Do FtsZ Proteins Have Other Cytoskeletal Functions in the Chloroplast?
Recently, Kiessling et al. 2000 described the presence of FtsZ-containing, cytoskeletal-like networks in the chloroplasts of Physcomitrella. These were visualized by transient expression of the two Physcomitrella chloroplast FtsZ-GFP fusion proteins referred to above. Our current and previous results regarding the effects of AtFtsZ1-1 and AtFtsZ1-1–GFP accumulation and localization in Arabidopsis parallel those of the moss study in two respects. First, AtFtsZ1-1, AtFtsZ1-1–GFP, and the two moss fusion proteins all behaved similarly in their transgenic hosts, causing dosage-dependent defects in plastid division. Second, all of these proteins could be detected in filamentous networks when they were overexpressed. The authors of the Physcomitrella study proposed that these networks represent a normally occurring in vivo structure which they termed the “plastoskeleton” and postulated its involvement in maintaining chloroplast integrity (Kiessling et al. 2000). The idea that FtsZ proteins p
