title: The relocation of starch metabolism to chloroplasts: when, why and how.
abstract: Plastid endosymbiosis was accompanied by the appearance of a novel type of semi-cristalline storage polysaccharide (starch). Interestingly, starch is found in the cytoplasm of Rhodophyceae and Glaucophyta but is localized to the chloroplast stroma of Chloroplastida. The pathway is presumed to have been cytosolic in the common ancestor of the three Archaeplastida lineages. The means by which in green plants and algae an entire suite of nuclear-encoded starch-metabolism genes could have had their protein products rewired simultaneously to plastids are unclear. This opinion article reviews the timing and the possible reasons underlying this rewiring and proposes a hypothesis that explains its mechanism. The consequences of this mechanism on the complexity of starch metabolism in Chloroplastida are discussed.
authors.affiliation: Laboratoire de Chimie Biologique, Université des Sciences et technologies de Lille, CNRS, UMR8576, Cité Scientifique, Villeneuve d'Ascq, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Deschamps
authors.forename: Ilka
authors.initials: I
authors.lastname: Haferkamp
authors.forename: Christophe
authors.initials: C
authors.lastname: d'Hulst
authors.forename: H Ekkehard
authors.initials: HE
authors.lastname: Neuhaus
authors.forename: Steven G
authors.initials: SG
authors.lastname: Ball
mesh_terms: D005075:Biological Evolution; D002736:Chloroplasts / Q000378:metabolism*; D000458:Cyanobacteria / Q000378:metabolism; D006003:Glycogen / Q000096:biosynthesis / Q000378:metabolism; D009844:Oligosaccharides / Q000096:biosynthesis / Q000378:metabolism; D018087:Plastids / Q000235:genetics; D011134:Polysaccharides / Q000096:biosynthesis / Q000378:metabolism; D000461:Rhodophyta / Q000378:metabolism*; D013213:Starch / Q000378:metabolism*
chemical_list: D009844:Oligosaccharides; D011134:Polysaccharides; C021705:maltooligosaccharides; D013213:Starch; D006003:Glycogen