花瓣老化之乙烯生成及基因表現

Ethylene Biosynthesis and Gene Expression in Petal Senescence

乙烯（ethylene）是一種多效性的植物荷爾蒙，在植物生長發育過程中扮演著重要的角色。高等植物中，乙烯的生合成循著甲硫氨酸（methionine）→SAM→ACC→乙烯途徑進行，其作用上最大的特性是外加乙烯可誘導自身乙烯的合成，即自動催化作用。此外在某些條件下，也有自動抑制作用的產生。對更年性的花卉而言，老化的花瓣中會產生大量的乙烯，外加乙烯也能誘導花瓣的老化。在切花保鮮上，乙烯生合成及作用抑制劑應用的相當普遍。研究顯示，乙烯促進花瓣老化的作用是由於乙烯在轉錄或轉譯層次調節基因表現的結果。在香石竹中，乙烯可調控許多老化相關基因的表現，包括glutathion-s-transferase, ACC合成酶及乙烯形成酶等基因表現，目前發現某些 受乙烯調控的基因，其啟動子區域有乙烯反應區存在（ethylene responsive box）。

Ethylene is a pleiotropic plant hormone, which regulates many aspects of growth and development in plants. The biosynthesis of ethylene in higher plants proceed by the following pathway: methionine→SAM→ACC→ethylene. The most notable characteristic in ethylene reaction is that ethylene promotes its own synthesis (autocatalytic), however, in certain condition, the autoinhibition effect also has been observed. In climacteric flowers, the senescence of petals often accompanied ethylene biosynthesis, and the exogeneous ethylene also induced petal senescence. To lengthen the vase life of cut flowers, the application of ethylene inhibitors is very common. According to the research data, ethylene promotes the petal senescence by regulating the senescence-related gene expression at transcriptional or translational level. In carnation, ethylene regulates many senescence-related gene expression including glutathion-s-transferase, ACC synthetase and ethylene forming enzyme. The existence of ethylene responsive box in the promoters of ethylene-regulated genes have been reported.