Abstract
摘要:隨著國民所得的提升,我們對於生活的品質也愈來愈重視。花朵一向就是人們用來
美化環境提升生活品質的重要元素,也因此花卉產業也愈來愈受到重視。花卉的價值決
定於花的外觀及花期的長短,因此延遲花朵的老化將有助於提升花朵的價值,也使得花
卉產業受益。
乙烯這個天然的植物荷爾蒙在很多的花朵中是調節花朵老化的主要因子。這些花暴
露在乙烯中會造成花的早凋,使用乙烯作用抑制劑則能阻止這個現象。然而花的萎凋並
非全由乙烯調控,像水仙、蘭花一類的花雖說對乙烯敏感,但乙烯作用抑制劑的處理並
不會延長花的壽命。因此花朵老化是由複雜的調節網所控制。
為了了解這複雜的網路,我們選用了矮牽牛作為模式作物,因為它是個重要的園藝
作物,且它具有一致且清晰的老化過程,它的生長期短容易培育,容易進行基因轉殖,
目前已有成熟的遺傳學及分子生物學的技術支援,並且我們已發展出以病毒誘導基因靜
默化(VIGS)來進行大量且快速的功能性基因體研究。
在我們之前的研究中就發現MADS-box 基因群很可能在花朵老化的調節上扮演重
要角色。將控制花瓣形成的基因如GP 或是FBP4 給靜默化不但造成花瓣的結構傾向花
萼,也同時延緩了花朵的萎凋。為了清楚的分辨在花瓣發育及花瓣老化所扮演的角色,
我計畫生產MADS-box 基因(GP or FBP4)只在花老化時被靜默化的轉殖矮牽牛,藉由一
個老化專一性promoter (SAG12 promoter)來調控一個MADS-box 基因的反轉重複序列
(inverted repeat)。這個promoter 已被證實在矮牽牛有很好的效果。經由此項研究,我們
將可知道花瓣的發育是否在花老化時扮演重要角色,並且也可知道花瓣形成是只需誘發
或是需要MADS-box 基因來維持。這也是植物發育學家們一直在探討的問題。
此外我們也從矮牽牛的EST 資料庫中發現總共35 個MADS-box 基因。其中29 個
尚未做過分析,並且大部分功能未知。我計畫延續我之前利用VIGS 進行功能性基因體
研究的計畫。用VIGS 來完成對那29 個基因的分析,並將重點放在它們對花老化的影
響。此項計畫的成果將可幫助我們更了解MADS-box 基因群,也使我們更了解花朵老化
的調控。
Abstract: Flowers are always one of the important elements that we use to beautify our living environment and express our feeling in a special occasion. Due to the reason, garden and floral industry has been a fast growing business. The quality of ornamental crops is determined by their beauty and longevity of their flowers and foliage. The delay of flower senescence is therefore beneficial to both the industry and customers.
Flower senescence of many flowers, including roses, carnations, and chrysanthemums, is regulated by a plant hormone, ethylene. Premature senescence occurs when this type of flowers exposure to ethylene. This event can often be prevented by applying ethylene action inhibitors. In spite of the importance of ethylene in flower senescence regulation, ethylene action inhibitors have little or no effect on flower senescence to flowers like daffodils, irises, and orchids. It is believed that the regulation of flower senescence is through a complex network.
Petunia has a significant value to garden and floral industry. There are also several advantages, such as a well defined senescence pattern, easy growth habit and relatively short lifecycle, a well defined transformation procedure, and availability of many genetic and molecular tools, making petunia a good model for flower senescence studies.
I have previously developed a virus-induced gene silencing (VIGS) system in petunia for fast functional screening. During the screening, MADS box genes were identified as a potential gene family that has great impact on flower longevity. Silencing of genes that regulate petal identity resulted in prolonging flower longevity as well as homeotic conversions of petals toward sepals. To distinguish the involvement of MADS box genes between petal identity and flower senescence. I propose to generate the transgenic plants with the down-regulation of petal identity regulation genes specifically in senescing tissues by using a senescence specific promoter from Arabidopsis, SAG12 promoter. The promoter has been proved usefully in petunia flowers. Flowers of transgenic petunia containing PSAG12:IPT showed a delayed senescence due to the production of cytokinin in senescing tissues. The transgenic petunias that we are planning to generate will allow us to understand whether regulation of petal identity is an important factor for flower senescence regulation or not, and whether petal identity determination in petunia is just an initiation event or requiring maintenance.
Thirty-five unique MADS box genes have been identified. Functions of many of them are remained unknown. I propose to use the well developed VIGS system to examine their functions especially on flower senescence regulation. The data of this studies will improve our knowledge on MADS box gene as well as flower senescence regulation.
Keyword(s)
花朵老化
MADS-box基因
病毒誘導基因靜默化(VIGS)
矮牽牛
Flower senescence
MADS box genes
Virus-induced gene silencing
Petunia