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Chlamydomonas CHT7 Is Required for an Effective Quiescent State by Regulating Nutrient-Responsive Cell Cycle Gene
Tomomi Takeuchi1,2, Barbara B Sears2,3, Chase Lindeboom1
1Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824.
The Plant Cell
|February 1, 2020
Summary
The Chlamydomonas CHT7 protein regulates gene expression during nitrogen deprivation, impacting cell cycle progression and viability. Its C-terminal domain, not the DNA-binding domain, is crucial for these functions.
Area of Science:
- Molecular Biology
- Cell Biology
- Plant Science
Background:
- The COMPROMISED HYDROLYSIS OF TRIACYLGLYCEROLS7 (CHT7) gene in Chlamydomonas reinhardtii influences gene transcription during nutrient availability changes.
- Previous studies indicated CHT7's role in regulating specific gene subsets during nitrogen-replete conditions and refeeding.
Purpose of the Study:
- To investigate the role of CHT7 during nitrogen deprivation in Chlamydomonas reinhardtii.
- To elucidate the molecular mechanisms by which CHT7 affects cellular processes and gene expression under nutrient stress.
Main Methods:
- Transcriptome analysis (RNA sequencing) of cht7 mutants versus wild-type under nitrogen deprivation.
- Phenotypic analysis of cell cycle progression, nuclear replication, and cell division in cht7 mutants.
- Functional analysis of CHT7 domains by assessing mutant complementation.
Main Results:
- Nitrogen deprivation in cht7 mutants leads to widespread gene misregulation, including derepression of DNA metabolism and cell cycle genes, and downregulation of oxidoreductases and nutrient transporters.
- cht7 cells exhibit defects in growth arrest, nuclear replication, and cell division during nitrogen deprivation, and show reduced viability and abortive divisions upon refeeding.
- The unstructured C-terminal half of CHT7, containing protein-binding domains, is essential for CHT7 function, while the canonical CXC DNA-binding domain is not required for reversing mutant phenotypes and restoring transcription.
Conclusions:
- CHT7 plays a critical role in modulating cell cycle gene expression in response to nitrogen availability, essential for establishing quiescence.
- The C-terminal domain of CHT7 is vital for its function in regulating gene expression and cellular processes, independent of its canonical DNA-binding domain.
- CHT7 is crucial for coordinated growth resumption following nutrient refeeding in Chlamydomonas.
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