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Chapter 14 : Cell-to-Cell Communication in Rhizobia: Quorum Sensing and Plant Signaling

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Abstract:

This chapter briefly describes the nodulation process and some of the quorum-sensing regulatory systems that rhizobia use to monitor their population density. Conjugation is common among , and there are very strong selection pressures to optimize growth in the rhizosphere and nodulation competitiveness. The regulation of gene transfer by quorum-sensing regulation is common among rhizobia. Individual rhizobial strains can contain up to four different LuxI-type acyl-homoserine lactone (AHL) synthases and associated regulators plus several other LuxR-type regulators lacking dedicated AHL synthases. Mutations in and delayed and decreased the growth rate of ; because such altered growth was not observed in or mutants, this suggests that different sets of genes are induced via this quorum-sensing regulon in these two species. Bradyoxetin activity was found in extracts of all α-proteobacteria tested. This suggests that compounds similar to bradyoxetin may play an important role, not only in rhizobial symbiosis, but also in other plant- and animal-bacterial interactions. Elegant studies by researchers suggest that quorum sensing modulates both intra- and inter-species cell-cell communications. It was demonstrated that the halogenated furanones modulate LuxR activity through accelerated degradation of the transcriptional activator, rather than by blocking or displacing the binding of the AHL signal. Another potential way to interfere with quorum sensing is through the degradation or inactivation of the AHL signal molecules.

Citation: Downie J, González J. 2008. Cell-to-Cell Communication in Rhizobia: Quorum Sensing and Plant Signaling, p 213-232. In Winans S, Bassler B (ed), Chemical Communication among Bacteria. ASM Press, Washington, DC. doi: 10.1128/9781555815578.ch14

Key Concept Ranking

Type III Secretion System
0.42538798
Type I Secretion System
0.42538798
Type III Secretion System
0.42538798
Type I Secretion System
0.42538798
0.42538798
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Figures

Image of FIGURE 1
FIGURE 1

Arrangement of plasmid transfer and replication genes in different plasmids in the The characterized genes involved in plasmid replication , conjugation and regulation of conjugation are shown. The and genes on pRL8JI are in the opposite orientation to those in the other strains. The and genes have not been sequenced on pRL1JI and pRme41 but are probably present. The and genes are not present on pRL7JI.

Citation: Downie J, González J. 2008. Cell-to-Cell Communication in Rhizobia: Quorum Sensing and Plant Signaling, p 213-232. In Winans S, Bassler B (ed), Chemical Communication among Bacteria. ASM Press, Washington, DC. doi: 10.1128/9781555815578.ch14
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Image of FIGURE 2
FIGURE 2

Model for recipient-induced transfer of plasmid pRL1JI from bv. . BisR is activated by CinI-made 3-OH-C-HSL from potential recipients (i), resulting in the induction of expression. The induction of (ii) and the resulting TraI-made AHLs induce a positive feedback loop (iii), causing high-level expression of the operon; the plasmid-replication operon is induced in parallel with the operon. Premature accumulation of TraR is avoided by the expression of the TraR anti-activator TraM (iv). BisR, produced when pRL1JI is present, represses expression (v), thereby preventing 3-OH-C-HSL activation of TraR in pRL1JI-containing strains. The repression of and induction of by BisR enable the pRL1JI donor to respond to CinI-made 3-OH-CHSL from potential recipients. Figure adapted from Danino et al. ( ) with permission from Blackwell Publishing.

Citation: Downie J, González J. 2008. Cell-to-Cell Communication in Rhizobia: Quorum Sensing and Plant Signaling, p 213-232. In Winans S, Bassler B (ed), Chemical Communication among Bacteria. ASM Press, Washington, DC. doi: 10.1128/9781555815578.ch14
Permissions and Reprints Request Permissions
Download as Powerpoint

References

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Tables

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TABLE 1

Rhizobial quorum-sensing systems

Citation: Downie J, González J. 2008. Cell-to-Cell Communication in Rhizobia: Quorum Sensing and Plant Signaling, p 213-232. In Winans S, Bassler B (ed), Chemical Communication among Bacteria. ASM Press, Washington, DC. doi: 10.1128/9781555815578.ch14

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