Department of Plant and Soil Sciences and the Kentucky Tobacco Research and Development Center, University of Kentucky, 1401 University Drive, Lexington, KY 40546 USA.
Department of Plant and Soil Sciences and the Kentucky Tobacco Research and Development Center, University of Kentucky, 1401 University Drive, Lexington, KY 40546 USA; South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
Plant Sci. 2020 Apr;293:110408. doi: 10.1016/j.plantsci.2020.110408. Epub 2020 Jan 9.
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.
植物中的转录因子（TF）基因簇，如番茄、土豆、矮牵牛、烟草和杏仁，其在各种特殊代谢物生物合成中的作用已得到了描述。在长春花中，三个 AP2/ERF TFs，ORCA3、ORCA4 和 ORCA5，被证明存在于同一基因组支架上，形成一个调节具有重要药用价值的萜类吲哚生物碱（TIAs）生物合成的簇。我们对最近更新的长春花基因组序列的分析表明，ORCA 簇包含另外两个 AP2/ERFs，即先前表征的 ORCA2 和一个新鉴定的成员 ORCA6。转录组分析表明，ORCAs 在茎中高度表达，其次是叶、根和花。ORCAs 的表达对茉莉酸甲酯和乙烯处理有差异诱导。此外，ORCA6 在烟草细胞中激活了苦马豆素合酶（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 启动子的激活显著增加。此外，ORCA6 在长春花花瓣中的瞬时过表达激活了 TIA 途径基因表达和 TIA 积累。这里描述的结果增进了我们对 ORCA 基因簇对 TIA 途径的调控以及植物 ERF 基因簇进化的理解。
