Strategies to Study Dark Growth Deficient or Slower Mutants in Chlamydomonas reinhardtii

Photosynthesis is the most important chemical reaction on the earth, and about 60% of the CO₂ is fixed by algae through photosynthesis. Photosynthetic organisms including algae experience half of the entire life in the dark due to diel cycles, and dark metabolism is critical and necessary for photosynthetic organisms to restart photosynthesis when receiving light again. Briefly, dark metabolism provides necessary materials and energy for restoring photosynthesis, reoxidizes NADH to form NAD⁺, rationally stores photosynthates, and maintains correct redox balance. Chlamydomonas reinhardtii grows under both autotrophic and heterotrophic conditions, making it an ideal organism to study photosynthesis, dark metabolism, and light dark transitions as well. In addition, it provides a good model to identify key molecular components and elucidate the molecular regulatory mechanisms of heterotrophic, which provides new clues to understand how photosynthetic organisms restart photosynthesis from the dark. Chlamydomonas mutants with dark growth deficiency or slower growth phenotypes are likely caused by the inefficient uptake and transport of acetate, the damaged proteins of mitochondrial electron transport chain, the malfunctioned mitochondrion, the redox state alteration in the dark or failed communication between mitochondrion and other organelles, the imbalanced redox or the disrupted distribution of the photosynthetic products. Here we summarize the methods and strategies for analyzing these mutants in Chlamydomonas reinhardtii.