Lind Martin I, Carlsson Hanne, Duxbury Elizabeth M L, Ivimey-Cook Edward, Maklakov Alexei A
Animal Ecology, Department of Ecology and Genetics, Uppsala University, Uppsala, SE-75236, Sweden.
School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
Proc Biol Sci. 2021 Feb 10;288(1944):20201728. doi: 10.1098/rspb.2020.1728. Epub 2021 Feb 3.
Ageing evolves because the force of selection on traits declines with age but the proximate causes of ageing are incompletely understood. The 'disposable soma' theory of ageing (DST) upholds that competitive resource allocation between reproduction and somatic maintenance underpins the evolution of ageing and lifespan. In contrast, the developmental theory of ageing (DTA) suggests that organismal senescence is caused by suboptimal gene expression in adulthood. While the DST predicts the trade-off between reproduction and lifespan, the DTA predicts that age-specific optimization of gene expression can increase lifespan without reproduction costs. Here we investigated the consequences for lifespan, reproduction, egg size and individual fitness of early-life, adulthood and post-reproductive onset of RNAi knockdown of five 'longevity' genes involved in key biological processes in . Downregulation of these genes in adulthood and/or during post-reproductive period increases lifespan, while we found limited evidence for a link between impaired reproduction and extended lifespan. Our findings demonstrate that suboptimal gene expression in adulthood often contributes to reduced lifespan directly rather than through competitive resource allocation between reproduction and somatic maintenance. Therefore, age-specific optimization of gene expression in evolutionarily conserved signalling pathways that regulate organismal life histories can increase lifespan without fitness costs.
衰老之所以会演化，是因为对性状的选择力会随着年龄增长而下降，但衰老的直接原因仍未完全明了。衰老的“可抛弃体细胞”理论（DST）认为，繁殖与体细胞维持之间的竞争性资源分配是衰老和寿命演化的基础。相比之下，衰老的发育理论（DTA）则表明，机体衰老由成年期次优基因表达所致。虽然DST预测了繁殖与寿命之间的权衡，但DTA预测，基因表达的年龄特异性优化可延长寿命且无需付出繁殖成本。在此，我们研究了对参与关键生物学过程的五个“长寿”基因进行RNA干扰敲低，在生命早期、成年期及生殖后期开始产生的对寿命、繁殖、卵大小和个体适合度的影响。在成年期和/或生殖后期下调这些基因可延长寿命，而我们发现繁殖受损与寿命延长之间存在关联的证据有限。我们的研究结果表明，成年期的次优基因表达通常直接导致寿命缩短，而非通过繁殖与体细胞维持之间的竞争性资源分配。因此，在调控机体生命历程的进化保守信号通路中进行基因表达的年龄特异性优化，可在不影响适合度的情况下延长寿命。
