Expression profiling and proteomic analysis of isolated photosynthetic cells of the non-Kranz C₄ species Bienertia sinuspersici

Bienertia sinuspersici Akhani represents one form of C₄ photosynthesis that occurs without Kranz anatomy in family Chenopodiaceae. Analysis of transcript profiles and proteomics were made to gain information on this single-cell C₄ photosynthetic mechanism. Chlorenchyma cells were isolated and purified from mature leaves. From these cells, a cDNA library was made from which sequences were obtained on 2385 clones using conventional methods. To obtain a protein profile, the multi dimensional protein identification technique was used, resulting in identification of 322 unique proteins in chlorenchyma cells. After analysing datasets from the EST library and proteomics, genes and proteins were classified into 23 and 17 categories according to types of biological processes, respectively. These include photosynthesis and photorespiration, other biosynthetic and metabolic processes, cell wall modification, defence response, DNA repair, electron transport, other cellular and developmental processes, protein folding, protein targeting, protein modification, proteolysis, redox and ion homeostasis, response to biotic and abiotic stresses, RNA modification, transcription, translation, transport and unknowns. Sequence and phylogenetic analyses were made of C₄ cycle enzymes to characterise the relationship between homologues found in Bienertia with public gene sequences from other chenopods and representative C₃ and C₄ species from other families. Identified photosynthetic genes and proteins are discussed with respect to the proposed function of an NAD-ME type C₄ cycle in this single-cell C₄ system.