Experimentally increased codon bias in the Drosophila Adh gene leads to an increase in larval, but not adult, alcohol dehydrogenase activity.
Although most amino acids can be encoded by more than one codon, the synonymous codons are not used with equal frequency. This phenomenon is known as codon bias and appears to be a universal feature of genomes. The translational selection hypothesis posits that the use of optimal codons, which match the most abundant species of isoaccepting tRNAs, results in increased translational efficiency and accuracy. Previous work demonstrated that the experimental reduction of codon bias in the Drosophila alcohol dehydrogenase (Adh) gene led to a significant decrease in ADH protein expression. In this study we performed the converse experiment: we replaced seven suboptimal leucine codons that occur naturally in the Drosophila melanogaster Adh gene with the optimal codon. We then compared the in vivo ADH activities imparted by the wild-type and mutant alleles. The introduction of optimal leucine codons led to an increase in ADH activity in third-instar larvae. In adult flies, however, the introduction of optimal codons led to a decrease in ADH activity. There is no evidence that other selectively constrained features of the Adh gene, or its rate of transcription, were altered by the synonymous replacements. These results are consistent with translational selection for codon bias being stronger in the larval stage and suggest that there may be a selective conflict over optimal codon usage between different developmental stages.
Hense
Winfried
W
Department of Biology, American University, Washington, DC 20016, USA.
Anderson
Nathan
N
Hutter
Stephan
S
Stephan
Wolfgang
W
Parsch
John
J
Carlini
David B
DB
D000375:Aging; D000426:Alcohol Dehydrogenase / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000483:Alleles; D000818:Animals; D001483:Base Sequence; D003062:Codon / Q000235:genetics*; D029721:Drosophila Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D019143:Evolution, Molecular; D005260:Female; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D007814:Larva / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D007930:Leucine; D008297:Male; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D014176:Protein Biosynthesis; D014170:Transformation, Genetic; D019076:Transgenes / Q000235:genetics
D003062:Codon; D029721:Drosophila Proteins; C073796:ADH protein, Drosophila; D000426:Alcohol Dehydrogenase; D007930:Leucine