Dynamic changes of genome sizes and gradual gain of cell-specific distribution of C enzymes during C evolution in genus Flaveria.

C plants are believed to have evolved from C plants through various C -C intermediate stages in which a photorespiration-dependent CO concentration system known as C photosynthesis operates. Genes involved in the C cycle were thought to be recruited from orthologs present in C species and developed cell-specific expression during C evolution. To understand the process of establishing C photosynthesis, we performed whole-genome sequencing and investigated expression and mesophyll- or bundle-sheath-cell-specific localization of phosphoenolpyruvate carboxylase (PEPC), NADP-malic enzyme (NADP-ME), pyruvate, orthophosphate dikinase (PPDK) in C , C -C intermediate, C -like, and C Flaveria species. While genome sizes vary greatly, the number of predicted protein-coding genes was similar among C , C -C intermediate, C -like, and C Flaveria species. Cell-specific localization of the PEPC, NADP-ME, and PPDK transcripts was insignificant or weak in C -C intermediate species, whereas these transcripts were expressed cell-type specific in C -like species. These results showed that elevation of gene expression and cell-specific control of pre-existing C cycle genes in C species was involved in C evolution. Gene expression was gradually enhanced during C evolution, whereas cell-specific control was gained independently of quantitative transcriptional activation during evolution from C -C intermediate to C photosynthesis in genus Flaveria.