12-oxo Phytodienoic acid (OPDA) is a biologically active, immediate precursor of 7-epi jasmonic acid.[1] In addition to its link with jasmonic acid activity, OPDA appears to play an independent role in mediating resistance to pathogens and pests. As an endogenous signal transducer, OPDA has been shown to increase alkaloid biosynthesis in E. californica cell cultures, increase tendril coiling of B. dioica, and suppress jasmonic acid-induced programmed cell death in a conditional A. flu mutant. [2]

Reference:
[1]. Schaller, A., and Stintzi, A. Enzymes in jasmonate biosynthesis - Structure, function, regulation. Phytochemistry 70, 1532-1538 (2009).
[2]. Bottcher, C., and Pollmann, S. Plant oxylipins: Plant responses to 12-oxo-phytodienoic acid are governed by its specific structural and functional properties. FEBS Journal 276, 4693-4704 (2009).