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Open Access Research article

Over-expressing the C3 photosynthesis cycle enzyme Sedoheptulose-1-7 Bisphosphatase improves photosynthetic carbon gain and yield under fully open air CO2 fumigation (FACE)

David M Rosenthal1, Anna M Locke2, Mahdi Khozaei3, Christine A Raines4, Stephen P Long5 and Donald R Ort6*

Author Affiliations

1 Global Change and Photosynthesis Research Unit, United States Department of Agriculture, Institute for Genomic Biology, 1206 West Gregory Drive, Urbana, IL, 61801, USA

2 Department of Plant Biology, Institute for Genomic Biology, 1206 West Gregory Drive, University of Illinois, Urbana, IL, 61801, USA

3 Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, UK, CO43SQ. Current address: Department of Biology, University of Isfahan, Iran

4 Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO43SQ, UK

5 Department of Plant Biology and Crop Sciences, Institute for Genomic Biology, 1206 West Gregory Drive, University of Illinois, Urbana, IL, 61801, USA

6 Global Change and Photosynthesis Research Unit, United States Department of Agriculture, Institute for Genomic Biology, 1206 West Gregory Drive, Urbana, IL, 61801, USA; Department of Plant Biology and Crop Sciences, University of Illinois, Urbana, IL, 61801, USA

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BMC Plant Biology 2011, 11:123  doi:10.1186/1471-2229-11-123

Published: 31 August 2011

Abstract

Background

Biochemical models predict that photosynthesis in C3 plants is most frequently limited by the slower of two processes, the maximum capacity of the enzyme Rubisco to carboxylate RuBP (Vc,max), or the regeneration of RuBP via electron transport (J). At current atmospheric [CO2] levels Rubisco is not saturated; consequently, elevating [CO2] increases the velocity of carboxylation and inhibits the competing oxygenation reaction which is also catalyzed by Rubisco. In the future, leaf photosynthesis (A) should be increasingly limited by RuBP regeneration, as [CO2] is predicted to exceed 550 ppm by 2050. The C3 cycle enzyme sedoheptulose-1,7 bisphosphatase (SBPase, EC 3.1.3.17) has been shown to exert strong metabolic control over RuBP regeneration at light saturation.

Results

We tested the hypothesis that tobacco transformed to overexpressing SBPase will exhibit greater stimulation of A than wild type (WT) tobacco when grown under field conditions at elevated [CO2] (585 ppm) under fully open air fumigation. Growth under elevated [CO2] stimulated instantaneous A and the diurnal photosynthetic integral (A') more in transformants than WT. There was evidence of photosynthetic acclimation to elevated [CO2] via downregulation of Vc,max in both WT and transformants. Nevertheless, greater carbon assimilation and electron transport rates (J and Jmax) for transformants led to greater yield increases than WT at elevated [CO2] compared to ambient grown plants.

Conclusion

These results provide proof of concept that increasing content and activity of a single photosynthesis enzyme can enhance carbon assimilation and yield of C3 crops grown at [CO2] expected by the middle of the 21st century.

Keywords:
climate change; photosynthetic carbon reduction cycle; C3 plants; RuBP regeneration; electron transport; improving photosynthesis