The Relationship Between The Suppression Protein HetN And Cell Division Protein FtsZ In Anabaena Sp.PCC 7120

Anabaena sp.PCC 7120 is a filamentous and photoautotrophic cyanobacterium,and is an ideal material to study prokaryotic signal transduction and cell differentiation.When combined nitrogen becomes short in the environment,there will be 5%-10%of the cell along the filaments transforming into heterocysts,which are able to fix nitrogen from the air and supply the fixed nitrogen to neighboring cells,supporting the normal growth of the whole filaments.Heterocysts are terminally differentiated cells and could not undergo division any longer.Cells on the filament will stop division,when they are ready to develop into heterocysts.Studies in the past years have showed that the cell division and heterocyst differentiation are inextricablyintrinsically linked in the past years,while the underlying mechanisms remained unclear.The purpose of this study is to explore mutual effects of cell division and heterocyst differentiation by investigating the relationship between the cell division protein FtsZ and the heterocyst formation regulator HetN.Bacterial cell division is accomplished by many of the proteins,including FtsZ,which is very conserved in many organisms.FtsZ has the structure similar to that of eukaryotic tubulin.At the initial stage of cell division,FtsZ was gathered at the splitting location,forming a Z ring to recruit many other proteins involved in the cell division.HetN is one of the negative regulators for heterocyst development in Anabaena sp.PCC 7120.When HetN is overexpressed,heterocyst differentiation will be completely inhibited;whereas when it is inactivated,multiple continuous heterocysts will form along the filaments while nitrogen is depleted.We found that overexpression FtsZ in Anabaena sp.PCC 7120 led to the formation of multiple contiguous heterocysts upon nitrogen depletion,a phenotype similar to that of the hetN mutant.We investigated the intracellular localization of HetN by expressing the HetN-GFP fusion protein in vivo.The GFP fluorescence was mainly localized at the cell plate in dividing cells,suggesting there may be interaction between HetN with FtsZ.By bacterial two-hybrid assay and far-western blot we comfirmed such interaction.The findings suggest that FtsZ may affect heterocyst differntiation by interacting with HetN.