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The triacylglycerol (TAG) is the major storage form of oil in plants. The sn-Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the acylation at sn-1position of glycerol-3-phosphate to produce lysophosphatidic acid (LPA). LPA is an important intermediate for the formation of different types of acyl-lipids. Three types of GPAT have been found in plants, localizing to plastids, mitochondria and endoplasmic reticulum, respectively. GPATs are involved in many fatty acids biosynthesis pathways and play some important roles in the process of the plant development.The Arabidopsis GPAT gene family has9members, from GPAT1to GPAT9. GPAT1, GPAT4, GPAT6, GPAT8have been cloned and the biochemical functions of GPAT4and GPAT8have been identified. But we don’t know whether other GPATs involve in the sythesis of seed oil and what the biochemical functions of other GPATs are. This paper mainly studies the functions of AtGPAT6,7,9in terms of the seed-oil content and composition, and the regulation of salt resistance. Cloned the AtGPAT6,7,9promoter and analysis their organs localization by the fluorescence quantitative PCR technique and GUS staining method. The study finds that AtGPAT6is expressed mainly in the flowers, and the expression level of AtGPAT7is higher in root. In addition, AtGPAT6,7,9also are expressed in the seeds, especially GPAT9.The gpat6,7,9deletion mutants were identified. The coding sequences of GPAT6,7,9were cloned. Furthermore, we constructed the overexpression vector (pCAMBIA1300-GPAT6,7,9) and used the method of the Agrobacterium infection to get the overexpression homozygous lines of Aravidopsis. Determined the content of fatty acid and TAG between wild type, mutants, and overexpression by using the gas chromatography (GC) and analyzed the functions of AtGPAT6,7,9in terms of the plant seed oils.The results indicate that, comparing with the wild type, some unsaturated fatty acids content in seeds of the GPAT7,9overexpression lines increase, especially C18:2,while that in seeds of the gapt9mutant decrease and that do not change in gapt7mutant. From the results, we analyze that GPAT7and GPAT9may contribute to the synthesis of some unsaturated fatty acids, and that role of GPAT9is stronger than GPAT7.In addition, compared with the wild type, the TAG content in plant seeds of GPAT7,9overexpression lines increase5%-9%and decease5%in gapt9mutant lines. The TAG content of gapt7mutant do not change which compared with the wild type. The content of fatty acids and TAG between wild type, gpat6mutant and the overexpression lines are no obvious difference.We used the different concentration of salt (NaCl) to treat the seedlings of wild type, mutants and the overexpression lines. The study find the seedling mortalities of the gpat6,7mutants are more than the wild type, while those of the GPAT6,7overexpression lines are smaller. There are no obvious differences between wild type, gpat9mutant and the overexpression lines under the salt tolerance. The results indicate GPAT6and GPAT7may positively regulate salt tolerance in Arabidopsis.
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