Poster: Lipids & related molecules

Abs # 308: Altered N-Acylethanolamine (NAE) Amidohydrolase Expression in Arabidopsis thaliana Alters the Sensitivity of Seedlings toward Exogenous NAE Lipid Mediators

Presenter:	Shrestha, Rhidaya , rhidaya@yahoo.com
Authors	Shrestha, Rhidaya  (A)   Wang, Yu S (B)   Blancaflor, Elison  (B)   Chapman, Kent D (A)
Affiliations:	(A): Div of Biochemistry and Molecular Biology, University of North Texas (B): Plant Biology Division, Samuel Robert Noble Foundation

Recently we reported the molecular identification of a functional homologue of the mammalian fatty acid amide hydrolase in Arabidopsis thaliana that degrades a wide range of N-acylethanolamines (NAEs) to their corresponding free fatty acids in vitro. Here, two T-DNA insertional mutant lines with disruptions in the Arabidopsis NAE amidohydrolase gene (At5g64440) were identified (Salk Institute-generated lines, 095108 and 118043). Homozygous mutants exhibited seed germination, seedling growth and root development phenotypes. The mutant seedlings were more sensitive than wild-type seedlings to exogenously applied NAE 12:0. For example, NAE dose-dependent reduction in primary root length was measured for seedlings at daily intervals for the first week after planting. The concentration of exogenous NAE 12:0 that effectively reduced the rate of primary root elongation to half of that of untreated seedlings (EC₅₀) was 29 μM for wild type, but was substantially lower for T-DNA mutants (18 or 23 μM for Salk118043 or 095108, respectively). On the other hand, transgenic seedlings over-expressing the NAE amidohydrolase enzyme (as a GFP fusion protein) showed noticeably greater tolerance than that of the wild-type toward exogenous NAE 12:0. Seeds of over-expressors germinated and grew almost normally at 20 μM exogenous NAE 12:0. Taken together, our results are consistent with a metabolic role in vivo for the NAE amidohydrolase gene, At5g64440, in the catabolism of NAEs, and suggest that this lipid hydrolytic pathway may be important for normal seed germination and seedling growth.