Disturbance in the natural growth habitat causes stress responses in plants that enable them to resist, tolerate or adapt to these changes. Such stress responses often involve activation of a network of metabolic signals. The main objective of this project is to study the metabolism and role of a unique lipid metabolite called anandamide in the development of dehydration tolerance in moss plants. Anandamide typically occurs in mammals, and has not been reported in higher plants, despite its occurrence in mosses. In mammals, this compound is involved in neuronal signaling, raising the possibility that it also acts as a signal in mosses. Moss plants are naturally tolerant to many stresses and this study is expected to determine if the unique lipids present in mosses, but absent in higher plants, play a role in the greater dehydration tolerance shown by mosses. The findings from this study will reveal novel functional and evolutionary insights into lipid-mediated biological responses that may be widely applicable in plants. Such insights may lead to development of strategies to generate stress tolerant crop plants in the future, helping to maintain food production during droughts and on marginal lands. The project also offers much needed research opportunities to graduate and undergraduate students and a research associate at East Tennessee State University, which is a primarily undergraduate institution that attracts many regional, first-generation students from the Appalachian region.
N-acylethanolamines (NAEs) are a class of fatty acid derivatives that are widely distributed among eukaryotes. Among the various types of NAEs, anandamide is known to bind to cannabinoid receptors and acts as a neuromodulator for a variety of physiological processes in mammals. Recently, anandamide, a 20-carbon, polyunsaturated omega-6 fatty acid ethanolamide (NAE 20:4) was identified in moss plants but not in higher plants. This discovery has opened the possibility that NAEs in early land plants may play a unique role that is akin to that in animals and beyond what is known in flowering plants. The presence of unconventional lipids in bryophytes has long been considered crucial for their successful transition from water to land because lipids may have imparted them with natural ability to resist high temperatures and tolerate osmotic and salt stresses and dehydration. Therefore, it is hypothesized that mosses may have evolutionarily retained unique NAE metabolites, such as anandamide, and mechanisms by which they mediate stress tolerance. To address this premise, three main objectives will be pursued, using Physcomitrella patens: 1) Biochemically and molecularly characterize the NAE metabolic pathway, 2) Determine NAE metabolite profiles and their effects on development, and 3) Elucidate the physiological role of NAEs in abscisic acid-mediated dehydration tolerance. Studies will take advantage of discoveries made in other eukaryotic systems, including the enzymes that regulate NAE metabolic pathway and lipid-profiling techniques. Long-term goals of the project are to elucidate the mechanisms by which mosses maintain tolerance to abiotic stress, which perhaps may have been altered or lost in vascular plants, and reveal novel functional and evolutionary insights into lipid-mediated biological responses in plants.
