Fate of transgenes in the forest tree genome

Abstract

During the last two decades, genetic engineering (GE) has been progressing at a steady pace in the forest trees. Transgenic trees carrying a variety of different transgenes have been produced, and are undergoing confined field trials in the world. However, there are questions regarding stability of transgene expression, and transgene escape that need to be addressed in the long-lived forest trees. Although relatively stable transgene expression has been reported for several target traits, including herbicide resistance, insect resistance, and lignin reduction in the vegetative propagules of several forest tree species, there were still unintended unstable events in transgenic plants. Long-term stability of transgene expression involved in these traits and others affecting yield (impacting growth) would be desirable in the vegetative propagules, and also in the generative progeny of the forest trees. Transgene escape through pollen, seed, and vegetative propagules from GE trees to native forest populations, although inevitable, remains an important regulatory issue. However, it may be possible to manage/minimize the risk of transgene spread via isolation in confined areas, and use of incompatible genotypes of feral tree populations in the vicinity of transgenic forest trees. Therefore, it is desirable to produce genetically stable transgenic trees, and have biocontainment measures in place for testing and deployment of the GE forest trees. Toward these goals (transgene stability and containment), innovative biotech strategies are being actively pursued, with reasonable success, in forest trees.