Dynamic localization of a cytoplasmic signal transduction response regulator controls morphogenesis during the Caulobacter cell cycle

We present evidence that a bacterial signal transduction cascade that coupl es morphogenesis with cell cycle progression is regulated by dynamic locali zation of its components. Previous studies have implicated two histidine ki nases. DiVJ and PleC, and the response regulator, DivK, in the regulation o f morphogenesis in the dimorphic bacterium Caulobacter crescentus. Here, we show that the cytoplasmic response regulator, D[VK, exhibits a dynamic, cy clical localization that culminates in asymmetric distribution of DivK with in the two cell types that are characteristic of the Caulobacter cell cycle ; DivK is dispersed throughout the cytoplasm of the progeny swarmer cell an d is localized to the pole of the stalked cell. The membrane-bound DivJ and PleC histidine kinases, which are asymmetrically localized at the opposite poles of the predivisional cell, control the temporal and spatial localiza tion of DivK. DivJ mediates DivK targeting to the poles whereas PleC contro ls its release from one of the poles at times and places that are consisten t with the activities and location of DivJ and PleC in the tate predivision al cell. Thus, dynamic changes in subcellular location of multiple componen ts of a signal transduction cascade may constitute a novel mode of prokaryo tic regulation to generate and maintain cellular asymmetry.