Bleecker A B, Kende H
Departments of Botany and Genetics, University of Wisconsin, Madison, Wisconsin 53706-1381, USA.
Annu Rev Cell Dev Biol. 2000;16:1-18. doi: 10.1146/annurev.cellbio.16.1.1.
Ethylene regulates a multitude of plant processes, ranging from seed germination to organ senescence. Of particular economic importance is the role of ethylene as an inducer of fruit ripening. Ethylene is synthesized from S-adenosyl-L-methionine via 1-aminocyclopropane-1-carboxylic acid (ACC). The enzymes catalyzing the two reactions in this pathway are ACC synthase and ACC oxidase. Environmental and endogenous signals regulate ethylene biosynthesis primarily through differential expression of ACC synthase genes. Components of the ethylene signal transduction pathway have been identified by characterization of ethylene-response mutants in Arabidopsis thaliana. One class of mutations, exemplified by etr1, led to the identification of the ethylene receptors, which turned out to be related to bacterial two-component signaling systems. Mutations that eliminate ethylene binding to the receptor yield a dominant, ethylene-insensitive phenotype. CTR1 encodes a Raf-like Ser/Thr protein kinase that acts downstream from the ethylene receptor and may be part of a MAP kinase cascade. Mutants in CTR1 exhibit a constitutive ethylene-response phenotype. Both the ethylene receptors and CTR1 are negative regulators of ethylene responses. EIN2 and EIN3 are epistatic to CTR1, and mutations in either gene lead to ethylene insensitivity. Whereas the function of EIN2 in ethylene transduction is not known, EIN3 is a putative transcription factor involved in regulating expression of ethylene-responsive genes. Biotechnological modifications of ethylene synthesis and of sensitivity to ethylene are promising methods to prevent spoilage of agricultural products such as fruits, whose ripening is induced by ethylene.
乙烯调节众多植物过程，从种子萌发到器官衰老。乙烯作为果实成熟诱导剂的作用具有特别重要的经济意义。乙烯由S-腺苷-L-甲硫氨酸经1-氨基环丙烷-1-羧酸（ACC）合成。催化该途径中两个反应的酶是ACC合酶和ACC氧化酶。环境和内源信号主要通过ACC合酶基因的差异表达来调节乙烯生物合成。通过对拟南芥乙烯反应突变体的表征，已鉴定出乙烯信号转导途径的组成部分。一类以etr1为例的突变导致了乙烯受体的鉴定，结果发现其与细菌双组分信号系统有关。消除乙烯与受体结合的突变产生显性的乙烯不敏感表型。CTR1编码一种Raf样丝氨酸/苏氨酸蛋白激酶，其作用于乙烯受体下游，可能是MAP激酶级联反应的一部分。CTR1突变体表现出组成型乙烯反应表型。乙烯受体和CTR1都是乙烯反应的负调节因子。EIN2和EIN3对CTR1上位，任一基因的突变都会导致乙烯不敏感。虽然EIN2在乙烯转导中的功能尚不清楚，但EIN3是一种推定的转录因子，参与调节乙烯反应基因的表达。对乙烯合成和对乙烯敏感性进行生物技术改造是防止水果等农产品变质的有前景的方法，水果的成熟是由乙烯诱导的。
