Quorum Sensing in Pseudomonas savastanoi pv. savastanoi and Erwinia toletana: Role in Virulence and Interspecies Interactions in the Olive Knot

Abstract

The olive knot disease ( L.) is caused by the bacterium pv. savastanoi. pv. savastanoi in the olive knot undergoes interspecies interactions with the harmless endophyte ; pv. savastanoi and colocalize and form a stable community, resulting in a more aggressive disease. pv. savastanoi and produce the same type of the-acylhomoserine lactone (AHL) quorum sensing (QS) signal, and they share AHLs In this work, we have further studied the AHL QS systems of pv. savastanoi and in order to determine possible molecular mechanism(s) involved in this bacterial interspecies interaction/cooperation. The AHL QS regulons of pv. savastanoi and were determined, allowing the identification of several QS-regulated genes. Surprisingly, the pv. savastanoi QS regulon consisted of only a few loci whereas in many putative metabolic genes were regulated by QS, among which are several involved in carbohydrate metabolism. One of these loci was the aldolase-encoding gene, which was found to be essential for both colocalization of pv. savastanoi and cells inside olive knots as well as knot development. This study further highlighted that pathogens can cooperate with commensal members of the plant microbiome. This is a report on studies of the quorum sensing (QS) systems of the olive knot pathogen pv. savastanoi and olive knot cooperator These two bacterial species form a stable community in the olive knot, share QS signals, and cooperate, resulting in a more aggressive disease. In this work we further studied the QS systems by determining their regulons as well as by studying QS-regulated genes which might play a role in this cooperation. This represents a unique interspecies bacterial virulence model and highlights the importance of bacterial interspecies interaction in disease.

Impact of plant genotype and plant habitat in shaping bacterial pathobiome: a comparative study in olive tree

“…Furthermore, when inoculated together with Pss they both promoted tumors size increases in olive trees 37,38 . Although it is not known how exactly P. agglomerans and E. toletana modulates the OK-disease severity, a number of studies provided evidences of a crosstalk between Pss, P. agglomerans and E. toletana that could have a role on Pss virulence 12,39 . Interestingly, apart from Pss, Pantoea and Erwinia, other Pseudomonas species were found to be associated with knots, both as an epiphyte and endophyte.…”

Lipopeptide families at the interface between pathogenic and beneficialPseudomonas-plant interactions

“…Such QS cross-talk has been inferred from phenotypic complementation of LPQ-associated phytopathogenicity in a gnotobiotic Arabidopsis system upon co-inoculation with a non-virulent QS mutant and a different non-pathogenic LPQ strain (Melnyk et al 2019). Cooperative phytopathogenicity driven by commensal AHL sharing has been observed for the olive tree pathogen P. savastanoi (Hosni et al 2011;Caballo-Ponce et al 2018). Conceivably, such signal sharing may also support cooperative microbial antagonism contributing to biocontrol (Besset-Manzoni et al 2018).…”

Synergistic interaction between the type III secretion system of the endophytic bacterium Pantoea agglomerans DAPP‐PG 734 and the virulence of the causal agent of olive knot Pseudomonas savastanoi pv. savastanoi DAPP‐PG 722

“…In the same fashion as E. toletana DAPP-PG 735 (Caballo-Ponce et al, 2018;Passos da Silva et al, 2014), P. agglomerans DAPP-PG 734 communicates with P. savastanoi pv. savastanoi DAPP-PG 722 through a QS system mediated by N-acyl-homoserine lactones (AHLs) (Buonaurio et al, 2015;Hosni et al, 2011).…”

“…In the same fashion as E . toletana DAPP‐PG 735 (Caballo‐Ponce et al, 2018 ; Passos da Silva et al, 2014 ), P. agglomerans DAPP‐PG 734 communicates with P . savastanoi pv.…”