The deficit of male-biased genes on the D. melanogaster X chromosome is expression-dependent: a consequence of dosage compensation?
In Drosophila, there is a consistent deficit of male-biased genes on the X chromosome. It has been suggested that male-biased genes may evolve from initially unbiased genes as a result of increased expression levels in males. If transcription rates are limited, a large increase in expression in the testis may be harder to achieve for single-copy X-linked genes than for autosomal genes, because they are already hypertranscribed due to dosage compensation. This hypothesis predicts that the larger the increase in expression required to make a male-biased gene, the lower the chance of this being achievable if it is located on the X chromosome. Consequently, highly expressed male-biased genes should be located on the X chromosome less often than lowly expressed male-biased genes. This pattern is observed in our analysis of publicly available data, where microarray data or EST data are used to detect male-biased genes in D. melanogaster and to measure their expression levels. This is consistent with the idea that limitations in transcription rates may prevent male-biased genes from accumulating on the X chromosome.
Vicoso
Beatriz
B
Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Road, Edinburgh, EH9-3JT, UK. b.vicoso@ed.ac.uk
Charlesworth
Brian
B
D000818:Animals; D015982:Bias; D004303:Dosage Compensation, Genetic; D004331:Drosophila melanogaster / Q000235:genetics*; D020224:Expressed Sequence Tags; D005260:Female; D005786:Gene Expression Regulation; D017344:Genes, Insect / Q000235:genetics*; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D010802:Phylogeny; D012727:Sex Characteristics; D014960:X Chromosome / Q000235:genetics*