采后玉露桃果实冷害发生与ROP基因的表达调控

Occurrence of chilling injury and regulation of ROP gene expression in Yulu peach fruit during storage

以软溶质玉露桃果实为材料,于8℃、5℃、0℃和LTC(8℃锻炼3d再转到0℃贮藏)下贮藏30d后转至货架(20℃)2d,对各个处理果实的腐烂和冷害程度、果实品质变化规律以及ROP基因的表达模式进行了比较,以探讨ROP基因与低温胁迫的关系。结果表明,经5℃和0℃贮藏30d的玉露桃果实在货架期间褐变加重,经5℃处理的果实褐变最重,经0℃处理果实表现后熟障碍;经8℃贮藏30d以及后续2d货架期的果实不出现冷害症状,但果实腐烂严重;LTC处理果实经冷藏后在货架期后熟正常,且果实冷害和腐烂均被明显抑制。各处理桃果实在采后低温贮藏过程中总可溶性糖和总有机酸质量分数均趋下降,其中5℃处理果实总可溶性糖质量分数下降幅度最大。结合应用EST检索和RT-PCR克隆扩增,分离出桃ROP基因(PpROP)。实时定量PCR结果显示,PpROP在5℃下表达迅速增强,第5天达到高峰,其丰度明显高于其他处理,LTC处理使PpROP表达维持较低水平。

In this study, effects of 4 temperature treatments,including 8 ℃, 5 ℃, 0 ℃ and LTC （stored at 8℃ for 3 d,then transferred to 0 % ）, were studied on the occurrence of chilling injury, changes in fruit quality and expression of ROP gene in the fruit of flesh-melting textured peach cuhivar Yulu during 30 d storage at low temperature and subsequent 2 d shelf life at 20 ℃. Flesh browning was observed under 5℃ and 0℃ treatments, and more severe for 5℃-treated fruit and failure of norreal ripening for 0 %-treated fruit. Chilling injury symptoms were not observed on fruits at 8 ℃ during 30 d storage. However, the decay rate was high during the subsequent 2 d shelf life. LTC treated fruits ripened normally during shelf life, and more- over, both chilling injury and fruit decay were greatly inhibited. For all the temperature treatments, both total sugar content and total organic acid content declined during storage, and the decrease in total sugar content was highest for fruits stored at 5 ℃. In combination of EST BLAST and RT-PCR, PpROPgene was identified from peach fruits. Q-PCR analysis revealed that expression was immediately activated at 5℃ and so was the mRNA abundance. The transcript level of PpROP at 5℃ was much higher than that at other temperatures and it peaked on the 5th day. The expression of PpROP maintained at a constant low level during LTC storage.