月季花瓣感应乙烯启动衰老的发育调节机制解析

Rose (Rosa hybrida) is one of the most important ornamental crops worldwide. Petals are the major organ representing the economic value of rose flowers, and senescence of petals would result in great loss of flower quality and value. Petal senescence is a highly programmed and irreversible process controlled by development events. Our previous work revealed that ethylene could induce petal senescene in a development-depedent manner. We defined the onset of petal senescence, namely the developmental phase when petals obtain the competence to respond to ethylene and senesce, based on the phenotypic, anatomical and cellular observation. By using RNA-seq and iTRAQ approches, we identified 1842 DEGs and 250 proteins whose expression was changed at the onset of petal senescence in rose, including 122 genes related to hormone biosynthesis and signaling, such as ethylene and cytokinin. Here, we try to determine the hormone types significantly changed at the onset of petal senescence through GC-MS approach. Considering that epigenetic modification of chromatin is a major way for developmental regulation, we will conduct ChIP-seq to identify the genes which are regulted by histone modification at the onset of petal senescence. And we will screen the candidate genes by integrated analysis of ChIP-seq data and DEGs mentioned above. Then we are going to screen and invesigate the important candidate genes involved in the onset of petal senescence through VIGS and stable tranformation. Furthermore, we will establish the regulaory networks of the important candidate genes through identifying their possible upstream regulators, direct downstream targets and interaction partners. Finally, we will test if the important candidate genes play a conserved role in the onset of petal senescence in various rose germplasms with different petal longivety. This project aims to understand how the developmental events regulate ethylene sensitivity of petals to trigger onset of petal senescence in rose. This work will contribute to the development of post-harvest technology and genetic improvement of flower longivety in rose in the future.

月季是全球重要的观赏作物。花瓣是月季品质的核心载体，其衰老严重影响花朵品质和价值。花瓣衰老是受发育调节的高度程序化过程，一旦启动则不可逆转。申请者前期工作中，通过表型和基因表达等指标确定了花瓣能够感应乙烯启动衰老的关键发育时期；基于转录组和蛋白质组分析，获得了这一时期差异表达的基因1842个、蛋白250个，其中包括了与乙烯和CTK等激素相关的基因122个。基于此，本项目拟重点通过ChIP-seq初选差异表达基因中受发育信号调控、发生组蛋白修饰的成员；通过VIGS和稳定转化对初选基因进行功能鉴定，确定其中参与花瓣衰老启动的重要基因，并对其上下游基因及互作蛋白进行筛选和鉴定；最后，在不同衰老特性的种质中验证重要基因作用的保守性。本项目旨在揭示发育信号调节月季花瓣乙烯敏感性以启动衰老的分子生理机制，将为延长月季花瓣寿命的采后技术研发提供理论支撑，为花朵寿命改良的分子育种提供改良思路和基因储备。

月季是全球重要的观赏作物。花瓣是月季品质的核心载体，其衰老严重影响花朵品质和价值。花瓣衰老是受发育调节的高度程序化过程，一旦启动则不可逆转。前期工作已经明确花瓣衰老受到乙烯调节，但乙烯在月季衰老启动中的调节机制尚不明确。本研究取得以下主要进展：.1）确定了响应乙烯启动衰老的关键时期.通过乙烯及其抑制剂处理，从外观表型、解剖学、基因表达等多个层面，确定了花朵开放2级，即花蕾充分发育期为花瓣能够感应乙烯启动衰老的关键发育时期。.2）筛选出响应乙烯启动衰老的相关基因.以衰老启动关键时期、即花朵开放2级为中心点，通过转录组和蛋白组测序，筛选出花瓣衰老过程中差异表达的候选基因。利用病毒诱导基因沉默（VIGS）技术对初选基因进行了快速功能鉴定，获得了调控月季花瓣衰老的重要基因。.3）从多个层面初步阐明了月季花瓣衰老的分子机制.在国际上首次发现，光敏色素互作因子RhPIF8通过激活RhBBX28的表达，控制花瓣中活性氧的含量，进而调控花瓣衰老。.明确了泛素化参与了花瓣衰老过程中的信号转导，RhSAF通过介导赤霉素受体的泛素化来调控花瓣的衰老。.发现组蛋白甲基化和乙酰化参与了花瓣衰老的调节。RhSAP30和RhHD2的表达受衰老进程和乙烯的诱导，沉默前者（RhSAP30）加快花瓣衰老，而沉默后者（RhHD2）则延缓衰老进程；并且后者（RhHD2）通过调控乙烯合成相关基因而影响到衰老。.综上所述，本项目从转录、转录后以及表观修饰等多个层面初步阐明了乙烯调控月季花瓣衰老的机制，为研究月季响应乙烯启动衰老奠定了良好的基础；为延长月季花朵寿命的采后技术研发和分子育种提供了新的思路和基因储备。