The Eukaryotic CO2-Concentrating Organelle Is Liquid-like and Exhibits Dynamic Reorganization.

TitleThe Eukaryotic CO2-Concentrating Organelle Is Liquid-like and Exhibits Dynamic Reorganization.
Publication TypeJournal Article
Year of Publication2017
AuthorsRosenzweig, ESFreeman, Xu, B, Cuellar, LKuhn, Martinez-Sanchez, A, Schaffer, M, Strauss, M, Cartwright, HN, Ronceray, P, Plitzko, JM, Förster, F, Wingreen, NS, Engel, BD, Mackinder, LCM, Jonikas, MC
Date Published2017 Sep 21
KeywordsAlgal Proteins, Carbon Dioxide, Chlamydomonas reinhardtii, Chloroplasts, Cryoelectron Microscopy, Organelle Biogenesis, Ribulose-Bisphosphate Carboxylase

Approximately 30%-40% of global CO2 fixation occurs inside a non-membrane-bound organelle called the pyrenoid, which is found within the chloroplasts of most eukaryotic algae. The pyrenoid matrix is densely packed with the CO2-fixing enzyme Rubisco and is thought to be a crystalline or amorphous solid. Here, we show that the pyrenoid matrix of the unicellular alga Chlamydomonas reinhardtii is not crystalline but behaves as a liquid that dissolves and condenses during cell division. Furthermore, we show that new pyrenoids are formed both by fission and de novo assembly. Our modeling predicts the existence of a "magic number" effect associated with special, highly stable heterocomplexes that influences phase separation in liquid-like organelles. This view of the pyrenoid matrix as a phase-separated compartment provides a paradigm for understanding its structure, biogenesis, and regulation. More broadly, our findings expand our understanding of the principles that govern the architecture and inheritance of liquid-like organelles.

Alternate JournalCell
PubMed ID28938114
PubMed Central IDPMC5671343
Grant ListT32 GM007276 / GM / NIGMS NIH HHS / United States