Malonylation of Glucosylated N-Lauroylethanolamine: A NEW PATHWAY THAT DETERMINES N-ACYLETHANOLAMINE METABOLIC FATE IN PLANTS.

ABSTRACT

N-Acylethanolamines (NAEs) are bioactive fatty acid derivatives present in trace amounts in many eukaryotes. Although NAEs have signaling and physiological roles in animals, little is known about their metabolic fate in plants. Our previous microarray analyses showed that inhibition of Arabidopsis thaliana seedling growth by exogenous N-lauroylethanolamine (NAE 120) was accompanied by the differential expression of multiple genes encoding small molecule-modifying enzymes. We focused on the gene At5g39050, which encodes a phenolic glucoside malonyltransferase 1 (PMAT1), to better understand the biological significance of NAE 120-induced gene expression changes. PMAT1 expression was induced 3-5-fold by exogenous NAE 120. PMAT1 knockouts (pmat1) had reduced sensitivity to the growth-inhibitory effects of NAE 120 compared with wild type leading to the hypothesis that PMAT1 might be a previously uncharacterized regulator of NAE metabolism in plants. To test this hypothesis, metabolic profiling of wild-type and pmat1 seedlings treated with NAE 120 was conducted. Wild-type seedlings treated with NAE 120 accumulated glucosylated and malonylated forms of this NAE species, and structures were confirmed using nuclear magnetic resonance (NMR) spectroscopy. By contrast, only the peak corresponding to NAE 120-glucoside was detected in pmat1 Recombinant PMAT1 catalyzed the reaction converting NAE 120-glucoside to NAE 120-mono- or -dimalonylglucosides providing direct evidence that this enzyme is involved in NAE 120-glucose malonylation. Taken together, our results indicate that glucosylation of NAE 120 by a yet to be determined glucosyltransferase and its subsequent malonylation by PMAT1 could represent a mechanism for modulating the biological activities of NAEs in plants.