Development of a clickable designer monolignol for interrogation of lignification in plant cell walls

Lignin is an abundant and essential polymer in land plants. It is a prime factor in the recalcitrance of lignocellulosic biomass to agricultural and industrial end-uses such as forage, pulp and papermaking, and biofuels. To better understand lignifi cation at the molecular level, we are developing a lignin spectroscopic and imaging toolbox on one "negligible" auxiliary. Toward that end, we describe the design, synthesis, and characterization of a new designer monolignol, 3-O-propargylcaffeyl alcohol, which contains a bioorthogonal alkynyl functional group at the 3-O-position. Importantly, our data indicate that this monolignol does not alter the fidelity of lignification. We demonstrate that the designer monolignol provides a platform for multiple spectroscopic and imaging approaches to reveal temporal and spatial details of lignification, the knowledge of which is critical to reap the potential of energyrich renewable plant biomass for sustainable liquid fuels and other diverse economic applications. (Chemical Equation Presented).