Production of secoiridoids by adventitious root culture of Swertia japonica

Swertia japonica is an important Japanese folk medicine used as a remedy for stomach disease, and secoiridoids are the main active constituents. Towards producing secoiridoids using large-scale tissue culture, we investigated the effects of phytohormone conditions on callus induction and redifferentiation of adventitious roots from calli of S. japonica and the associated production of secoiridoids. Here, we report efficient conditions for induction of callus and adventitious roots and confirmed that adventitious roots produced the secoiridoids, swertiamarin, and gentiopicroside. Moreover, redifferentiation of adventitious roots was enhanced when cultured with a low concentration of auxin, while secoiridoid biosynthesis was elevated with a high concentration of cytokinin. In a time course of secoiridoid changes in adventitious roots, maximum secoiridoid production occurred 15 d after redifferentiation of adventitious roots of a 10-d-old culture, suggesting that relatively mature root development may be necessary for the in vitro production of secoiridoids in S. japonica.