Major evolutionary events hypothesized in the evolution of the lignin biosynthetic pathway across the eukaryotic tree. The tree is a consensus of current phylogenetic analyses of the eukarotic domain [1,36,49]. Major events indicated by labeled arrows on the tree are hypothesized from our genome survey and phylogenetic analyses of the putative p-coumaryl alcohol biosynthesis enzymes. Taxonomic groups in which three or more enzymes catalyzing consecutive steps in the lignin biosynthesis pathway were found are colored. The chemical detection of polymerized lignin is indicated in the margin for each taxonomic group, with the type of lignin (either H, G or S) specified. A question mark (?) indicates that some putative lignin biosynthetic enzymes were found and fuctionally predicted but that there is currently no biochemical evidence of polymerized lignin. Arrows indicate the origin and direction of putative EGT and LGT events (solid arrows are used for events that are conclusive, dashed arrows when events are hypothesized).