MICROSCOPY Vol.44▶No.1 2009
â– Researches Today

FtsZ ring formation and division of the cyanelle which is a chloroplast with a peptidoglycan layer

Mayuko Sato, Kiminori Toyooka, Aiko Hirata, Tamotsu Nagumo and Shigeyuki Kawano

Abstract: Glaucocystophytes are protists that contain cyanobacteria-like endosymbionts called cyanelles, which are thought to be evolutionary intermediates between free-living autotrophs and chloroplasts. Cyanelles retain primitive feature such as a peptidoglycan wall. We isolated a full-length prokaryotic plastid division gene, FtsZ, from the glaucocystophyte alga Cyanophora paradoxa (CpFtsZ-cy). Immunofluorescence microscopy showed that CpFtsZ-cy forms a ring-like structure at the division plane of cyanelles. In addition, an FtsZ arc and a split FtsZ ring emerge during the early and late stages of cyanelle division, respectively. The FtsZ arc and FtsZ ring formed even when peptidoglycan synthesis was inhibited by ampicillin. Thus, the formation of the FtsZ arc and FtsZ ring is the earliest sign of cyanelle division, followed by constriction and septum formation. In this study, we also investigated the dynamics of the surface of dividing cyanelles using a field emission scanning electron microscopy (FE-SEM). The resulting micrographs show that shallow furrows form on the surface of the kidney-shaped cyanelles. A shallow furrow forms where the FtsZ arc exists beneath the surface. Based on the results of FE-SEM and TEM, we concluded that an internal mechanical force related to septum formation, rather than an external force, generates the force that constricts the cyanelle.

Key words: cyanelle, peptidoglycan, plastid division, FtsZ