Green fluorescent protein as a tool for monitoring transgene expression in forest tree species.

The gene coding for green fluorescent protein (GFP) from the jellyfish Aequorea victoria was successfully used as a vital marker for the transformation of three woody plant species, black spruce (Picea mariana (Mill.) BSP), white pine (Pinus strobus L.) and poplar (Populus spp.). The gfp gene and the gene conferring resistance to kanamycin (nptII) were introduced by microprojectile bombardment or Agrobacterium tumefaciens-mediated technology. Screening by fluorescence microscopy of the transformed plant material, under the selection of kanamycin, identified five to eight cell lines from each tree species that clearly expressed GFP. Expression of GFP was observed in somatic embryonal cells of the coniferous species and in stem sections of poplar. For all species, GFP transgene expression was stable over multiple subcultures. Stable integration of the gfp gene into plant genomes was confirmed by Southern hybridization or polymerase chain reaction (PCR) analysis. We conclude that GFP can be used as a vital marker and reporter protein in transformation experiments with gymnosperms and deciduous trees.