Abstract：Seedless fruit has strong market competitiveness and the considerable economic value, seedless trees can effectively reduce the pollution of the environment, seedless transgenic plants can help prevent foreign gene dispersal. Barnase gene comes from Bacillus amyloliquefaciens, encoding a 12 kD small molecule extracellular ribonuclease (RNAase). In the absence of its natural inhibitor Barstar, the expression of Barnase gene usually causes the death of its host cell. The T-DNA vector i. e. pBIloxP2 PNap TAibarnase carrying Barnase gene driven by Brassica napus seed-specific promoter Napin was constructed and transformed into tobacco(Nicotiana benthamiana) with the leaf disc transformation method, and 55 tobacco transformants were obtained. In which, 10 transformants were randomly selected for floral morphology analysis. Comparison of floral organs indicated that no obvious morphological difference was observed at different developmental stages between the transgenic and non-transgenic plants before pollination. Whereas, the floral organs of transgenic plants were gradually shrinking and dry, and failing to produce seeds after pollination; the petals of non-transgenic tobaccos were normally withered and can produce seeds within torus after pollination. In order to understand the mechanism of seed abortion of transgenic tobaccos, the cross between transgenic and non-transgenic plants were performed. However, no seed was obtained with the transgenic plants either as female parent or male parent. The hybrid results revealed that the seed abortion of transgenic tobacco was not caused by the self-incompatibility. To analyze the pollen activity, Alexander solution was used to stain the pollens of transgenic and non-transgenic tobaccos, then we observed the size, shape and color of pollens from transgenic and non-transgenic tobaccos with microscope, no difference was found. Therefore both the transgenic and non-transgenic tobaccos could generate active pollens. It is concluded that the seed specific promoter Napin used in this study only drives the Barnase gene expression in the seed, and no leakage expression takes place in pollens. We successfully obtain seedless transgenic tobaccos through expressing the Barnase gene in the seed tissue. The present study creates a novel model of producing seedless plants via genetic transformation, especially for vegetatively propagated crops.
