Isolation and transfer of genes of key enzymes to improve the quality of fruit

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This project was conducted by 2 groups. The first group tried the purification and cloning of some enzymes which concern closely the improvement of fruit quality. The base sequence coding cDNA of sorbitol dehydrogenase which converts sorbitol of translocating sugar in Rosaceae fruit to fructose was determined in apple fruit. In tomato fruit, cDNAs of 6 isozymes of ACCsynthase were isolated and the expressions were investigated using the specific antibody for each isozyme. From melon fruit, the cDNA encoding ACCsynthase and ACCoxidase were isolated, the base sequences were determined and the gene expression were investigated with fruit development. The base sequence of cDNA encoding sucrose phosphate synthase, sucrose synthase and acid invertase concverning the biosynthesis and degradation of sucrose of translocating sugar in Citrus were determined. The gene encoding cysteine protease which functions the maturation and senscence was isolated from French bean seed and Vigna mungo seedling, and the structure of promotor and the gene expression were investigated. alpha-Arabinofurano sidase concerning the softening of Japanese pear fruit was purified.The second group tried to establish the plant-regeneration system and gene transfer method to for the transgenic fruit tree. In apples, the plant-regeneration from the callus of apple cultivar and the gene transfer via Agrobacterium became possible, and we succeeded the transfer of S6PDH chimeric gene. In persimmon, the plant was regenerated from callus and protoplast, and the recombinant of marker gene was formed through Agrobacterium infection. Further, in grape and citurs belonging sub-family of Rutaceae, we succeeded to get the embryogenic callus and to form the recombinant of GUS gene by co-culturing the callus with Agrobacterium. As described above, we could collect some genes concerning closely the fruit quality, and establish the plant-regeneration method and the gene trans fer method in main fruits crops in Japan.