Biochemistry

Abstract

CS-6-3 - Elucidating the metabolic origins and pathways of specialized plant 1,4-naphthoquinones

Sunday, July 15
3:58 PM - 4:18 PM

Specialized plant 1,4-naphthoquinones are a diverse group of natural products that collectively facilitate ecological roles in plant-plant (allelopathy), plant-insect, and plant-microbe interactions.  Metabolic pathways leading to the formation of specialized 1,4-naphthoquinones have independently evolved in several discrete angiosperm lineages.  Though classical tracer studies revealed the upstream metabolites that provide precursors for each route, virtually all specialized 1,4-naphthoquinone pathway genes remain unknown.  We hypothesize that certain specialized 1,4-naphthoquinone pathways rely on immediate precursors shared with or derived from pathways involved in synthesizing photosynthetic or respiratory quinones.  Combining comparative transcriptomics with targeted metabolic profiling and stable-isotopic labeling, we provide evidence that biosynthesis of juglone, the specialized 1,4-naphthoquinone responsible for the allelopathic effects of black walnut (Juglans nigra) trees, uses biochemical steps shared with the phylloquinone pathway to synthesize its naphthalenoid moiety.  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.  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.   It also points to the existence of critical regulatory factors to mediate carbon flux distribution between production of phylloquinone, a vital one-electron carrier in photosystem I, and juglone, which provides black walnut with competitive advantages for growth and development.  The knowledge gained from this research is expected to 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-naphthoquinones in other species being investigated by our group.


 

Co-Authors

Rachel McCoy – Purdue University; Sagar Utturkar – Purdue University; Joseph Crook – Purdue University; Jyothi Thimmapuram – Purdue University

Joshua Widhalm, PhD

Assistant Professor
Purdue University

Dr. Josh Widhalm is an Assistant Professor of Horticulture and an affiliated faculty member in the Center for Plant Biology at Purdue University in West Lafayette, Indiana, United States. He was selected as a 2018 Scialog Fellow by the Research Corporation for Science Advancement and The Gordon and Betty Moore Foundation. His research group studies the metabolism of plant natural products and is particularly focused on investigating the biosynthesis of specialized plant quinones and their intersection with the metabolism of quinones involved in photosynthesis and respiration. Before joining the Horticulture faculty at Purdue, Dr. Widhalm was a postdoctoral researcher in the Department of Biochemistry at Purdue and he was a Life Sciences Research Foundation Fellow of The Gordon and Betty Moore Foundation. Dr. Widhalm received his BS in biochemistry, his MS in horticulture, and his PhD in agronomy via the Center for Plant Science Innovation at the University of Nebraska-Lincoln.

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CS-6-3 - Elucidating the metabolic origins and pathways of specialized plant 1,4-naphthoquinones



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