Rashidi Armin, Kirkwood Thomas B L, Shanley Daryl P
Institute for Ageing and Health, Campus for Ageing and Vitality, Newcastle University, Newcastle Upon Tyne, NE4 5PL, UK,
Subcell Biochem. 2012;57:315-30. doi: 10.1007/978-94-007-2561-4_14.
Mother cell-specific ageing is a well-known phenomenon in budding yeast Saccharomyces cerevisiae. Asymmetric segregation of damage and its accumulation in the mother cell has been proposed as one important mechanism. There are, however, unicellular organisms such as the fission yeast Schizosaccharomyces pombe, which replicates with almost no asymmetry of segregation of damage and the pathogenic yeast Candida albicans, which falls around the middle of the segregation spectrum far from both complete symmetry and complete asymmetry. The ultimate evolutionary cause that determines the way damage segregates in a given organism is not known. Here we develop a mathematical model to examine the selective forces that drive the evolution of asymmetry and discover the conditions in which symmetry is the optimal strategy. Three main processes are included in the model: protein synthesis (growth), protein damage, and degradation of damage. We consider, for the first time, the costs to the cell that might accompany the evolution of asymmetry and incorporate them into the model along with known trade-offs between reproductive and maintenance investments and their energy requirements. The model provides insight into the relationship between ecology and cellular trade-off physiology in the context of unicellular ageing, and applications of the model may extend to multicellular organisms.
母细胞特异性衰老在出芽酵母酿酒酵母中是一种众所周知的现象。损伤的不对称分离及其在母细胞中的积累被认为是一种重要机制。然而，存在一些单细胞生物，如裂殖酵母粟酒裂殖酵母，其复制时几乎不存在损伤分离的不对称性，以及致病酵母白色念珠菌，它处于分离谱的中间位置，既远离完全对称也远离完全不对称。决定给定生物体中损伤分离方式的最终进化原因尚不清楚。在此，我们开发了一个数学模型来研究驱动不对称性进化的选择力，并发现对称是最优策略的条件。该模型包括三个主要过程：蛋白质合成（生长）、蛋白质损伤和损伤降解。我们首次考虑了不对称性进化可能给细胞带来的成本，并将其与已知的生殖和维持投资及其能量需求之间的权衡一起纳入模型。该模型在单细胞衰老的背景下洞察了生态与细胞权衡生理学之间的关系，并且该模型的应用可能扩展到多细胞生物。
