RNase E affects the expression of the acyl-homoserine Lactone synthase gene sinI in Sinorhizobium meliloti.

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    • Abstract:
      Quorum sensing of Sinorhizobium meliloti relies on N-acyl-homoserine lactones (AHLs) as autoinducers. AHL production increases at high population density and this depends on the AHL synthase SinI and two transcriptional regulators: SinR and ExpR. Our study demonstrates that ectopic expression of the rne gene coding for RNase E, an endoribonuclease that is probably essential for growth, prevents the accumulation of AHLs at detectable levels. The ectopic rne expression led to a higher level of rne mRNA and lower level of sinI mRNA independently of the presence of ExpR, the AHL receptor, and AHLs. In line with this, IPTG(isopropyl-β-D-thiogalactopyranoside)-induced overexpression of rne resulted in a shorter half-life of sinI mRNA and a strong reduction of AHL accumulation. Moreover, using translational sinI-egfp fusions we found that sinI expression is specifically decreased upon induced overexpression of rne, independently of the presence of the global post-transcriptional regulator Hfq. The 28 nucleotide 5'-UTR of sinI mRNA was sufficient for this effect. 5'-RACE analyses revealed a potential RNase E cleavage site at position +24 between the Shine-Dalgarno site and the translation start. We postulate therefore that RNase E-dependent degradation of sinI mRNA from the 5'-end is one of the steps mediating a high turn-over of sinI mRNA, which allows the Sin quorum sensing system to respond rapidly to changes in transcriptional control of AHL production. [ABSTRACT FROM AUTHOR]
    • Abstract:
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