BIOLIPOL · Unraveling the biosynthesis of fatty acid-based lipid polymers in plants

Cutin and suberin are plant-specific extracellular lipid polymers that are involved in critical water and pathogen barrier functions at the interface between plants and their environment. The biosynthesis of these glycerol- and fatty acid-based polymers remains largely unknown. Understanding how plant cells oxidize, activate, transfer and polymerize acyl chains in the pathway of biosynthesis of cutin and suberin would be helpful to manipulate the composition of plant hydrophobic barriers and obtain crops with higher resistance to pathogens or desiccation. In addition, the reactions of lipid polyester biosynthesis involving oxidized fatty acids are likely to be highly relevant to the bottlenecks that are currently limiting the production in plants of high amounts of omega-hydroxy fatty acids and dicarboxylic acids, which are biomolecules with potential to replace petroleum for the synthesis of polymers and specialty chemicals. The applicant and his colleagues at Michigan State University have identified the first mutant affected in suberin synthesis, characterized a family of glycerol acyltransferases involved in polyester biosynthesis in the model plant Arabidopsis thaliana and shown that these acyltransferases are key partners of P450 fatty acid oxidases for the production of oxidized fatty acids in plant cuticles. In order to further understand the acyl activation, acyl oxidation and acyltransfer reactions required for the biosynthesis of lipid polymers in plants and to identify more players in this pathway, the applicant proposes to: 1) Pursue a knock-out/overexpression approach in Arabidopsis on a larger scale. 2) Co-overexpress various combinations of these Arabidopsis enzymes in yeast in an attempt to characterize their activity and determine the minimal number of genes required to produce polyacylglycerols containing hydroxy-fatty acids and/or dicarboxylic acids. 3) Determine the subcellular location of the enzymes identified.