Exogenous stimulation of Tanacetum vulgare roots with pipecolic acid leads to tissue-specific responses in terpenoid composition
Tanacetum vulgare L., known as tansy, is a perennial plant with a highly variable terpenoid composition, with mono- and sesquiterpenoids being the most abundant. The high diversity of terpenoids is known to play an important role in mediating ecological interactions. However, the distribution of terpenoids in different tissues and the inducibility of terpenoids in these tissues by biotic stress are poorly understood. In this study, we investigated the changes in terpenoid profiles and concentrations in different plant organs following treatment of roots with pipecolic acid (Pip). Pipecolic acid is a non-proteinogenic amino acid that triggers defense responses in plants. It is often used to induce systemic resistance (SAR) in plants under controlled conditions. Examination of the tissues showed that the leaves and midribs contained mainly monoterpenoids, while the coarse and fine roots of the plants contained mainly sesquiterpenoids. The rhizomes occupied an intermediate position by presenting the terpenoid profiles of both the midribs and roots but also the unique compounds of its own. Treatment with pipecolic acid led to an increase in the concentration of mono- and sesquiterpenoids in all tissues except rhizomes. However, a significantly higher amount of sesquiterpenoids was formed in root tissues in response to Pip compared to shoots. The metabolic atlas for terpenoids presented here shows that there is an exceptionally strong differentiation of terpenoid patterns and terpenoid contents in the different tissues of tansy. This, together with the differential inducibility by biotic stress, suggests that the chemical diversity of terpenoids may play an important role in the ecological interactions of tansy and in the defense against biotic stressors that feed on the below- and above-ground organs of the plant.