Discovery and Implications of a Mammalian Endocannabinoid Ligand in Moss
Recently, the occurrence of a mammalian endocannabinoid ligand N-arachidonoylethanolamide (anandamide, AEA, NAE20:4), was reported in early land plants. Unlike seed plants, bryophytes such as Physcomitrella patens possess unique fatty acid composition that includes long-chain fatty acids such as arachidonic acid (AA, 20:4) and eicosapentaenoic acid (EPA, 20:5). We performed targeted lipid profiling to discovere long-chain N-acylethanolamines (NAEs) and their corresponding N-acylphosphatidylethanolamine (NAPE) precursors in Physcomitrella and Selaginella. In protonemal tissues, N-arachidonyl-PE and N-20:5-PE contributed to about 49 % and 30 %, respectively. Matured gametophytes on the other hand showed a 12 % increase in N-20:4-PE and 20 % decline in N-20:5-PE, relative to NAPE content in protonemata. In all haploid developmental stages analyzed, NAE20:4 levels contributed to ~ 23 % of the total NAE while NAE 20:5 remained as a minor component (5 %). Interestingly, in Selaginella moellendorffi, an early vascular plant, N-18:2-PE species was most abundant and 20C-NAEs were present in trace amounts. To understand biological implications of anadamide, we examined the effects of exogenously applied AEA and its corresponding fatty acid (AA) on moss protonemata growth. Both AEA and AA inhibit growth of gametophytes and protonemata in a dose dependent manner, while AEA exclusively affected actin-mediated tip growth. Additionally, we identified moss ortholog for NAPE-hydrolyzing phospholipase D (NAPE-PLD) enzyme that likely generates AEA and a fatty acid amide hydrolase (FAAH) that catabolizes AEA. Both putative PpNAPEPLD and PpFAAH are expressed in E. coli for further characterization. Our data demonstrates the occurrence of evolutionarily conserved NAE metabolic pathway in the moss, with unique composition. Functional and evolutionary implications of this mammalian endocannabinoid in early land plants, however, remains elusive.
Kilaru, Aruna; Chilufya, Jedaidah; Shinde, Suhas; Devaiah, Shivakumar; and Welti, Ruth. (false). 2017. Discovery and Implications of a Mammalian Endocannabinoid Ligand in Moss. American Society for Plant Biologists Southern Section Meeting,, Orlando, FL. http://www.ss-aspb.org/resources/Program-2017-SS-ASPB_with-Abstracts.pdf