Necessity of a Functional Octadecanoic Pathway for Indole Alkaloid Synthesis by Catharanthus roseus Cell Suspensions Cultured in an Auxin-Starved Medium

The effect of methyl jasmonate (mJA), jasmonic acid and traumatic acid, derivatives of the octadecanoic pathway, on the production of alkaloids by cell suspension cultures of Catharanthus roseus L. (G) Don was investigated. Cells cultured in the presence of auxin (m-cells) did not accumulate alkaloids. The addition of exogenous mJA to mcells restored the ability to produce alkaloids. In cells cultured in a 2,4-D-starved medium (p-cells), exogenous mJA greatly increased alkaloid production. Similar data were obtained for jasmonic acid. In contrast, traumatic acid had no effect on alkaloid production. The sensitivity of cell suspension cultures to exogenous mJA was restricted to the first four days of subculture corresponding to the active growth phase, whereas the alkaloid accumulation occurred only during the stationary phase of the subculture (days 6 to 10). When p-cells were treated with octadecanoic pathway inhibitors, the ability to produce alkaloids was strongly reduced. The addition of exogenous mJA always restored the ability to produce alkaloids. These data suggest that in response to auxin depletion, endogenous mJA could be produced and act by linking physiological events thus leading to alkaloid biosynthesis activation.