title: Species having C4 single-cell-type photosynthesis in the Chenopodiaceae family evolved a photosynthetic phosphoenolpyruvate carboxylase like that of Kranz-type C4 species.
abstract: Spatial and temporal regulation of phosphoenolpyruvate carboxylase (PEPC) is critical to the function of C(4) photosynthesis. The photosynthetic isoform of PEPC in the cytosol of mesophyll cells in Kranz-type C(4) photosynthesis has distinctive kinetic and regulatory properties. Some species in the Chenopodiaceae family perform C(4) photosynthesis without Kranz anatomy by spatial separation of initial fixation of atmospheric CO(2) via PEPC from C(4) acid decarboxylation and CO(2) donation to Rubisco within individual chlorenchyma cells. We studied molecular and functional features of PEPC in two single-cell functioning C(4) species (Bienertia sinuspersici, Suaeda aralocaspica) as compared to Kranz type (Haloxylon persicum, Salsola richteri, Suaeda eltonica) and C(3) (Suaeda linifolia) chenopods. It was found that PEPC from both types of C(4) chenopods displays higher specific activity than that of the C(3) species and shows kinetic and regulatory characteristics similar to those of C(4) species in other families in that they are subject to light/dark regulation by phosphorylation and display differential malate sensitivity. Also, the deduced amino acid sequence from leaf cDNA indicates that the single-cell functioning C(4) species possesses a Kranz-type C(4) isoform with a Ser in the amino terminal. A phylogeny of PEPC shows that isoforms in the two single-cell functioning C(4) species are in a clade with the C(3) and Kranz C(4) Suaeda spp. with high sequence homology. Overall, this study indicates that B. sinuspersici and S. aralocaspica have a C(4)-type PEPC similar to that in Kranz C(4) plants, which likely is required for effective function of C(4) photosynthesis.
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos, Facultad de Ciencias Bioquímicas y Farmacéuticas, Rosario 2000, Argentina.
authors.forename: María Valeria
authors.initials: MV
authors.lastname: Lara
authors.forename: Simon D X
authors.initials: SD
authors.lastname: Chuong
authors.forename: Hossein
authors.initials: H
authors.lastname: Akhani
authors.forename: Carlos Santiago
authors.initials: CS
authors.lastname: Andreo
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Edwards
mesh_terms: D000595:Amino Acid Sequence; D019663:Chenopodiaceae / Q000201:enzymology* / Q000235:genetics; D002940:Circadian Rhythm; D019143:Evolution, Molecular; D007526:Isoelectric Point; D007700:Kinetics; D008969:Molecular Sequence Data; D010730:Phosphoenolpyruvate Carboxylase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010788:Photosynthesis / Q000502:physiology*; D013045:Species Specificity
chemical_list: D010730:Phosphoenolpyruvate Carboxylase