A full-length cDNA of dehydrin BcDh2 from Boea crassifolia and its antisense nucleotidesequence have been transferred into tobacco (Nicotiana tabacum) NC89 under the controlof a caulifower mosaic virus 35S promoter. Under a progressive water stress, photosyntheticrate, transpiration rate and stomatal conductance of the sense and antisense plantsreduced, and those of the control reduced much more. Photosynthetic rate, transpirationrate and stomatal conductance of all plants tested increased significantly 24 hourslater after recoveried water supply, and those of the sense and antisense plants werehigher than control. These indicated that overexpression of a dehydrin gene in tobaccomay improve tolerance to water stress for plants, however, antisense BcDh2 gene intransgenic plant did not influence physiological conditions. The results of germinationexperiment of the transgenic seeds showed that on MS medium with different concentrationPEG (8000), sense seed could more endure drought than control, while antisense seed wassensitive to drought. The results suggested that the overexpression of a dehydrin genein tobacco might improve the tolerance to water stress for plants.
Cre site-specific recombinase-mediated DNA excision system was driven by the heat shock promoter Gmhsp17.5C. In this system, the DNA fragment with CaMV35S-GUS franked by two identical orientation loxp sites could be excised from the transgenic tobacco (Nicotiana tabacum L. cv. W38) by Cre expression under control of heat shock promoter. This transgenic system has been determined by quantitative PCR and showed Cre/lox mediated recombination efficiency. Results showed that 41% of DNA fragment with CaMV35S-GUS in the transgenic tobacco could be excised after a two-hour heat shock treatment. Based on several advantages of heat shock-inducible site-specific recombination system such as easy manipulation, sensitivity to heat shock and no background expression, it can be potentially used for inducible DNA manipulation in transgenic plant.
A copper-inducible, Cre-loxP recombination-mediated DNA excision system has been developed in transgenic tobacco plants. The copper inducible system derived from yeast was used for the control of the expression of the Cre recombinase. Upon copper induction, the GVS reporter gene expression unit flanked by two direct lox sites was excised from the transgenic tobacco genome. Quantitative fluorometric GUS assays, Northern blot and PCR analyses showed a high-efficient, copper-dependent and Cre-loxP mediated DNA recombination in all the tested transgenic lines. The copper inducible foreign gene excision might be of great potential in genetic control of transgenic crops.
PENG Xiang-lei, LIANG Bin, CHEN Ming, HU Yuan-lei and LIN Zhong-ping(National Key Laboratory of Protein Engineering and Plant Genetic Engineering , Peking University , Beijing 100871 , P. R. China)
