Application Of Stomotal-specific Promoter-KST1 To Improve Plant Drought Tolerance

The plant hormone abscisic acid (ABA) plays important roles in seed maturation and dormancy and in adaptation to a variety of environmental stresses. One of important roles of ABA is to accelate to close stomata. The stomatal pore is the main pathway for the change of water and gas between the plants and the environments around, and it plays important regulation roles during the processes of plant photosynthesis and transpiration. An effort to engineering plants with elevated ABA levels and subsequent stress tolerance has been shown that 9-cis-epoxycarotenoid dioxygenase (NCED) is a key enzyme in abscisic acid biosynthesis under drought-stressed conditions. Plants overexpressing NCED showed an improvement in drought tolerance. However, plants maybe have not good growth with too high level of ABA in the plant body. To minimize the negative effects on the plant growth and elevate the useful value during environment stress of ABA , we have studied the potential function of stomatal-specific promoter-KSTl to improve the drought tolerance of plants.We have created transgenic tobacco plants in which expression of the AtNCED3 coding region is under strong constitutive 35S cauliflower mosaic virus (35S) promoter, stress-inducible RD29A promoter or stomotal-specific KST1 promoter by Agrobacterium tumefaciens-mediated transformation. Overexpression of AtNCED3 in transgenic tobaccos caused an great increase in endogenous ABA level under normal conditions, and KST1 plants less than 35S,then RD29A and wild-type plants. Tobacco plants also elevated ABA content, and transgenic plants had significantly higher leaf ABA content compared to the wild type under stress conditions. RD29A plants had a highest ABA content ,than 35S,KST1 and wild-type plants.Expression of AtNCED3 driven by 35S promoter, rd29A promoter or KST1 promoter has greatly affected the growth and stomotal movement and drought tolerance in the transgenic tobacco plants . We observed the 35S:iAtNCED3 plants showed severe growth retarda- tion ,and vd29A:AtNCED3 plants exhibited slight growth retardation, however we also observed the KST1:: AtNCEDs plants had a good growth under normal conditions. Expression of AtNCED3 made the stomata of transgenic tobacco plants more sensitive promoting the somatal opening induced by light for some time and'the stomatal closing induced by darkness.Under drought stress conditions, they indicated an drastic improvement in drought tolerance than wild-type plants.With all these results , we may make such a conclusion that KST1 promoter is quite useful to realize the spatial and quantitative expression patterns of AtNCED3 in order to improve water use efficiency in plants by manual manipulation.