How do single cell c 4 species form dimorphic chloroplasts?

Abstract

Bienertia sinuspersici is one of only three higher land plant species known to perform C4 photosynthesis without Kranz anatomy through partitioning of photosynthetic functions between dimorphic chloroplasts in a single photosynthetic cell. We recently reported the successful separation of the two chloroplast types and biochemical and functional analyses revealed differences in protein composition and specialization of photosynthetic functions. In Kranz type C4 species, spatial (or cell-specific) control of transcription of nuclear genes contributes to development of dimorphic chloroplasts, but obviously this cannot be involved in formation of dimorphic chloroplasts within individual photosynthetic cells. Therefore, we address here the question of how nuclear encoded proteins could be selectively targeted to plastids within a cell to form two types of chloroplasts. We discuss current knowledge of chloroplast differentiation in single cell C4 species and present three hypothetical mechanisms for how this could occur. © 2011 Landes Bioscience.