Abstract: [Objective] This paper tries to study whether the exogenous Bt gene stably existed and expressed in 8-year-old grafted transgenic 741 poplar[Populus alba×(P. davidiana+P. simonii)×P. tomentosa], which have adapted to the complex natural environment many years after planting, and to explore patterns of sites, volume and direction of transportation and accumulation of Bt toxin protein in adult poplar.[Method] Poplar 741(741) and transgenic poplar 741(Pb29) with BtCry1Ac gene were grafted reciprocally as scion and stock. 8 years after planting in natural conditions, the two types of grafted poplars(741/Pb29, Pb29/741) were used for detection and validation of BtCry1Ac gene by PCR. In addition, the content of toxin protein in different tissues and different parts of adult grafted poplar was detected by means of ELISA technical system.[Result] The PCR test of BtCry1Ac gene showed that specific bands at the same size as that of the positive control were detected for both the scion of Pb29/741 and the rootstock of 741/Pb29, but not for the rest of non-transgenic parts and the negative control, proving that the Bt gene existed stably in the transgenic tissue of grafted poplar and no gene loss happened. Bt toxin protein was detected in all of the leaves, phloem, xylem and pith by the ELISA test, proving that Bt gene were expressed stably in 8-year-old transgenic grafted poplar 741, and Bt toxin can be transported between scion and stock in adult grafted transgenic poplar 741. As for the Pb29/741 adult plants, which had non-transgenic parts underground and transgenic parts above ground, we found that the Bt toxin protein could be expressed in above ground tissue and be transported to and accumulated in the non-transgenic tissue of roots and stem base mainly through phloem. And the content of the toxic protein gradually increased from outer to the inner of the crown, and decreased downward along the trunk progressively. While for the 741/Pb29 adult plants, which with transgenic roots and non-transgenic ground stems, we also found that the Bt toxin protein could be expressed in roots and stem base and be transported to and accumulated in the outer crown mainly through phloem. It showed that the content of Bt toxin protein gradually decreased upward along the non-transgenic trunk, and it increased from the inside tree crown to the outer.[Conclusion] The transportation of Bt toxin protein in the perennial grafted poplar showed a similar trend though the grafting methods were different. Additionally, the Bt toxin protein could be transported from transgenic part to non-transgenic part, and the content of toxin protein performed a similar transportation and accumulation trend from source to library. Transgenic poplars could be widely applied in production by a traditional way of grafting, which would improve the ecological safety of transgenic trees.

Key words: transgenic poplar, grafting, Bt toxin protein, gene expression, protein transportation