Fig. 5: GacA and CsrA mediate the biosynthesis of pseudoiodinine. | Nature Communications

Fig. 5: GacA and CsrA mediate the biosynthesis of pseudoiodinine.

From: The natural pyrazolotriazine pseudoiodinine from Pseudomonas mosselii 923 inhibits plant bacterial and fungal pathogens

Fig. 5

a Antibacterial activity assays of P. mosselii 923, ΔrsmY, ΔrsmZ, and ΔrsmYZ mutant and complemented mutants CΔrsmY, CΔrsmZ, and CΔrsmYZ. Panels b, d, HPLC profiles (Method B, detected at 500 nm) of the mutants and complemented strains compared with the wild-type 923. Panels c, e, pseudoiodinine production by different strains. The numbers on y-axes show pseudoiodinine yields. c The wild-type 923, rsmY, rsmZ, and rsmYZ mutants and their corresponding complemented strains in LB medium. Error bars show means ± SD (n = 3 biological independent replicates) and significant differences at ***P < 0.001, ***P = 0.0002, = 2.5 × 10−14, = 1.5 × 10−10 in sequence. e Pseudoiodinine yields in wild-type P. mosselii 923 in LB and TSB medium, the csrA1, csrA2, csrA3, csrA1A2, csrA1A3, csrA2A3 and csrA1A2A3 mutants, and overexpressing and RBS-swapped strains in TSB medium. Error bars show means ± SD (n = 3 biological independent replicates) and significant differences at ***P < 0.001, **P < 0.01, **P = 0.005, ***P = 4.5 × 10−10, = 1.1 × 10−9, = 9.3 × 10−17 in sequence. One-way ANOVA followed by LSD test. Experiments were performed three times independently with similar results. f Proposed model of GacA/CsrA-mediated regulation of pseudoiodinine biosynthesis in P. mosselii 923. In strain 923, the GacS/GacA TCS responds to uncharacterized signals, and GacA activates transcription of two non-coding RNAs (rsmY and rsmZ) by binding to their promoters, thereby positively regulating pseudoiodinine production. The two CsrA/RsmA homologs, CsrA2 and CsrA3, inhibit the initiation of pseudoiodinine synthesis. CsrA2 and CsrA3 interact predominantly with GGA-containing sequences/loops in the 5’-untranslated region of psdA mRNAs; this site overlaps the RBS and interferes with translation of the psdA transcript. RsmY and RsmZ contain multiple CsrA/RsmA binding sites within the predicted stem-loops that compete with mRNAs for CsrA2 and CsrA3 binding, thus antagonizing the suppression of translation.

Back to article page