| Soil salinization is a serious problem in agriculture, which affects the agricultural production and ecological environments, and leads to a great reduction output in rice. The total acreage of salinizes and alkaline land is about 1/3 of the irrigated land in the world. In our country the salt disperative soil is about 1/5 of arable land and it will be expanded in the future. The production loss caused by soil salinization is too large to be estimated. In addition, decrease of arable land and shortage of freshwater will compelled people to exploit and utilize vast saline and coastal soil. Therefore, the research on the mechanism of plant salt-tolerance and breeding for salt-tolerant crops will become an attention research field.In order to relieve the damage of salt to the cell, many plants accumulate some low-molecular weight compounds called osmoprotectants, such as betaine, polyamines and mannitol, etc. Therefore, if the genes controlling the enzymes, which were responsible in synthesizing of these osmoprotectants, were transformed into rice, the salt-tolerance of the transgenic plants might be increased significantly.In this paper, the transformation of BADH gene (encoding betaine aldehyde dehydrogenase) and SAMDC gene (encoding s-adenosylmethionine decarboxylase) into rice by the methods of bombarment and Agrobacteriwn tumefaciens mediated were conducted, in order to enhance the salt tolerance in rice significantly. The main results were as follows:1. Five rice cultivars were transformed in this experiment, using the embryogenic calli derived from mature and immature embryo as acceptor. A total of 263 rice plants were obtained from three cultivars. The transformation efficiency among the different genotypes was varying greatly, for example Taibei309 was 18 times higher than that of 752, and the transformation efficiency was decreased with the increasing of the size of plasmid. In addition, the comparisons were made between bombarment method and Agrobacteriwn tumefaciens mediated gene transfer system in this paper.2. The different selective antibiotic was compared in this paper. The suppression of Kan to embryogenic calli in rice was not as good as expect, it can not be used as the selective material in rice transformation as the experiment shown. However, lOOmg/L of G418 can basically suppress the growth of embryogenic calli. As far as rice transformation wasconcerned, if the selective marker gene is Npt II, G418 should be used as antibiotic. And if Hpt gene was the selective marker gene, 50mg/L hygromicine can suppress the growth of embryogenic calli completely.3. The PCR results showed that the target genes had integrated into the rice genome. Southern-blot analysis of BADH gene demonstrated that BADH gene integrated into the genome, and most of transformed rice plants had five or more loci, regardless of the transgenic plants obtained by bombarment method or by Agrobacterium mediated transformation. The integration mode in several seedlings from one clone was the same, according to the southern blot analysis.4. The activity of betaine aldehyde dehydrogenase had been detected in the transgenic rice plants, while the enzymatic activity of those without transformation could not be detected. However, the activity of betaine aldehyde dehydrogenase in different transgenic individuals was quite different. Mean time, the activity of betaine aldehyde dehydrogenase in transgenic rice can be increased greatly when they were treated with salt, and the average value was between 250U and 300U, and varied a little in difference seedlings from the same transgenic lines.5. The transgenic plants and its background cultivars were transplanted to the salt pool containing 0.5% NaCl (W/V) and the growth under salt stress was observed. All the transgenic plants could grow normally and produce seeds in the autumn under 0.5% NaCl stress. However, when they were transplant into the pool with 0.5% NaCl, the control plants could not grow any more and the leaves would... |
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