Acyl Lipids: pathways

ARABIDOPSIS
ACYL-LIPID METABOLISM

Legend: This biosynthetic scheme represents one possible scenario for the synthesis of suberin building blocks (i.e. acyl glycerols), where we assume that acyl oxidation occurs after elongation and before esterification to glycerol (or G3P). So far, the order of such reactions remains unclear. Likewise, subcellular compartments where these pathways may take place are unknown, but fatty acid-modification and acyl glycerol synthesis steps are believed to take place in the ER membranes. Transport mechanisms required to transfer monomers or oligomers/polymers to the site of polyester assembly remains hypothetical (Pollard et al., 2008). ABC transporters and a recently membrane-bound LTP (LTPG1) have been associated with cuticular wax synthesis (DeBono et al., 2009), and homologous proteins could be involved in suberin assembly. Polyester synthase(s), required to link monomers to produce high molecular weight polyesters, as well as polymerization site(s) remain unknown, although an extracellular protein (BDG) belonging to the ab-hydrolase superfamily, has been proposed as a cutin synthase (Kurdyukov et al., 2006). (A) The synthesis of aliphatic suberin monomers. (B) The synthesis of aromatic suberin monomers for the aliphatic domain. (C) Potential transport mechanisms involved in the assembly of suberin polyesters.
Abbreviations: ABC, ATP binding cassette transporter; ACP, acyl carrier protein; AlcFAR, alcohol-forming fatty acyl-CoA reductase; ASFT, aliphatic suberin feruloyl transferase; 4CL, 4-coumarate ligase; CCoAOMT, caffeoyl coA O-methyltransferase; FAH, Fatty acyl ?-hydroxylase; G3P, glycerol-3-phosphate; GPAT, glycerol 3-phosphate acyltransferase; LACS, long chain acyl-coA synthase; LTP, lipid transport protein; LTPG, glycosylphosphatidyl-inositol (GPI)-anchored protein; OHFA, ?-hydroxy fatty acid, MAG, monoacylglycerol; PS, polyester synthase;

Contributors: Isabel Molina and Rochus Franke

Suberin2