Planta

, Volume 223, Issue 6, pp 1191–1200

Epidermis is a pivotal site of at least four secondary metabolic pathways in Catharanthus roseus aerial organs

  • Samira Mahroug
  • Vincent Courdavault
  • Martine Thiersault
  • Benoit St-Pierre
  • Vincent Burlat
Original Article

DOI: 10.1007/s00425-005-0167-y

Cite this article as:
Mahroug, S., Courdavault, V., Thiersault, M. et al. Planta (2006) 223: 1191. doi:10.1007/s00425-005-0167-y

Abstract

Catharanthus roseus produces a wide range of secondary metabolites, some of which present high therapeutic values such as antitumoral monoterpenoid indole alkaloids (MIAs), vinblastine and vincristine, and the hypotensive MIA, ajmalicine. We have recently shown that a complex multicellular organisation of the MIA biosynthetic pathway occurred in C. roseus aerial organs. In particular, the final steps of both the secoiridoid–monoterpene and indole pathways specifically occurred in the epidermis of leaves and petals. Chorismate is the common precursor of indole and phenylpropanoid pathways. In an attempt to better map the spatio-temporal organisation of diverse secondary metabolisms in Catharanthus roseus aerial organs, we studied the expression pattern of genes encoding enzymes of the phenylpropanoid pathway (phenylalanine ammonia-lyase [PAL, E.C. 4.3.1.5], cinnamate 4-hydroxylase [C4H, E.C. 1.14.13.11] and chalcone synthase [CHS, E.C. 2.3.1.74]). In situ hybridisation experiments revealed that CrPAL and CrC4H were specifically localised to lignifying xylem, whereas CrPAL, CrC4H and CrCHS were specifically expressed in the flavonoid-rich upper epidermis. Interestingly, these three genes were co-expressed in the epidermis (at least the upper, adaxial one) together with three MIA-related genes, indicating that single epidermis cells were capable of concomitantly producing a wide range of diverse secondary metabolites (e.g. flavonoïds, indoles, secoiridoid–monoterpenes and MIAs). These results, and data showing co-accumulation of flavonoids and alkaloids in single cells of C. roseus cell lines, indicated the spatio-temporal feasibility of putative common regulation mechanisms for the expression of these genes involved in at least four distinct secondary metabolisms.

Keywords

CatharanthusEpidermisFlavonoidsIn situ hybridisationMicroscopyMonoterpenoid indole alkaloids

Abbreviations

MIA(s)

Monoterpenoid indole alkaloid(s)

PAL

Phenylalanine ammonia-lyase

C4H

Cinnamate 4-hydroxylase

CHS

Chalcone synthase

MEP

2C-methyl-d-erythritol 4-phosphate

DXS

1-deoxy-d-xylulose 5-phosphate (DXP) synthase

DXR

DXP reductoisomerase

MECS

2C-methyl-d-erythritol 2,4-cyclodiphosphate (MEC) synthase

G10H

Geraniol 10-hydroxylase

SLS

Secologanin synthase

TDC

Tryptophan decarboxylase

STR

Strictosidine synthase

D4H

Desacetoxyvindoline 4-hydroxylase

DAT

Deacetylvindoline 4-O-acetyltransferase

2,4-D

2,4-dichlorophenoxyacetic acid

MM

Maintenance medium

PM

Production medium

FAA

Formaldehyde acetic acid ethyl alcohol

2-APB

2-aminoethyldiphenyl borinate

AP

Alkaline phosphatase

BCIP

5-Bromo-4-chloro-3-indolyl phosphate

NBT

Nitro blue tetrazolium chloride

ORCA

Octadecanoid-responsive Catharanthus AP2 transcription factor

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Samira Mahroug
    • 1
    • 2
  • Vincent Courdavault
    • 1
  • Martine Thiersault
    • 1
    • 2
  • Benoit St-Pierre
    • 1
    • 2
  • Vincent Burlat
    • 1
    • 2
  1. 1.Université François-Rabelais de ToursEA 2106 “Biomolécules et Biotechnologies Végétales” UFR Sciences et TechniquesToursFrance
  2. 2.Université François-Rabelais de ToursUnité sous Contrat reconnue par l’INRA “Facteurs de transcription et ingénierie métabolique végétale”ToursFrance