Essential Cell Cycle Pathways in Chlamydomonas

Breker et al. provide a large collection of mutants in cell-cycle-essential pathways in the green alga Chlamydomonas reinhardtii

By Michal Breker

Background: The cell division cycle is a set of tightly regulated and orchestrated events that lead to accurate duplication of all cellular constituents and their division to two daughter cells. Appropriate division is therefore crucial for the organism development and growth; and division misregulation may otherwise lead to fatal diseases. Cell cycle control has been extensively studied in animals and fungi. However, findings stemming from these studies may be less applicable in plants since these two lineages diverged early in their evolutionary history. The single-celled green alga Chlamydomonas reinhardtii is a member of the plant superkingdom with several features that make it a promising model for genetic studies. We therefore made use of Chlamydomonas to pave the way to address open questions in plant cell cycle regulation.

Question: We set out to continue an ongoing effort to construct a complete set of all cell cycle-essential mutants in Chlamydomonas in order to both identify the relevant genes and build a platform to investigate their molecular function.

Findings: We developed efficient methodologies for mutant isolation, and for determining critical gene mutations. We identified highly conserved cell cycle components recognizable from studies in fungi and animals, as well as plant kingdom-specific factors. Overall, 75% of the genes identified have clear orthologs in land plants genomes, increasing the relevance of these mutants to study plant cell biology.

Next steps: The collection is now sufficiently complete to allow inactivation of almost all cell-cycle-regulatory pathways. Therefore, the most important next step is to investigate mechanistically the various pathways, and to understand their function in the plant context and the differences to the cell-cycle models developed in fungi and animals.

Breker et al. (2018). Comprehensive Discovery of Cell-Cycle-Essential Pathways in Chlamydomonas reinhardtii. Plant Cell