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

从跃变果实中的香蕉和甜瓜，以及非跃变果实中的葡萄和黄瓜中克隆了几个MADS-box基因，研究了跃变果实和非跃变果实中乙烯生物合成的内反馈调控的差异。这些基因在跃变期和非跃变期果实中都有结构性表达。通过LeMADS-RIN基因的断裂，将葡萄浆果中的VvmadsRIN类基因导入不成熟突变体Rin番茄。类VvmadsRIN与LeMADS-RIN互补，转化的RIN番茄果实表现出正常的成熟现象。从野生番茄中分离到一个新的乙烯信号转导基因LeEIL4，研究了3种类型梨果实的软化特性及乙烯在软化过程中的作用。在跃变期果实中，‘La France’果实的乙烯释放量显著降低，而‘雅丽’果实在果实成熟过程中，尽管产生了大量的乙烯，但果肉硬度和质地没有明显变化。‘Nijisseiki’是一种非跃变型水果，果肉硬度没有明显下降。这些果实软化的差异与内切多聚半乳糖醛酸酶基因的表达有很好的相关性。在‘La France’果实成熟过程中，PC-PG1和PC-pg2有表达，而在‘Nijisseiki’果实中只有PC-pg2表达，在‘雅丽’果实中没有表达。尽管细胞壁多糖在果实成熟过程中发生了数量和质量的变化，但果胶聚合物发生了质的变化，而半纤维素聚合物没有发生质的变化。

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.