Tissue- and Stage-Dependent Dosage Compensation on the Neo-X Chromosome in Drosophila pseudoobscura
Tissue- and Stage-Dependent Dosage Compensation on the Neo-X Chromosome in Drosophila pseudoobscura
复制标题
DOI：
10.1093/molbev/mst239
复制
发表时间：
2014-03-01
影响因子：
10.7
通讯作者：
Gojobori, Takashi
中科院分区：
文献类型：
--
作者：
Nozawa, Masafumi;Fukuda, Nana;Gojobori, Takashi
性染色体剂量补偿（DC）在各种生物中被广泛接受。这一概念主要得到染色体之间和性别之间基因表达的比较的支持。然而，X染色体和常染色体上的基因大多不同源，即使在DC下，这些染色体上的平均基因表达水平也可能不相同，这使得染色体之间的比较变得复杂。许多具有性别偏见表达的基因也使性别之间的比较变得困难。为了克服这些问题，我们通过比较拟暗果蝇中新X连锁基因的表达与其他果蝇物种中其常染色体直系同源基因的表达来研究DC。在DC下，男性中前者与后者的比例为1，而在没有DC的情况下，前者与后者的比例为0.5。我们发现，成人全身的比率类似于0.85，表明成人整体的新X染色体上的DC是不完整的。该比率（类似于0.90）也显着小于1的成年人身体没有性腺，而它是类似于1.0的成年人的头。这些结果表明，DC在组织之间是不同的。我们对该比率的滑动窗口分析还显示，在所分析的所有组织中，男性中新X连锁基因的上调发生在染色体范围内，表明了全局上调机制。然而，我们发现基因功能也影响DC的水平。此外，大多数最近转移到X的基因在幼虫阶段就已经处于DC之下，而不是在成虫阶段。这些结果表明，DC在果蝇物种中以组织/阶段依赖的方式运作。
Sex chromosome dosage compensation (DC) is widely accepted in various organisms. This concept is mostly supported by comparisons of gene expression between chromosomes and between sexes. However, genes on the X chromosome and autosomes are mostly not homologous, and the average gene expression level on these chromosomes may not be the same even under DC, which complicates comparisons between chromosomes. Many genes with sex-biased expression also make comparisons between sexes difficult. To overcome these issues, we investigated DC by comparing the expression of neo-X-linked genes in Drosophila pseudoobscura with those of their autosomal orthologs in other Drosophila species. The ratio of the former to the latter in males would be 1 under DC, whereas it becomes 0.5 without DC. We found that the ratio was similar to 0.85 for adult whole bodies, indicating that the DC is incomplete on the neo-X chromosome in adults as a whole. The ratio (similar to 0.90) was also significantly less than 1 for adult bodies without gonads, whereas it was similar to 1.0 for adult heads. These results indicate that DC varies among tissues. Our sliding-window analysis of the ratio also revealed that the upregulation of neo-X-linked genes in males occurred chromosome wide in all tissues analyzed, indicating global upregulation mechanisms. However, we found that gene functions also affected the levels of DC. Furthermore, most of the genes recently moved to the X were already under DC at the larval stage but not at the adult stage. These results suggest that DC in Drosophila species operates in a tissue/stage-dependent manner.