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First published online August 18, 2006; 10.1104/pp.106.085829 Plant Physiology 142:673-684 (2006) © 2006 American Society of Plant Biologists Species Having C4 Single-Cell-Type Photosynthesis in the Chenopodiaceae Family Evolved a Photosynthetic Phosphoenolpyruvate Carboxylase Like That of Kranz-Type C4 Species1Centro de Estudios Fotosintéticos y Bioquímicos, Facultad de Ciencias Bioquímicas y Farmacéuticas, Rosario 2000, Argentina (M.V.L., C.S.A.); School of Biological Sciences, Washington State University, Pullman, Washington 99164–4236 (S.D.X.C., G.E.E.); and Department of Biology, Faculty of Science, University of Tehran, Tehran, Iran (H.A.)
Spatial and temporal regulation of phosphoenolpyruvate carboxylase (PEPC) is critical to the function of C4 photosynthesis. The photosynthetic isoform of PEPC in the cytosol of mesophyll cells in Kranz-type C4 photosynthesis has distinctive kinetic and regulatory properties. Some species in the Chenopodiaceae family perform C4 photosynthesis without Kranz anatomy by spatial separation of initial fixation of atmospheric CO2 via PEPC from C4 acid decarboxylation and CO2 donation to Rubisco within individual chlorenchyma cells. We studied molecular and functional features of PEPC in two single-cell functioning C4 species (Bienertia sinuspersici, Suaeda aralocaspica) as compared to Kranz type (Haloxylon persicum, Salsola richteri, Suaeda eltonica) and C3 (Suaeda linifolia) chenopods. It was found that PEPC from both types of C4 chenopods displays higher specific activity than that of the C3 species and shows kinetic and regulatory characteristics similar to those of C4 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 C4 species possesses a Kranz-type C4 isoform with a Ser in the amino terminal. A phylogeny of PEPC shows that isoforms in the two single-cell functioning C4 species are in a clade with the C3 and Kranz C4 Suaeda spp. with high sequence homology. Overall, this study indicates that B. sinuspersici and S. aralocaspica have a C4-type PEPC similar to that in Kranz C4 plants, which likely is required for effective function of C4 photosynthesis.
1 This work was supported by the National Science Foundation (grant no. IBN–0131098 to G.E.E. and grant no. IBN–0236959 to G.E.E. and S.D.X.C.), by the United Nations Educational, Scientific and Cultural Organization-L'Oréal (grant to M.V.L.), and by the University of Tehran (project no. 6104037/1/01 to H.A.). M.V.L. and C.S.A. are Researcher Career Members of the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Gerald E. Edwards (edwardsg{at}wsu.edu). www.plantphysiol.org/cgi/doi/10.1104/pp.106.085829 * Corresponding author; e-mail edwardsg{at}wsu.edu; fax 509–335–3184. Received June 27, 2006; accepted August 13, 2006; published August 18, 2006. Related articles in Plant Physiol.:
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