2002 Fiscal Year Final Research Report Summary
Molecular genetic on the storage capability and preharvest dropness of apple fruit
| Project/Area Number |
12660001
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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 |
Breeding science
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| Research Institution | Hirosaki University |
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Principal Investigator |
HARADA Takeo Hirosaki University, Department of Agriculture and Life Science, Associate Professor, 農学生命科学部, 助教授 (10228645)
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| Project Period (FY) |
2000 – 2002
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| Keywords | Apple / Ethylene / ACC synthase / Fruit Storage / Malus / Fruit drop / DNA marker |
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| Research Abstract |
The onset of apple (Malus × domestica Borkh.) fruit maturity is preceded by the production of ethylene, the ripening hormone, which induces fruit ripening. The amount of ethylene produced by the fruits depends on the level of transcription of the ripening-specific 1-aminocycloropropane-1-carboxylate (ACC) synthase genes. We have found that an allele (MdACS1-2) which contains an inserted retroposon-like sequence at the 5'-flanking region is transcribed at a lower level than the wild-type (MdACS1-1). MdACS1-2/2 homozygous fruits produce a lower level of ethylene at the climacteric stage than does the wild type fruit. We have also found that the preharvest drop rates of apple cultivars and strains of MdACS1-2/2 trees have less fruit drop than the MdACS1-1/1 or MdACS1-1/2 trees. Treatment of the MdACS1-2/2 trees with 1-MCP, an ethylene receptor blocker, further decreased fruit drop. Analysis of commercial apple cultivars for the presence of the MdACS1-2/2 allele may help in the early detec
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tion of apple cultivars with a low fruit drop rate.
Six cDNAs encoding expansins were isolated from cultured shoots (MdExp1), the flesh of ripening fruit (MdExp2, MdExp3, MdExp4), and fruit pedicel tissue (MdExp5, MdExp6) of apple (Malus × domestica Borkh.). We report here the expression characteristics of these MdExp genes during fruit ontogeny. MdExp1 was expressed in an up-down-up cycle from full-bloom stage to just before ripening. The expression of MdExp2 and MdExp5 was initiated when cell expansion was started after the cell proliferation stage; the expression of MdExp5 was limited to the early rapid growth period. The up-down-up cycles were also detected in the transcripts of MdExp3 and MdExp4 throughout both growth stages, but the expression of MdExp3 was increased in the ripening stage. Transcripts of MdExp6 were not detected in any growth stage, but were induced by wounding. These results suggest that apple fruit requires at least five expansin genes during ontogeny, and that MdExp3 is a ripening-related expansin gene. Less
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Research Products
(3 results)
