Content area
Full Text
R E S O U R C E
Comparative analyses of C4 and C3 photosynthesis in developing leaves of maize and rice
Lin Wang1,11, Angelika Czedik-Eysenberg2, Rachel A Mertz1, Yaqing Si3,11, Takayuki Tohge2,
Adriano Nunes-Nesi2,11, Stephanie Arrivault2, Lauren K Dedow1,11, Douglas W Bryant1, Wen Zhou3, Jiajia Xu4, Sarit Weissmann1, Anthony Studer1, Pinghua Li5,11, Cankui Zhang6,11, Therese LaRue7, Ying Shao1,11, Zehong Ding5, Qi Sun8, Rohan V Patel9, Robert Turgeon6, Xinguang Zhu4, Nicholas J Provart9,
Todd C Mockler1, Alisdair R Fernie2, Mark Stitt2, Peng Liu3 & Thomas P Brutnell1,10
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.
npg 201 4 Nature America, Inc. All rights reserved.
C4 photosynthesis evolved from ancestral C3 photosynthesis during a global decline in atmospheric CO2 levels1. C3 photosynthesis uses the three-carbon molecule 3-phosphoglycerate (3-PGA) for carbon fixation, but in C4 photosynthesis a carbon shuttle system evolved in which carbon is first fixed by incorporation of carbon dioxide into a four-carbon moleculeoxaloacetate (OAA). OAA is transported from the outer mesophyll (ME) cells to inner bundle sheath (BS) cells in the form of malate or aspartate. In maize, CO2 is liberated inside the bundle sheath chloroplastswhich are enclosed by cell walls impregnated with suberin, a waxy substancethrough decarboxylation by malic enzyme, thereby creating a microenvironment with an increased CO2 concentration in the vicinity of the Rubisco enzyme. This greatly reduces energetically wasteful photorespiration and enables Rubisco to function near its enzymatic Vmax, thus allowing...