Genetic transformation of sweetgum (Liquidambar styraciflua L.) proembryogenic masses by microprojectile bombardment
Walsh, Michael Jason
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To date, transformation of sweetgum from microprojectile bombardment of embryogenic cells has not been reported. Growth of sweetgum (Liquidambar styraciflua) proembryogenic masses (PEMs) cultures was characterized while improving yields of size-fractionated PEMs for microprojectile bombardment. Transformation and selection parameters for PEMs were identified. Pre-bombardment osmotic conditioning of PEMs with 0.5 M equimolar mannitol and sorbitol produced the highest transient beta-glucuronidase (GUS) expression from 3 lines. Postbombardment recovery periods tested for PEMs prior to initiation of selection revealed that initiating selection of PEMs immediately following bombardment allowed for the identification and recovery of transformed PEMs, while longer recovery periods did not. Stable integration of the pBI 426 transgene was confirmed by Southern analysis. A protocol from this work could be applied to embryogenic cell cultures to produce transgenic sweetgum.