Abstract
Predictions suggest that current crop production needs to double by 2050 to meet global food and energy demands. Based on theory and experimental studies, overexpression of the photosynthetic enzyme sedoheptulose-1,7-bisphosphatase (SBPase) is expected to enhance C3 crop photosynthesis and yields. Here we test how expression of the cyanobacterial, bifunctional fructose-1,6/sedoheptulose-1,7-bisphosphatase (FBP/SBPase) affects carbon assimilation and seed yield (SY) in a major crop (soybean, Glycine max). For three growing seasons, wild-type (WT) and FBP/SBPase-expressing (FS) plants were grown in the field under ambient (400 μmol mol−1) and elevated (600 μmol mol−1) CO2 concentrations [CO2] and under ambient and elevated temperatures (+2.7 °C during daytime, +3.4 °C at night) at the SoyFACE research site. Across treatments, FS plants had significantly higher carbon assimilation (4–14%), Vc,max (5–8%), and Jmax (4–8%). Under ambient [CO2], elevated temperature led to significant reductions of SY of both genotypes by 19–31%. However, under elevated [CO2] and elevated temperature, FS plants maintained SY levels, while the WT showed significant reductions between 11% and 22% compared with plants under elevated [CO2] alone. These results show that the manipulation of the photosynthetic carbon reduction cycle can mitigate the effects of future high CO2 and high temperature environments on soybean yield.
Highlights
Crop productivity may have to increase by 60–110% over Bruinsma, 2012; OECD/FAO, 2012) to meet growing global 2005 levels by 2050
Western blotting showed that the bifunctional FBP/SBPase was present in the transgenic plants and appeared to have little effect on native SPBase levels (Fig. 2)
This study builds upon previous research showing that SBPase overexpression leads to higher A and higher biomass production in tobacco (Miyagawa et al, 2001; Lefebvre et al, 2005; Rosenthal et al, 2011; Simkin et al, 2015), which we extend to show an effect on yield in a major food crop and under simulated climate change conditions in the field
Summary
Crop productivity may have to increase by 60–110% over Bruinsma, 2012; OECD/FAO, 2012) to meet growing global 2005 levels by 2050 Approaches to improve crop yields need to take global climate change and the predicted future environmental conditions into account. C3 photosynthesis (A) is mostly limited by the capacity for carboxylation by Rubisco, while under future elevated [CO2] and higher temperatures, the leaf photosynthesis model of carbon uptake and assimilation (Farquhar et al, 1980; von Caemmerer and Farquhar, 1981; von Caemmerer, 2000) predicts that limitation will shift towards the regeneration capacity of RuBP (Long et al, 2004). Enhancing RuBP regeneration capacity would be an effective strategy to adapt A to the higher atmospheric [CO2] and temperatures expected as climate change progresses
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