Data from: X-linkage is not a general inhibitor of tissue-specific gene expression in Drosophila melanogaster

As a consequence of its difference in copy number between males and females, the X chromosome is subject to unique evolutionary forces and gene regulatory mechanisms. Previous studies of Drosophila melanogaster have shown that the expression of X-linked, testis-specific reporter genes is suppressed in the male germline. However, it is not known whether this phenomenon is restricted to testis-expressed genes or if it is a more general property of genes with tissue-specific expression, which are also underrepresented on the X chromosome. To test this, we compared the expression of three tissue-specific reporter genes (ovary, accessory gland and Malpighian tubule) inserted at various autosomal and X-chromosomal locations. In contrast to testis-specific reporter genes, we found no reduction of X-linked expression in any of the other tissues. In accessory gland and Malpighian tubule, we detected higher expression of the X-linked reporter genes, which suggests that they are at least partially dosage compensated. We found no difference in the tissue-specificity of X-linked and autosomal reporter genes. These findings indicate that, in general, the X chromosome is not a detrimental environment for tissue-specific gene expression and that the suppression of X-linked expression is limited to the male germline.

由于X染色体（X chromosome）在雌雄个体间的拷贝数存在差异，其受制于独特的进化压力与基因调控机制。此前针对黑腹果蝇（Drosophila melanogaster）的研究表明，X连锁（X-linked）的睾丸特异性报告基因（reporter gene）在雄性生殖系中的表达会受到抑制。然而目前尚不清楚该现象是否仅局限于睾丸表达的基因，亦或是组织特异性表达基因的普遍特性——这类基因在X染色体上的占比同样偏低。为验证这一问题，我们比较了插入至不同常染色体与X染色体位点的三种组织特异性报告基因的表达情况，这三种基因分别对应卵巢、附腺与马氏管（Malpighian tubule）。与睾丸特异性报告基因的情况相反，我们未在其余任一组织中观察到X连锁基因的表达下调。在附腺与马氏管组织中，我们检测到X连锁报告基因的表达水平更高，这表明这类基因至少存在部分剂量补偿（dosage compensation）效应。我们未发现X连锁与常染色体报告基因在组织特异性方面存在差异。上述研究结果表明，总体而言X染色体并非组织特异性基因表达的不利环境，且X连锁基因的表达抑制现象仅局限于雄性生殖系中。