Small RNAs Controlled by Two-Component Systems

Abstract

Two-component systems (TCSs) allow bacteria to monitor diverse environmental cues and to adjust gene expression accordingly at the transcriptional level. It has been recently recognized that prokaryotes also regulate many genes and operons at a posttranscriptional level with the participation of small, noncoding RNAs which serve to control translation initiation and stability of target mRNAs, either directly by establishing antisense interactions or indirectly by antagonizing RNA-binding proteins. Interestingly, the expression of a subset of these small RNAs is regulated by TCSs and in this way, the small RNAs expand the scope of genetic control exerted by TCSs. Here we review the regulatory mechanisms and biological relevance ofa number of small RNAs under TCS control in Gram-negative and -positive bacteria. These regulatory systems govern, for instance, porin-dependent permeability of the outer membrane, quorum-sensing control of pathogenicity, or biocontrol activity. Most likely, this emerging and rapidly expanding field of molecular microbiology will provide more and more examples in the near future.

RNA pentaloop structures as effective targets of regulators belonging to the RsmA/CsrA protein family

“…17,18 In pathogenic bacteria such as P. aeruginosa, Salmonella enterica or Vibrio cholerae, the Gac/Rsm signal transduction pathway is instrumental for virulence. 19,20 In target mRNAs, repeated and appropriately spaced GGA motifs are also essential for effective recognition by RsmA/CsrA proteins. For several E. coli mRNAs binding of CsrA to these GGA motifs has been demonstrated and, similarly, five GGA motifs in the 5' leader of hcnA mRNA of P. fluorescens have been shown to be involved in binding RsmA and RsmE.…”

Bacterial Volatiles Mediating Information Between Bacteria and Plants

“…The wild type of Pseudomonas fluorescens (CHA0) exhibited a strong volatile-dependent retardation of A. thaliana fresh weight, which was partially reestablished in cocultures with the HCN negative mutant P. fluorescens CHA207 (Fig. 6) Other volatiles than HCN also contribute to seedling growth retardation because co-cultivation with a global regulatory P. fluorescens mutant (CHA1144), affected in the synthesis of several secondary metabolites (Valverde and Haas 2008), fully reestablished seedling growth (Fig. 6).…”

Pseudomonas and Azospirillum

“…For instance, P. fl uorescens F113 experiences phase variation during colonization of alfalfa roots, and this is caused by both the activity of a site-specifi c recombinase encoded by the sss gene (the main factor of phase variation) and by a point mutation in the gacA gene that alters the phenotype (Sanchez-Contreras et al 2002 ). Provided the gacA gene is member of a global regulatory system controlling many phenotypes in different pseudomonads (Valverde and Haas 2008 ), phase variation may affect a plethora of other physiological and biochemical traits not as easily visualized as changes in colony aspect. For these reasons, we strongly suggest avoiding repeated subculturing of Pseudomonas isolates or strains, and to keep instead stock cultures under long-term preservation conditions (see Sect.…”