Transient Gene Expression in Two Pine Species by Microprojectile Bombardment

A biolistic particle delivery system was used to transform the uidA reporter gene driven by a maize polybiquitin promoter to cotyledons of P. roxburghii and embryos of P. contorta. Successful gene delivery was demonstrated by transient GUS expression as evaluated by standard histochemical assay. Transgene expression was monitored from 1 day to 3 weeks after bombardment. Expression was enhanced 5-told when the material was placed on medium containing 0.5 uM sucrose instead of standard 0.09 uM sucrose for 1-2 hrs before the bombardment. Gold microprojectiles of diameter 1.6 uM and 1.5-3.0 uM gave 4-5 fold more transient expression than that of 1.2 uM diameter. In P. roxburghii, reporter gene expression was observed for at least 3 weeks after bombardment, in some cases in cells within adventitious buds. However, in P. contorta the expression was observed only upto 7 days.