A blind spot in jasmonate biology - How does JA-Ile biosynthesis start?

The lipid-derived phytohormone JA-Ile is a critical regulator of environmental and developmental responses in flowering plants. This signaling molecule protects plants against biotic and abiotic challenges and plays essential roles in reproductive development. JA-Ile production starts with polyunsaturated fatty acids esterified in plastidial membranes that are converted to OPDA, which is then transported to peroxisomes for JA formation, and finally conjugated to Ile in the cytosol to produce the bioactive hormone. While the genetic components involved in JA-Ile biosynthesis, perception and signaling have been uncovered, intracellular signaling events activating JA-Ile production and molecular mechanisms regulating biosynthetic enzyme functions have remained elusive. This review summarizes the current understanding of JA-Ile biosynthesis initiation, primarily in Arabidopsis, and highlights both recent advances and remaining challenges, with implications from long-distance signaling and emphasis on local wound responses.