MOLECULAR APPROACH ON THE DIFFERENCE OF INTERNAL REGULATION IN ETHYLENE BIOSYNTHESIS BETWEEN CLIMACTERIC AND NONCLIMACTERIC FRUITS

研究了乙烯生物合成内部反馈调控在更年期果实和非更年期果实中的差异。从更年期果实中的香蕉和甜瓜以及非更年期果实中的葡萄和黄瓜中克隆了多个MADS-box基因。在更年期和非更年期果实中，这些基因在整个生长和成熟过程中都有组成性表达。从这些MADS-box基因中，通过断裂LeMADS-RIN基因，将葡萄浆果中的vvmadsrin样基因引入到具有不成熟特征的突变体rin番茄中。VvmadsRIN-like对LeMADS-RIN和转化后的rin番茄果实均表现出正常的成熟现象。从野生型番茄中分离到一种新的乙烯信号基因LeEIL4。研究了乙烯对三种梨果实的软化特性及其在软化过程中的作用。在更年期果实中，“La France”随着乙烯的产生而急剧软化，而“Yali”在成熟过程中尽管产生了大量乙烯，但果肉的紧致度和质地没有显着变化。非更年期水果“nijisisiki”的果肉紧致度没有明显下降。果实软化的差异与内切多半乳糖醛酸酶基因的表达密切相关。PC-PG1和PC-PG2在‘La France’果实成熟过程中表达，而‘Nijisseiki’果实成熟过程中只有PC-PG2表达，‘Yali’果实成熟过程中PC-PG1和PC-PG2均未表达。以无花果果实为材料，研究了成熟过程中细胞壁多糖的变化。尽管细胞壁多糖在果实成熟过程中发生了定量和定性变化，但定性变化发生在果胶聚合物中，而在半纤维素聚合物中则没有。

Differences of the internal feedback regulation in ethylene biosynthesis between climacteric and nonclimacteric fruits were investigated.Several MADS-box genes were cloned from banana and melon in climacteric fruits, and grape and cucumber in nonclimacteric fruits. Constitutive expression of these genes throughout growth and ripening was observed in both climacteric and nonclimacteric fruits.From these MADS-box genes, VvmadsRIN-like gene from grape berries was introduced into rin tomato, a mutant with non-ripening feature by break of LeMADS-RIN gene. VvmadsRIN-like complimented LeMADS-RIN and the transformed rin tomato fruit showed normal ripening phenomena. From wild-type tomatoes, a novel ethylene signaling gene, LeEIL4, was isolated.The softening characteristics and the role of ethylene in the softening process were investigated in three types of pear fruit. In climacteric fruit, ‘La France' softened dramaticall with ethylene production, while ‘Yali' showed no significant changes in flesh firmness and texture during ripening despite of large amount of ethylene production. ‘Nijisseiki', a nonclimacteric fruit, did not show detectable decrease in flesh firmness. These difference in fruit softening correlated well with endo-polygalacturonase gene expression. PC-PG1 and PC-PG2 were expressed in ‘La France' fruit during ripening, while, only PC-PG2 did in ‘Nijisseiki', and neither of PC-PG1 or PC-PG2 did in ‘Yali'.Alterations in cell wall polysaccharides during ripening were investigated using fig fruit. Even though quantitative and qualitative changes in cell wall polysaccharides occurred during fruit ripening, qualitative variations occurred in the pectic polymers but not in the hemicellulosic polymers.