Date of Award

Winter 12-21-2022

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Plant & Microbial Biosciences)

Degree Name

Master of Arts (AM/MA)

Degree Type



Understanding the molecular mechanisms influencing cell size control has long been confounded by the crosstalk between cell size regulation and cell growth rate. The unicellular green alga Chlamydomonas reinhardtii is an ideal organism for studying cell size control due to its multiple fission cell cycle, which decouples cell size checkpoints from biomass accumulation rate. Chlamydomonas strains with mutations in the MAT3/RB and DP1 genes, homologs of two components of the retinoblastoma tumor suppressor complex (RBC), display striking defects in cell size regulation that are consistent with the canonical RBC mechanism in which RB represses the DP1/E2F-mediated activation of cell cycle progression, typically via transcriptional regulation of essential cell cycle genes.

The goal of my research was to identify the molecular mechanisms by which the Chlamydomonas RBC affects cell cycle progression and thereby cell size regulation. To test my hypothesis that the Chlamydomonas RBC may be operating canonically via transcriptional control of cell cycle genes, I examined genome-wide transcript abundances in wild type, mat3-4, and dp1-1 strains, searching for evidence of mis-expression of cell cycle genes. My analysis here agreed with prior published work showing no strong evidence supporting a role for the RBC in transcriptional regulation of cell cycle gene, nor any other functionally related genes.

To test my alternative hypothesis that the Chlamydomonas RBC may be functioning via a non-transcriptional mechanism, such as recruitment of chromatin-modifying enzymes to non-genic regions of the genome, I used top-down mass spectrometric characterization of global histone post-translational modification profiles across the wild type cell cycle and in the RBC mutant strains. I also used chromatin immunoprecipitation sequencing to identify the DNA-binding sites of the Chlamydomonas RBC, which may support either the canonical or alternative hypothesis. My research laid the groundwork for using Chlamydomonas to better understand cell size regulatory mechanisms in eukaryotic organisms.


English (en)

Chair and Committee

Elizabeth Haswell

Committee Members

James Umen, Dmitri Nusinow, Susan Dutcher, Douglas Chalker

Available for download on Monday, December 21, 2122