Regulation Of The Cell Division Mechanism By Alr1550 In Anabaena Sp.PCC 7120

The filamentous cyanobacterium Anabaena sp.strain PCC 7120 is not only able to use combined nitrogen sources,such as nitrate or ammonium,but also atmospheric N2.In the latter case N2 is fixed by heterocysts,which are specialized from vegetative cells for nitrogen fixation in diazotrophic growth condition.Thus,Anabaena sp.strain PCC 7120 is one of the simplest model for the study of cellular differentiation and multicellular pattern formation.Heterocysts are terminally differentiated cells and cannot undergo cell division.Despite several studies have shown that heterocyst differentiation is tightly coupled with cell division,the relationship between cell division and cell differentiation has not been revealed yet.Previous studies in our lab have shown that the expression of alr1550 is up-regulated significantly in response to nitrogen deprivation,and such up-regulation is directly controlled by NtcA in Anabaena sp.PCC 7120.The studies also showed that inactivation of Alr1550 affects heterocyst development and overexpression of it causes abnormal cell morphology and asymmetrical cell division,strongly suggesting that Alr1550 may function as one of an important link between cell division and cell differentiation.In this study I focused on investigating the role of Alr1550 in cell division in Anabaena sp.PCC 7120.I found that overexpression of Alr550 and FtsZ in Anabaena sp.PCC 7120 showed similar phenotypes,which include asymmetric cell division and abnormal cell morphology.E.coli cells having Alr1550 overexpressed exhibited similar phenotypes as well.It seems that overexpression of Alr1550 did not have an effect on cellular DNA content,as examined by DAPI staining.By exploiting several methods including Far-Western Blotting,Co-purification and bacterial two hybrid assay,it was demonstrated that Alr1550 could physically interact with FtsZ.In the strain overexpressing Alr1550,the protein level of FtsZ was similar to that of the wild-type strain,but the subcellular localization of FtsZ was dramatically altered.These results suggest that Alr1550 may modulate cell division by regulating the subcellular localization of FtsZ via their protein-protein interaction.