Adaptive Evolution of C4 Photosynthesis

C₄ photosynthesis evolved multiple times independently in the angiosperms and over 22 times in the grasses suggesting that the ancestral genomes were primed for the acquisition of C₄ traits. However, the identification of the genes and networks associated with the transition from C₃ to C₄ have to date remained elusive. To accelerate the pace of gene discovery in the grasses, we have exploited the close phylogentic relationship of the panicoid grasses and deep genomic sequencing to identify signatures of adaptive evolution. Importantly, This approach does not rely on any a priori knowledge of the genes that contribute to biochemical or anatomical innovations associated with C₄ photosynthesis. Enabled by the collinearity of grass genomes and the recently sequenced genome of Dichanthelium oligosanthes, this analysis identified both known and novel components that likely underlie C₄ traits, including traits that are shared among all C₄ panicoids and those that are specific to one lineage.