Vindoline formation in shoot cultures of Catharanthus roseus is synchronously activated with morphogenesis through the last biosynthetic step.
OBJECTIVE
The Madagascar periwinkle (Catharanthus roseus) produces the monoterpenoid alkaloid vindoline, which requires a specialized cell organization present only in the aerial tissues. Vindoline content can be affected by photoperiod and this effect seems to be associated with the morphogenetic capacity of branches; this association formed the basis of the study reported here.


METHODS
Vindoline-producing in vitro shoot cultures were exposed either to continuous light or a 16-h photoperiod regime. New plantlet formation and alkaloid biosynthesis were analysed throughout a culture cycle.


RESULTS
In cultures under the photoperiod, the formation of new plantlets occurred in a more synchronized fashion as compared to those under continuous light. The accumulation of vindoline in cultures under the photoperiod occurred in co-ordination with plantlet formation, in contrast to cultures under continuous light, and coincided with a peak of activity of deacetylvindoline acetyl CoA acetyltransferase (DAT), the enzyme that catalyses the last step in vindoline biosynthesis. When new plantlet formation was blocked in cultures under the photoperiod by treatment with phytoregulators, vindoline synthesis was also reduced via an effect on DAT activity. No association between plantlet formation and other biosynthetic enzymes, such as tryptophan decarboxylase (TDC) and deacetoxyvindoline 4-hydroxylase (D4H), was found. Effects of light treatment on vindoline synthesis were not mediated by ORCA-3 proteins (which are involved in the induction of alkaloid synthesis in response to elicitation), suggesting that the presence of a different set of regulatory proteins.


CONCLUSIONS
The data suggest that vindoline biosynthesis is associated with morphogenesis in shoot cultures of C. roseus.
Campos-Tamayo
Freddy
F
Unidad de Bioquímica y Biología Molecular de Plantas, Centro de Investigación Científica de Yucatán, Calle 43 No. 130 Chuburná, Mérida Yucatán 97200, México.
Hernández-Domínguez
Elizabeta
E
Vázquez-Flota
Felipe
F
D000123:Acetyltransferases / Q000378:metabolism; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism; D030008:Catharanthus / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism*; D008027:Light; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009024:Morphogenesis; D017440:Photoperiod; D010940:Plant Proteins / Q000378:metabolism; D018520:Plant Shoots / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014747:Vinblastine / Q000031:analogs & derivatives* / Q000096:biosynthesis
C410983:ORCA3 protein, plant; D010940:Plant Proteins; D014157:Transcription Factors; C009667:vindoline; D014747:Vinblastine; D006899:Mixed Function Oxygenases; C052273:hyoscyamine (6S)-dioxygenase; D000123:Acetyltransferases; C064442:acetylcoenzyme A-deacetylvindoline 4-O-acetyltransferase; D001142:Aromatic-L-Amino-Acid Decarboxylases