Mutualistic cooperation is one of the most fascinating issue in evolutionary biology and legume-rhizobia symbiosis represent models of cross-kingdom mutualism. However, not all strains of the same rhizobial species have the same mutualistic phenotype, specifically they show different symbiotic performances and up to now only a few studies addressed the genetic basis of these differences (Galardini et al. 2011). In this context one of the most intriguing gene is that encoding the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase (acdS) present in the dispensable genome of the model species Sinorhizobium meliloti. AcdS is supposed to be involved in the sequestering and cleaving of plant-produced ACC, the precursor of the plant stress hormone ethylene (Glick 2005). However, the role of acdS in the mutualistic behavior of strains of S. meliloti is still under debate and few data are available on the effect of such gene in symbiotic competitiveness (Ma et al. 2004) and then on the selective benefit it may confer. To clarify this issue, an extensive phylogenetic and comparative genomic analysis of acdS orthologs has been performed in genomes of S. meliloti strains and functional studies have been carried out by expressing acdS in the model strain S. meliloti Rm1021, which lacks acdS gene. Then, the symbiotic and endophytic phenotypes of recombinant vs the parental strain have be evaluated with respect to competition for root nodule occupancy, plant colonization and modulation of ethylene production by the host plant. Data showed that acdS orthologs present in S. meliloti are polyphyletic and may indeed derive from different alphaproteobacteria representatives. No increase in fitness for nodule occupancy was found in the acdS-derivative strain compared to the parental one, but modulation of plant ethylene levels was detected, possibly via a higher endophytic colonization of non-nodule plant tissue of the acdS-expressing strain. We conclude that acdS in S. meliloti could be more related to the endophytic life-style (Pini et al. 2012) than to the symbiotic interaction. 1) Galardini et al. 2011. BMC Genomics 12: 253. 2) B.R. Glick 2005 FEMS Microbiol. Lett. 251: 1–7. 3) Ma et al. 2004 Appl. Environ. Microbiol. 70: 5891-5897. 4) Pini et al. 2012 BMC Microbiol. 12: 78.
Exploring the genetic basis of symbiotic performance in rhizobia: acdS gene in Sinorhizobium meliloti / Checcucci, Alice; Bazzicalupo, M.; De Carlo, A.; Emiliani, G.; Mengoni, Alessio. - ELETTRONICO. - (2014), pp. 0-0. (Intervento presentato al convegno 11 European Nitrogen Fixation Conference tenutosi a Tenerife (Spain) nel 7-10 September 2014).
Exploring the genetic basis of symbiotic performance in rhizobia: acdS gene in Sinorhizobium meliloti
CHECCUCCI, ALICE;M. Bazzicalupo;MENGONI, ALESSIO
2014
Abstract
Mutualistic cooperation is one of the most fascinating issue in evolutionary biology and legume-rhizobia symbiosis represent models of cross-kingdom mutualism. However, not all strains of the same rhizobial species have the same mutualistic phenotype, specifically they show different symbiotic performances and up to now only a few studies addressed the genetic basis of these differences (Galardini et al. 2011). In this context one of the most intriguing gene is that encoding the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase (acdS) present in the dispensable genome of the model species Sinorhizobium meliloti. AcdS is supposed to be involved in the sequestering and cleaving of plant-produced ACC, the precursor of the plant stress hormone ethylene (Glick 2005). However, the role of acdS in the mutualistic behavior of strains of S. meliloti is still under debate and few data are available on the effect of such gene in symbiotic competitiveness (Ma et al. 2004) and then on the selective benefit it may confer. To clarify this issue, an extensive phylogenetic and comparative genomic analysis of acdS orthologs has been performed in genomes of S. meliloti strains and functional studies have been carried out by expressing acdS in the model strain S. meliloti Rm1021, which lacks acdS gene. Then, the symbiotic and endophytic phenotypes of recombinant vs the parental strain have be evaluated with respect to competition for root nodule occupancy, plant colonization and modulation of ethylene production by the host plant. Data showed that acdS orthologs present in S. meliloti are polyphyletic and may indeed derive from different alphaproteobacteria representatives. No increase in fitness for nodule occupancy was found in the acdS-derivative strain compared to the parental one, but modulation of plant ethylene levels was detected, possibly via a higher endophytic colonization of non-nodule plant tissue of the acdS-expressing strain. We conclude that acdS in S. meliloti could be more related to the endophytic life-style (Pini et al. 2012) than to the symbiotic interaction. 1) Galardini et al. 2011. BMC Genomics 12: 253. 2) B.R. Glick 2005 FEMS Microbiol. Lett. 251: 1–7. 3) Ma et al. 2004 Appl. Environ. Microbiol. 70: 5891-5897. 4) Pini et al. 2012 BMC Microbiol. 12: 78.File | Dimensione | Formato | |
---|---|---|---|
Checcucci_ENFC2014_poster.pptx
Accesso chiuso
Descrizione: Poster presentato
Tipologia:
Pdf editoriale (Version of record)
Licenza:
Tutti i diritti riservati
Dimensione
751.14 kB
Formato
Microsoft Powerpoint XML
|
751.14 kB | Microsoft Powerpoint XML | Richiedi una copia |
I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.