Global Analysis of Type Three Secretion System and Quorum Sensing Inhibition of Pseudomonas savastanoi by Polyphenols Extracts from Vegetable Residues

Abstract

Protection of plants against bacterial diseases still mainly relies on the use of chemical pesticides, which in Europe correspond essentially to copper-based compounds. However, recently plant diseases control is oriented towards a rational use of molecules and extracts, generally with natural origin, with lower intrinsic toxicity and a reduced negative environmental impact. In this work, polyphenolic extracts from vegetable no food/feed residues of typical Mediterranean crops, as Olea europaea, Cynara scolymus, and Vitis vinifera were obtained and their inhibitory activity on the Type Three Secretion System (TTSS) and the Quorum Sensing (QS) of the Gram-negative phytopathogenic bacterium Pseudomonas savastanoi pv. nerii strain Psn23 was assessed. Extract from green tea (Camellia sinensis) was used as a positive control. Collectively, the data obtained through gfp-promoter fusion system and real-time PCR show that all the polyphenolic extracts here studied have a high inhibitory activity on both the TTSS and QS of Psn23, without any depressing effect on bacterial viability. Extracts from green tea and grape seeds were shown to be the most active. Such activity was confirmed in planta by a strong reduction in the ability of Psn23 to develop hyperplastic galls on explants from adult oleander plants, as well as to elicit hypersensitive response on tobacco. By using a newly developed Congo red assay and an ELISA test, we demonstrated that the TTSS-targeted activity of these polyphenolic extracts also affects the TTSS pilus assembly. In consideration of the potential application of polyphenolic extracts in plant protection, the absence of any toxicity of these polyphenolic compounds was also assessed. A widely and evolutionary conserved molecular target such as Ca2+-ATPase, essential for the survival of any living organism, was used for the toxicity assessment.

Hydrolysable Tannins in Agriculture

“…By using an in vitro plant model system, both these tannin extracts were demonstrated to be able to give a statistical reduction of the hyperplastic symptoms produced by the inoculation of Pseudomonas savastanoi p v. nerii strain Psn23 on cuttings from 2-year-old twigs of Nerium oleander, in comparison to those untreated. In addition, a significant decrease of bacterial multiplication was observed on tannin-treated plants, which was comparable to the in planta growth of the ΔhrpA nonpathogenic mutant of Psn23 [39].…”

“…SR belongs to the ubiquitous and highly conserved proteins of the so-called P-type ATPase family, whose members are present in the cellular membrane of any living organism and involved in numerous transport processes. Conversely, copper suppresses almost completely Ca 2+ -ATPase activity at just 0.1 μM concentration Cu 2+ ions [39].…”

“…Tannic and gallic acid are efficient to give a total inhibition of D. chrysanthemi pectate lyase at concentrations of 400 and 800 μg/ml, respectively [42]. At last, tannins can also negatively interfere with other bacterial systems which are essential for their pathogenicity and virulence on plants, such as the Type Three Secretion System and the Quorum Sensing, respectively [39,43].…”

The plant compound rosmarinic acid induces a broad quorum sensing response in Pseudomonas aeruginosa PAO1

“…On the other hand, plants were found to synthesize compounds that interfere with bacterial QS (Venturi and Fuqua, 2013). It has been shown that mixtures of plant-derived compounds, including extracts (Biancalani et al, 2016;Tiwary et al, 2017), macerates (Ferluga et al, 2007;Subramoni et al, 2011;Rekha et al, 2017) and exudates (Teplitski et al, 2000;Gao et al, 2003;Nievas et al, 2017) interfere with bacterial QS mechanisms. Insight is now being gained into the nature of plant-derived QS modulating compounds that include flavonoids, phenolic acids and terpenoids (Silva et al, 2016).…”

A MATE Transporter is Involved in Pathogenicity and IAA Homeostasis in the Hyperplastic Plant Pathogen Pseudomonas savastanoi pv. nerii

“…The overexpressing mutant Psn23_pT3-matE was also constructed. The recombinant plasmid pT3-matE (Table S1) was produced starting from the vector pLPVM-T3A, which contains the native promoter of hrpA gene for Psn23 [33]. The matE gene, amplified from pK18-matE using the primers pT3_matE_BamHI_For/pT3_matE_KpnI_Rev, was cloned into the KpnI and BamHI restriction sites of pLPVM-T3A and then electroporated into Psn23 cells.…”