The rolB and rolC genes activate synthesis of anthraquinones in Rubia cordifolia cells by mechanism independent of octadecanoid signaling pathway

Several studies have recently revealed an interesting ability of the rolC and rolB oncogenes of Agrobacterium rhizogenes to stimulate secondary metabolite production in plant cells. We have studied the role of the octadecanoid signaling pathway in the signal transduction initiated by the rol genes in transformed Rubia cordifolia cell cultures. None of the octadecanoid pathway inhibitors tested (diethyldithiocarbamate, propyl gallate, salicylhydroxamic acid and piroxicam) inhibited anthraquinone accumulation in the normal and transformed cultures. This result indicates that the octadecanoid pathway is not involved in the rolB and rolC gene-mediated increase of anthraquinone production. Summarizing the data of previously reported and present investigations, we suggest that the rolB and rolC genes act downstream of Ca 2+ signaling, H 2O 2-generating NADPH oxidase, as well as downstream of salicylic acid-mediated and octadecanoid pathways or perturb secondary metabolism by unknown for plants way. An unusual effect of piroxicam, a member of non-steroidal anti-inflammatory drugs on anthraquinone production was detected: this inhibitor stimulated anthraquinone production in a greater extent then methyl jasmonate.