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The cDNA of AtPLDα (Arabidopsis thaliana Phospholipase Dα) gene was introduced into P. tomentosa (Populus tomentosa) under the control of the Cauliflower mosaic virus 35S promoter. Southern and Northern blot analyses suggested that the AtPLDα gene has been transferred into the P. tomentosa genome. No obvious morphological or developmental difference was observed between the transgenic and wild-type (WT) plants. Drought and salt tolerance and gene expression of seedlings of several transgenic lines and WT plants (control) were studied. The results showed that the rhizogenesis rate and the average root-length of transgenic lines were significantly higher than WT plants after mannitol and NaCI treatment under the same growth conditions. Northern blot analysis indicated that the higher the PLDα expression in the transgenic plants, the more tolerant the transgenic plants are to drought and salt treatment. Meanwhile, another group of these transgenic lines and WT plants (control) were treated with PEG6000 and NaCI separately. The contents of chlorophylls and the activities of some antioxidant enzymes (superoxide dismutase, guaiacol peroxidase and catalase) as well as malondialdehyde and relative electrical conductivity were analyzed. Altogether, our results demonstrated that overexpression of the PLDα gene can enhance the drought and salt tolerance in transgenic P. tomentosa plants. [ABSTRACT FROM AUTHOR]

Reports that the inclusion of MARs in transgene cassettes enhances their expression and reduces position-effect variations in the transgenic host. Statement that four new MARs (TM2, TM3, AM1 and AM2) were isolated from tobacco and Arabidopsis by PCR method; Reference to nuclei isolated from suspensioncultured cells of rice used to prepare nuclear matrix; Report that with a characterized MAR (TM1) as a positive control, the Matrix-MAR interactions were tested by an in vitro binding assay to identify the DNA sequences as MARs and their binding strength to nuclear matrix in vitro was compared; Results showing that TM2 and TM3 had stronger binding strength than TM1; Procedure used to determine the functions of the four new MARs in vivo; Modification of binary vectors pBI121 carrying a u/dA GUS reporter gene with direct repeat MARs inserted on both sides of the reporter gene cassette; Transferance into tobaccos via Agrobacterium-mediated transformation procedure. Statement that quantitative GUS assays of the transgenie tobaccos showed that when flanking a GUS reporter gene TM1, TM2, TM3 and AM1 increased u/dA GUS gene expression level approximately 1.5-fold, 5-fold, 1.35-fold, 1.3-fold respectively and AM2 has no effect on gene expression. Discovery that TM2 was found to be a strong MAR that could effectively increase gene expression level and could be used as an effective enhancing element to construct high efficient expression vectors; Discussion of the relations among the sequence features, binding strength in vitro and function in vivo of the five MARs that were analyzed, and the potential significance of TM2 in plant genetic engineering.