A differentially regulated AP2/ERF transcription factor gene cluster acts downstream of a MAP kinase cascade to modulate terpenoid indole alkaloid biosynthesis in Catharanthus roseus

Abstract

Catharanthus roseus produces bioactive terpenoid indole alkaloids (TIAs), including the chemotherapeutics, vincristine and vinblastine. Transcriptional regulation of TIA biosynthesis is not fully understood. The jasmonic acid (JA)-responsive AP2/ERF transcription factor (TF), ORCA3, and its regulator, CrMYC2, play key roles in TIA biosynthesis. ORCA3 forms a physical cluster with two uncharacterized AP2/ERFs, ORCA4 and 5. Here, we report that (1) the ORCA gene cluster is differentially regulated; (2) ORCA4, while overlapping functionally with ORCA3, modulates an additional set of TIA genes. Unlike ORCA3, ORCA4 overexpression resulted in dramatic increase of TIA accumulation in C. roseus hairy roots. In addition, CrMYC2 is capable of activating ORCA3 and co-regulating TIA pathway genes concomitantly with ORCA3. The ORCA gene cluster and CrMYC2 act downstream of a MAP kinase cascade that includes a previously uncharacterized MAP kinase kinase, CrMAPKK1. Overexpression of CrMAPKK1 in C. roseus hairy roots upregulated TIA pathways genes and increased TIA accumulation. This work provides detailed characterization of a TF gene cluster and advances our understanding of the transcriptional and post-translational regulatory mechanisms that govern TIA biosynthesis in C. roseus.

Transcriptional Factors Regulate Plant Stress Responses Through Mediating Secondary Metabolism

“…After that, a jasmonic acid-inducible ORCA3 TF was found to bind to the JERE element in promoters of two TIA biosynthesis genes encoding strictosidine synthase and tryptophan decarboxylase [43]. Recently, one AP2/ERF gene cluster containing ORCA3, 4, and 5 was identified to regulate TIA biosynthesis through mutual regulation in the cluster genes and acting on MAPKs in C. roseus [44,45]. These TIAs, such as catharanthine, have been related to resistance against fungi and insects by protecting the surface of C. roseus leaves from pathogen infections and insect infestations [46].…”

GATA and Phytochrome Interacting Factor Transcription Factors Regulate Light-Induced Vindoline Biosynthesis in Catharanthus roseus

“…These TFs include the Apetala2/Ethylene Response Factors (AP2/ERFs) ORCA2/ORCA3/ORCA4/ORCA5 and CR1 (Menke et al, 1999;van der Fits and Memelink, 2000;Pan et al, 2012;Li et al, 2013;Liu et al, 2017;Paul et al, 2017), basic helix-loop-helix (bHLH) TFs CrMYC2, BIS1/BIS2, and RMT1 (Zhang et al, 2011;Van Moerkercke et al, 2015Patra et al, 2018), Cys 2 /His 2 -type zinc finger proteins ZCT1/ZCT2/ ZCT3 (Pauw et al, 2004), MYB-like factor CrBPF1 (van der Fits et al, 2000;, G-box-binding factors CrGBF1 and CrGBF12 (Sibéril et al, 2001;Sui et al, 2018), WRKY TF CrWRKY1 (Suttipanta et al, 2011), and the jasmonate ZIM domain (JAZ) proteins (Patra et al, 2018). ORCA3, ORCA4, and ORCA5, which form a physical cluster, regulate a number of genes in the TIA pathway through overlapping yet distinct mechanisms (van der Fits and Memelink, 2000;Paul et al, 2017). CrMYC2 activates ORCA3 by binding to a qualitative sequence in the promoter (Zhang et al, 2011), whereas it indirectly activates ORCA4 and ORCA5 (Paul et al, 2017).…”

“…ORCA3, ORCA4, and ORCA5, which form a physical cluster, regulate a number of genes in the TIA pathway through overlapping yet distinct mechanisms (van der Fits and Memelink, 2000;Paul et al, 2017). CrMYC2 activates ORCA3 by binding to a qualitative sequence in the promoter (Zhang et al, 2011), whereas it indirectly activates ORCA4 and ORCA5 (Paul et al, 2017). In addition, CrMYC2 interacts with CrGBF1 and CrGBF2 to modulate TIA biosynthesis (Sui et al, 2018).…”

ER-Anchored Transcription Factors bZIP17 and bZIP60 Regulate Triterpene Saponin Biosynthesis inMedicago truncatula1[OPEN]

“…Conversely, a similar scenario has been reported for JA-inducible genes by Van der Does et al (2013) (ORA 59). In C. roseus, the production of MIAs is regulated by the bHLH TF CrMYC2 (Zhang et al, 2015;Paul et al, 2017;Schweizer et al, 2018). Overexpression of CrMYC2 induces expression of the genes encoding bZIP G-box binding factors (GBFs), resulting in reduced alkaloid accumulation in C. roseus hairy roots (Sui et al, 2018).…”