Peebles Christie A M, Hughes Erik H, Shanks Jacqueline V, San Ka-Yiu
Department of Bioengineering, Rice University, Houston, TX, USA.
Metab Eng. 2009 Mar;11(2):76-86. doi: 10.1016/j.ymben.2008.09.002. Epub 2008 Oct 11.
Jasmonic acid (JA) activates the transcriptional regulator ORCA3, which has a role in regulating the terpenoid indole alkaloid (TIA) pathway within Catharanthus roseus. The TIA pathway leads to the production of the anticancer drugs vinblastine and vincristine. This work explores the transient effects of overexpressing ORCA3 under the control of a glucocorticoid-inducible promoter system in C. roseus hairy roots along with the simultaneous feeding of JA. The changes in TIA metabolites and in mRNA transcripts of pathway genes and regulators were tracked for 72h. Upon induction of ORCA3 expression and elicitation with JA, ORCA3 transcripts increased 170-fold whereas ORCA3 expression caused an 89-fold increase and JA elicitation caused a 5-fold increase in ORCA3 transcripts. JA treatment caused the largest increase in TIA metabolites and transcripts of pathway genes. These transcripts displayed a transient response with the maximum expression reached between 12 and 24h. In the samples overexpressing ORCA3, the largest increase in the transcripts of ZCT1 and ZCT2 (ZCT-zinc finger-binding protein), TIA transcriptional repressors, coincided with the largest increase in ORCA3 transcripts. This counter response of transcriptional repressors may explain why the large increase in ORCA3 transcripts do not correspond with larger increases in transcripts of TIA pathway genes.
茉莉酸（JA）可激活转录调节因子ORCA3，该调节因子在调控长春花中的萜类吲哚生物碱（TIA）途径中发挥作用。TIA途径可产生抗癌药物长春碱和长春新碱。这项研究探讨了在糖皮质激素诱导型启动子系统控制下，过表达ORCA3以及同时添加JA对长春花毛状根产生的瞬时效应。对TIA代谢产物以及途径基因和调节因子的mRNA转录本的变化进行了72小时的跟踪。在诱导ORCA3表达并用JA诱导后，ORCA3转录本增加了170倍，而ORCA3的表达导致其转录本增加了89倍，JA诱导使其转录本增加了5倍。JA处理使TIA代谢产物和途径基因的转录本增加最多。这些转录本呈现出瞬时反应，在12至24小时之间达到最大表达量。在过表达ORCA3的样本中，TIA转录抑制因子ZCT1和ZCT2（ZCT-锌指结合蛋白）的转录本增加最多，这与ORCA3转录本的最大增加量一致。转录抑制因子的这种反作用可能解释了为什么ORCA3转录本的大幅增加与TIA途径基因转录本的更大增加不相对应。
