The C 4 Ppc promoters of many C 4 grass species share a common regulatory mechanism for gene expression in the mesophyll cell

C photosynthetic plants have evolved from C ancestors and are characterized by differential expression of several hundred genes. Strict compartmentalization of key C enzymes either to mesophyll (M) or bundle sheath cells is considered a crucial step towards the evolution of C photosynthesis. In this study, we demonstrate that the 5'-flanking sequences of the C type phosphoenolpyruvate carboxylase (Ppc) gene from three C grass species could drive M-cell-specific expression of a reporter gene in rice. In addition to that, we identified about 450 bp (upstream of their transcription start site) of the analyzed C Ppc promoters contain all the essential regulatory elements for driving M-cell-specific expression in rice leaves. Importantly, four motifs of conserved nucleotide sequences (CNSs) were also determined, which are essential for the activity of the promoter. A putative interaction between the CNSs and an unknown upstream element(s) is required for driving M-cell-specific expression. This work identifies the evolutionary conservation of C Ppc regulatory mechanisms of multiple closely related C grass species.