Maize Tricin-Oligolignol Metabolites and Their Implications for Monocot Lignification . Issue 2 (1st April 2016) - Lan, Wu
Abstract : Tricin-oligolignol maize metabolites, including variously acylated derivatives, validate combinatorial lignification and the incorporation of tricin into monocot lignins. Abstract: Lignin is an abundant aromatic plant cell wall polymer consisting of phenylpropanoid units in which the aromatic rings display various degrees of methoxylation. Tricin [5, 7-dihydroxy-2-(4-hydroxy-3, 5-dimethoxyphenyl)-4H-chromen-4-one], a flavone, was recently established as a true monomer in grass lignins. To elucidate the incorporation pathways of tricin into grass lignin, the metabolites of maize ( Zea mays ) were extracted from lignifying tissues and profiled using the recently developed 'candidate substrate product pair' algorithm applied to ultra-high-performance liquid chromatography and Fourier transform-ion cyclotron resonance-mass spectrometry. Twelve tricin-containing products (each with up to eight isomers), including those derived from the various monolignol acetate and p -coumarate conjugates, were observed and authenticated by comparisons with a set of synthetic tricin-oligolignol dimeric and trimeric compounds. The identification of such compounds helps establish that tricin is an important monomer in the lignification of monocots, acting as a nucleation site for starting lignin chains. The array of tricin-containing products provides further evidence for the combinatorial coupling model of general lignification and supports evolving paradigms for the unique nature of lignification in monocots.