MapZ marks the division sites and positions FtsZ rings in Streptococcus pneumoniae

Abstract

In every living organism, cell division requires accurate identification of the division site and placement of the division machinery. In bacteria, this process is traditionally considered to begin with the polymerization of the highly conserved tubulin-like protein FtsZinto a ringthat locates precisely atmid-cell1.Over thepast decades, several systems have been reported to regulate the spatiotemporal assembly and placement of the FtsZ ring2-5. However, the human pathogen Streptococcus pneumoniae, in common withmany other organisms, is devoid of these canonical systems and the mechanisms of positioning the divisionmachinery remain unknown4,6.Herewe characterize a novel factor that locates at the division site before FtsZ and guides septumpositioning in pneumococcus. Mid-cell-anchored protein Z (MapZ) forms ring structures at the cell equator and moves apart as the cell elongates, therefore behaving as a permanent beacon of division sites.MapZ then positions the FtsZ ring through direct protein-proteininteractions.MapZ-mediated control differs frompreviously described systems mostly on the basis of negative regulation of FtsZ assembly.Furthermore,MapZis an endogenous targetof the Ser/Thr kinase StkP, which was recently shown to have a central role in cytokinesis and morphogenesis of S. pneumoniae7-9.Weshow that both phosphorylated andnon-phosphorylated forms ofMapZare required for proper Z-ring formation and dynamics. Altogether, this work uncovers a newmechanismfor bacterial cell division that is regulated by phosphorylation and illustrates that nature has evolved a diversity of cell division mechanisms adapted to the different bacterial clades.