FtsZ of Filamentous, Heterocyst-Forming Cyanobacteria Has a Conserved N-Terminal Peptide Required for Normal FtsZ Polymerization and Cell Division

Abstract

Filamentous cyanobacteria grow by intercalary cell division, which should involve distinct steps compared to those producing separate daughter cells. The N-terminal region of FtsZ is highly conserved in the clade of filamentous cyanobacteria capable of cell differentiation. A derivative of the model strain Anabaena sp. PCC 7120 expressing only an FtsZ lacking the amino acids 2–51 of the N-terminal peptide (ΔN-FtsZ) could not be segregated. Strain CSL110 expresses both ΔN-FtsZ, from the endogenous ftsZ gene promoter, and the native FtsZ from a synthetic regulated promoter. Under conditions of ΔN-FtsZ predominance, cells of strain CSL110 progressively enlarge, reflecting reduced cell division, and show instances of asymmetric cell division and aberrant Z-structures notably differing from the Z-ring formed by FtsZ in the wild type. In bacterial 2-hybrid assays FtsZ interacted with ΔN-FtsZ. However, ΔN-FtsZ-GFP appeared impaired for incorporation into Z-rings when expressed together with FtsZ. FtsZ, but not ΔN-FtsZ, interacted with the essential protein SepF. Both FtsZ and ΔN-FtsZ polymerize in vitro exhibiting comparable GTPase activities. However, filaments of FtsZ show a distinct curling forming toroids, whereas ΔN-FtsZ form thick bundles of straight filaments. Thus, the N-terminal FtsZ sequence appears to contribute to a distinct FtsZ polymerization mode that is essential for cell division and division plane location in Anabaena.

Interactions of PatA with the Divisome during Heterocyst Differentiation in Anabaena

“…We have also studied the localization of FtsZ upon N-stepdown in Anabaena strain CSSC19, which expresses a ftsZ-gfp-mut2 gene fusion placed at the ftsZ locus and which keeps an intact copy of ftsZ also expressed from the native promoter ( 19 ) ( Fig. 2A ).…”

“…Localization of FtsZ during heterocyst differentiation in Anabaena. (A) Schematic of the genome structure of strain CSSC19 (ftsZ-gfp-mut2)(19) in comparison to PCC 7120 (WT). The gray trace represents an inserted plasmid encoding resistance to Sm and Sp.…”

“…Visualization of FtsZ in a patA mutant background. (A) Schematic of the genome structure of strain CSSC19 (ftsZ-gfp-mut2 in WT background)(19) and strain CSAV38 (ftsZ-gfp-mut2 in patA mutant background) (see Materials and Methods for details). (B) Nitrate-grown filaments were observed under a fluorescence microscope and photographed.…”

Assembly properties of FtsZ from cyanobacteriumSynechocystissp. PCC 6803

“…It indicates that the FtsZ circles might be useful for its function. Recently, Corrales-Guerrero L et al (41) reported that deletion of N-terminus of Anabaena FtsZ, another cyanobacterial FtsZ, only formed straight bundles. These mutant FtsZs might cause the aberrant Z-structures and asymmetric cell division.…”

“…These mutant FtsZs might cause the aberrant Z-structures and asymmetric cell division. It indicated that the formation of the medium circles might be necessary for its function, and even it cannot be excluded the possibility that deletion might affect the binding with the other association proteins (41).…”