title: Photorespiration and the evolution of C4 photosynthesis.
abstract: C(4) photosynthesis is one of the most convergent evolutionary phenomena in the biological world, with at least 66 independent origins. Evidence from these lineages consistently indicates that the C(4) pathway is the end result of a series of evolutionary modifications to recover photorespired CO(2) in environments where RuBisCO oxygenation is high. Phylogenetically informed research indicates that the repositioning of mitochondria in the bundle sheath is one of the earliest steps in C(4) evolution, as it may establish a single-celled mechanism to scavenge photorespired CO(2) produced in the bundle sheath cells. Elaboration of this mechanism leads to the two-celled photorespiratory concentration mechanism known as C(2) photosynthesis (commonly observed in C(3)-C(4) intermediate species) and then to C(4) photosynthesis following the upregulation of a C(4) metabolic cycle.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada. r.sage@utoronto.ca
authors.forename: Rowan F
authors.initials: RF
authors.lastname: Sage
authors.forename: Tammy L
authors.initials: TL
authors.lastname: Sage
authors.forename: Ferit
authors.initials: F
authors.lastname: Kocacinar
mesh_terms: D005075:Biological Evolution; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes / Q000032:analysis; D019069:Cell Respiration / Q000502:physiology*; D019663:Chenopodiaceae / Q000145:classification; D057231:Climate Change; D017753:Ecosystem; D005580:Fossils; D019684:Magnoliopsida / Q000145:classification; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D010802:Phylogeny; D010944:Plants / Q000145:classification* / Q000378:metabolism*; D006109:Poaceae / Q000145:classification; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D013045:Species Specificity
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide; D002244:Carbon; D012273:Ribulose-Bisphosphate Carboxylase; D010100:Oxygen