Abstract Detail

Evolution of Plant Chemical Diversity: Renaissance of comparative biochemistry

Widhalm, Joshua [1].

Investigating the metabolic links between primary and specialized plant 1,4-naphthoquinones.

The 1,4-naphthoquinones (1,4-NQs) are a diverse class of redox active molecules present throughout various organisms representing all kingdoms of life. While the biosynthesis of a few 1,4-NQs is well conserved across multiple species to fulfill vital functions, most 1,4-NQs are lineage-specific metabolites that are suggested to contribute toward adaptation to ecological niches. Perhaps the greatest diversity of specialized 1,4-NQs is found amongst the hundreds that are collectively produced by some Angiosperms to mediate plant-plant (allelopathy), plant-insect, and plant-microbe interactions. To date, virtually none of the genes involved in synthesizing specialized plant 1,4-NQs have been identified, though classical labeling studies indicate that several biochemical pathways have independently evolved across discrete flowering plant lineages. In the Widhalm laboratory, we hypothesize that certain specialized 1,4-NQ pathways rely on immediate precursors shared with or derived from pathways involved in synthesizing photosynthetic or respiratory quinones. To facilitate investigating the occurrence of such connections between primary and specialized quinone metabolic pathways in non-model plants, we are combining comparative transcriptomics with targeted metabolic profiling and stable-isotopic labeling. In this talk, I will present evidence linking the biosynthesis of juglone, the specialized 1,4-NQ responsible for the allelopathic effects of black walnut (Juglans nigra) trees, with the phylloquinone pathway. Phylloquinone (vitamin K1) is a liposoluble 1,4-NQ found in plants, green algae, and some cyanobacteria where it functions as a vital one-electron carrier in photosystem I. The evolution of phylloquinone biosynthesis in plants has been marked by extraordinary events of gene fusion, duplication, horizontal gene transfer, and reorganization of pathway architecture that we propose have contributed to the potential for phylloquinone pathway intermediates to be re-routed to the production of other metabolites. By extension of knowledge of phylloquinone synthesis, this work has in effect uncovered five of the a priori seven genes needed to synthesize juglone from chorismate, the product of the shikimate pathway. Our data also indicate that juglone can be de novo synthesized in black walnut roots without the contribution of immediate precursors translocated from aerial tissues. The knowledge gained from this research advances basic understanding of plant quinone metabolic networks and will inform synthetic biology approaches for harnessing juglone as a novel natural product-based herbicide. This study is also serving as a guide for the discovery of pathway genes involved in synthesizing specialized 1,4-NQs in other species being investigated by our group.

Related Links:
Widhalm lab website

1 - Purdue University, Horticulture and Landscape Architecture, 625 Agriculture Mall Drive, West Lafayette, IN, 47907, USA

Keywords:
Specialized metabolism
quinone
juglone
phylloquinone (vitamin K1).

Presentation Type: Symposium Presentation
Session: SY5, Evolution of Plant Chemical Diversity: Renaissance of comparative biochemistry
Location: 102/Mayo Civic Center
Date: Wednesday, July 25th, 2018
Time: 10:45 AM
Number: SY5007
Abstract ID:235
Candidate for Awards:None