Abstract
During C4 photosynthesis, CO2 is concentrated around the enzyme RuBisCO. The net effect is to reduce photorespiration while increasing water and nitrogen use efficiencies. Species that use C4 photosynthesis have evolved independently from their C3 ancestors on more than 60 occasions. Along with mimicry and the camera-like eye, the C4 pathway therefore represents a remarkable example of the repeated evolution of a highly complex trait. In this review, we provide evidence that the polyphyletic evolution of C4 photosynthesis is built upon pre-existing metabolic and genetic networks. For example, cells around veins of C3 species show similarities to those of the C4 bundle sheath in terms of C4 acid decarboxylase activity and also the photosynthetic electron transport chain. Enzymes of C4 photosynthesis function together in gluconeogenesis during early seedling growth of C3Arabidopsis thaliana Furthermore, multiple C4 genes appear to be under control of both light and chloroplast signals in the ancestral C3 state. We, therefore, hypothesize that relatively minor rewiring of pre-existing genetic and metabolic networks has facilitated the recurrent evolution of this trait. Understanding how these changes are likely to have occurred could inform attempts to install C4 traits into C3 crops.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'.
Highlights
Photosynthesis has shaped life on the Earth by allowing the energy from sunlight to be harvested and used for the assimilation of carbon dioxide
It has been proposed that high rates of oxygenation by RuBisCO led to the evolution of increased specificity for CO2, and that an inescapable trade-off between specificity and the rate of catalysis led to a lower turnover rate [9]
Owing to the relatively low rate of catalysis of RuBisCO, C3 species are associated with significant losses of water via stomata, and large investments in nitrogen are required to produce the amounts of RuBisCO needed to maintain reasonable rates of photosynthesis [10]
Summary
Photosynthesis has shaped life on the Earth by allowing the energy from sunlight to be harvested and used for the assimilation of carbon dioxide. There is considerable natural variation in the activity of RuBisCO [11] in photosynthetic lineages as diverse as the cyanobacteria, algae and land plants, it is thought that low CO2 concentrations before the Anthropocene led to the evolution of carbon concentrating mechanisms. These include the carboxysome in cyanobacteria [12], the pyrenoid in algae and hornworts [13], as well as crassulacean acid metabolism [14] and C4 photosynthesis in angiosperms. We propose that rewiring of pre-existing metabolic and genetic networks has facilitated the evolution of this novel metabolic pathway
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Philosophical Transactions of the Royal Society B: Biological Sciences
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
