Background

Numerous groups of plants have adapted to CO₂ limitations by independently evolving C₄ photosynthesis. This trait relies on concerted changes in anatomy and biochemistry to concentrate CO₂ within the leaf and thereby boost productivity in tropical conditions. The ecological and economical importance of C4 photosynthesis has motivated intense research, often relying on comparisons between distantly related C₄ and non-C₄ plants. The photosynthetic type is fixed in most species, with the notable exception of the grass Alloteropsis semialata. This species includes populations exhibiting the ancestral C₃ state in southern Africa, intermediate C₃+C₄ populations in the Zambezian region and C₄ populations spread around the paleotropics.  

Scope

We compile here the knowledge on the distribution and history of Alloteropsis as a whole and discuss how this has furthered our understanding of C₄ evolution. We further generate a chromosome-level reference genome for a C₃ individual and compare the genomic architecture to that of a C₄ accession. 

Conclusions

Alloteropsis semialata represents one of the best systems to investigate the evolution of C₄ photosynthesis as the genetic and phenotypic variation provides a fertile ground for comparative and population-level studies. Initial comparative genomics show the C₃ and C₄ genomes are highly syntenic and have undergone a modest amount of gene duplication and translocation since the different photosynthetic groups divided. The background knowledge and publicly available genomic resources make Alloteropsis semialata a great model for further comparative analyses of photosynthetic diversification.

Please see manuscript for full details of methods.