Figure 1.

Uridine level in C. elegans is impacted by the CRP–CytR complex in E. coli (dietary bacteria) and two CDDs in C. elegans. (A,B) Cartoon illustrations of the IS2 insertion (and a 5-nucleotied [nt] target site duplication [nucleotides 530–534]) identified in the cytR gene of the HT115 E. coli strain and the 15-nt deletion identified in the crp gene of the HT115/crp⁻ E. coli strain. The number 1 in the cartoon indicates the nucleotide of the start codon. (C) Cartoon illustration of the established role of cytidine as an inducer of the CRP–CytR complex in E. coli. Binding of cellular cytidine to CytR dissociates CytR from the complex, resulting in transcriptional activation of CRP-regulated genes (Pedersen et al. 1991). The CRP–CytR-regulated genes are listed by functional categories (adapted from the EcoCyc E. coli Database). (D) Uridine levels in OP50 and OP50/cytR⁻ E. coli strains measured by high-performance liquid chromatography (HPLC)-UV analysis. The bars represent the mean of three independent experiments and are expressed on the Y-axis as area counts of uridine UV absorption peaks (identified by Analyst software) per OD₆₀₀ of the starting bacterial cultures. (E) HPLC-UV analysis graphs of small nucleosides extracted from wild-type and cdd-1/2 DKO worms. The identities of the peaks are indicated.