ABSTRACTIDENTIFICATION OF A BAHD ACYLTRANSFERASE INVOLVED IN THE ACETYLATION OF MONOLIGNOLS IN KENAF (Hibiscus cannabinus)BySasha Annabel PeersPlant cell walls are the most abundant renewable resource on Earth and as such, have been proposed as a major feedstock for the production of biofuels. Lignin is a component of cell walls that provides structural integrity, hydrophobicity, and support to vascular tissues. These properties are also responsible for lignin being the major obstacle for the processing of plant biomass to biofuels. Lignin structure can be altered by acylation of lignin monomer units, or monolignols, namely, p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol. The significance of this phenomenon has not been established primarily because the enzyme(s) responsible for the acylation of monolignols have not been identified. This study sought to identify the enzyme(s) responsible for acetylation in phloem fiber lignin in kenaf (Hibiscus cannabinus). Kenaf is a non-woody plant whose lignin has a high syringyl content and extensive acetylation of syringyl units. This study reports on the identification of an enzyme (AMT; acetyl monolignol transferase) that catalyzes the synthesis of sinapyl acetate using a codon-optimized synthetic gene for a BAHD acyltransferase present in kenaf. AMT had a high activity with sinapyl alcohol and very little activity with coniferyl alcohol, which is the expected selectivity given the acetylation found in kenaf lignin. AMT was transformed into arabidopsis and seedlings are being screened for AMT expression. The significance of lignin acylation is an intriguing unanswered question in plant cell wall biology. Elucidating the enzymes involved in monolignol acylation will provide a basis for uncovering their functional role in lignin structure and whether changes to acylation levels in plants will prompt facile processing of biomass into biofuels.
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