, which have been argued to depend on Dpp activity differences, are not reliant on the Dpp gradient. We next analyzed cell proliferation in discs with uniformly high Dpp or uniformly low Fat signaling activity and found that these pathways regulate growth in?a complementary manner. While the Dpp mediator Brinker inhibits growth in the primordium primarily in the lateral regions, Fat represses growth mostly in the medial region. Together, our results indicate that the activities of both signaling pathways are regulated in a parallel rather than sequential manner and that uniform proliferation is achieved by their complementary action on growth. 相似文献
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Microsatellite variation in Drosophila melanogaster and Drosophila simulans: a reciprocal test of the ascertainment bias hypothesis 总被引:1,自引:1,他引:1
Interspecific comparisons of microsatellite loci have repeatedly shown that
the loci are longer and more variable in the species from which they are
derived (the focal species) than are homologous loci in other (nonfocal)
species. There is debate as to whether this is due to directional evolution
or to an ascertainment bias during the cloning and locus selection
processes. This study tests these hypotheses by performing a reciprocal
study. Eighteen perfect dinucleotide microsatellite loci identified from a
Drosophila simulans library screen and 18 previously identified in an
identical Drosophila melanogaster library screen were used to survey
natural populations of each species. No difference between focal and
nonfocal species was observed for mean PCR fragment length. However,
heterozygosity and number of alleles were significantly higher in the focal
species than in the nonfocal species. The most common allele in the
Zimbabwe population of both species was sequenced for 31 of the 36 loci.
The length of the longest stretch of perfect repeat units is, on average,
longer in the focal species than in the non-focal species. There is a
positive correlation between the length of the longest stretch of perfect
repeats and heterozygosity. The difference in heterozygosity can thus be
explained by a reduction in the length of the longest stretch of perfect
repeats in the nonfocal species. Furthermore, flanking-sequence length
difference was noted between the two species at 58% of the loci sequenced.
These data do not support the predictions of the directional-evolution
hypothesis; however, consistent with the ascertainment bias hypothesis, the
lower variability in nonfocal species is an artifact of the microsatellite
cloning and isolation process. Our results also suggest that the magnitude
of ascertainment bias for repeat unit length is a function of the
microsatellite size distribution in the genomes of different species.
相似文献
80.
Peder Zipperlen Knud Nairz Ivo Rimann Konrad Basler Ernst Hafen Michael Hengartner Alex Hajnal 《Genome biology》2004,6(2):R19
Small insertions or deletions (InDels) constitute a ubiquituous class of sequence polymorphisms found in eukaryotic genomes.
Here, we present an automated high-throughput genotyping method that relies on the detection of fragment-length polymorphisms
(FLPs) caused by InDels. The protocol utilizes standard sequencers and genotyping software. We have established genome-wide
FLP maps for both Caenorhabditis elegans and Drosophila melanogaster that facilitate genetic mapping with a minimum of manual input and at comparatively low cost. 相似文献