| Summary: | 博士 === 國立中興大學 === 農藝學系所 === 97 === Flavonoids and isoflavonoids are plants specific secondary metabolites. These C6-C3-C6 compounds are derived from the flavonoid biosynthetic pathway and play important roles in pigment production, pathogen defense, UV protection, hormone biosynthesis, and so on. Recently, the antioxidant properties of flavonoids elevate their value in human health and nutrition. One of the genes participates in flavonoid and isoflavonoid biosynthesis, chalcone isomerase, was cloned from soybean seed coat. A CHI1 cDNA and a CHI genomic DNA contains CHI1, CHI2 and CHI3 in a cluster, were isolated by library screening and genomic walking, respectively. RFLP analysis showed that the cluster of CHI genes present as a single copy corresponding to the results of physical mapping. The genomic organization of soybean CHI cluster was first identified and characterized in this study, and provides an opportunity to define their precise functions and relationship in the flavonoid biosynthesis in soybean. The enzyme, flavonoid 3’, 5’ hydroxylase (F3’, 5’H), that hydroxylates both 3’ and 5’ in B-ring of flavonoid controls the formation of blue anthocyanin, delphinidin. The GmF3’, 5’H cDNA was cloned from the black seed coats by library screening, and transcripts were expressed in flower and late stages of seed coat during seed development. The regulatory regions of GmF3’, 5’H gene were cloned by genome walking from TW1, Tw1, tW1, tw1 genotypes. Methylation of gene may possible involve in controlling gene regulation in soybean seed coats. The overexpression of GmF3’, 5’H in transgenic tobacco not only contributed delphinidin accumulation but also increased cyanidin production. This is quite different with most cloned F3’, 5’H that accumulated only delphinidin in transgenic plants. The dual function of soybean F3’, 5’H would be good choice for investigation and metabolic engineering application such as creation of novel flower pigment.
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