Lasserre E, Bouquin T, Hernandez J A, Bull J, Pech J C, Balagué C
Laboratoire Ethylène et Mécanismes Moléculaires de la Maturation des Fruits UA-INRA, Ecole Nationale Supérieure Agronomique de Toulouse, France.
Mol Gen Genet. 1996 Apr 24;251(1):81-90. doi: 10.1007/BF02174348.
The enzyme ACC oxidase catalyses the last step of ethylene biosynthesis in plants, converting 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene. We have previously described the isolation and characterization of a cDNA clone (pMEL1) encoding an ACC oxidase homolog from melon (Cucumis melo L.). Here we report the isolation and characterization of three genomic clones, corresponding to three putative members of the ACC oxidase gene family in melon. All are transcriptionally active. The sequences of these genes have been determined. One genomic clone (CM-ACO1), corresponding to the cDNA previously isolated, presents a coding region interrupted by three introns. Its transcription initiation site has been defined with RNA from ripe fruit and ethylene-treated leaves. The other two genes (CM-ACO2, CM-ACO3) have only two introns, at positions identical to their counterparts in CM-ACO1. The degree of DNA homology in the coding regions of CM-ACO2 and CM-ACO3 relative to CM-ACO1 is 59% and 75%, respectively. CM-ACO2 and CM-ACO3 are 59% homologous in their coding regions. These three genes have close homology to PH-ACO3, a member of the ACC oxidase multigene family of petunia. The predicted amino acid sequences of CM-ACO1 and CM-ACO3 are 77% to 81% identical to those encoded by the tomato and petunia genes, while the deduced amino acid sequence of CM-ACO2 shows only 42% to 45% homology. RT-PCR analysis using gene-specific primers shows that the three genes are differentially expressed during development, ethylene treatment and wounding. CM-ACO1 is induced in ripe fruit and in response to wounding and to ethylene treatment in leaves. CM-ACO2 is detectable at low level in etiolated hypocotyls. CM-ACO3 is expressed in flowers and is not induced by any of the stimuli tested.
乙烯形成酶催化植物中乙烯生物合成的最后一步，将1-氨基环丙烷-1-羧酸（ACC）转化为乙烯。我们之前描述过从甜瓜（Cucumis melo L.）中分离和鉴定一个编码ACC氧化酶同源物的cDNA克隆（pMEL1）。在此，我们报告了三个基因组克隆的分离和鉴定，它们对应于甜瓜ACC氧化酶基因家族的三个推定成员。所有这些克隆都具有转录活性。这些基因的序列已经确定。一个基因组克隆（CM-ACO1），对应于之前分离的cDNA，其编码区被三个内含子打断。利用成熟果实和乙烯处理叶片的RNA确定了其转录起始位点。另外两个基因（CM-ACO2、CM-ACO3）只有两个内含子，其位置与CM-ACO1中的对应内含子相同。相对于CM-ACO1，CM-ACO2和CM-ACO3编码区的DNA同源性分别为59%和75%。CM-ACO2和CM-ACO3的编码区同源性为59%。这三个基因与矮牵牛ACC氧化酶多基因家族的成员PH-ACO3具有密切的同源性。CM-ACO1和CM-ACO3的预测氨基酸序列与番茄和矮牵牛基因编码的序列有77%至81%的同一性，而CM-ACO2推导的氨基酸序列仅显示42%至45%的同源性。使用基因特异性引物进行的RT-PCR分析表明，这三个基因在发育、乙烯处理和创伤过程中差异表达。CM-ACO1在成熟果实中以及在叶片受到创伤和乙烯处理时被诱导。CM-ACO2在黄化下胚轴中低水平可检测到。CM-ACO3在花中表达，不受任何测试刺激的诱导。
