Septal localization of forespore membrane proteins during engulfment in Bacillus subtilis.
In Bacillus subtilis, many membrane proteins localize to the sporulation septum, where they play key roles in spore morphogenesis and cell-specific gene expression, but the mechanism for septal targeting is not well understood. SpoIIQ, a forespore-expressed protein, is involved in engulfment and forespore-specific gene expression. We find that SpoIIQ dynamically localizes to the sporulation septum, tracks the engulfing mother cell membrane, assembles into helical arcs around the forespore and is finally degraded. Retention of SpoIIQ in the septum requires one or more mother cell-expressed proteins. We also observed that any forespore-expressed membrane protein initially localizes to the septum and later spreads throughout the forespore membrane, suggesting that membrane protein insertion occurs at the forespore septal region. This possibility provides an attractive mechanism for how activation of mother cell-specific gene expression is restricted to adjacent sister cells, since direct insertion of the signaling protein SpoIIR into the septum would spatially restrict its activity. In keeping with this hypothesis, we find that SpoIIR localizes to the septum and is transiently expressed.
Rubio
Aileen
A
Division of Biological Sciences, University of California-San Diego, La Jolla, CA, USA.
Pogliano
Kit
K
D001412:Bacillus subtilis / Q000166:cytology* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D013171:Spores, Bacterial / Q000166:cytology* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C092468:spoIIR protein, Bacillus subtilis