Arachidonylethanolamide (AEA) is a bioactive lipid ligand for mammalian cannabinoid receptors (CB). Thus far, AEA was reported to occur only in animals and was shown to regulate a wide range of physiological responses. Our recent fi nding of the occurrence of AEA in moss has led us hypothesize that AEA might mediate stress responses in plants, similar to that in animals. In mammals, AEA is generated from hydrolysis of N-acylphosphatidylethanolamine (NAPE) by a NAPE-specifi c phospholipase D (NAPE-PLD), and degraded by a fatty acid amide hydrolase (FAAH) and this metabolic pathway is highly conserved among eukaryotes. Here, using in silico approach, putative genes encoding for AEA pathway enzymes, were identifi ed in moss. Full-length coding sequences for putative NAPE-PLD and FAAH were isolated from Physcomitrella patens and were cloned and expressed into a heterologous expression vector. Biochemical characterization of AEA pathway enzymes is underway and is expected to lead to generation of AEA metabolite mutants in moss. Such mutants will allow for elucidation of the role of AEA in development of moss and mediating stress responses. Overall, this study will provide novel insights into functional and evolutionary role of lipid-mediated signaling in plants.

Anandamide (NAE 20:4) or arachidonlyethanolamine (AEA) is the most widely studied N-acylethanolamine (NAE) because it mediates several physiological functions in mammals. In vascular plants, 12-18C NAEs inhibit growth in an abscisic acid (ABA)-dependent and -independent manner. Anandamide, which is unique to bryophyte Physcomitrella patens, inhibited gametophyte growth and reduced chlorophyll content when applied exogenously. It is hypothesized that anandamide mediates its responses through morphological and cellular changes. Following growth inhibition by short-term anandamide-treatment, microscopic analyses revealed relocated chloroplasts and depolymerized F-actin in protonemal tips. Long-term treatment showed partially bleached gametophyte cells with degraded and browning chloroplasts. These anandamide-mediated responses have physiological implications as AEA may function as a signal for gametophytes to activate secondary dormancy as seen with ABA. Future studies will investigate the role of AEA in mediating stress responses and possible interaction with ABA.