Fig. 5.

Extended compartmentalized lignin pathway model in B. distachyon. Conversion of p-coumaric acid to p-coumaroyl CoA by 4CL and diffusion flux D₉ are necessary to explain label incorporation into H-lignin in experiments with labeled phenylalanine. Conversion of p-coumaric acid to caffeic acid by C3H and the diffusion flux D₁₀ are necessary to explain label incorporation into ferulic acid in the same labeling experiments with phenylalanine. The metabolic channel in the ER compartment keeps some of the ¹³C-label from being diluted by the cytosol diffusion fluxes and permits preferential incorporation of phenylalanine and tyrosine in S- and G-lignin