Study On The Molecular Mechanism Of ABA Regulating Arabidopsis Seed Dormancy

Seeds is one of the most important agricultural resources and its quanlity have a direct impact on the growth and development of plants.Seed germination and dormancy is a crucial process in the initial stage of growth and developemnt of evey individual plant.Understanding the regulatory mechanisms of seed dormancy is important for improving seed viability,resistance of seedlings to adverse conditions as well as crop yields.The plant hormone abscisic acid(ABA)can inhibit seed germination and promote seed dormancy.ABI1 gene plays a key role in mediating this regulatory role.Previous studies have shown that a mutantion that changes the 180 th amino acid glycine to aspartic acid results in ABA insensitivity and transgenic plants that constitutively express the above-mentioned mutated form of ABI1 protein also display an ABA insentive phenotype during seed germination.However,it is unclear where ABI1's function in seed dormancy has any tissue specificity.In this study,I address this question by expressing abi1 in different tissues of Arabidopsis thaliana plants using tissue-specific promoter and the GAL4/UAS expression system.Seed germination were examined in the resulting transgenic plants on media containg different ABA concentrations.The main results are as follows:(1)Transgenic plants with specific expression of abi1 gene in the root tip stem cell regions show an decreased sensitivity to ABA during seed germination in comparison with wild type plants,but with no significant changes in the speed of seed germination.(2)Transgenic plants that specifically express the abi1 gene in the stem cell region of the shoot apical meristems were more sensitive to ABA and has a lower germination reate in the absence of ABA in comparison with wild type plants.(3)Expression of abi1 under the control of the GAL4 line J2133 leads to an decrease in ABA sensitivity during seed germination...