SpxA1 and SpxA2 Function as a Stoichiometry-Dependent Regulatory Rheostat Governing Virulence Gene Expression in Group A Streptococcus — NanoString nCounter dataset

SpxA2 is directly regulated by the LiaFSR three-component system in response to antimicrobial peptide (AMP) stress. To define how SpxA1 and SpxA2 influence virulence gene expression under cell envelope stress, we performed NanoString nCounter analysis using a custom 119-probe codeset (116 endogenous targets plus 3 housekeeping probes: tufA, gyrA, guaB) in wild-type MGAS10870 (emm3) and isogenic deletion mutants (deltaSpxA1 and deltaSpxA2) under three conditions: uninduced (UI), sub-MIC bacitracin (BAC), and sub-MIC human neutrophil peptide-1 (hNP-1).

Differential expression analysis identified condition- and paralog-specific changes in CovR-regulated virulence factor-encoding genes consistent with a stoichiometry-dependent regulatory model.