C₄ photosynthesis: from evolutionary analyses to strategies for synthetic reconstruction of the trait

C₄ photosynthesis represents the most productive modes of photosynthesis in land plants and some of the most productive crops on the planet, such as maize and sugarcane, and many ecologically important native plants use this type of photosynthesis. Despite its ecological and economic importance, the genetic basis of C₄ photosynthesis remains largely unknown. Even many fundamental aspects of C₄ biochemistry, such as the molecular identity of solute transporters, and many aspects of C₄ plant leaf development, such as the Kranz anatomy, are currently not understood. Here, we review recent progress in gaining a mechanistic understanding of the complex C₄ trait through comparative evolutionary analyses of C₃ and C₄ species.