Bacteriophytochromes control conjugation in Agrobacterium fabrum

Area of Science:

• Microbiology
• Molecular Biology
• Plant Science

Background:

• Bacterial conjugation is a key mechanism for horizontal gene transfer, mediated by type IV secretion systems.
• Phytochromes are photoreceptors sensitive to red and far-red light, regulating various plant processes.
• The role of phytochromes in bacterial conjugation is largely unexplored.

Purpose of the Study:

• To investigate the role of phytochromes Agp1 and Agp2 in modulating bacterial conjugation in Agrobacterium fabrum.
• To determine if light influences conjugation rates via phytochrome signaling.

Main Methods:

• Conjugation assays were performed using a transmissible artificial plasmid reporter in Agrobacterium fabrum.
• Experiments utilized wild-type, agp1(-), agp2(-), and double knockout strains.
• Conjugation rates were measured under varying light conditions (dark, red, far-red) and temperatures.

Main Results:

• Phytochromes Agp1 and Agp2 were found to suppress conjugation in wild-type Agrobacterium fabrum.
• Loss of Agp1 or Agp2 in donor or recipient cells led to increased conjugation.
• Red or far-red light significantly downregulated conjugation in wild-type strains, while knockouts showed altered responses.
• Conjugation decreased with temperature, correlating with phytochrome autophosphorylation.

Conclusions:

• The phytochrome system in Agrobacterium fabrum has evolved to inhibit bacterial conjugation in response to light.
• Phytochromes act as negative regulators of conjugation, with light signaling playing a crucial role.
• Temperature influences phytochrome activity and consequently conjugation rates.