title: Promotion of cyclic electron transport around photosystem I during the evolution of NADP-malic enzyme-type C4 photosynthesis in the genus Flaveria.
abstract: C4 plants display higher cyclic electron transport activity than C3 plants. This activity is suggested to be important for the production of ATPs required for C4 metabolism. To understand the process by which photosystem I (PSI) cyclic electron transport was promoted during C4 evolution, we conducted comparative analyses of the functionality of PSI cyclic electron transport among members of the genus Flaveria, which contains several C3, C3-C4 intermediate, C4-like and C4 species. The abundance of NDH-H, a subunit of NADH dehydrogenase-like complex, increased markedly in bundle sheath cells with the activity of the C4 cycle. By contrast, PROTON GRADIENT REGULATION5 (PGR5) and PGR5-LIKE1 increased in both mesophyll and bundle sheath cells in C4-like Flaveria palmeri and C4 species. Grana stacks were drastically reduced in bundle sheath chloroplasts of C4-like F. palmeri and C4 species; these species showed a marked increase in PSI cyclic electron transport activity. These results suggest that both the expression of proteins involved in PSI cyclic electron transport and changes in thylakoid structure contribute to the high activity of cyclic electron flow in NADP-malic enzyme-type C4 photosynthesis. We propose that these changes were important for the establishment of C4 photosynthesis from C3-C4 intermediate photosynthesis in Flaveria.
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Nakamura
authors.forename: Megumi
authors.initials: M
authors.lastname: Iwano
authors.forename: Michel
authors.initials: M
authors.lastname: Havaux
authors.forename: Akiho
authors.initials: A
authors.lastname: Yokota
authors.forename: Yuri Nakajima
authors.initials: YN
authors.lastname: Munekage
mesh_terms: D002244:Carbon / Q000378:metabolism*; D004579:Electron Transport; D019143:Evolution, Molecular; D037142:Flaveria / Q000201:enzymology* / Q000502:physiology*; D008291:Malate Dehydrogenase / Q000378:metabolism*; D058503:Mesophyll Cells / Q000378:metabolism / Q000648:ultrastructure; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D002244:Carbon; D008291:Malate Dehydrogenase; C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)
keywords: C4 evolution; C4 photosynthesis; Flaveria; cyclic electron transport; thylakoid structure