The Proteomic and Transcriptomic Landscapes Altered by Rgg2/3 Activity in Streptococcus pyogenes

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• *Streptococcus pyogenes* (Group A Streptococcus, GAS) is a significant human pathogen.
• Understanding GAS environmental sensing and response is crucial for disease mechanism elucidation.
• The Rgg2/3 quorum sensing (QS) system regulates GAS surface changes in response to environmental factors like metals and carbohydrates.

Purpose of the Study:

• To investigate the impact of the Rgg2/3 QS system on *S. pyogenes* physiology.
• To define the pheromone-dependent regulon of the Rgg2/3 QS system.
• To explore the connection between Rgg2/3 QS and the stringent response under exaggerated pheromone conditions.

Main Methods:

• RNA-sequencing (RNA-seq) and tandem mass tag (TMT)-LC-MS/MS analysis were employed.
• Comparative analysis of wild-type, pheromone-induced, and *rgg3* deletion mutant strains.
• Genetic manipulation of stringent response genes (*relA*, *sasA*, *sasB*) and Rgg2/3 signaling.

Main Results:

• Pheromone stimulation primarily induced operons with known Rgg2/3 binding sequences in wild-type strains.
• Disruption of *rgg3* led to extensive transcriptome and proteome alterations, indicative of stress responses.
• A link between Rgg2/3 QS and the stringent response was identified, with mutations affecting GAS physiology and QS induction.
• Excessive pheromone exposure induced stress responses indirectly altering the proteome and transcriptome.

Conclusions:

• The Rgg2/3 QS system directly regulates specific gene sets in *S. pyogenes*.
• Exaggerated pheromone signaling triggers stress responses, including the stringent response, impacting GAS physiology.
• Disruption of the stringent response impairs the Rgg2/3 QS system's ability to respond to normal induction.
• This study enhances understanding of how *S. pyogenes* responds to environmental stress and communication signals.