Selection of 3-fluorotyrosine tolerant callus lines in two cultivars of opium poppy (Papaver somniferum L.) and regeneration of plants through somatic embryogenesis

摘要

Six variant callus lines exhibiting differential tolerance to 3-fluorotyrosine (3FT, a tyrosine analogue) have been isolated in two cultivars of opium poppy ('Sanchita' and 'Shweta'). The selected trait was stably maintained in the absence or under sustained selection pressure of the analogue stress. Growth characteristics of the selected lines showed that lines having threshold tolerance up to sub-lethal level of 3FT (150-200 muM) had a growth index comparable to that of wild type on unstressed medium. One of the lines (Shw L-200) exhibited the capacity to gradually build up its tolerance up to supralethal (250 muM) level of 3FT. In the presence of analogue stress, all the selected lines showed a 1.5 to 2.0-fold increase in their free amino acid pool. The selected line Shw L-250 showed a 4.5-fold increase in free tyrosine in the presence of 3FT stress, which was three-fold more than in the wild type maintained on stress-free medium. Selected and non-selected lines showed high frequency of plant regeneration via somatic embryogenesis when the analogue stress was temporarily withdrawn during early stages of organogenesis. Leaves of the regenerated plants of the selected lines showed the capability to initiate callusing on 3FT stressed medium, indicating thereby the persistence of the selected trait at whole plant level. The relevance of the selected variants in relation to their possible exploitation in metabolic engineering of benzylisoquinoline alkaloids is proposed.