Cyanobacteria are the earliest known oxygenic photosynthetic organisms on Earth, and they played decisive roles in the evolution of the environment and the life on our planet. Cell morphology and cell size of different cyanobacteria species vary widely, but each species has inheritable and distinct cell morphology and cell size that are stably maintained through the generations. The underlying mechanisms of such a homeostasis have been unknown. In a study published in Proceedings of the National Academy of Sciences, the research group led by Prof. Zhang Chengcai from the Institute of Hydrobiology (IHB) of the Chinese Academy of Sciences reported a new cell size regulation mechanism which represents an important advance in understanding cell morphology and cell size controlling of cyanobacteria. Previous studies by Prof. Zhang’s group have showed that the second messenger c-di-GMP may be an intracellular proxy for cell size control in the filamentous cyanobacterium Anabaena PCC 7120. However, it was unclear how this chemical signal is perceived in cells. In addition, all c-di-GMP receptors known in other organisms are not conserved in cyanobacteria, posing a challenge to understand the physiological function of c-di-GMP in cyanobacteria.
In this study, the researchers identified and characterized the first c-di-GMP receptor, CdgR, from the cyanobacterium Anabaena. Crystal structural analysis and genetic studies showed that CdgR binds c-di-GMP at the dimer interface, and this binding is required for the control of cell size in a c-di-GMP-dependent manner.
By Liu Jia, Chinese Academy of Sciences
Article can be accessed on: phys.org