Selection and characterization of Solanum xanthocarpum cell line with augmented steroid metabolism

Cell lines of Solanum xanthocarpum resistant to 25 μM mevinolin, with augmented steroid metabolism were selected using the cell plating technique. Characterisation of this cell line was carried out by analysing the steroidal contents and rate of steroid metabolism. The selected cell line contained nearly 2 fold more sterols compared to the wild type call line. Steroidal alkaloid solasodine was overproduced more than 3 fold compared to the controi line. The rate of synthesis of sterols was determined based on the rate of 14 C acetate incorporation into sterols. Incorporation of acetate into the selected cell line was 2.1 and 3 fold more compared to the wild type cell line when they were grown in the absence or presence of mevinolin respectively. Mevinolin (5.0 μM) inhibited the incorporation of acetate in to sterols of wild type cell line by 44% while there was no significant inhibition of acetate incorporation into sterols of the selected cell line. Activity of 3-hydroxy 3-methylglutaryl CoA reductase (HMGR), the gateway enzyme of mevalonate pathway was compared and selected cell line showed 2.5 fold more activity compared to the wild type cell line. The present study demonstrates development of a higher plant cell line with augmented steroid metabolism and increased HMGR activity by cell line selection. Results also point to the probable rate limiting role of HMGR in the isoprenoid pathway.