Mank Judith E, Hultin-Rosenberg Lina, Axelsson Erik, Ellegren Hans
Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
Mol Biol Evol. 2007 Dec;24(12):2698-706. doi: 10.1093/molbev/msm208. Epub 2007 Sep 24.
The powerful pressures of sexual and natural selection associated with species recognition and reproduction are thought to manifest in a faster rate of evolution in sex-biased genes, an effect that has been documented particularly for male-biased genes expressed in the reproductive tract. However, little is known about the rate of evolution for genes involved in sexually dimorphic behaviors, which often form the neurological basis of intrasexual competition and mate choice. We used microarray data, designed to uncover sex-biased expression patterns in embryonic chicken brain, in conjunction with data on the rate of sequence evolution for >4,000 coding regions aligned between chicken and zebra finch in order to study the role of selection in governing the molecular evolution for sex-biased and unbiased genes. Surprisingly, we found that female-biased genes, defined across a range of cutoff values, show a higher rate of functional evolution than both male-biased and unbiased genes. Autosomal male-biased genes evolve at a similar rate as unbiased genes. Sex-specific genomic properties, such as heterogeneity in genomic distribution and GC content, and codon usage bias for sex-biased classes fail to explain this surprising result, suggesting that selective pressures may be acting differently on the male and female brain.
与物种识别和繁殖相关的性选择和自然选择的强大压力被认为表现为性别偏向基因的进化速度更快，这种效应在生殖道中表达的雄性偏向基因中尤为明显。然而，对于参与两性异形行为的基因的进化速度知之甚少，两性异形行为通常构成同性竞争和配偶选择的神经基础。我们使用旨在揭示鸡胚胎大脑中性别偏向表达模式的微阵列数据，结合鸡和斑胸草雀之间比对的4000多个编码区的序列进化速率数据，以研究选择在控制性别偏向基因和无偏向基因的分子进化中的作用。令人惊讶的是，我们发现，在一系列截止值范围内定义的雌性偏向基因，其功能进化速率高于雄性偏向基因和无偏向基因。常染色体上的雄性偏向基因与无偏向基因的进化速率相似。性别特异性的基因组特性，如基因组分布和GC含量的异质性，以及性别偏向类别的密码子使用偏好，都无法解释这一惊人结果，这表明选择性压力可能在雄性和雌性大脑上的作用有所不同。
