Spatial distribution and hormonal regulation of gene products from methyl erythritol phosphate and monoterpene-secoiridoid pathways in Catharanthus roseus.
The monoterpene indole alkaloids (MIAs) from Madagascar periwinkle (Catharanthus roseus) are secondary metabolites of high interest due to their therapeutical values. Secologanin, the monoterpenoid moiety incorporated into MIAs, is derived from the plastidial methyl-D: -erythritol 4-phosphate (MEP) pathway. Here, we have cloned a cDNA encoding hydroxymethylbutenyl diphosphate synthase (HDS), a MEP pathway enzyme, and generated antibodies to investigate the distribution of transcripts and protein in MIA-producing aerial tissues. Consistent with our earlier work, transcripts for the genes encoding the so-called early steps in monoterpenoid biosynthesis (ESMB) enzymes (HDS, others MEP pathway enzymes and geraniol 10-hydroxylase) were preferentially co-localized to internal phloem associated parenchyma (IPAP) cells. By contrast, transcripts for the enzyme catalysing the last biosynthetic step to secologanin, secologanin synthase, were found in the epidermis. A coordinated response of ESMB genes was also observed in cell cultures stimulated to synthesise MIAs by hormone treatment, whereas no changes in SLS expression were detected under the same experimental conditions. Immunocytolabelling studies with the HDS-specific serum demonstrated the localisation of HDS to the plastid stroma and revealed that HDS proteins were most abundant in IPAP cells but could also be found in other cell types, including epidermal and mesophyll cells. Besides showing the existence of post-transcriptional mechanisms regulating the levels of HDS in C. roseus cells, our results support that intercellular translocation likely plays an important role during monoterpene-secoiridoid assembly.
Oudin
Audrey
A
EA 2106 Biomolécules et Biotechnologies Végétales, UFR des Sciences Pharmaceutiques, Université François Rabelais de Tours, Tours, France. audrey.oudin@univ-tours.fr
Mahroug
Samira
S
Courdavault
Vincent
V
Hervouet
Nadège
N
Zelwer
Charles
C
Rodríguez-Concepción
Manuel
M
St-Pierre
Benoit
B
Burlat
Vincent
V
D000595:Amino Acid Sequence; D000906:Antibodies / Q000276:immunology; D030008:Catharanthus / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics; D004798:Enzymes / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D004896:Erythritol / Q000031:analogs & derivatives / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D017403:In Situ Hybridization; D039823:Iridoids / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D039821:Monoterpenes / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction; D013403:Sugar Phosphates / Q000096:biosynthesis*; D014158:Transcription, Genetic / Q000235:genetics
D000906:Antibodies; D018076:DNA, Complementary; D004798:Enzymes; D039823:Iridoids; D039821:Monoterpenes; D013403:Sugar Phosphates; C421242:hydroxymethylbutenyl 4-diphosphate synthase; D004896:Erythritol