title: SepG coordinates sporulation-specific cell division and nucleoid organization in Streptomyces coelicolor.
abstract: Bacterial cell division is a highly complex process that requires tight coordination between septum formation and chromosome replication and segregation. In bacteria that divide by binary fission a single septum is formed at mid-cell, a process that is coordinated by the conserved cell division scaffold protein FtsZ. In contrast, during sporulation-specific cell division in streptomycetes, up to a hundred rings of FtsZ (Z rings) are produced almost simultaneously, dividing the multinucleoid aerial hyphae into long chains of unigenomic spores. This involves the active recruitment of FtsZ by the SsgB protein, and at the same time requires sophisticated systems to regulate chromosome dynamics. Here, we show that SepG is required for the onset of sporulation and acts by ensuring that SsgB is localized to future septum sites. Förster resonance energy transfer imaging suggests direct interaction between SepG and SsgB. The beta-lactamase reporter system showed that SepG is a transmembrane protein with its central domain oriented towards the cytoplasm. Without SepG, SsgB fails to localize properly, consistent with a crucial role for SepG in the membrane localization of the SsgB-FtsZ complex. While SsgB remains associated with FtsZ, SepG re-localizes to the (pre)spore periphery. Expanded doughnut-shaped nucleoids are formed in sepG null mutants, suggesting that SepG is required for nucleoid compaction. Taken together, our work shows that SepG, encoded by one of the last genes in the conserved dcw cluster of cell division and cell-wall-related genes in Gram-positive bacteria whose function was still largely unresolved,coordinates septum synthesis and chromosome organization in Streptomyces.
authors.affiliation: Molecular Biotechnology, Institute of Biology, Leiden University, PO Box 9505, 2300RA Leiden, The Netherlands.
authors.forename: Le
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Molecular Biotechnology, Institute of Biology, Leiden University, PO Box 9505, 2300RA Leiden, The Netherlands.
authors.forename: Joost
authors.initials: J
authors.lastname: Willemse
authors.affiliation: Molecular Biotechnology, Institute of Biology, Leiden University, PO Box 9505, 2300RA Leiden, The Netherlands.
authors.forename: Dennis
authors.initials: D
authors.lastname: Claessen
authors.affiliation: Molecular Biotechnology, Institute of Biology, Leiden University, PO Box 9505, 2300RA Leiden, The Netherlands g.wezel@biology.leidenuniv.nl.
authors.forename: Gilles P
authors.initials: GP
authors.lastname: van Wezel
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D002455:Cell Division; D017124:Conserved Sequence; D031541:Fluorescence Resonance Energy Transfer; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D021381:Protein Transport; D013171:Spores, Bacterial / Q000502:physiology* / Q000648:ultrastructure; D013302:Streptomyces / Q000166:cytology* / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins
keywords: FtsZ; SsgA-like proteins; cell division control; development