Document Type
Dissertation
Degree
Doctor of Philosophy
Major
Biology, Molecular and Cellular Biology
Date of Defense
11-3-2022
Graduate Advisor
James Umen, PhD
Committee
Wendy Olivas, PhD
Lon Chubiz, PhD
Sam Wang, PhD
Abstract
Size homeostasis is achieved by a balance between cell growth and cell division, but the underlying mechanisms are yet fully understood. Green alga Chlamydomonas reinhardtii (Chlamydomonas) is a unique model for size control. Instead of the canonical binary fission cell cycle, Chlamydomonas uses a multiple fission cell cycle where a prolonged G1 phase is followed by rapid alternative n rounds of S/M (DNA synthesis and mitosis) cycles to produce 2n daughter cells. Two size checkpoints show size-dependence: the Commitment checkpoint governs a minimum size for a cell to divide at least once, and the S/M checkpoint governs the division number to ensure uniformly sized new-born daughters. A conserved retinoblastoma (RB) tumor suppressor is known to be the master regulator for cell cycle progression in animal cells and higher plants. Previous studies support the idea that the RB pathway in Chlamydomonas regulates the S/M checkpoint. I established microscopy-based mathematic models to explain the mitotic behaviors in the multiple fission cell cycle of Chlamydomonas and characterized additional sizer proteins functioning in the Chlamydomonas RB pathway. I related the molecular mechanisms for size control in yeast, higher plants, and animal early embryogenesis, and further concluded that size sensing in eukaryotes can be explained by general titration mechanisms where cell cycle inhibitors titrate against DNA(/genome) to govern the cell cycle progression.
Recommended Citation
Liu, Dianyi, "Cell Size Control Mechanisms in the Multiple Fission Cell Cycle of Chlamydomonas" (2022). Dissertations. 1266.
https://irl.umsl.edu/dissertation/1266