乙烯的生物合成与信号及其对种子萌发和休眠的调控

宋松泉,刘军,徐恒恒,张琪,黄荟,伍贤进

Biosynthesis and signaling of ethylene and their regulation on seed germination and dormancy

Song-Quan SONG,Jun LIU,Heng-Heng XU,Qi ZHANG,Hui HUANG,Xian-Jin WU

图1 乙烯生物合成途径 S-腺苷甲硫氨酸(S-AdoMet)合成酶催化从甲硫氨酸形成S-AdoMet, 合成1分子的S-AdoMet消耗1分子的ATP(1)。ACC合酶催化S-AdoMet转化成为ACC是乙烯合成的限速步骤(2)。随着ACC的合成, 甲硫腺苷(MTA)是ACC合酶产生的副产物。MTA回到甲硫氨酸的再循环保存了甲硫基, 能够维持细胞中恒定的甲硫氨酸浓度。ACC丙二酰化作用成为丙二酰-ACC 使ACC库枯竭并减少乙烯的产生。ACC氧化酶利用ACC作为底物, 催化乙烯合成的最后步骤, 同时产生二氧化碳和氰化物(3)。氰化物被β-氰丙氨酸合酶代谢产生无毒的物质。ACC合酶和ACC氧化酶被同源异构蛋白、发育和环境信息的转录调节用虚线箭头表示。引自Lin等[19]。

Fig. 1 Ethylene biosynthetic pathway The formation of S-adenosyl methionine (S-AdoMet) from methionine is catalysed by S-AdoMet synthetase at the expense of one molecule of ATP per molecule of S-AdoMet synthesized (1). A rate-limiting step of ethylene synthesis is the conversion of S-AdoMet to ACC by ACC synthase (2). Methylthioadenosine (MTA) is the by-product generated, along with ACC, by ACC synthase. Recycling of MTA back to methionine conserves the methylthio group and is able to maintain a constant concentration of methionine in cells. Malonylation of ACC to malonyl-ACC depletes the ACC pool and reduces ethylene production. ACC oxidase catalyses the final step of ethylene synthesis using ACC as substrate and generates carbon dioxide and cyanide (3). Cyanide is metabolized by β-cyanoalanine synthase to produce non-toxic substances. Transcriptional regulation of both ACC synthase and ACC oxidase by homeotic proteins and developmental and environmental cues is indicated by dashed arrows. From Lin et al. [19]