The Acyl-CoA Synthetase Encoded by LACS2 Is Essential for Normal Cuticle Development in Arabidopsis
Judy Schnurr, Jay Shockey, and John Browse
Long-chain acyl-CoA synthetase (LACS) activities are encoded by a family of at least nine genes in Arabidopsis (Arabidopsis thaliana). These enzymes have roles in lipid synthesis, fatty acid catabolism, and the transport of fatty acids between subcellular compartments. Here, we show that the LACS2 gene (At1g49430) is expressed in young, rapidly expanding tissues, and in leaves expression is limited to cells of the adaxial and abaxial epidermal layers, suggesting that the enzyme may act in the synthesis of cutin or cuticular waxes. A lacs2 null mutant was isolated by reverse genetics. Leaves mutant plants supported pollen germination and released chlorophyll faster than wild-type leaves when immersed ethanol, indicating a defect in the cuticular barrier. The composition of surface waxes extracted from lacs2 leaves similar to the wild type, and the total wax load was higher than the wild type (111.4 mg/dm2 versus 76.4 mg/dm2, respectively). However, the thickness of the cutin layer on the abaxial surface of lacs2 leaves was only 22.3 6 1.7 nm compared with 2.0 nm for the wild type. In vitro assays showed that 16-hydroxypalmitate was an excellent substrate for recombinant enzyme. We conclude that the LACS2 isozyme catalyzes the synthesis of v-hydroxy fatty acyl-CoA intermediates pathway to cutin synthesis. The lacs2 phenotype, like the phenotypes of some other cutin mutants, is very pleiotropic, causing reduced leaf size and plant growth, reduced seed production, and lower rates of seedling germination establishment. The LACS2 gene and the corresponding lacs2 mutant will help in future studies of the cutin synthesis pathway and in understanding the consequences of reduced cutin production on many aspects of plant biology.