Induction of Transgenic Hairy Roots in Medicinal Plant Poppy (Papaver Somniferum L.) by Agrobacterium Rhizogenes-Mediated Transformation

Opium poppy plant (Papaver somniferum L.) is one of the oldest known medicinal plants. Since the potential of medicinal components production in medicinal plants is very limited in natural conditions, plant tissue culture, as a new technology, has an important role in industrial production of secondary metabolites in medicinal plants. Among different tissue culture systems, hairy root is very stable in hormone-free culture conditions and these roots stably produce secondary metabolites over a long period due to their inherent genetic and biochemical stability. Hence, the objective of this study was to evaluate the effect of some different parameters on optimization of hairy production in P. somniferum.
In the present research, for the optimization of hairy root in papaver, a factorial experiment was conducted based on a completely randomized design with 4 replications. The factors included different Agrobacterium rhizogenes strains (ATCC15834, A4 and GMI9534), medium (MS and ½ MS medium), two temperatures (17 and 25 °C) at co-cultivation period, and two different explants (excised shoot and hypocotyl). Different traits were evaluated including percentage of induced hairy roots, number of lateral branches/1cm, number of hairy root per explants and days after inoculation (DAI).
Hairy roots were induced at the wound site of explants after weeks of culture. Analysis of the results showed that strain ATCC15834, ½ MS medium, temperature 25 °C and excised shoot explant were the best treatment combination for hairy roots induction in the poppy plant. Transformed hairy roots were confirmed by polymerase chain reaction (PCR) using rolB gene specific primers.
All of the A. rhizogenes strains led to hairy root induction, but there were no hairy roots formed from control explants. Differences in virulence, morphology and growth rate can be partially explained by the variety of plasmids harbored by the A. rhizogenesis strains. In the present study, excised shoot explants were highly and significantly susceptible to infection by each strain of A. rhizogenes and hypocotyl explants showed low rate of hairy root induction.