Fatty acid amide lipid mediators in plants

Abstract

Fatty acid amides are a group of nitrogen-containing, lipid-soluble fatty acid derivatives, many of which display potent biological activities at very low concentrations. This group of compounds includes the family of N-acylethanolamines (NAE), minor lipid constituents naturally present in a variety of organisms from fungi to plants to mammals. Most of the work on NAE thus far has been in mammalian systems where these lipids exert diverse physiological, behavioral and neurological roles as part of the endocannabinoid signaling system. Corresponding studies on the function of NAE in plants have appeared only recently and much remains to be understood regarding the role of these fatty acid amides in plant physiology. The potent effects of NAE on plants, and the recent discovery of plant proteins that bind to, and catalyze the synthesis and degradation of NAE, point to the possibility that a signaling pathway similar to the endocannabinoid system occurs in plants. However, recent evidence suggests that the plant fatty acid amide hydrolase (FAAH), an enzyme involved predominantly in NAE catabolism, may have other functions that are independent of its catalytic activity, particularly in regard to salicylic acid (SA) and abscisic acid (ABA) signaling. Furthermore, the recent identification of a plant N-acylphosphatidylethanolamine (NAPE) synthase, the enzyme that catalyzes the formation of NAPE, the immediate lipid precursor of NAE, represents a significant breakthrough not only for plant NAE research but also for studies on the endocannabinoid system in animals. Although plants, like animals, possess the cellular machinery for metabolizing and responding to NAE, research in plants points to intriguing aspects of NAE signaling that have not been uncovered in studies with animals. Additional examples of bioactive plant fatty acid amides such as alkamides, N-acyl-homoserines, and amino acid-conjugated fatty acids (e.g., N-jasmonyl-isoleucine) may interact with this endogenous NAE metabolic machinery and modulate various phytohormone signaling pathways.