Fig. 4: Arginine regulates mucoidy by increasing rmpADC transcription in an ArgR-dependent manner.

KPPR1 and the ∆argR mutant were cultured under different amino acid conditions (M9 + All, M9-Arg, M9 + Glyc, M9 + Glyc + Arg). A Rmp promoter (P_rmp) activity was measured by GFP expression via a promoter fusion. RNA was isolated from mid-log cultures of KPPR1 in the four media or from ∆argR and the complementation vectors (KPPR1 + EV, argR + EV, or argR+pargR) in M9 + All. B−E The relative abundance of rmpA, rmpD, and rmpC RNA under the different conditions was determined by qRT-PCR and normalized to gap2 transcript abundance. B, C Relative transcript levels in KPPR1 cultured in M9-Arg or M9+Glyc+Arg were compared to M9 + All or M9 + Glyc, respectively, while (D) the ∆argR mutant (cultured in M9 + All) transcript levels were compared to wildtype, KPPR1. (E) The complementation transcript levels were compared to KPPR1 + EV. Data presented are the mean, and error bars represent the standard error of the mean. Statistical significance was determined in panel (A) with a two-way ANOVA with Tukey’s post-test. The statistics displayed above the data bars represent values relative to M9 + All. Statistics connected by lines identify other direct comparisons. In panels (B–E) significance was determined using a two-tailed unpaired t-test to determine. p-values are displayed above each comparison; *p < 0.05; **p < 0.01; ***p < 0.001; # p < 0.0001. Exact P-values: (A) left to right above data bars: <0.0001, <0.0001; connected by lines: <0.0001, <0.0001, 0.0005, <0.0001; (B) left to right: 0.0002, 0.0002, 0.0199; (C) left to right: 0.0007, 0.0012, 0.0018; (D) left to right: 0.0127, 0.0060, 0.0008; (E) left to right: 0.0107, 0.0398, 0.0009, <0.0001. Experiments were performed ≥ 3 independent times (for graph A, n = 9 with biological replicates and for graph B-E, n = 3 with technical replicates). Source data are provided as a Source Data file.