Dirigent Protein Roadmap to Lignans and Other Vascular Plant Phenol Classes

This chapter addresses DP gateway entry points to distinct vascular plant phenol classes, while focusing on DPs involved in lignan biosynthesis. Structurally diverse lignans are typically phenylpropanoid dimers and higher oligomers, with physiological roles mainly in vascular plant defense. Many lignans are optically active, with diverse coupling modes, although the inter-unit linkage. Such biochemical processes were also of critical evolutionary importance, as they ultimately led to emergence of terrestrial-based plant life (from aquatic forerunners), including initially the successful colonization of land which, in turn, led to the circa 391,000 vascular plant species in existence today. Dirigent Protein (DP) involvement in Casparian strip lignification is considered to be part of a hypothesized lignin-forming protein complex containing a Casparian strip domain protein scaffold, DPs, various oxidative enzymes, and other enzymes affording cofactors, such as hydrogen peroxide. The range of heterogeneity that can be accommodated in the second radical substrate, including whether it needs to be a propenylphenol radical.