The pyrophosphohydrolase RppH is involved in the control of RsmA/CsrA expression in Azotobacter vinelandii and Escherichia coli

Publication date: Available online 18 May 2018
Source:Microbiological Research
Author(s): Leidy Patricia Bedoya-Pérez, Luis Felipe Muriel-Millán, Soledad Moreno, Elva Quiroz-Rocha, Nancy Rivera-Gómez, Guadalupe Espín
In bacteria, the 5′-end-dependent RNA degradation is triggered by the RNA pyrophosphohydrolase RppH converting tri/diphosphate to monophosphate transcripts. This study shows that in the soil bacterium Azotobacter vinelandii, inactivation of rppH gene negatively affected the production of bioplastic poly-β-hydroxybutyrate (PHB) by reducing the expression at the translational level of PhbR, the specific transcriptional activator of the phbBAC biosynthetic operon. The effect of RppH on the translation of phbR seemed to be exerted through the translational repressor RsmA, as the inactivation of rsmA in the rppH mutant restored the phbR expression. Interestingly, in Escherichia coli inactivation of rppH also affected the expression of CsrA, the RsmA homolog. The level of the csrA transcript was higher and more stable in the E. coli rppH mutant than in the wild type strain. Additionally, and in contrast to the csrA mutants that are known to have a defective swimming phenotype, the E. coli rppH mutant showed a hyper-swimming phenotype that was suppressed by a csrA mutation, and the AvRppH restored to wild type level the swimming phenotype to the E. coli rppH mutant. We propose that in both A. vinelandii and E. coli, RppH activity plays a role in the expression of the translational repressor protein RsmA/CsrA.



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