Changes in the concentration of trigonelline in a semi-arid leguminous plant (Prosopis laevigata) induced by an arbuscular mycorrhizal fungus during the presymbiotic phase

An in vitro presymbiotic system between mesquite [Prosopis laevigata (Willd.) M.C. Johnst], a semi-arid leguminous plant, and pregerminated spores of Gigaspora rosea Nicol. & Schenck was established. After characteristic hyphal branching, high performance liquid chromatographic analyses of methanol extracts from P. laevigata roots revealed a concentration change in one ultraviolet-detectable product. This product was identified by nuclear magnetic resonance and mass spectrometry as trigonelline, a pyridine alkaloid. The concentration of trigonelline was constant in the aerial parts of the plant with or without G. rosea, but its concentration in the roots increased 1.8-fold when G. rosea was present. Trigonelline may be a regulatory factor during early signal events in the establishment of the arbuscular mycorrhizal symbiosis in P. laevigata.