Comparative analyses of C₄ and C₃ photosynthesis in developing leaves of maize and rice.

C₄ and C₃ photosynthesis differ in the efficiency with which they consume water and nitrogen. Engineering traits of the more efficient C₄ photosynthesis into C₃ crops could substantially increase crop yields in hot, arid conditions. To identify differences between C₄ and C₃ photosynthetic mechanisms, we profiled metabolites and gene expression in the developing leaves of Zea mays (maize), a C₄ plant, and Oryza sativa (rice), a C₃ plant, using a statistical method named the unified developmental model (UDM). Candidate cis-regulatory elements and transcription factors that might regulate photosynthesis were identified, together with differences between C₄ and C₃ nitrogen and carbon metabolism. The UDM algorithms could be applied to analyze and compare development in other species. These data sets together with community viewers to access and mine them provide a resource for photosynthetic research that will inform efforts to engineer improvements in carbon fixation in economically valuable grass crops.