1National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute, New Delhi 110 012, India
Centre for Biotechnology, Faculty of Science, Hamdard University, New Delhi 110 062, India
*Corresponding author. E-mail: pss410@rediffmail.com
Abbreviations: Asp, Asparagine; BAP, 6-Benzylaminopurine; 2,4-D, 2,4-dichlorophenoxyacetic acid; GA3, Gibberellic acid; Glu, Glutamine; INO, Indicine-N-oxide; MS, Murashige and Skoog; NAA, Naphthaleneacetic acid.
Heliotropium indicum L (Boraginaceae) contains the anticancer pyrrolizidine alkaloid, indicine-N-oxide (INO). To study the yield of INO as a function of plant development, plantlets were regenerated in vitro from nodal and hypocotyl explants and also from hypocotyl callus, on Murashige and Skoog's (MS) medium supplemented with 1-naphthaleneacetic acid (NAA), 6-benzylaminopurine (BAP), asparagine (Asp) and glutamine (Glu). The regenerated plantlets were rooted on MS supplemented with Glu or gibberellic acid (GA3). While 5-week-old seedlings showed a high amount of INO (0.12% dry wt) that depleted gradually as the plants attained maturity and flowered, fast growing callus produced a much higher yield of INO (0.32% dry wt). As the callus cultures differentiated into shoots and subsequently into plantlets, the INO content decreased to about 0.2% dry wt. It appears that INO is the primary product of pyrrolizidine alkaloid biosynthetic pathway in rapidly growing meristematic tissue of Heliotropium indicum, later reduced to its alkaloidal base and reallocated to other tissues. The article includes an efficient micropropagation method for Heliotropium indicum.
Heliotropium indicum, indicine-N-oxide, pyrrolizidine alkaloids, regeneration
