Paquin Frédérique, Cristescu Melania E, Blier Pierre U, Lemieux Hélène, Dufresne France
Département de biologie, Université du Québec à Rimouski, 300 allée des ursulines, Rimouski, Québec G5L 3A1, Canada.
Department of Biology, McGill University, 1205 Docteur Penfield, Montréal, Québec H3A 1B1, Canada.
Mitochondrion. 2025 Jan;80:101976. doi: 10.1016/j.mito.2024.101976. Epub 2024 Oct 31.
The impact of mutations on the mitochondria deserves specific interest due to the crucial role played by these organelles on numerous cellular functions. This study examines the effects of repeated bottlenecks on mitochondrial function and fitness. Daphnia pulex mutation accumulation lines (MA) lines were maintained for over 120 generations under copper and no copper conditions. Following the MA propagation, Daphnia from MA lines were raised under optimal and high temperatures for two generations before assessing mitochondrial and phenotypic traits. Spontaneous mutation accumulation under copper led to a later age at maturity and lowered fecundity in the MA lines. Mitochondrial respiration was found to be 10% lower in all mutation accumulation (MA) lines as compared to the non-MA control. MtDNA copy number was elevated in MA lines compared to the control under optimal temperature suggesting a compensatory mechanism. Three MA lines propagated under low copper had very low mtDNA copy number and fitness, suggesting mutations might have affected genes involved in mtDNA replication or mitochondrial biogenesis. Overall, our study suggests that mutation accumulation had an impact on life history traits, mtDNA copy number, and mitochondrial respiration. Some phenotypic effects were magnified under high temperatures. MtDNA copy number appears to be an important mitigation factor to allow mitochondria to cope with mutation accumulation up to a certain level beyond which it can no longer compensate.
由于线粒体在众多细胞功能中发挥着关键作用，突变对线粒体的影响值得特别关注。本研究考察了重复瓶颈效应在线粒体功能和适应性方面的影响。在有铜和无铜条件下，将蚤状溞突变积累品系（MA）维持超过120代。在MA繁殖之后，将来自MA品系的蚤状溞在最适温度和高温下饲养两代，然后评估线粒体和表型特征。在有铜条件下的自发突变积累导致MA品系成熟年龄延迟且繁殖力降低。与非MA对照相比，所有突变积累（MA）品系的线粒体呼吸均降低了10%。在最适温度下，MA品系的线粒体DNA拷贝数相比于对照有所升高，提示存在一种补偿机制。在低铜条件下繁殖的三个MA品系的线粒体DNA拷贝数和适应性非常低，表明突变可能影响了参与线粒体DNA复制或线粒体生物发生的基因。总体而言，我们的研究表明突变积累对生活史特征、线粒体DNA拷贝数和线粒体呼吸有影响。在高温下，一些表型效应会被放大。线粒体DNA拷贝数似乎是一个重要的缓解因素，可使线粒体在一定水平内应对突变积累，超过该水平则无法再进行补偿。
