41.柑橘およびマメ科植物におけるクマリン化合物生合成酵素の探索(口頭発表)

概要

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Coumarins are ubiquitously found as the plant secondary metabolites in plants. They are thought to play important roles in plant defense due to their antimicrobial and antioxidative activities. Coumarins are biosynthesized via ortho-hydroxylations of cinnamates (C2'H). This is a key step in the lactone ring formation in coumarin biosynthesis, and C2'H is classified into the 2-oxoglutarate-dependent dioxygenase (2OGD) family. Arabidopsis roots accumulate scopoletin β-glucoside, and Arabidopsis C2'H shows the high substrate specificity to feruloyl-CoA but does not accept ferulic acid as a substrate. Sweet potato (Ipomoea batatas L.) tubers accumulate the β-glucosides of scopoletin and umbelliferone, and C2'H of sweet potato can accept feruloyl-CoA and p-coumaroyl-CoA as its substrates to form scopoletin and umberiferone, respectively. These results suggest that the substrate specificity of C2'H determines the accumulation patterns of coumarins in each plant species. In this study, we have found that there are C2'H homologs in the EST database of citrus and legume (Medicago truncatula and Lotus japonicus). Citrus fruits are known to accumulate furanocoumarins, but little is known about coumarin synthesis in M. truncatula and L. japonicus. In order to explore coumarin biosynthesis in citrus and the legume plants, we have performed the functional analysis of the C2'H homologs of these plants.
2009-10-06