N-Acylethanolamines (NAEs) are bioactive acylamides which are involved in diverse biological functions in eukaryotes. Although NAEs are ubiquitous in plants and animals, occurrence of N-arachidonoylethanolamide (anandamide, AEA, NAE20:4) is limited to mammals and early land plants. Metabolism of NAEs and their functional implications in plants are yet to be fully discovered. Unlike seed plants, bryophytes possess unique fatty acid composition that includes abundance of polyunsaturated fatty acids such as arachidonic acid (AA, 20:4) and eicosapentaenoic acid (EPA, 20:5). Moss Physcomitrella patens contains ~18.7 and 15.9 % of AA in gametophores and protonemata, respectively. Therefore, it is hypothesized that P. patens may exhibit a unique NAE metabolite profile. To this extent, we performed lipid profiling and discovered long-chain NAEs and their corresponding N-acyl-phosphatidylethanolamine (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; minor amounts of N-20:3-PE, N-20:4-PE and N-20:5-PE were also present with only a traceable quantity of NAE20:4. To understand biological implications of AEA, 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. Additionally, we identified moss ortholog for NAPE-hydrolyzing phospholipase D (NAPE-PLD) enzyme that likely generates AEA. Putative PpNAPE-PLD has been expressed in E. coli for further characterization. Our data demonstrates the occurrence of evolutionarily conserved NAE metabolic pathway in the moss, with an exclusive occurrence of AEA. However, functional and evolutionary implications of this mammalian endocannabinoid in early land plants remain elusive.
| Identifer | oai:union.ndltd.org:ETSU/oai:dc.etsu.edu:etsu-works-6019 |
| Date | 11 April 2017 |
| Creators | Shinde, Suhas, Devaiah, Shivakumar, Welti, Ruth, Kilaru, Aruna |
| Publisher | Digital Commons @ East Tennessee State University |
| Source Sets | East Tennessee State University |
| Detected Language | English |
| Type | text |
| Source | ETSU Faculty Works |
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