Abstract
Protein polarization underlies differentiation in metazoans and in bacteria. How symmetric polarization can instate functional asymmetry remains elusive. Here, we show by super-resolution photo-activated localization microscopy and edgetic mutations that the bitopic zinc-finger protein ZitP implements specialized developmental functions - pilus biogenesis and multifactorial swarming motility - while shaping distinct nanoscale (bi)polar architectures in the asymmetric model bacterium Caulobacter crescentus. Polar assemblage and accumulation of ZitP and its effector protein CpaM are orchestrated in time and space by conserved components of the cell cycle circuitry that coordinate polar morphogenesis with cell cycle progression, and also act on the master cell cycle regulator CtrA. Thus, this novel class of potentially widespread multifunctional polarity regulators is deeply embedded in the cell cycle circuitry.
Highlights
Some regulatory proteins that execute important developmental, cytokinetic or morphogenetic functions are localized in monopolar fashion, whereas others are sequestered to both cell poles (Dworkin, 2009; Martin and Goldstein, 2014; Shapiro et al, 2002; St Johnston and Ahringer, 2010)
ZitP and CpaM are not restricted to the Caulobacter lineage as BLASTP searches revealed orthologs in many a-proteobacterial clades (Figure 1D)
While ZitP acts on pilus assembly by recruiting CpaM and, subsequently, the CpaC pilus channel to the pole opposite the stalk (1B and 4E), CpaM is required for efficient activation of CtrA-dependent promoters by an unknown mechanism
Summary
Some regulatory proteins that execute important developmental, cytokinetic or morphogenetic functions are localized in monopolar fashion, whereas others are sequestered to both cell poles (Dworkin, 2009; Martin and Goldstein, 2014; Shapiro et al, 2002; St Johnston and Ahringer, 2010). It is unclear if bipolar proteins can confer specialized functions from each polar site, but examples of proteins with a bipolar disposition have been reported for eukaryotes and prokaryotes (Davis et al, 2013; Martin and Berthelot-Grosjean, 2009; Tatebe et al, 2008; Treuner-Lange and SogaardAndersen, 2014). Upon sequential transcriptional activation of developmental factors during the cell
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