"Reinventing the wheel or making it rounder? On the evolution of multiple pathways to lignin in land plants.”

Juergen Ehlting
Department of Biology & Centre for Forest Biology, University of Victoria
Friday, November 8, 2019 - 11:00am
Ramsay Wright Building, Room 432
“Tree-like growth has evolved multiple times during land plant evolution, and in each case it involved cell-wall reinforcements using lignin. In flowering plants, a rate-limiting step to the major lignin subunits involves a metabolic detour linking it to the upstream shikimate pathway, likely to allow metabolic regulation of carbon into this major carbon sink. We followed enzymatic properties of the respective CYP98 hydroxylases throughout all major land plant lineage and found that specialization towards the shikimate ester only occurred within the angiosperms. In contrast, CYP98’s from a moss, a lycopod, and a fern have very distinct substrate utilization profiles, suggesting that alternative intermediates and / or enzymes are involved in lignin biosynthesis in these lineages. Alternative pathways have been identified in lycopods and recently in monocots, and we propose that also in ferns and possibly even in conifers alternative pathways may exist. This suggests that despite its ubiquitous occurrence and its crucial adaptive role in allowing erect plant growth, lignin biosynthesis has been reinvented through extensive pathway evolution continuously during land plant evolution.”
Dinesh Christendat
Dept of Cell and Systems Biology