Exopolysaccharides Produced by Plant Pathogenic Bacteria Affect Ascorbate Metabolism in Nicotiana tabacum

Abstract

The role of the exopolysaccharides (EPSs) produced by plant pathogenic bacteria has not completely clarified, they are considered either molecules able to avoid or delay the activation of plant defences, or acting as signal in the plantpathogen cross-talk. In order to understand whether EPSs are recognized by infected plant cells and are able to induce the activation of plant defence responses, their capability to induce metabolic alteration in tobacco cells has been analysed. The results indicate that several EPSs, even if not chemically related, induce increases in phenylalanine ammonia-lyase, a marker enzyme of defence responses of plants against stress; but others are completely ineffective. The EPSs affecting phenylalanine ammonia-lyase also induce an increase in hydrogen peroxide production. Moreover, they alter the metabolism of ascorbate, another parameter indicative of the presence of stress conditions and the involvement of which in the hypersensitive reaction has been recently reported. The possibility that specific EPSs could act as signals in the plant-pathogenic bacteria interaction is discussed.

Hydrogen peroxide is involved in nitric oxide‐induced cell death in maize leaves

“…1998, 2001), which is similar to animals. The same results were observed in tobacco cultured cells, there was no effect on cell death when an NO donor and an H 2 O 2 generator were added separately; however, when NO and H 2 O 2 were added simultaneously, cells died in a concentration‐dependent manner (de Pinto et al. 2002, 2003).…”

A Metabolic Profiling Strategy for the Dissection of Plant Defense against Fungal Pathogens

“…The recognition of the pathogen by plants triggers ROS production, which also plays an important role in virulence and development of pathogens [54]. In addition to the abovementioned metabolites exhibiting antioxidant activities, other metabolites with well-established scavenging properties synthesized during interactions in pathosystems such as, resveratrol [55], ascorbate [56], ornithine [57], and members of the B6 complex [58] were involved in the soybean- Rhizoctonia interaction. Furthermore, this is mirrored by increases in glutamate, proline and γ -aminobutyric acid (GABA) that can, directly or indirectly, exhibit ROS scavenging activity [59], [60].…”

Ralstonia solanacearum Extracellular Polysaccharide Is a Specific Elicitor of Defense Responses in Wilt-Resistant Tomato Plants

“…ciccaronei and P. savastonoi pv. nerii caused necrotic lesions when infiltrated into tobacco leaves, induced H 2 O 2 release from tobacco cells in culture medium, and decreased cytosolic ascorbate peroxidase (APX), one of the main enzymes for ROS scavenging in plant cells; EPS extracts from the related plant pathogen P. caryophylli had no such effects [38]. EPS from an incompatible isolate of Xanthomonas campestris pv.…”