Abstract:Legumes of the Medicago genus form symbiosis with the bacterium Sinorhizobium meliloti and develop root nodules housing large numbers of the intracellular symbionts. Members of the Nodule-specific Cysteine Rich peptide (NCRs) family induce the endosymbionts into a terminal differentiated state. Individual cationic NCRs are antimicrobial peptides that have the capacity to kill the symbiont but the nodule cell environment prevents killing. Moreover, the bacterial broad-specificity peptide uptake transporter BacA… Show more
“…Broad host range rhizobia or engineered strains that have a switched host range, will form terminally differentiated bacteroids or not according to the host species in which they are found. This suggests that the terminal differentiation is in the first place determined by the plant, although also the bacterial genetic repertoire contributes to the extent of the bacteroid differentiation process (Mergaert et al 2006;Nicoud et al 2020).…”
Section: Symbiotic Infection and Differentiationmentioning
confidence: 99%
“…Second, as mentioned above NCRs are similar to antimicrobial peptides and they indeed have antimicrobial activity. S. meliloti bacteroids use several mechanisms to protect themselves against this harmful activity of the NCRs (Haag et al 2011;Montiel et al 2017;Arnold et al 2018;Nicoud et al 2020). The most notable among them is mediated by the peptide transporter BacA.…”
Section: The Ncr Peptides Host Effectors Of Bacteroid Differentiationmentioning
Sinorhizobium meliloti of the Alphaproteobacteria class has a fascinating spectrum of lifestyles, thriving as a free-living soil saprophyte, as an endophyte and as a nitrogen-fixing legume symbiont. In symbiosis, it undergoes a striking cellular differentiation process, which is controlled by the host plant through the activity of NCR peptides. NCRs interfere with the cell cycle of S. meliloti and transform the regular cycle consisting of strict successions of single DNA replication followed by cell division into an endoreduplication cycle of multiple genome duplications without divisions. This cellular differentiation results in giant and polyploid symbiotic bacterial cells that fix atmospheric nitrogen. Here we discuss the regulation of the free-living cell cycle in S. meliloti and present the hypothesis that the master regulator CtrA is the ultimate target of the NCR peptides, provoking the cell cycle switch in symbiosis.
“…Broad host range rhizobia or engineered strains that have a switched host range, will form terminally differentiated bacteroids or not according to the host species in which they are found. This suggests that the terminal differentiation is in the first place determined by the plant, although also the bacterial genetic repertoire contributes to the extent of the bacteroid differentiation process (Mergaert et al 2006;Nicoud et al 2020).…”
Section: Symbiotic Infection and Differentiationmentioning
confidence: 99%
“…Second, as mentioned above NCRs are similar to antimicrobial peptides and they indeed have antimicrobial activity. S. meliloti bacteroids use several mechanisms to protect themselves against this harmful activity of the NCRs (Haag et al 2011;Montiel et al 2017;Arnold et al 2018;Nicoud et al 2020). The most notable among them is mediated by the peptide transporter BacA.…”
Section: The Ncr Peptides Host Effectors Of Bacteroid Differentiationmentioning
Sinorhizobium meliloti of the Alphaproteobacteria class has a fascinating spectrum of lifestyles, thriving as a free-living soil saprophyte, as an endophyte and as a nitrogen-fixing legume symbiont. In symbiosis, it undergoes a striking cellular differentiation process, which is controlled by the host plant through the activity of NCR peptides. NCRs interfere with the cell cycle of S. meliloti and transform the regular cycle consisting of strict successions of single DNA replication followed by cell division into an endoreduplication cycle of multiple genome duplications without divisions. This cellular differentiation results in giant and polyploid symbiotic bacterial cells that fix atmospheric nitrogen. Here we discuss the regulation of the free-living cell cycle in S. meliloti and present the hypothesis that the master regulator CtrA is the ultimate target of the NCR peptides, provoking the cell cycle switch in symbiosis.
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