| Rice is an important crop. However, water shortage and salinity soil have become most serious constraint to rice production and yield stability in many rice-growing areas. Producing drought- and salt-tolerance rice lines by plants gene engineering was the most importent approach in rice breeding at present and in the fuilture. In this study, OsNHX1 and AtNCED3 were transformed into upland rice and lower land rice respectively. To obtain new rice lines with enhancing drought, salt and lower temperature tolerance but without affecting their growth and development, we selected the inducible promoter rd29A to overexpres the AtNCED3 gene in rice.Mature embryo derived calli from IRAT109 cultivar were as starting material and had been co-cultivated with A. tumefaciens LBA4404 habaring plasmid p3301/OsNHX1. Seven independent transgenic lines overexpressing OsNHXl gene were created and the object gene has been integrated in the upland genome by PCR assay. Moreover, Northern bolt analysis showed that the expression levels of OsNHXl in leaves of three independent transgenic plant lines were significantly higher than those of wild type plants. The transgenic plants grew faster than wild type plants during the recovery growth upon the removal of 100 mM NaCl treatment for 5days. Under the 200 mM NaCl treatment, the transgenic plants showed delayed appearance of damage symptoms, suggesting their increased salt tolerance. We found that the Na+ content was higher and the osmotic potential was lower in leaves and roots of transgenic plants than that of wild type plants in the present of 200mM or 50mM NaCl, indicating that transgenic plants had more Na+/H+ antiporter and can compartmentalize Na+ into vacuoles, thus enhancing the ability of cells absorbing water by osmosis and maintaining the cytosol ion balance.Through the mothed of Agrobacterium tumefaciens-mediated transformation, we generated a number of independent transgenic upland rice and lower land rice lines in which the AtNCED3 encoding region is under control of stress-inducible rd29A promoter or of strong constitutive Ubi-1 promoter. On the analysis of ABA content in leaves or calli of transgenic plantsfrom Zhongzuo 93 cultivar, we found that constitutive overexpression of AtNCED3 in rice plants caused a great increase amount of ABA content in both transgenic hygrimacin resistant calli and plant leaves under both normal and drought stress conditions. Nonetheless, inducible overexpression of \heAtNCED3 plants resulted in enhancing ABA levels only under drought stress condition. These demonstrate that the manipulation of ABA biosynthese enzyme genes can elevate the ABA content in plants.According to the phenotype, the assay of physiological traits and abiotic tolerance between the control and transgenic plants, we found that Ubi::AtNCED3 plants result in severe growth retardation, delayed flower, significantly decreased transpiration rate and stomatal conductance, and inhibited cell cleavage and elongation. However, the rd29AvAtNCED3 plants exhibited significant drought, salt and lower temperature tolerance under multi-stress conditions, although slight growth retardation were observed during the vegetative growth stage. These results showed that the rd29Apromoter is quite useful to realize efficient expression patterns of AtNCED3 in rice plants with improved drought-, salt- and lower temperature tolerance by manual manipulation.In this study, we have obtained salt tolerance upland lines and abiotic tolerance rice plants using the inducible promoter rd29A overexpressing AtNCED3 gene. We generated the rd29A::AtNCED3 new rice lines, which not only have multi-stress tolerance characteristics but also grow normally. These works laid the foundation of using plant engineering techniques to enhance abiotic stress tolerance in crops. Meanwhile, we can use the transgenic plants to further study the function of AtNCED3 gene and the mechanism of ABA action.
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