TY - JOUR

T1 - The basic helix-loop-helix transcription factor BIS2 is essential for monoterpenoid indole alkaloid production in the medicinal plant Catharanthus roseus

AU - Van Moerkercke, Alex

AU - Steensma, Priscille

AU - Gariboldi, Ivo

AU - Espoz, Javiera

AU - Purnama, Purin C.

AU - Schweizer, Fabian

AU - Miettinen, Karel

AU - Vanden Bossche, Robin

AU - De Clercq, Rebecca

AU - Memelink, Johan

AU - Goossens, Alain

N1 - Funding Information: The authors thank Annick Bleys for help in preparing the manuscript and helpful comments. This work was supported by funding from the European Union Seventh Framework Program FP7/2007-2013 under grant agreement number 222716-SMARTCELL, the Short-Term Scientific Missions (STSM) program from the European Union COST Action FA1006-PlantEngine and the Research Foundation Flanders (FWO; project number G005212N). A.V.M. is indebted to the European Molecular Biology Organization for a long-term fellowship (EMBOCOFUND2010) and the European Commission support from Marie Curie Actions (GA-2010-267154), P.S. to French Space Agency (CNES/CSG) for a scholarship, F.S. to the Swiss National Foundation for an Early Postdoc Mobility grant, J.E. to the Advanced Human Capital Program (Becas Chile No. 73140628-CONICYT) for a scholarship, and P.C.P. to the Directorate General of Higher Education of the Republic Indonesia for a scholarship. Publisher Copyright: © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd

PY - 2016

Y1 - 2016

N2 - Monoterpenoid indole alkaloids (MIAs) are produced as plant defence compounds. In the medicinal plant Catharanthus roseus, they comprise the anticancer compounds vinblastine and vincristine. The iridoid (monoterpenoid) pathway forms one of the two branches that feed MIA biosynthesis and its activation is regulated by the transcription factor (TF) basic helix-loop-helix (bHLH) iridoid synthesis 1 (BIS1). Here, we describe the identification and characterisation of BIS2, a jasmonate (JA)-responsive bHLH TF expressed preferentially in internal phloem-associated parenchyma cells, which transactivates promoters of iridoid biosynthesis genes and can homodimerise or form heterodimers with BIS1. Stable overexpression of BIS2 in C. roseus suspension cells and transient ectopic expression of BIS2 in C. roseus petal limbs resulted in increased transcript accumulation of methylerythritol-4-phosphate and iridoid pathway genes, but not of other MIA genes or triterpenoid genes. Transcript profiling also indicated that BIS2 expression is part of an amplification loop, as it is induced by overexpression of either BIS1 or BIS2. Accordingly, silencing of BIS2 in C. roseus suspension cells completely abolished the JA-induced upregulation of the iridoid pathway genes and subsequent MIA accumulation, despite the presence of induced BIS1, indicating that BIS2 is essential for MIA production in C. roseus.

AB - Monoterpenoid indole alkaloids (MIAs) are produced as plant defence compounds. In the medicinal plant Catharanthus roseus, they comprise the anticancer compounds vinblastine and vincristine. The iridoid (monoterpenoid) pathway forms one of the two branches that feed MIA biosynthesis and its activation is regulated by the transcription factor (TF) basic helix-loop-helix (bHLH) iridoid synthesis 1 (BIS1). Here, we describe the identification and characterisation of BIS2, a jasmonate (JA)-responsive bHLH TF expressed preferentially in internal phloem-associated parenchyma cells, which transactivates promoters of iridoid biosynthesis genes and can homodimerise or form heterodimers with BIS1. Stable overexpression of BIS2 in C. roseus suspension cells and transient ectopic expression of BIS2 in C. roseus petal limbs resulted in increased transcript accumulation of methylerythritol-4-phosphate and iridoid pathway genes, but not of other MIA genes or triterpenoid genes. Transcript profiling also indicated that BIS2 expression is part of an amplification loop, as it is induced by overexpression of either BIS1 or BIS2. Accordingly, silencing of BIS2 in C. roseus suspension cells completely abolished the JA-induced upregulation of the iridoid pathway genes and subsequent MIA accumulation, despite the presence of induced BIS1, indicating that BIS2 is essential for MIA production in C. roseus.

KW - alkaloid

KW - basic helix-loop-helix

KW - Catharanthus roseus

KW - iridoid

KW - jasmonate

KW - Madagascar periwinkle

KW - monoterpenoid

KW - terpenoid

U2 - 10.1111/tpj.13230

DO - 10.1111/tpj.13230

M3 - Journal article

C2 - 27342401

AN - SCOPUS:84982085352

VL - 88

SP - 3

EP - 12

JO - Plant Journal

JF - Plant Journal

SN - 0960-7412

IS - 1

ER -