N-Acyl Homoserine Lactones and Lux Solos Regulate Social Behaviour and Virulence of Pseudomonas syringae pv. actinidiae.

The phyllosphere is a complex environment where microbes communicate through signalling molecules in a system, generally known as quorum sensing (QS). One of the most common QS systems in Gram-negative proteobacteria is based on the production of N-acyl homoserine lactones (AHLs) by a LuxI synthase and their perception by a LuxR sensor. Pseudomonas syringae pv. actinidiae (Psa), the aetiological agent of the bacterial canker of kiwifruit, colonises plant phyllosphere before penetrating via wounds and natural openings. Since Psa genome encodes three LuxR solos without a cognate LuxI, this bacterium may perceive diffusible signals, but it cannot produce AHLs, displaying a non-canonical QS system. The elucidation of the mechanisms underlying the perception of environmental cues in the phyllosphere by this pathogen and their influence on the onset of pathogenesis are of crucial importance for a long-lasting and sustainable management of the bacterial canker of kiwifruit. Here, we report the ability of Psa to sense its own population density and the presence of surrounding bacteria. Moreover, we show that Psa can perceive AHLs, indicating that AHL-producing neighbouring bacteria may regulate Psa virulence in the host. Our results suggest that the ecological environment is important in determining Psa fitness and pathogenic potential. This opens new perspectives in the use of more advanced biochemical and microbiological tools for the control of bacterial canker of kiwifruit.

Postural rehabilitation and Kinesio taping for axial postural disorders in Parkinson's disease.

OBJECTIVE: To assess the effects of postural rehabilitation (PR) on trunk asymmetry and balance, with and without Kinesio taping (KT) of the back muscles as additional treatment, in patients with Parkinson's disease (PD) who have postural disorders. DESIGN: Single-blind, randomized controlled trial with 1-month follow-up. SETTING: Ambulatory care in referral center. PARTICIPANTS: Patients (N=20) with PD showing postural abnormalities of the trunk, in the sagittal and/or coronal plane. INTERVENTIONS: Four weeks of patient-tailored proprioceptive and tactile stimulation, combined with stretching and postural reeducation, was provided to 13 subjects (PR group), while 7 received no treatment (control group). Six of the 13 subjects receiving PR also had KT strips applied to their trunk muscles, according to the features of their postural abnormalities. MAIN OUTCOME MEASURES: Berg Balance Scale, Timed Up and Go, and degrees of trunk bending in the sagittal and coronal planes were assessed at the enrollment (t0), 1 month later (t1), and 2 months later (t2). RESULTS: At t1, all treated patients showed a significant improvement in trunk posture in both the sagittal (P=.002) and coronal planes (P=.01), compared with baseline. Moreover, they showed an improvement in measures of gait and balance (P<.01). Benefits persisted at t2 for all measures, except lateral trunk bend. No differences were found when comparing the PR and KT groups. CONCLUSIONS: The combination of active posture correction and trunk movements, muscle stretching, and proprioceptive stimulation may usefully impact PD axial symptoms. Repeated training is advocated to avoid waning of the effect.

Host-specific signal perception by PsaR2 LuxR solo induces Pseudomonas syringae pv. actinidiae virulence traits.

Plant-associated bacteria, including pathogens, recognise host-derived signals to activate specific responses. The genome of Pseudomonas syringae pv. actinidiae (Psa), the aetiological agent of bacterial canker of kiwifruit, encodes for three putative LuxR-like receptors. Proteins of this family are usually involved in the quorum sensing system, through the perception of autoinducers (AHLs) produced by a cognate LuxI. However, Psa does not produce AHLs according to the lack of LuxI-encoding gene. It has been proposed that the so-called LuxR solos may be involved in the perception of environmental stimuli. We thus hypothesised that Psa LuxR-like receptors could be involved in host-derived signal sensing. Psa virulence traits, i.e., biofilm formation, motility and endophytic colonisation, were stimulated by growing the pathogen in host plant extracts, but not in non-host plant extracts or rich medium. Moreover, the phenotypic analyses of Psa mutant strains lacking the LuxR solo-encoding genes, demonstrated that PsaR2 plays a major role in host recognition and induction of virulence responses. The heterologous expression of PsaR2, followed by affinity chromatography and fraction activity assessment, confirmed the specific recognition of plant-derived components by this sensor. Overall, these data provide a deeper understanding of the regulation of Psa virulence through interkingdom communication, which represents a interesting target for the development of tolerant/resistant genotypes or innovative control strategies.