ABSTRACT ProACO4–GUS expression and RT-PCR analysis revealed that ACO4 is predominantly expressed in shoots of Arabidopsis seedlings under light conditions. ACO4-overexpressed mutant 35S–ACO4 produced more ethylene relative to the wild-type, which resulted in reduced growth of Arabidopsis seedlings. The abnormal growth of seedlings recurred after the application of Co2+ ions, suggesting that ACO4 is a functional ACO necessary to regulate the growth and development of Arabidopsis seedlings. Exogenously-applied brassinosteroids (BRs) inhibited the expression of ACO4, and an enhanced ACO4 expression was found in det2, a BR-deficient mutant. Additionally, expression of ACO4 was decreased in bzr1-D (a BZR1-dominant mutant), implying that BR signaling negatively regulates ACO4 expression via BZR1 in Arabidopsis. In the intergenic region of ACO4, four E-boxes and a BR regulatory element (BRRE) are found. Electrophoretic mobility shift and chromatin immunoprecipitation assays showed that BZR1 binds directly to the BRRE in the putative promoter region of ACO4. By binding of BZR1 to BRRE, less ethylene was produced, which seems to regulate the growth and development of Arabidopsis seedlings.

中文翻译：

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通过 BZR1 信号传递的油菜素类固醇下调 ACC 氧化酶 4 的表达以控制拟南芥幼苗的生长

摘要 ProACO4-GUS 表达和 RT-PCR 分析表明 ACO4 主要在光照条件下在拟南芥幼苗的枝条中表达。与野生型相比，ACO4 过表达的突变体 35S-ACO4 产生更多的乙烯，这导致拟南芥幼苗的生长减少。施用Co2+离子后幼苗的异常生长再次出现，表明ACO4是调节拟南芥幼苗生长发育所必需的功能性ACO。外源性应用油菜素类固醇 (BRs) 抑制 ACO4 的表达，并且在 BR 缺陷突变体 det2 中发现 ACO4 表达增强。此外，ACO4 在 bzr1-D（BZR1 显性突变体）中的表达降低，这意味着 BR 信号在拟南芥中通过 BZR1 负向调节 ACO4 的表达。在 ACO4 的基因间区域，发现了四个 E-box 和一个 BR 调节元件 (BRRE)。电泳迁移率变化和染色质免疫沉淀分析表明 BZR1 直接与 ACO4 的推定启动子区域中的 BRRE 结合。通过将 BZR1 与 BRRE 结合，产生较少的乙烯，这似乎调节了拟​​南芥幼苗的生长和发育。