Revisiting the ORCA gene cluster that regulates terpenoid indole alkaloid biosynthesis in Catharanthus roseus

Identification of two new AP2/ERFs expands the ORCA gene cluster of Catharanthus roseus to a total of five members. The ORCAs differentially respond to methyl jasmonate and ethylene. The ORCAs act downstream of a MAP-kinase cascade to regulate gene expression of the terpenoid indole alkaloid (TIA) pathway. Overexpression of the newly identified ORCA6 alters TIA pathway gene expression. ORCAs are likely parts of the positive amplification and negative regulatory loops. We found that two recently sequenced medicinal plants, Calotropis gigantea and Gelsemium sempervirens, contain analogous ERF gene clusters.