N-Acylphosphatidylethanolamines (NAPEs) are precursors of endogenous bioactive lipids, N-acylethanolamines (NAEs). NAPEs, which occur as a minor membrane lipid, are hydrolyzed in a single enzymatic step catalyzed by a type of phospholipase D (PLD) to generate fatty acid ethanolamides. Although, the occurrence of NAPE is widespread in the plant kingdom, the physiological roles remain under appreciated due to the lack of sensitive tools to quantify the pathway metabolites. In Kilaru et al. (2012, Planta, DOI 10.1007/s00425-012-1669-z), comprehensive mass spectrometry (MS)-based methods were developed to gain a clearer understanding of the complex network of metabolites that participate in NAE metabolic pathway. This targeted lipidomics approach allowed insights to be drawn into the implications of altered NAE levels on NAPE content and composition, and the overall regulation of PLD-mediated hydrolysis in Arabidopsis. Based on these results, we point out here the important need for the identification of the precise isoform(s) of PLD in plants that is (are) involved in the regulated hydrolysis of NAPE and formation of NAE lipid mediators in vivo.

Mutual cell communication in the human body ensures the proper functioning of the essential mechanisms necessary for the life of the individual and preserving the homeostasis of the whole organism. Such communication is established by various types of signal transmission from the recipient cell to the donor cell, depending on the location and type of communicating cells. One such type is signalization through receptor molecules found on the surface or within the cell receiving the signal. These receptors receive the signal molecule in the form of a ligand and bind it to themselves, while activating the receptor and then triggering the intracellular signaling pathways. The most widely represented receptors in the eukaryotic organism include G-protein-coupled receptors, which represent signaling ensured by activation of the intracellular G-protein complex, and one of the main mechanisms occurring in neuronal signaling and signal transmission in the form of a neurotransmitter. Regulation of the amount of receptors on the surface of the cell and transport of the signal molecule into the intracellular spaces of the cell is ensured by the mechanism of endocytosis, whereby internalization of the ligand- bound receptor in the cytoplasm occurs. One of the most researched mechanisms is clatharin-mediated...

Endocannabinoid signaling is well studied in mammals and known to be involved in numerous pathological and physiological processes. Fatty acid amide hydrolase (FAAH) terminates endocannabinoid signaling in mammals. In Physcomitrella patens, we identified nine orthologs of FAAH (PpFAAH1 to PpFAAH9) with the characteristic catalytic triad and amidase signature sequence. Kinetics of PpFAAH1 showed specificity towards anandamide (AEA) at 37°C and pH 8.0. Further biophysical and bioinformatic analyses revealed that, structurally, PpFAAH1 to PpFAAH4 were closely associated to the plant FAAH whereas PpFAAH6 to PpFAAH9 were more closely associated to the animal FAAH. A substrate entry gate or ‘dynamic paddle’ in FAAH is fully formed in vertebrates but absent or not fully developed in non-vertebrates and plants. In planta analysis revealed that PpFAAH responded differently with saturated and unsaturated N-acylethanolamines (NAEs). In vivo amidohydrolase activity showed specificity associated with developmental stages. Additionally, overexpression of PpFAAH1 indicated the need for NAEs in developmental transition. To understand and identify key molecules related to endocannabinoid signaling in P. patens, we used high-throughput RNA sequencing. We analyzed temporal expression of mRNA and long non-coding RNA (lncRNA) in response not only to exogenous anandamide but also its precursor arachidonic acid and abscisic acid (ABA, a stress hormone). From the 40 RNA-seq libraries generated, we identified 4244 novel lncRNAs. The highest number of differentially expressed genes (DEGs) for both mRNA and lncRNA were detected on short-term exposure (1 h) to AEA. Furthermore, gene ontology enrichment analysis showed that 17 genes related to activation of the G protein-coupled receptor signaling pathway were highly expressed along with a number of genes associated with organelle relocation and localization. We identified key signaling components of AEA that showed significant difference when compared with ABA. This study provides a fundamental understanding of novel endocannabinoid signaling in early land plants and a future direction to elucidate its functional role.