Transformation of hybrid black poplar with selective and reporter genes affects leaf proteome, yet without indication of a considerable environmental hazard

Poplar is an economically important forest tree used for multiple applications, including bioenergy production. Although genetic engineering allows a quick introduction of desirable traits, simultaneously, it may deliver unintended side effects. Herein, we compared the protein composition in leaves of microclonally propagated fast-growing hybrid clone of Populus deltoides × Populus nigra (Populus × euroamericana) , genetically modified with a reporter (GUS) and selective (NPTII) traits, and its non-transgenic parental genotype. By two-dimensional gel electrophoresis, we revealed that 5.5% of 330 detected protein spots were differentially accumulated. The vast majority of them showed lower abundance in the transgenic line. These proteins were mainly involved in primary metabolism, energy production, and protein synthesis/homeostasis; notably, none of them was directly linked to neomycin phosphotransferase or β-glucuronidase activities. Some of the differentially accumulated proteins could be associated with stress response caused by Agrobacterium -mediated transformation. Furthermore, the lower abundance of two cytosolic glutamine synthase isoforms and accumulation of bark storage protein A in the transgenic line, plausibly indicated impaired nitrogen metabolism and storage. The insertion of a model genetic construct did not alter the neighboring genetic loci, and neither toxins nor allergens were differentially abundant. In essence, we detected no protein indicating considerable health or environmental hazard in the transgenic hybrid black poplar.