Deep Evolutionary Comparison of Gene Expression Identifies Parallel Recruitment of Trans-Factors in Two Independent Origins of C4 Photosynthesis
(A) Schematic showing M or BS accumulation of transcripts involved in the C4 cycle. Shared parts of the pathway are annotated in red, while differences between the species are shown in grey. CA, carbonic anhydrase; PPC, phosphoenolpyruvate carboxylase; PEPC Kin, phosphoenolpyruvate carboxylase kinase, ASPAT, aspartate aminotransferase; ALAAT, alanine aminotransferase; PPDK, pyruvate-orthophosphate dikinase; TPI, triose phosphate isomerase; PGK, phosphoglycerate kinase; FBA, fructose-bisphosphate aldolase; SBP, sedoheptulose-bisphosphatase; TKL, transketolase; PRK, phosphoribulokinase; RbcS, RubisCO small subunit; RCA, RubisCO activase; FBP, fructose 1,6-bisphosphate phosphatase; RPE, D-ribulose-5-phosphate-3-epimerase; NAD-ME, NAD-dependent malic enzyme, MDH malate dehydrogenase. (B) Venn diagrams representing transcripts expressed in M (left panel) and BS (right panel) of C. gynandra and maize. Cell-specific maize data represents the overlap between two independent experiments , . (C) Venn diagrams of transcription factors expressed in M or BS in maize and C. gynandra. (D–G) Expression in M and BS cells of the 18 homologous transcription factors showing co-ordinated induction with C4 photosynthesis genes during leaf maturation of both maize and C. gynandra. Abbreviations: Cg data from C. gynandra (this study), while Zm1 data are from Li et al (2010)  and Chang et al (2012)  respectively.