Plant-endophytes interaction influences the chemical properties in Echinacea purpurea

The medicinal plant Echinacea purpurea (L.) Moench (Asteraceae) is known worldwide for its immune-modulatory effects and used for preventing and treating the common cold, flu, and upper respiratory tract infections1. Medicinal benefits seem to result by several bioactive compounds, especially alkamides, caffeic acid derivatives and polysaccharides2. In particular, the highest level of alkamides is found in the E. purpurea root compartment3. The relationship between bacterial endophytic communities of the medicinal plants and their secondary metabolites production is reported4. Previous studies have shown the differences in the cultivable bacterial communities isolated from the stem/leaf (SL) and root (R) compartments of E. purpurea and E. angustifolia grown in the same soil5-7. Here, we investigate the influence of E. purpurea endophytic community on the alkamides production within the plant. We have developed an experimental model for miming the in vivo conditions: axenic in vitro E. purpurea plants have been infected with a pool of bacteria isolated from the SL compartment of E. purpurea plants grown in soil. The alkamides biosynthesis pathway seems to be alterated by the bacterial infection since the level content of alkamides is resulted different between control and infected plants. Moreover, the expression level of BCCA decarboxylase gene, coding for the enzyme involved in the amine moiety formation of the Echinacea alkamides8, is resulted higher in the infected roots than in the other tissues. Therefore, these results indicate that the infection of axenic plants with their endophytes could restore the in vivo biochemical profile of the alkamides.