A c-di-GMP binding effector controls cell size in a cyanobacterium

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Cyclic-di-GMP (c-di-GMP) is a crucial bacterial second messenger regulating diverse cellular processes.
• Cyanobacteria utilize c-di-GMP for cell size control, aggregation, and phototaxis, yet their receptors remain unidentified.
• Understanding c-di-GMP signaling is vital for cyanobacteria's ecological and evolutionary significance.

Purpose of the Study:

• To identify and characterize c-di-GMP receptors in cyanobacteria.
• To elucidate the molecular mechanism of c-di-GMP-mediated cell size regulation.
• To investigate the role of c-di-GMP signaling in the filamentous cyanobacterium *Anabaena* PCC 7120.

Main Methods:

• Crystal structural analysis of the identified receptor.
• Genetic studies involving gene manipulation and protein interaction assays.
• Conditional depletion and site-directed mutagenesis of key proteins.

Main Results:

• Identification of CdgR as a novel c-di-GMP receptor in *Anabaena* PCC 7120.
• CdgR binds c-di-GMP at the dimer interface, regulating cell size in a c-di-GMP-dependent manner.
• CdgR interacts with the transcription factor DevH, with c-di-GMP inhibiting this interaction, essential for cell viability.

Conclusions:

• A novel c-di-GMP signaling pathway regulating cell size in cyanobacteria has been revealed.
• CdgR represents a key mediator of c-di-GMP effects on cell size and interacts with DevH.
• The conserved nature of CdgR in cyanobacteria suggests broad implications for understanding c-di-GMP roles in these organisms.