Histone dynamics during the life cycle of Chlamydomonas
EMSL Project ID
49263
Abstract
Diurnal cycles are central drivers of gene expression in photosynthetic organisms including cyanobacteria, algae and land plants. The model unicellular green alga Chlamydomonas reinhardtii has unique advantages for deciphering the system-wide regulatory mechanisms that control gene expression and chromatin in photosynthetic eukaryotes. First, its life cycle can be tightly synchronized under natural diurnal conditions leading to a system with unparalleled precision for investigating daily cycles of gene expression and metabolism. In addition, mutants are available that allow functional dissection of the relationship between cell-cycle states and chromatin. In recently published work with diurnal samples taken at 1 hr. or 30 min. time points for a 24 hour cycle we found that over 80% of the detectable transcriptome in Chlamydomonas cycles with high amplitude in a continuous process of differentiation where expression clusters are highly correlated with states of metabolism, cell growth and cell division. Histone modifications have been studied extensively in the context of gene expression in diverse eukaryotes, but the cell cycle dynamics of histones and taxon-specific modifications of histones--particularly in the green lineage--are not well understood. The retinoblastoma (RB) tumor suppressor is a conserved eukaryotic chromatin associated protein complex whose functions in transcriptional control and chromatin remodeling remain poorly understood in plants and algae. Subunits of the Chlamydomonas RB complex are encoded by single copy genes that when mutated disrupt not only cell division control but also impact biomass partitioning, photosynthetic stress, and survival and exit from quiescence, highlighting the impact of cell cycle chromatin states on bioenergy and biomass traits. We propose here to leverage our unique expertise in synchronizing and controlling the cell cycle of Chlamydomonas in combination with the expertise of EMSL in histone profiling and proteomics to gain insight into the life cycle dynamics of histones and chromatin in Chlamydomonas, an important model organism and representative of the Chlorophyte algal lineage. The Aims of this proposal are as follows: 1. Generate a comprehensive quantitative profile of Chlamydomonas combinatorial histone modifications in synchronous cultures taken from key time points during the cell cycle.
2. Use mutants in the chromatin-associated retinoblastoma (RB) tumor suppressor complex to examine the functional requirements and temporal ordering of histone modifications during the cell cycle.
3. Purify and characterize by mass spectrometry the subunits of the RB complex where it is predicted to undergo dynamic changes in composition and posttranslational modification of its subunits at specific stages of the cell cycle, including changes in association with predicted chromatin modifying complexes/proteins.
This study will provide the most comprehensive and detailed map of cell cycle/life cycle histone dynamics in a green eukaryote to date, and will synergize with two other projects being done in collaboration with the Merchant laboratory that examine proteomic and metabolic changes in Chlamydomonas during the diurnal cycle (Proposal 49262) and mapping of chromatin marks by ChIP-Seq across the diurnal cycle (JGI 2016 CSP 1921).
Project Details
Project type
Large-Scale EMSL Research
Start Date
2016-10-01
End Date
2018-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)