| Summary: | 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 of === Botany, Department of === Graduate
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