Integration of the Cell Cycle and Development in Agrobacterium tumefaciens

A bacterium’s ability to properly sense and respond to its internal and external environments is crucial for the survival of the bacterium. As such, alphaproteobacteria like Agrobacterium tumefaciens have evolved key two-component systems and phosphorelays to quickly adapt to these changes. Several of these key phosphotransfer systems regulate cell cycle progression and affect key developmental phenotypes including attachment and biofilm formation, motility, cell morphology, and virulence. In this chapter, we describe the primary A. tumefaciens cell cycle regulatory pathway: the DivJ/PleC/PdhS-DivK/PleD and CckA-ChpT-CpdR/CtrA phosphorelays and their associated proteins. We aim to focus on each protein involved in these phosphorelays, describing the current state of Agrobacterium research while providing a fundamental background of the history of these proteins in other alphaproteobacteria. This chapter covers the gene regulation, protein biosynthesis and degradation, and downstream effects caused by the overexpression or deletion of these cell cycle-associated proteins. Finally, we address current shortcoming in Agrobacterium cell cycle research while highlighting emerging data and trends.