Evolutionary consequences of nascent multicellular life cycles.
Evolutionary consequences of nascent multicellular life cycles.
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DOI：
10.7554/elife.84336
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发表时间：
2023-10-27
期刊：
影响因子：
7.7
通讯作者：
Ratcliff WC
中科院分区：
文献类型：
--
作者：
Pentz JT;MacGillivray K;DuBose JG;Conlin PL;Reinhardt E;Libby E;Ratcliff WC
在向多细胞生物进化过渡的过程中，一个关键步骤是多细胞群体作为具有适应能力的生物个体的起源。理论支持的比较工作表明，克隆发展应促进这一转变，虽然这一假设从未在一个单一的模型系统中进行过测试。我们进化了20个复制群体的其他同基因克隆繁殖的“雪花”酵母（Δ ace 2/Acrace 2）和聚集性的“絮状”酵母（GAL 1 p：：FLO 1/GAL 1 p：：FLO 1），每天选择在液体培养基中快速生长，这有利于更快的细胞分裂，然后选择快速沉降，这有利于更大的多细胞群体。虽然这两种基因型都适应了这种制度，在群体选择阶段生长得更快，存活率更高，但进化动力学存在明显差异。聚集絮凝酵母获得几乎所有的增加健身从更快的增长，而不是提高群体生存;表明选择主要作用于细胞水平。相比之下，克隆雪花酵母主要受益于更高的群体依赖适应性，表明达尔文个体性水平从细胞到群体的转变。通过基因组测序和数学建模，我们表明，克隆生命周期中的遗传瓶颈也驱动更高的遗传漂移率，这一结果与复杂的影响，这种进化过渡。我们的研究结果强调了早期多细胞生命周期在多细胞适应过程中的核心作用。
A key step in the evolutionary transition to multicellularity is the origin of multicellular groups as biological individuals capable of adaptation. Comparative work, supported by theory, suggests clonal development should facilitate this transition, although this hypothesis has never been tested in a single model system. We evolved 20 replicate populations of otherwise isogenic clonally reproducing ‘snowflake’ yeast (Δace2/∆ace2) and aggregative ‘floc’ yeast (GAL1p::FLO1 /GAL1p::FLO1) with daily selection for rapid growth in liquid media, which favors faster cell division, followed by selection for rapid sedimentation, which favors larger multicellular groups. While both genotypes adapted to this regime, growing faster and having higher survival during the group-selection phase, there was a stark difference in evolutionary dynamics. Aggregative floc yeast obtained nearly all their increased fitness from faster growth, not improved group survival; indicating that selection acted primarily at the level of cells. In contrast, clonal snowflake yeast mainly benefited from higher group-dependent fitness, indicating a shift in the level of Darwinian individuality from cells to groups. Through genome sequencing and mathematical modeling, we show that the genetic bottlenecks in a clonal life cycle also drive much higher rates of genetic drift—a result with complex implications for this evolutionary transition. Our results highlight the central role that early multicellular life cycles play in the process of multicellular adaptation.