Additional bands of different intensity, not detected in the S. meliloti total RNA, corresponding to RNA species smaller than the full-length transcripts PND-1186 mouse were also visible when CoIP RNA was hybridized to SmrC9, SmrC16 and SmrC45 probes. A recent report addressing the stability of the seemingly homologous SmrC15 and SmrC16 sRNAs in a S. meliloti 2011 Δhfq mutant suggested that Hfq protects both full-length transcripts from degradation and stabilises degradation products corresponding
Sotrastaurin supplier specifically to the 3′-half of SmrC16 . Our results corroborate that both, SmrC15 and SmrC16 sRNAs do bind Hfq and also suggest that the major band detected by the SmrC16 probe could correspond to a degradation product of this transcript interacting with a particular high efficiency with the protein. Nonetheless, the identity of this SmrC16-derived product remains controversial since the probe used in our study hybridizes to the 5′-half JAK inhibitor rather than to the 3′-end of the full-length transcript. Thus, further verifications should be carried out to elucidate this apparent contradiction. Similarly, the additional
faint hybridization bands detected with SmrC9 and SmrC45 probes could be interpreted as corresponding to degradation products of these sRNAs retaining a less efficient binding capacity to Hfq than the full-length transcripts. Figure 7 Binding of S. meliloti sRNAs to a FLAG-epitope
tagged Hfq protein. Western-blot showing the specific recognition of the chromosomally encoded 3 × FLAG tagged Hfq protein by ANTI-FLAG M2® monoclonal antibodies in total protein extracts of two independent 1021hfq FLAG strains (i.e. two different clones arising from the second cross-over event) (left panel); and Northern analysis of CoIP RNA from the 1021hfq FLAG and wild-type strains for the detection of the Smr sRNAs (right panel). Lane 1 shows the expression pattern of the corresponding sRNAs in the wild-type strain. Discussion There is increasing evidence that the ubiquitous RNA chaperone Hfq acts as a global post-transcriptional regulator controlling gene networks underlying key steps in the interactions of pathogenic bacteria with their eukaryotic hosts . However, why its role in beneficial host-microbe interactions had not been investigated in detail. Here, we have genetically addressed the function of Hfq in the nitrogen-fixing endosymbiont S. meliloti, both as free-living bacterium and during the symbiotic interaction with its legume host alfalfa. As summarized in the model shown in Fig. 8, our results suggest the involvement of Hfq in bacterial pathways affecting central metabolism, rhizospheric competence, survival within the nodule cells and symbiotic nitrogen fixation.