Development, subcellular positioning and selective protein accumulation in the dimorphic chloroplasts of single-cell C4 species

C-4 photosynthesis is typically associated with a carbon concentrating mechanism based on close collaboration between two photosynthetic cell types (Kranz C-4). Surprisingly, four species in the family Chenopodiaceae have been described, which perform all required steps for a functional and effective C-4 cycle within individual photosynthetic cells. These single-cell C-4 species utilize a unique subcellular compartmentation and two functionally different chloroplast types that mimic the functions of the two cell types of the Kranz C-4 system. In this review, we will summarize and discuss studies on chloroplast development, positioning and selective accumulation of nuclear encoded proteins, which ultimately allow the operation of a C-4 carbon concentrating mechanism within individual cells.