牡丹开花和衰老期间MAPK级联途径在ABA、乙烯和过氧化氢信号应答中的功能研究

Tree peony (Paeonia suffruticosa), is an important and distinguished ornamental plant native to China. However, the florescence of tree peony is quite short and concentrated in just few days. The florescence of single flower usually lasts no more than one week, and cut flowers in vitro senesce much faster than in vivo. We have already found that tree peony is an ethylene-sensitive flower characterized by a typical climacteric during flowering and senescence. The longevity of cut peony flowers in vitro can be prolonged if the production of ethylene and peroxide hydrogen is inhibited. Due to the fact that the rapid increase of ABA is prior to that of ethylene, we propose that peroxide hydrogen, ABA and ethylene signals have important effects on the opening and senescence of tree peony flowers, and the MAPK cascade is an important factor of the signal response system. In this study, two peony cultivar types of differing in vitro flower longevity will be analyzed to illustrate the mechanism of MAPK cascade on signal responses of ABA, ethylene and peroxide hydrogen during six phases of opening and senescence of tree peony flowers. The interactions between the key factors of endogenous ABA and ethylene signal transduction and MAPK cascade will be analyzed by applying with exogenous peroxide hydrogen, ABA and ethylene synthesis inhibitor. We attempt to clarify the molecular and physiological mechanisms of opening and senescence of tree peony flowers in order to provide theoretical bases for florescence regulation and preservation of cut flowers of tree peony.

牡丹是原产中国的重要特色花卉，作为观赏和高档切花花材的应用潜力巨大。然而牡丹存在着花期集中、花期短暂的问题，一朵花从开到谢不足一周，切花脱离母体后衰败更快。我们已经探明牡丹属乙烯敏感型花卉，牡丹开花和衰老过程中存在着典型的呼吸跃变现象，控制乙烯的释放与信号传导能够延长牡丹切花的寿命。研究发现，脱落酸的快速升高早于乙烯的升高，推测脱落酸和乙烯在牡丹开花和衰老过程中起着重要的调控作用，过氧化氢是脱落酸与乙烯应答的重要信号分子。试验将牡丹开花和衰老过程划分为六个时期，从生理生化和分子水平上研究过氧化氢介导的脱落酸和乙烯信号应答的作用机制，并通过外源脱落酸和乙烯及其合成抑制剂、模拟水分胁迫分析内源脱落酸和乙烯信号转导关键基因的差异表达情况。从而揭示牡丹开花和衰老的分子生理机制，为牡丹花期延长和切花保鲜技术提供理论支撑。

项目按照计划书的安排，已经完成MAPK激酶活性测定方法平台的构建，分析了牡丹开花衰老期间花瓣乙烯、ABA代谢特征，以及乙烯生物合成及信号转导的变化。研究结果表明，牡丹品种‘洛阳红’、‘胡红’和芍药品种‘桃花飞雪’的乙烯代谢特征不同。不同发育时期牡丹、芍药花枝以及花瓣的乙烯释放速率有明显的跃变峰，整枝花乙烯释放表现为跃变型与末期上升型两种类型。花瓣与花枝呼吸速率均有明显的跃变，花瓣的跃变峰早于整枝花。花瓣的乙烯释放速率及呼吸速率均明显高于花枝，揭示花瓣是花枝产生乙烯的主要器官，花瓣的乙烯释放决定了花枝的开放与衰老进程，ACS 是影响乙烯生物合成的限制因子。采用MAPKs抑制剂PD098059和SB202190预处理都增大了牡丹‘洛阳红’切花的最大花径，延长了最佳观赏期和瓶插寿命，改善了牡丹切花瓶插期间的水分状况；PD0980959预处理降低了呼吸峰，抑制了内源乙烯的释放；SB202190预处理延迟了呼吸峰的到来时间，降低了呼吸峰，促进了切花内源乙烯的释放。结果提示两种MAPK抑制剂的作用机制之间存在一定的差异，MAPK级联途径参与了牡丹花乙烯生物合成与信号转导过程。