Biosynthesis and accumulation of very-long-chain alkylresorcinols in cuticular waxes of Secale cereale and Brachypodium distachyon

5-Alkylresorcinols are a class of phenolic lipids which have been identified in the cuticular waxes of various cereal crops. Due to their antifungal and antibacterial properties, ARs have potential applications as nutraceuticals. They are biosynthesized by type-III polyketide synthases (PKSs). Two candidate PKS genes were previously isolated from the two model grass species Secale cereale and Brachypodium distachyon, and were shown to encode alkylresorcinol synthases (ScARS and BdARS, respectively). Here I report the further characterization of these two enzymes, with the goal to test whether they are involved in the formation of cuticular wax alkylresorcinols. Series of alkylresorcinols were identified and quantified, containing ARs with C₁₉-C₂₇ alkyl chains in S. cereale waxes, and C₁₇-C₂₅ on B. distachyon waxes. In addition, a new series of methyl-branched alkylresorcinols was identified with C₁₉-C₂₅ chains. The accumulation of ARs was monitored in waxes on various organs of etiolated and normal plants, and the product amounts found to correlate with the expression patterns of the putative ARS genes in each species. Subcellular localization using GFP fusions showed that the ARS proteins are associated with ER membranes of epidermal cells, where very-long-chain acyl CoA substrates of ARSs are known to accumulate. Overall, my data indicate that both enzymes are indeed involved in the biosynthesis of grass surface alkylresorcinols.Science, Faculty ofBotany, Department ofGraduat