Abstract: To explore the role of xyloglucan endotransglycosylase (XET) in the softening of kiwi fruit ( Actinidia chinensis Planch. ) fruit during fruit ripening, the expression pattern of XET gene in relation to fruit softening was investigated. Northern analysis showed that XET mRNA was in very low level in the fruit at harvest time; treatment with 100 μL/L ethylene induced mRNA accumulation, the longer the ethylene treatment, the higher the mRNA level, thus promoted fruit softening. The mRNA level reached the highest at 24 h after ethylene treatment and had no significant change during ethylene climacteric as the ripening fruit stored at 20 ℃. A trace of mRNA level was determined in the fruit stored at 0 ℃ while fruit firmness did not change significantly. There was no marked change of mRNA level in the fruit when it was transferred to 20 ℃ after storing for 168 h at 0 ℃, however, the fruit softened quickly. It is proposed that XET might be a kind of inductase leading to xyloglucan depolymerization in the fruit cell wall and not play a key role of softening of kiwi fruit after ripening.

Key words: Actinidia chinensis, Fruit, Softening, Xyloglucan endotransglycosylase, Gene, Expression