Evolutionarily young genes are usually preferentially expressed in the testis across species. While it is known that older genes are generally more broadly expressed than younger genes, the properties that shaped this pattern are unknown. Older genes may gain expression across other tissues uniformly, or faster in certain tissues than others. Using Drosophila gene expression data, we confirmed previous findings that younger genes are disproportionately testis-biased and older genes are disproportionately ovary-biased. We found that the relationship between gene age and expression is stronger in the ovary than any other tissue, and weakest in testis. We performed ATAC-seq on Drosophila testis and found that while genes of all ages are more likely to have open promoter chromatin in testis than in ovary, promoter chromatin alone does not explain the ovary-bias of older genes. Instead, we found that upstream transcription factor (TF) expression is highly predictive of gene expression in ovary, but not in testis. In ovary, TF expression is more predictive of gene expression than open promoter chromatin, whereas testis gene expression is similarly influenced by both TF expression and open promoter chromatin. We propose that the testis is uniquely able to expresses younger genes controlled by relatively few TFs, while older genes with more TF partners are broadly expressed with peak expression most likely in ovary. The testis allows widespread baseline expression that is relatively unresponsive to regulatory changes, whereas the ovary transcriptome is more responsive to trans-regulation and has a higher ceiling for gene expression.

中文翻译：

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转录因子驱动果蝇性腺和雌性果蝇基因年龄与组织特异性之间的相反关系

进化上年轻的基因通常优先跨物种在睾丸中表达。虽然已知年长的基因通常比年幼的基因更广泛地表达，但形成这种模式的特性尚不清楚。较老的基因可能在其他组织中均匀地表达，或者在某些组织中比其他组织更快地表达。使用果蝇基因表达数据，我们证实了先前的发现，即年轻基因的睾丸偏向不成比例，而较老基因的卵巢偏向不成比例。我们发现，基因年龄与表达之间的关系在卵巢中比其他任何组织都强，而在睾丸中最弱。我们在果蝇睾丸上进行了ATAC-seq，发现尽管各个年龄段的基因在睾丸中比在卵巢中更可能具有开放的启动子染色质，仅启动子染色质不能解释较老基因的卵巢偏向。相反，我们发现上游转录因子（TF）的表达可高度预测卵巢中的基因表达，而不能预测睾丸中的基因表达。在卵巢中，TF表达比开放启动子染色质更能预测基因表达，而睾丸基因表达同样受TF表达和开放启动子染色质影响。我们认为，睾丸独特地能够表达由相对较少的TF控制的年轻基因，而具有更多TF伴侣的较老基因则广泛表达，最有可能在卵巢中表达高峰。睾丸允许广泛的基线表达，相对于调节变化相对不响应，而卵巢转录组对反式调节​​响应更强，并且基因表达的上限更高。