Conditions were established for efficient plant regeneration from four freshmarket cultivars of Lycopersicon esculentum. In order to increase the yield of viable protoplasts which are able to sustain cell divisions, the donor plants are preconditioned by incubation at 25°C in the dark for 18 hours, followed by a cold treatment at 4°C in the dark for the last 6 hours, prior to protoplast isolation. Browning of the dividing cell colonies can be prevented by culturing protoplasts in 100 μl droplets of low-melting agarose, surrounded by liquid medium. Alternatively, protoplasts can be cultured in liquid medium. In both procedures the plating efficiencies and percentage of shoot regeneration are increased, only when dilutions were performed with auxin-free culture medium. Shoot regeneration is obtained by using a two step procedure: initiation of greening of microcalli on a medium containing 0.2 M mannitol and 7.3 mM sucrose, which is followed by shoot development on a mannitol-free medium containing 0.5 M sucrose. In this way, plants can be regenerated within 3 months from the hybrid cultivars Bellina, Abunda, Sonatine and also from the true seedline Moneymaker. The latter one showed the highest regeneration frequency (30%).

When cells of Lithospermum erythrorhizon were transferred from B5 solid medium into M9 liquid medium and grown in the dark, they produced and accumulated shikonin and its derivatives; meanwhile, transcripts of PAL, 4CL, HMGR, PGT, and CYP98A6 were rapidly induced within 2 h, peaking within 6 h, and then decreasing over time. However, when L. erythrorhizon cells were cultured in M9 medium and grown under white light, a negative regulator for the biosynthesis of shikonin and its derivatives, the ''stimulating effect'' of the medium transition on the transcription of these genes was also displayed with similar patterns over 24 h of culture period.