The developmental regulator PatD modulates assembly of the cell‐division protein FtsZ in the cyanobacterium Anabaena sp. PCC 7120

Abstract

Summary FtsZ is a tubulin‐like GTPase that polymerizes to initiate the process of cell division in bacteria. Heterocysts are terminally differentiated cells of filamentous cyanobacteria that have lost the capacity for cell division and in which the ftsZ gene is downregulated. However, mechanisms of FtsZ regulation during heterocyst differentiation have been scarcely investigated. The patD gene is NtcA dependent and involved in the optimization of heterocyst frequency in Anabaena sp. PCC 7120. Here, we report that the inactivation of patD caused the formation of multiple FtsZ‐rings in vegetative cells, cell enlargement, and the retention of peptidoglycan synthesis activity in heterocysts, whereas its ectopic expression resulted in aberrant FtsZ polymerization and cell division. PatD interacted with FtsZ, increased FtsZ precipitation in sedimentation assays, and promoted the formation of thick straight FtsZ bundles that differ from the toroidal aggregates formed by FtsZ alone. These results suggest that in the differentiating heterocysts, PatD interferes with the assembly of FtsZ. We propose that in Anabaena FtsZ is a bifunctional protein involved in both vegetative cell division and regulation of heterocyst differentiation. In the differentiating cells PatD‐FtsZ interactions appear to set an FtsZ activity that is insufficient for cell division but optimal to foster differentiation.

Functions of the Essential Gene mraY in Cellular Morphogenesis and Development of the Filamentous Cyanobacterium Anabaena PCC 7120

“…This is in agreement with previous finding indicating that some members of the PBPs is necessary for PG layer formation or maintenance in heterocysts, thus for functional heterocyst formation (Lázaro et al, 2001;Leganés et al, 2005). It is also consistent with the enhanced HADA incorporation observed during heterocyst formation (Zhang et al, 2018;Wang et al, 2021). We found that even a low level of inducer added to strain TRS-mraY could restore heterocyst formation, but led to a high percentage of doublets heterocysts.…”

“…Therefore, we examined whether FtsZ-ring formation and PG biogenesis are altered in the TRS- mraY mutant under permissive and non-permissive conditions. For this, we constructed a ftsZ-cfp :TRS- mraY strain in which chromosomal copy of ftsZ was replaced by ftsZ-cfp fusion ( Wang et al, 2021 ). The fluorescence of FtsZ-CFP (cyan fluorescent protein) was then observed.…”

“…HetF and SepI are direct components of the divisome ( Springstein et al, 2020 ; Xing et al, 2021 ), and PatA also influences cell division ( Valladares et al, 2020 ). FtsZ is a dual functional protein for both cell division and the regulation of heterocyst development ( Wang et al, 2021 ). The enhanced activity of PG synthesis during heterocyst constitutes one interesting point for our further understanding of cell division and heterocyst development in Anabaena .…”

“…FtsI interacts with HetF, a protein required for heterocyst differentiation and participates in PG constriction during cell division under high light ( Xing et al, 2021 ). Another developmental regulator PatD controls the FtsZ activity in developing cells, and may be responsible for the control of heterocyst cell size with increased PG synthesis ( Wang et al, 2021 ). These studies indicate that the PG layers are important for heterocyst development and functioning.…”

A proteolytic pathway coordinates cell division and heterocyst differentiation in the cyanobacterium Anabaena sp. PCC 7120

“…At the late step of cell division, PG remodeling, catalyzed by enzymes of the divisome, occurs for cell constriction and septation. In Anabaena , FtsZ plays a role not only in cell division, but also in heterocyst development ( 30 ). The HetF protein appears to be a critical link between cell division and heterocyst differentiation ( 27 ).…”