C4 Photosynthesis in Seeds may Contribute to Climate Adaptation

The C4 pathway of photosynthesis provides and advantage to plants growing in hot and dry environments. Seed photosynthesis may contribute directly to seed biomass and result in enhanced yield. A key role of seed photosynthesis is in re-capture of carbon generated by respiration to support the biosynthesis of seed storage components such as starch and protein during. We recently identified a complete set of genes encoding enzymes of a C4 pathway in the wheat genome. These genes were expressed specifically in the pericarp of the developing seed. The anatomy of the pericarp seems were suited to supporting C4 photosynthesis. Significant variation in expression was found in domesticated wheat genotypes. This suggests the potential to select for enhanced levels of this trait to provide climate resilience in wheat. Strong metabolic flux from CO2 through malate to sugars has been reported in barley pericarp suggesting that this trait may be found in related species. The pathway has not been identified in rice possibly because, unlike wheat and barley that mature in a warming dry environment, rice evolved in an environment that did not provide a selective advantage for C4 photosynthesis.