Metabolome analysis and immunity of Phlomis purpurea against Phytophthora cinnamomi

Abstract

Phlomis purpurea is spontaneous in the southern Iberian Peninsula namely in cork oak (Quercus suber) forests. In a previous transcriptome analysis, we reported on its immunity against Phytophthora cinnamomi. However, little is known about the involvement of secondary metabolites on P. purpurea defence response. It is known though that root exudates are toxic to this pathogen. To understand the involvement of secondary metabolites in the defence of P. purpurea, a metabolome analysis was performed using leaves and roots of plants challenged with the pathogen along 72 h. The compounds putatively identified in challenged plants were constitutively produced. Alkaloids, fatty acids, flavonoids, glucosinolates, polyketides, prenol lipids, phenylpropanoids, sterols and terpenoids, were differentially produced in leaves or roots along the experiment timescale. It must be emphasized the constitutive production of taurine in leaves and its increase soon after challenging which suggests its role in P. purpurea immunity to the stress imposed by the oomycete. The rapid increase of secondary metabolites production by this plant species accounts for a concerted action of multiple compounds and genes on innate protection of P. purpurea against P. cinnamomi. The combination of metabolome with the transcriptome data previously disclosed, confirms the mentioned auto-immunity of this plant to a devastating pathogen and suggests its potential as antagonist for phytopathogens biological control opening a way for its application in green forestry / agriculture.