title: Rubisco small-subunit α-helices control pyrenoid formation in Chlamydomonas.
abstract: The pyrenoid is a subcellular microcompartment in which algae sequester the primary carboxylase, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). The pyrenoid is associated with a CO(2)-concentrating mechanism (CCM), which improves the operating efficiency of carbon assimilation and overcomes diffusive limitations in aquatic photosynthesis. Using the model alga Chlamydomonas reinhardtii, we show that pyrenoid formation, Rubisco aggregation, and CCM activity relate to discrete regions of the Rubisco small subunit (SSU). Specifically, pyrenoid occurrence was shown to be conditioned by the amino acid composition of two surface-exposed α-helices of the SSU: higher plant-like helices knock out the pyrenoid, whereas native algal helices establish a pyrenoid. We have also established that pyrenoid integrity was essential for the operation of an active CCM. With the algal CCM being functionally analogous to the terrestrial C(4) pathway in higher plants, such insights may offer a route toward transforming algal and higher plant productivity for the future.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom. mtm36@cam.ac.uk
authors.forename: Moritz T
authors.initials: MT
authors.lastname: Meyer
authors.forename: Todor
authors.initials: T
authors.lastname: Genkov
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Skepper
authors.forename: Juliette
authors.initials: J
authors.lastname: Jouhet
authors.forename: Madeline C
authors.initials: MC
authors.lastname: Mitchell
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Spreitzer
authors.forename: Howard
authors.initials: H
authors.lastname: Griffiths
mesh_terms: D000595:Amino Acid Sequence; D052818:Autotrophic Processes / Q000187:drug effects; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000494:pharmacology; D002696:Chlamydomonas / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development / Q000648:ultrastructure; D017353:Gene Deletion; D007700:Kinetics; D008969:Molecular Sequence Data; D015388:Organelles / Q000378:metabolism* / Q000648:ultrastructure; D010100:Oxygen / Q000378:metabolism; D010641:Phenotype; D010788:Photosynthesis / Q000187:drug effects; D017433:Protein Structure, Secondary; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry* / Q000378:metabolism*; D018724:Spinacia oleracea / Q000187:drug effects / Q000201:enzymology; D013329:Structure-Activity Relationship
chemical_list: D002245:Carbon Dioxide; D002244:Carbon; D012273:Ribulose-Bisphosphate Carboxylase; D010100:Oxygen