Inhibition of alkaloid accumulation by 2,4-D in Catharanthus roseus cell suspension is overcome by methyl jasmonate

In Catharanthus roseus cells (strain C20) 2,4-D exerted a dramatic inhibition on alkaloid terpenoid precursor availability. In this condition, ajmalicine content is less than 2 mu g/gDW. During one subculture the auxin depletion enhanced greatly the ajmalicine content: about 300 mu g/gDW. In presence of 2,4-D, exogenous methyl jasmonate (MJ) triggered an ajmalicine accumulation corresponding to 80 % of the one observed in a 2,4-D free medium. Thus MJ takes the auxin depletion signal place. In a 2,4-D free medium, inhibition of MJ synthesis by salicylhydroxamic acid or salicylic acid limits greatly alkaloid content which could be restored by exogenous MJ. Thus, MJ can be regarded as a secondary messenger in transduction of the auxin depletion signal.