Arabidopsis CER8 encodes LONG-CHAIN ACYL-COA SYNTHETASE 1 (LACS1) that has overlapping functions with LACS2 in plant wax and cutin synthesis

Plant cuticle is an extracellular lipid-based matrix of cutin and waxes, which covers aerial organs and protects them from many forms of environmental stress. We report here the characterization of CER8/LACS1, one of nine Arabidopsis long-chain acyl-CoA synthetases thought to activate acyl chains. Mutations in LACS1 reduced the amount of wax in all chemical classes on the stem and leaf, except in the very long-chain fatty acid (VLCFA) class wherein acids longer than 24 carbons (C-24) were elevated more than 155%. The C-16 cutin monomers on lacs1 were reduced by 37% and 22%, whereas the C-18 monomers were increased by 28% and 20% on stem and leaf, respectively. Amounts of wax and cutin on a lacs1-1 lacs2-3 double mutant were much lower than on either parent, and lacs1-1 lacs2-3 had much higher cuticular permeability than either parent. These additive effects indicate that LACS1 and LACS2 have overlapping functions in both wax and cutin synthesis. We demonstrated that LACS1 has synthetase activity for VLCFAs C-20-C-30, with highest activity for C-30 acids. LACS1 thus appears to function as a very long-chain acyl-CoA synthetase in wax metabolism. Since C-16 but not C-18 cutin monomers are reduced in lacs1, and C-16 acids are the next most preferred acid (behind C-30) by LACS1 in our assays, LACS1 also appears to be important for the incorporation of C-16 monomers into cutin polyester. As such, LACS1 defines a functionally novel acyl-CoA synthetase that preferentially modifies both VLCFAs for wax synthesis and long-chain (C-16) fatty acids for cutin synthesis.