Abstract Detail

Evolution of Plant Chemical Diversity: Renaissance of comparative biochemistry

Lopez-Nieves, Samuel [1], Yang, Ya [2], Feng, Tao [3], Timoneda, Alfonso [3], Oliveira, Marcos [1], Smith, Stephen [4], Brockington, Samuel [3], Maeda, Hiroshi [5].

Evolutionary tug-of-war underlies betalain vs. anthocyanin pigmentations in Caryophyllales.

The plant order Caryophyllales (e.g. beet, quinoa, cactus) uniquely produces red/yellow betalain pigments that are derived from the aromatic amino acid L-tyrosine (Tyr) and replaced the otherwise ubiquitous L-phenylalanine (Phe)-derived anthocyanins. In most plants, Tyr production is strongly feedback regulated by Tyr at arogenate dehydrogenase (ADH), the final enzyme of Tyr biosynthesis. Here we found that ADH enzymes in Caryophyllales recently duplicated into two isoforms, one of which (ADH?) exhibits relaxed sensitivity to Tyr inhibition. Notably, the de-regulated ADH? emerged before the evolution of the betalain biosynthetic pathway and was down-regulated or lost in many Caryophyllaceae species that reverted back to anthocyanin pigmentation. Metabolite profiling further revealed that other Tyr-derived compounds, such as dopamine and epinephrine derivatives, also accumulate in ADH?-containing Caryophyllales species. Phylogeny-guided structure function analysis of ADH enzymes from over one hundred of Caryophyllales transcriptome data identified key mutations responsible for the Tyr insensitivity of ADH? enzymes. Finally, heterologous expression of beet ADH? in various plants Nicotiana benthamiana and Arabidopsis thaliana resulted in hyper-accumulation of Tyr and decreased synthesis of Phe and Phe-derived compounds including anthocyanins. These results together suggest that de-regulation of Tyr biosynthesis redirected carbon flux from Phe to Tyr biosynthesis and facilitated the subsequent evolution of novel specialized metabolic pathways-e.g. biosynthesis of betalain pigments and other Tyr-derived metabolites. Our finding highlights the significance of upstream primary metabolic regulation for the evolutionary diversification of specialized metabolic pathways in plants.

1 - University of Wisconsin-Madison, Department of Botany, Madison, USA
2 - University of Minnesota-Twin Cities, Department of Plant and Microbial Biology, St. Paul, MN, USA
3 - University of Cambridge, Department of Plant Sciences, Cambridge, UK
4 - University of Michigan, Ecology and Evolutionary Biology, 2071A Kraus Natural Science Building, Ann Arbor, MI, 48109, USA
5 - University of Wisconsin-Madison, Department of Botany, 430 Lincoln Dr., Madison, WI, 53706, US

Keywords:
betalains
anthocyanins
biochemical evolution
tyrosine
Caryophyllales
Specialized metabolism.

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: 8:45 AM
Number: SY5003
Abstract ID:563
Candidate for Awards:None