New evidence for grain specific C4 photosynthesis in wheat

The C-4 photosynthetic pathway evolved to allow efficient CO2 capture by plants where effective carbon supply may be limiting as in hot or dry environments, explaining the high growth rates of C-4 plants such as maize. Important crops such as wheat and rice are C-3 plants resulting in efforts to engineer them to use the C-4 pathway. Here we show the presence of a C-4 photosynthetic pathway in the developing wheat grain that is absent in the leaves. Genes specific for C-4 photosynthesis were identified in the wheat genome and found to be preferentially expressed in the photosynthetic pericarp tissue (cross-and tube-cell layers) of the wheat caryopsis. The chloroplasts exhibit dimorphism that corresponds to chloroplasts of mesophyll- and bundle sheath-cells in leaves of classical C-4 plants. Breeding to optimize the relative contributions of C-3 and C-4 photosynthesis may adapt wheat to climate change, contributing to wheat food security.