Molecular genetic on the storage capability and preharvest dropness of apple fruit

苹果（Malus × arctica Borkh.）果实成熟之前产生乙烯，即诱导果实成熟的成熟激素。果实产生的乙烯量取决于成熟特异性1-氨基环丙烷-1-羧酸（ACC）合酶基因的转录水平。我们已经发现，在5 '侧翼区含有插入的逆转录酶样序列的等位基因（MdACS 1 -2）的转录水平低于野生型（MdACS 1 -1）。MdACS 1 -2/2纯合果实在跃变型阶段比野生型果实产生更低水平的乙烯。我们还发现，MdACS 1 -2/2树的苹果品种和品系的采前落果率比MdACS 1 -1/1或MdACS 1 -1/2树的落果率低。用乙烯受体阻断剂1-MCP处理MdACS 1 -2/2树，进一步减少落果。分析商品苹果品种中MdACS 1 -2/2等位基因的存在可能有助于早期检测， 关于我们 从苹果（Malus × arctica Borkh.）的培养枝（MdExp 1）、成熟果实的果肉（MdExp 2、MdExp 3、MdExp 4）和果梗组织（MdExp 5、MdExp 6）中分离到6个编码扩展素的cDNA。我们在这里报告这些MdExp基因在果实个体发育过程中的表达特点。MdExp 1在盛花期至成熟前表达呈up-down-up循环。MdExp 2和MdExp 5的表达在细胞增殖阶段后开始细胞扩增时开始; MdExp 5的表达仅限于早期快速生长期。MdExp 3和MdExp 4的转录本在两个生长阶段都存在上升-下降-上升的循环，但在成熟期MdExp 3的表达增加。MdExp 6的转录本在任何生长阶段都没有检测到，但由创伤诱导。这些结果表明，苹果果实发育过程中至少需要5个expansin基因，MdExp 3是一个成熟相关的expansin基因。少

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 … More 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