Fig. 1: Nitrogen uptake and transcriptional dynamics upon ppGpp accumulation.

RelQ catalyzes the ATP-dependent conversion of GDP to ppGpp. a RelQ cells with (●, RelQ-ox) or without (○, RelQ) 1 mM IPTG addition after 72 h of initial culturing in the presence of 17 mM sodium nitrate and 1% (v/v) CO₂ at different time-points. GDP and ppGpp levels were measured using a capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) system. Statistical significance was determined using Student’s t test (**p < 0.01, *p < 0.05). b Nitrate uptake response to ppGpp accumulation at different time-points. Each colored arrow indicates the timing of 1 mM IPTG addition as the final concentration (without IPTG, blue line; 2 d later, orange line; 3 d later, gray line; 4 d later, yellow line). c Changes in mRNA expression in RelQ cells. RNA-seq was performed for cells treated under the following conditions: RelQ cells after 6 h or 24 h with or without 1 mM IPTG addition. All panels present MA-plots (fold change vs. average) based on transcripts per million (TPM) normalization. Orange or green dots, with the gene name indicated, represent genes detected as differentially expressed with p ≤ 0.05 and Log₂FC ≥1, respectively. Genes that were not differentially expressed are colored in gray. Data are means of two biologically independent experiments.