Quantitative reverse transcription PCR (qRT-PCR) analysis and ProACO2::GUS expression showed that ACO2 was highly expressed in the shoots of Arabidopsis seedlings under light conditions. Exogenously applied aminocyclopropane-1-carboxylic acid (ACC) enhanced the expression of ACO2, whereas Co2+ ions suppressed its expression. In comparison with wild-type seedlings, the ACO2 knockdown mutant aco2-1 produced less ethylene, which resulted in the inhibited growth of Arabidopsis seedlings. Exogenously applied brassinolide reduced the expression of ACO2. ACO2 expression was increased in det2, a brassinosteroid (BR)-deficient mutant; however, it was decreased in bes1-D, a brassinosteroid insensitive 1-EMS-suppressor 1 (BES1)-dominant mutant. In the putative promoter region of ACO2, 11 E-box sequences for BES1 binding but not BR regulatory element sequences for brassinazole-resistant 1 (BZR1) binding were found. Chromatin immunoprecipitation assay showed that BES1 could directly bind to the E-boxes located in the putative promoter region of ACO4. Less ethylene was produced in bes1-D seedlings compared with wild-type seedlings, suggesting that the direct binding of BES1 to the ACO2 promoter may negatively regulate ACO2 expression to control the endogenous level of ethylene in Arabidopsis seedlings.

中文翻译：

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BES1负调控ACC氧化酶2的表达以控制拟南芥内源乙烯水平

定量逆转录 PCR (qRT-PCR) 分析和 ProACO2::GUS 表达表明 ACO2 在光照条件下在拟南芥幼苗的枝条中高表达。外源性应用的氨基环丙烷-1-羧酸 (ACC) 增强了 ACO2 的表达，而 Co2+ 离子抑制了其表达。与野生型幼苗相比，ACO2 敲低突变体 aco2-1 产生的乙烯较少，这导致拟南芥幼苗的生长受到抑制。外源性应用芸苔素内酯降低了 ACO2 的表达。det2 中的 ACO2 表达增加，这是一种油菜素类固醇 (BR) 缺陷型突变体；然而，它在 bes1-D 中下降，bes1-D 是一种油菜素类固醇不敏感的 1-EMS-抑制因子 1 (BES1)-显性突变体。在 ACO2 的推定启动子区域，发现了 11 个用于 BES1 结合的 E-box 序列，但没有发现用于芸苔素抗性 1 (BZR1) 结合的 BR 调节元件序列。染色质免疫沉淀分析表明，BES1 可以直接与位于 ACO4 假定启动子区域的 E-box 结合。与野生型幼苗相比，bes1-D 幼苗中产生的乙烯较少，这表明 BES1 与 ACO2 启动子的直接结合可能会负向调节 ACO2 表达以控制拟南芥幼苗中乙烯的内源水平。