Transcription factor (TF) gene clusters in plants, such as tomato, potato, petunia, tobacco, and almond, have been characterized for their roles in the biosynthesis of diverse array of specialized metabolites. In Catharanthus roseus, three AP2/ERF TFs, ORCA3, ORCA4, and ORCA5, have been shown to be present on the same genomic scaffold, forming a cluster that regulates the biosynthesis of pharmaceutically important terpenoid indole alkaloids (TIAs). Our analysis of the recently updated C. roseus genome sequence revealed that the ORCA cluster comprises two additional AP2/ERFs, the previously characterized ORCA2 and a newly identified member designated as ORCA6. Transcriptomic analysis revealed that the ORCAs are highly expressed in stems, followed by leaves, roots and flowers. Expression of ORCAs was differentially induced in response to methyl-jasmonate and ethylene treatment. In addition, ORCA6 activated the strictosidine synthase (STR) promoter in tobacco cells. Activation of the STR promoter was significantly higher when ORCA2 or ORCA6 was coexpressed with the mitogen-activated protein kinase kinase, CrMPKK1. Furthermore, transient overexpression of ORCA6 in C. roseus flower petals activated TIA pathway gene expression and TIA accumulation. The results described here advance our understanding of regulation of TIA pathway by the ORCA gene cluster and the evolution for plant ERF gene clusters.

中文翻译：

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重新审视调节长春花萜类吲哚生物碱生物合成的ORCA基因簇

植物（如番茄、马铃薯、矮牵牛、烟草和杏仁）中的转录因子 (TF) 基因簇因其在多种特殊代谢物的生物合成中的作用而被表征。在长春花中，三个 AP2/ERF TF，ORCA3、ORCA4 和 ORCA5，已被证明存在于同一基因组支架上，形成一个簇，调节药学上重要的萜类吲哚生物碱 (TIA) 的生物合成。我们对最近更新的 C. roseus 基因组序列的分析表明，ORCA 簇包含两个额外的 AP2/ERF，即先前表征的 ORCA2 和一个新鉴定的成员，称为 ORCA6。转录组学分析表明，ORCAs 在茎中高表达，其次是叶、根和花。响应茉莉酸甲酯和乙烯处理，ORCA 的表达被不同地诱导。此外，ORCA6 激活烟草细胞中的胡豆苷合酶 (STR) 启动子。当 ORCA2 或 ORCA6 与丝裂原活化蛋白激酶激酶 CrMPKK1 共表达时，STR 启动子的激活显着更高。此外，ORCA6 在蔷薇花花瓣中的瞬时过表达激活了 TIA 通路基因表达和 TIA 积累。这里描述的结果促进了我们对 ORCA 基因簇对 TIA 途径的调节和植物 ERF 基因簇进化的理解。当 ORCA2 或 ORCA6 与丝裂原活化蛋白激酶激酶 CrMPKK1 共表达时，STR 启动子的激活显着更高。此外，ORCA6 在蔷薇花花瓣中的瞬时过表达激活了 TIA 通路基因表达和 TIA 积累。这里描述的结果促进了我们对 ORCA 基因簇对 TIA 途径的调节和植物 ERF 基因簇进化的理解。当 ORCA2 或 ORCA6 与丝裂原活化蛋白激酶激酶 CrMPKK1 共表达时，STR 启动子的激活显着更高。此外，ORCA6 在蔷薇花花瓣中的瞬时过表达激活了 TIA 通路基因表达和 TIA 积累。这里描述的结果促进了我们对 ORCA 基因簇对 TIA 途径的调节和植物 ERF 基因簇进化的理解。