| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1998: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1997: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
Recently, the genetic manipulation of plants has tremendously advanced. The study of the mechanism of fruit ripening and softening at molecular level, will result directly to the development of transgenetic plants that have a longer self-life. In this study, we cloned genes encoding cellulase and polygalacturonase which have been known to modify cellulose and pectin substances respectively. We obtained six divergent clones which encode cellulase in melon fruit. The expression analysis indicated that those genes were divided into two groups. The first group is expressed in young and expanding fruit, suggesting a physiological role in cell growth, and other group is expressed constitutively and contains membrane spanning domain. Surprisingly, a cellulase gene expressed specifically in fruit that is undergoing ripening was not obtained from melon fruit. During the course of this study, polygalacutoronase gene of melon was reported by researchers in USA.We therefore turned to clone polygaracturonase genes from cucumber, that belongs to Cucumis family as same as melon, and from persimmon fruit that undergo an intensive and. rapid softening during fruit ripening. As for the results, one length polygalacturonase. gene was obtained from cucumber fruit. Expression analysis showed that the accumulation of the mRNA was induced with progress of fruit softening, by water stress or by exogenous ethylene. On the other hands the expression was inhibited by the pretreatment with 1-MCP, a strong inhibitor of ethylene action. The results suggest that the polygalacturonase gene is responsible for fruit softening induced by stress-ethylene.
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