Transgene copy number estimation and analysis of gene expression levels in Populus spp. transgenic lines

Background The genus Populus has certain important features, such as a relatively small nuclear genome, it can be easily regenerated easily in vitro and genetically transformed by Agrobacterium vector system, which make it ideal for gene transfer and molecular genetic studies in forest trees [1]. Insect-tolerant poplars have been obtained using several types of insecticidal genes coding for Bacillus thuringiensis-toxins. Regenerated plants with insectresistance were obtained in different studies. Agrobacterium-mediated transformation has been the favored method for the introduction of foreign genes into plants. The effectiveness of insect-resistance in transgenic plants is related to the side effects of gene transfer (site of gene insertion, copy number, gene silencing etc.). Moreover intransgenic plants, transgene copy number can greatly affect the expression level and genetic stability of the target gene, making estimation of transgene copy numbers an important area of genetically modified plant research [2]. Thus molecular biological analysis of transgenic plants, like real time PCR, widely used to detect and quantify DNA and cDNA [3], could represent an useful tool to investigate the genetic stability of transgenic forest trees having a long life cycleas well as for determining copy number in transformed plants.