Differential Activation of Phytoalexin Production and Induction of Proteins by Amino Acid Conjugates of Jasmonic Acid in Rice (Oryza sativa L.) Seedling Leaves

Jasmonic acid (JA) is an essential and important component of the rice ( Oryza sativa L.) plant self-defense response. Oh the other hand, its amino acid (aa) conjugates are suggested to play some role in the stressed tissues. Here we examined and compared in detail the effects of exogenously applied JA and JAaa conjugates on symptoms, phytoalexin production and protein profiles, in the leaves of young rice seedlings, using techniques in liquid chromatography and two-dimensional electrophoresis. Results revealed that among the four JAaa conjugates examined in this study, the phenylalanine and leucine conjugates were highly effective in causing necrotic symptoms, enhanced levels of naringenin 7-0-methyltamsferase activity and subsequent phytoalexin sakuranetin production, and changes in protein profiles. These results suggest that like the critical signalling molecule JA, the JAaa conjugates, especially the phenylalanine and leucine conjugates, might also be important endogenous components of the rice plant defense/stress response pathways.