The transient effect of jasmonic acid feeding along with ORCA3 overexpression in Catharanthus roseus hairy roots

Jasmonic acid is an important signaling molecule in plants that regulates a wide variety of cellular responses including the responses to abiotic and biotic stresses. The external application of jasmonic acid has been shown to increase the accumulation of the monomeric terpenoid indole alkaloids, TIAs, in Catharanthus roseus seedlings and hairy root cultures (1-3). Jasmonic acid regulates the expression of the ORCA3 (Octadecanoid-Responsive Catharanthus AP2/ERF-domain) transcription factor (4). The overexpression of ORCA3 in C. roseus cell suspension cultures resulted in an increase of the mRNA levels of the following TIA biosynthetic genes: anthranilate synthase, ASα, tryptophan decarboxylase, TDC, 1-deoxy-Dxylulose synthase, DXS, NADPH:cytochrome P-450 reductase, CPR, secologanin synthase, SLS, strictosidine synthase, STR, strictosidine beta-glucosidase, SGD, and desacetoxyvindoline 4-hydroxylase, D4H (5). The accumulation of mRNA transcripts did not result in an increase in TIA compounds which could be explained by the lack of an observed increase in the transcripts of geraniol 10 hydroxylase, G10H, and deacetyl vindoline 4-O-acetyl transferase, DAT (5).