Data from: Within-population Y-linked genetic variation for lifespan in Drosophila melanogaster

The view that the Y chromosome is of little importance for phenotypic evolution stems from early studies of Drosophila melanogaster. This species’ Y chromosome contains only 13 protein coding genes, is almost entirely heterochromatic, and is not necessary for male viability. Population genetic theory further suggests that non-neutral variation can only be maintained at the Y chromosome under special circumstances. Yet, recent studies suggest that the D. melanogaster Y chromosome trans-regulates hundreds to thousands of X and autosomal genes. This finding suggests that the Y chromosome may play a far more active role in adaptive evolution than has previously been assumed. To evaluate the potential for the Y chromosome to contribute to phenotypic evolution from standing genetic variation, we test for Y-linked variation in lifespan within a population of D. melanogaster. Assessing variation for lifespan provides a powerful test because lifespan i) shows sexual dimorphism, which the Y is primarily predicted to contribute to, ii) is influenced by many genes, which provides the Y with many potential regulatory targets, and iii) is sensitive to heterochromatin remodelling, a mechanism through which the Y chromosome is believed to regulate gene expression. Our results show a small but significant effect of the Y chromosome, and thus suggest that the Y chromosome has the potential to respond to selection from standing genetic variation. Despite its small effect size, Y-linked variation may still be important, in particular when evolution of sexual dimorphism is genetically constrained elsewhere in the genome.

认为Y染色体对表型进化影响甚微的观点，最初源于对黑腹果蝇（Drosophila melanogaster）的早期研究。该物种的Y染色体仅编码13个蛋白质编码基因，几乎完全由异染色质（heterochromatin）构成，且并非雄性存活所必需。群体遗传学理论进一步指出，非中性变异仅能在特殊情境下于Y染色体上得以维持。然而，近期研究表明，黑腹果蝇的Y染色体可反式调控数百至数千个X染色体及常染色体基因。这一发现提示，Y染色体在适应性进化中可能发挥着远比此前假设更为活跃的作用。
为评估Y染色体通过现有遗传变异（standing genetic variation）参与表型进化的潜力，我们在一个黑腹果蝇种群中检测了寿命相关的Y连锁变异。对寿命变异的评估是一项有力的检测手段，原因在于：其一，寿命表现出性二态性（sexual dimorphism），而这正是Y染色体被预测主要参与调控的性状；其二，寿命受众多基因影响，这为Y染色体提供了大量潜在的调控靶点；其三，寿命对异染色质重塑（heterochromatin remodelling）敏感，而这正是被认为的Y染色体调控基因表达的机制。
我们的研究结果显示，Y染色体存在微小但显著的效应，因此提示Y染色体具备响应现有遗传变异带来的选择压力的潜力。尽管效应量较小，但Y连锁变异仍可能具有重要意义，尤其是当基因组其他区域的性二态性进化受到遗传约束时。