Jasmonate Signaling: Toward an Integrated View
Oxylipins are biologically active signaling molecules derived from oxygenated polyunsaturated fatty acids and are found ubiquitously in most living organisms. In mammals, the eicosanoids, which include prostaglandins, are one of the best-studied groups of biologically important oxylipins. In addition to their essential roles in numerous other physiological functions, eicosanoids function as signaling molecules in vertebrate and invertebrate animals and in eukaryotic microbes (Stanley, 2006). The discovery of prostaglandins and related biologically active substances was recognized by the award of a Nobel Prize in Physiology or Medicine in 1982. Shortly after this, the pioneering work published in Plant Physiology by Vick and Zimmerman (1984) provided one of the first insights into the biosynthesis of jasmonate (JA), an oxylipin signaling molecule in plants. Indeed, of the various oxylipins synthesized enzymatically through the oxylipin (also known as octadecanoid) pathway, the plant hormones JAs (e.g. jasmonic acid and its methyl ester, MeJA) are often considered to be the structural and, in some cases, functional analogues of prostaglandins in animals. JAs are potent regulators of genes involved in cell growth and biotic and abiotic stress responses. Over the last decade or so, the JA signaling pathway has been studied extensively in dicot plant species, such as Arabidopsis (Arabidopsis thaliana), tomato (Solanum lycopersicum), and tobacco (Nicotiana tabacum), and to a somewhat limited extent in monocot plants, such as barley (Hordeum vulgare) and rice (Oryza sativa). Although much remains to be learnt, both forward and reverse genetic studies, particularly in Arabidopsis, have greatly expanded our understanding of the potential roles of JAs in plants.