Understanding metabolite transport and metabolism in C4 plants through RNA-seq.

RNA-seq, the measurement of steady-state RNA levels by next generation sequencing, has enabled quantitative transcriptome analyses of complex traits in many species without requiring the parallel sequencing of their genomes. The complex trait of C4 photosynthesis, which increases photosynthetic efficiency via a biochemical pump that concentrates CO2 around RubisCO, has evolved convergently multiple times. Due to these interesting properties, C4 photosynthesis has been analyzed in a series of comparative RNA-seq projects. These projects compared both species with and without the C4 trait and different tissues or organs within a C4 plant. The RNA-seq studies were evaluated by comparing to earlier single gene studies. The studies confirmed the marked changes expected for C4 signature genes, but also revealed numerous new players in C4 metabolism showing that the C4 cycle is more complex than previously thought, and suggesting modes of integration into the underlying C3 metabolism.