ABSTRACT

In eukaryotic organisms, polyunsaturated fatty acids have four main functions. They serve as structural components of the membrane, as energy stores, and as precursors for the biosynthesis of antimicrobial compounds and signaling molecules. In animals and plants, lipid signals are synthesized de novo from fatty acids that are released from membranes after a severe physical trauma (such as wounding or UV light) or a bacterial, viral, or parasitic infection. Among the fatty acid derived signals, cyclopentanoids represent key players in defense programs. The best-studied defense signals in plants are C-12, C-16, and C-18 cyclopentanoids derived from allene oxide intermediates via the allene oxide synthase pathway, collectively termed “jasmonates.” Jasmonates include the C-18 compound 12-oxo-phytodienoic acid (12-oxo-PDA) and the C-16 compound dinoroxo-phytodienoic acid (dinor-oxo-PDA) as well as all metabolites derived thereof, such as jasmonic acid (JA), JA methyl ester (MeJA), oxygenated derivatives of JA, as well as amino acid and sugar conjugates. Jasmonates show remarkable structural and biosynthetic similarities to prostaglandins (PGs) in animals (Fig. 1). PGs are, by definition, C-20 cyclopentanoids that are derived from bicyclo endoperoxide intermediates formed by a cyclooxygenase enzyme activity. As discussed in Section 2, the wide distribution of jasmonates and PGs in plants and mammals, respectively, is reflected by at least two common essential functions of these compounds, namely in the defense system and reproduction.