REGULATION OF BENZYLADENINE-INDUCED IN-VITRO SHOOT ORGANOGENESIS AND ENDOGENOUS PROLINE IN MELON (CUCUMIS-MELO L.) BY EXOGENOUS PROLINE, ORNITHINE, AND PROLINE ANALOGS

Melon (Cucumis melo L.) is an excellent system to study the role of pr oline in regulating benzyladenine-induced shoot organogenesis, which i s also an important system in our laboratory for investigating flavor and antioxidant metabolite synthesis in differentiated tissues. We hav e hypothesized that proline stimulated in vitro shoot organogenesis th rough the activation of the proposed proline-linked pentose phosphate pathway, which may regulate endogenous cytokinin and auxin biosynthesi s. To further investigate this hypothesis, it is essential to first co nfirm whether benzyladenine-induced shoot organogenesis can be stimula ted by enhancing proline synthesis through the use of proline analogue s and ornithine (proline precursor). In this study, benzyladenine-indu ced shoot organogenesis was substantially stimulated by exogenous prol ine and/or ornithine in combination with proline analogues such as aze tidine-2-carboxylate (A2C) and hydroxyproline (HP). Among these treatm ents, proline in combination with A2C or HP showed the highest stimula tion. The stimulation of organogenesis correlated closely with increas ed levels of endogenous proline content, thereby strengthening the hyp othesis that proline-linked activation of purine and aromatic metaboli sm via the stimulation of pentose phosphate pathway may be important f or in vitro organogenesis in melon.