scholarly journals Natural selection in a population of Drosophila melanogaster explained by changes in gene expression caused by sequence variation in core promoter regions

2016 ◽  
Vol 16 (1) ◽  
Author(s):  
Mitsuhiko P. Sato ◽  
Takashi Makino ◽  
Masakado Kawata
Keyword(s):  
Gene Expression ◽  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Sequence Variation ◽  
Core Promoter ◽  
Promoter Regions

scholarly journals Inter- and Intraspecific Variation in Drosophila Genes with Sex-Biased Expression

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Lena Müller ◽  
Sonja Grath ◽  
Korbinian von Heckel ◽  
John Parsch
Keyword(s):  
Gene Expression ◽  
Drosophila Melanogaster ◽  
Molecular Evolution ◽  
Protein Sequence ◽  
Sequence Variation ◽  
Purifying Selection ◽  
Sexually Dimorphic ◽  
Expression Divergence ◽  
Sexually Dimorphic Expression ◽  
Dimorphic Expression

Genes with sexually dimorphic expression (sex-biased genes) often evolve rapidly and are thought to make an important contribution to reproductive isolation between species. We examined the molecular evolution of sex-biased genes in Drosophila melanogaster and D. ananassae, which represent two independent lineages within the melanogaster group. We find that strong purifying selection limits protein sequence variation within species, but that a considerable fraction of divergence between species can be attributed to positive selection. In D. melanogaster, the proportion of adaptive substitutions between species is greatest for male-biased genes and is especially high for those on the X chromosome. In contrast, male-biased genes do not show unusually high variation within or between populations. A similar pattern is seen at the level of gene expression, where sex-biased genes show high expression divergence between species, but low divergence between populations. In D. ananassae, there is no increased rate of adaptation of male-biased genes, suggesting that the type or strength of selection acting on sex-biased genes differs between lineages.

scholarly journals GAA Trinucleotide Repeat Region Regulates M9/pMGA Gene Expression in Mycoplasma gallisepticum

2000 ◽  
Vol 68 (2) ◽  
pp. 871-876 ◽  
Author(s):  
Li Liu ◽  
Kevin Dybvig ◽  
Victor S. Panangala ◽  
Vicky L. van Santen ◽  
Christopher T. French
Keyword(s):  
Gene Expression ◽  
Trinucleotide Repeat ◽  
Mycoplasma Gallisepticum ◽  
Avian Host ◽  
Phase Variable ◽  
Repeat Region ◽  
Chromosomal Dna ◽  
Promoter Regions ◽  
Variable Expression ◽  
Gaa Repeats

ABSTRACT Mycoplasma gallisepticum, the cause of chronic respiratory infections in the avian host, possesses a family of M9/pMGA genes encoding an adhesin(s) associated with hemagglutination. Nucleotide sequences of M9/pMGA gene family members indicate extensive sequence similarity in the promoter regions of both the transcribed and silent genes. The mechanism that regulates M9/pMGA gene expression is unknown, but studies have revealed an apparent correlation between gene expression and the number of tandem GAA repeat motifs located upstream of the putative promoter. In this study, transposon Tn4001was used as a vector with the Escherichia coli lacZ gene as the reporter system to examine the role of the GAA repeats in M9/pMGA gene expression in M. gallisepticum. A 336-bp M9 gene fragment (containing the GAA repeat region, the promoter, and the translation start codon) was amplified by PCR, ligated with alacZ gene from E. coli, and inserted into the Tn4001-containing plasmid pISM2062. This construct was transformed into M. gallisepticum PG31. Transformants were filter cloned on agar supplemented with 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside (X-Gal) to monitor lacZ gene expression on the basis of blue/white color selection. Several cycles of filter cloning resulted in cell lineages in which lacZ gene expression alternated between the On and Off states in successive generations of progeny clones. The promoter regions of the M9-lacZ hybrid genes of individual progeny clones were amplified by PCR and sequenced. The only differences between the promoter regions of the blue and white colonies were in the number of GAA repeats. Clones that expressedlacZ had exactly 12 tandem copies of the GAA repeat. Clones that did not express lacZ invariably had either more than 12 (14 to 16) or fewer than 12 (5 to 11) GAA repeats. Southern analysis of M. gallisepticum chromosomal DNA confirmed that the phase-variable expression of the lacZ reporter gene was not caused by Tn4001 transposition. These data strongly indicate that changes in the length of the GAA repeat region are responsible for regulating M9/pMGA gene expression.

Interactions Between Natural Selection, Recombination and Gene Density in the Genes of Drosophila

Genetics ◽  
2002 ◽  
Vol 160 (2) ◽  
pp. 595-608 ◽  
Author(s):  
Jody Hey ◽  
Richard M Kliman
Keyword(s):  
Gene Expression ◽  
Natural Selection ◽  
Recombination Rate ◽  
Codon Bias ◽  
Gene Density ◽  
Drosophila Genome ◽  
Functional Variation ◽  
Subtle Effect ◽  
Efficiency Of Selection ◽  
The Impact

AbstractIn Drosophila, as in many organisms, natural selection leads to high levels of codon bias in genes that are highly expressed. Thus codon bias is an indicator of the intensity of one kind of selection that is experienced by genes and can be used to assess the impact of other genomic factors on natural selection. Among 13,000 genes in the Drosophila genome, codon bias has a slight positive, and strongly significant, association with recombination—as expected if recombination allows natural selection to act more efficiently when multiple linked sites segregate functional variation. The same reasoning leads to the expectation that the efficiency of selection, and thus average codon bias, should decline with gene density. However, this prediction is not confirmed. Levels of codon bias and gene expression are highest for those genes in an intermediate range of gene density, a pattern that may be the result of a tradeoff between the advantages for gene expression of close gene spacing and disadvantages arising from regulatory conflicts among tightly packed genes. These factors appear to overlay the more subtle effect of linkage among selected sites that gives rise to the association between recombination rate and codon bias.

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