Alloteropsis semialata as a study system for C4 evolution in grasses

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.

Methods
Please see manuscript for full details of methods.