1998 Fiscal Year Final Research Report Summary
Regulation of sugar composition in fruit by metabolic engineering
| Project/Area Number |
09660017
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
園芸・造園学
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| Research Institution | Tohoku University |
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Principal Investigator |
KANAYAMA Yoshinori Tohoku University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (10233868)
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| Project Period (FY) |
1997 – 1998
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| Keywords | sugar / fruit / tomato / fructose / fructokinase |
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| Research Abstract |
The important quality of fruit is flavor and in most fruit, consumer flavor preferences are dominated by sweetness. There is a difference in sweetness of hexose sugars, with fructose being approximately twice as sweet as glucose. Because many fruit accumulate approximately equal levels of the hexose isomers, fructose and glucose, metabolic engineering to enhance the proportion of fructose has the potential to enhance fruit sweetness. In this work, the expression patterns of two tomato fructokinase genes, Frk1 and Frk2, are described as well as a strategy to suppress their expression in transgenic tomato plants.
In situ hybridization using Frk1 and Frk2 probes showed differential expression of these two genes in tomato fruit. Frk2 mRNA is localized specifically for starch synthesis and seed development in young tomato fruit whereas Frk1 mRNA is widely distributed. The results from northern blot and in situ hybridization suggest that Frk1 plays a primary role in fructosemetabolism in plant cells while Frk2 is localized specifically in cells that import and utilize moresugar such as starch synthesizing cells and developing seed-related cells. An antisense gene was constructed using Frk1 cDNA and E8 promoter that are cloned to pBl121 binary vector. Approximately 50 transformants were grown and fruit were harvested from them. Although the levels of endogenous Frk1 mRNA were decreased in several t ransformants, any changes in fruct okinase activity and fructose content were not detected in the transformants. Therefore transformation works using Frk1 and Frk2 with 35S promoter were carried out. As a result, decreases in fructokinase activity were observed in some transformants with Frk2 antisense genes. The changes in activity possibly affect sugar composition in fruit.
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