FIG 4.

Cu-dependent misregulation of metal homeostasis genes. GAS ΔcopA mutant strain was cultured with or without added 0.5 μM Cu for the indicated times (n = 4). Transcript levels in Cu-treated cultures were determined by qPCR and normalized to the corresponding untreated samples that were cultured for the same time periods. Dotted horizontal lines represent the limit of the assay (log₂FC = ±0.5). A schematic representation of each gene and its cognate metallosensor is shown. Transcription of copZ or cadD is derepressed upon binding of Cu to CopY or Zn (or Cd) to CadR, respectively. Transcription of adcAII or siaA is repressed upon binding of Zn to AdcR or Mn (or Fe) to MtsR, respectively. (A) copZ. Cu treatment induced copZ expression t = 0 h (P = 0.0037 versus log₂FC = 0). This magnitude of induction remained unchanged over the growth period (ns, P = 0.53, 0.94, 0.47, and 0.90 for t = 2, 3, 4, and 5 h, respectively, versus t = 0 h). (B) cadD. Cu treatment upregulated cadD expression at t = 4 and 5 h (P = 0.0044 and < 0.0001, respectively, versus log₂FC = 0). (C) adcAII. Cu treatment downregulated adcAII expression at t = 4 and 5 h (P = 0.035 and 0.0004, respectively, versus log₂FC = 0). (D) siaA. Cu treatment downregulated siaA expression at t = 3, 4, and 5 h (P = 0.014, 0.012, and 0.084, respectively, versus log₂FC = 0).