A critical review on the improvement of photosynthetic carbon assimilation in C₃plants using genetic engineering

Abstract

Global warming is one of the most serious challenges facing us today. It may be linked to the increase in atmospheric CO2 and other greenhouse gases (GHGs), leading to a rise in sea level, notable shifts in ecosystems, and in the frequency and intensity of wild fires. There is a strong interest in stabilizing the atmospheric concentration of CO2 and other GHGs by decreasing carbon emission and/or increasing carbon sequestration. Biotic sequestration is an important and effective strategy to mitigate the effects of rising atmospheric CO2 concentrations by increasing carbon sequestration and storage capacity of ecosystems using plant photosynthesis and by decreasing carbon emission using biofuel rather than fossil fuel. Improvement of photosynthetic carbon assimilation, using transgenic engineering, potentially provides a set of available and effective tools for enhancing plant carbon sequestration. In this review, firstly different biological methods of CO2 assimilation in C3, C4 and CAM plants are introduced and three types of C4 pathways which have high photosynthetic performance and have evolved as CO2 pumps are briefly summarized. Then (i) the improvement of photosynthetic carbon assimilation of C3 plants by transgenic engineering using non-C4 genes, and (ii) the overexpression of individual or multiple C4 cycle photosynthetic genes (PEPC, PPDK, PCK, NADP-ME and NADP-MDH) in transgenic C3 plants (e.g. tobacco, potato, rice and Arabidopsis) are highlighted. Some transgenic C3 plants (e.g. tobacco, rice and Arabidopsis) overexpressing the FBP/SBPase, ictB and cytochrome c6 genes showed positive effects on photosynthetic efficiency and growth characteristics. However, over the last 28 years, efforts to overexpress individual, double or multiple C4 enzymes in C3 plants like tobacco, potato, rice, and Arabidopsis have produced mixed results that do not confirm or eliminate the possibility of improving photosynthesis of C3 plants by this approach. Finally, a prospect is provided on the challenges of enhancing carbon assimilation of C3 plants using transgenic engineering in the face of global warming, and the trends of the most promising approaches to improving the photosynthetic performance of C3 plants.

Regulation of assimilate import into sink organs: update on molecular drivers of sink strength

“…Researchers aiming to improve crop yield have focused on two key aspects of whole-plant carbohydrate partitioning: enhancing carbohydrate production in leaves (i.e., increasing source capacity) and/or improving the utilization of photoassimilates by sink organs (i.e., enhancing sink strength). Examples of strategies to enhance carbohydrate production include attempts to increase light interception either by increasing the number of leaves or total leaf area, breeding for stay-green traits, and enhancing photosynthesis by improving the capacity of the plant to fix carbon (Sakamoto et al, 2006; Hammer et al, 2009; Zheng et al, 2009; Zhu et al, 2010; Raines, 2011; Ruan et al, 2012a). In regards to the strategy of enhancing sink strength, researchers are attempting to increase the number, size, and carbohydrate-storing activity of sink organs (Ho, 1988; Marcelis, 1996; Herbers and Sonnewald, 1998; Smidansky et al, 2002).…”

Global plant-responding mechanisms to salt stress: physiological and molecular levels and implications in biotechnology

“…The halophytic plant Atriplex lentiformis is able to shift from C3 to C4 to respond to the salt stress (Meinzer & Zhu, 1999). Some transgenic C3 plants displayed higher photosynthetic efficiency and improved growth characteristics (Ruan et al, 2012). Moreover, salt stress can also weaken photosynthesis indirectly by reducing chlorophyll and total carotenoid content.…”

Understanding Plant Nitrogen Metabolism through Metabolomics and Computational Approaches

“…Along these lines, overexpression of PEPc in Vicia narbonensis seedlings resulted in increased C and N content [56]. Increasing photosynthetic production by bioengineering crops is not only important for increased carbon sequestration [57] and biofuel production [58], but may also provide enhanced NUE as a result. Transgenic lines with increased photosynthetic capacity should therefore be evaluated in terms of nitrogen use efficiency as well, and vice-versa.…”