Constructing the bundle sheath towards enhanced photosynthesis

Abstract

C4 photosynthesis is a carbon-concentrating mechanism that alleviates photorespiratory losses by elevating the concentration of CO2 around Rubisco. Extant genes evolved to form this CO2-concentrating mechanism through changes in cell-preferential enzyme activity and leaf morphology (termed Kranz anatomy). Relatively little is known about regulatory trans-factors that promoted these changes. Using an activation tagging screen in C3 Arabidopsis thaliana, Rooijen et al. (2019) identified NAC052, a H3K4 demethylase, as a possible regulator of an increased number of bundle sheath cells and chloroplasts. This study helps to decipher the genetic basis behind the evolutionary neofunctionalization of the bundle sheath in C3 species, which lead to morphological changes to facilitate C4 photosynthesis.