STIMULATION OF ROSMARINIC ACID IN SHOOT CULTURES OF OREGANO (ORIGANUMVULGARE) CLONAL LINE IN RESPONSE TO PROLINE, PROLINE ANALOG, AND PROLINE PRECURSORS

Tissue culture-generated shoot-based clonal lines are being used to in vestigate the role of proline-linked pentose phosphate pathway in stim ulating rosmarinic acid (RA). In this study is reported the stimulatio n of RA biosynthesis in oregano clonal line 0-1 in response to proline , proline precursors (ornithine and arginine), and proline analogue (a zetidine-2-carboxylate, A2C). Following exogenous treatment with proli ne and proline precursors in the presence or absence of proline analog ue A2C, significantly enhanced RA content and concurrently higher leve ls of endogenous proline were observed compared to control. Analogue ( A2C) treatment alone stimulated highest levels of RA without any incre ase in endogenous proline. Endogenous proline levels on day 30, howeve r, were significantly higher in all proline and ornithine treatments w ith or without A2C but not in treatments with A2C or arginine alone. T he stimulation of RA synthesis in response to proline or proline precu rsors with or without A2C suggested that deregulation and enhancement of proline synthesis or proline oxidation may be important for RA bios ynthesis in oregano. This stimulation of RA biosynthesis provided stro ng clues that proline synthesis may be linked to stimulation of the pe ntose phosphate pathway, driving key precursor metabolites toward shik imate and phenylpropanoid pathways. RA-stimulating compounds also enha nced total phenolics and hardened stem tissues, indicating possible li gnification due to polymerization of phenolic metabolites.