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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转录因子驱动雄性和雌性果蝇性腺基因年龄和组织特异性之间的相反关系

进化上年轻的基因通常优先在不同物种的睾丸中表达。虽然众所周知，较老的基因通常比较年轻的基因表达更广泛，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表达，或者在某些组织中比其他组织更快表达。使用果蝇基因表达数据，我们证实了之前的发现，即年轻的基因不成比例地偏向睾丸，而较老的基因不成比例地偏向卵巢。我们发现基因年龄和表达之间的关系在卵巢中比任何其他组织都更强，而在睾丸中最弱。我们对果蝇睾丸进行了 ATAC-seq，发现虽然所有年龄的基因在睾丸中比在卵巢中更有可能具有开放启动子染色质，但启动子染色质本身并不能解释较老基因的卵巢偏向性。相反，我们发现上游转录因子（TF）表达可以高度预测卵巢中的基因表达，但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到 TF 表达和开放启动子染色质的影响。我们认为，睾丸具有独特的能力来表达由相对较少的 TF 控制的较年轻的基因，而具有较多 TF 伴侣的较老的基因则广泛表达，最有可能在卵巢中达到峰值表达。睾丸允许广泛的基线表达，对调节变化相对不敏感，而卵巢转录组对反式调节​​更敏感，并且具有更高的基因表达上限。