Cloning and activity analysis of BpGT14 gene promoter in Betula platyphylla.

We cloned a 2 169 bp promoter sequence of BpGT14 gene from birch genomic DNA using the method of SiteFinding-PCR. The promoter sequence was analyzed by PLACE, and the result showed that this fragment contained promoter core elements and some elements which can respond to abiotic stress and hormones. Meanwhile, two important MYB transcription factor binding elements were found which regulate phenylpropanoid and lignin biosynthesis. To study the promoter activity, a 1 156 bp fragment was chosen to construct pBpGT14∷GUS plant expression vector and transformed into tobacco. GUS staining proved that the promoter had high activity in stem segments. When the tobacco was treated with GA and H2O2 at 4 ℃, the promoter had no significant response and the enzyme activity had a downward trend. In contrast, the promoter activity was significantly increased by ABA, NaCl, PEG and 37 ℃ treatment. Further transformation of birch cells using pBpGT14∷GFP plant expression vector indicated that the promoter had a similar response pattern to that of tobacco treated with abiotic stress and hormone except for a few time points. As the promoter was significantly and quickly responsive to drought stress, we have observed the GFP fluorescence protein in birch stem segments suspension cells transformed by GFP for 3, 6, 12 and 24 h with PEG treatment. The results showed that BpGT14 promoter had activity in birch stem segments suspension cells and fluorescence can be observed in the suspension cells, especially in cell walls. Successful implementation of this study has important significance for analysis of gene regulation and function. Meanwhile, it provides a theoretical basis for gene promoter function studies of other woody plants.