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SUMMARY:How do betalains evolved? Consequences of a de-regulated enzyme in
  Caryophyllales - Samuel Lopez\, Brockington group
DTSTART:20181122T130000Z
DTEND:20181122T133000Z
UID:TALK112168@talks.cam.ac.uk
CONTACT:Ronelle Roth
DESCRIPTION:Diverse natural products are synthesized in plants by speciali
 zed metabolic enzymes\, which are often lineage-specific and derived from 
 gene duplication followed by functional divergence. However\, little is kn
 own about the contribution of primary metabolism to the evolution of speci
 alized metabolic pathways. Betalain pigments\, uniquely found in the plant
  order Caryophyllales\, are synthesized from the aromatic amino acid L-tyr
 osine (Tyr) and replaced the otherwise phenylalanine-derived anthocyanins.
  Using biochemical\, molecular and phylogenetic analyses\, we uncovered a 
 coordinated evolution of Tyr and betalain biosynthetic pathways in Caryoph
 yllales. We found that Beta vulgaris\, which accumulates high levels of be
 talains and Tyr\, synthesizes Tyr via plastidic arogenate dehydrogenases (
 TyrAa/ADH) encoded by two ADH genes (BvADHα and BvADHβ). Unlike BvADHβ 
 and other plant ADHs that are strongly inhibited by Tyr\, BvADHα and othe
 r ADH orthologs in Caryophyllales exhibited relaxed sensitivity to Tyr. In
  addition\, we found that the de-regulated ADHα arose during the evolutio
 n of betalain pigmentation in the Caryophyllales and later experienced rel
 axed selection and gene loss in lineages that reverted from betalain to an
 thocyanin pigmentation\, such as Caryophyllaceae. Finally\, using phylogen
 y and targeted metabolic profile we showed that additional Tyr-derived com
 pounds are present in Caryophyllales plants having ADHα. These results su
 ggest that relaxation of Tyr pathway regulation increased Tyr production a
 nd contributed not only to the evolution of betalain pigmentation\, but al
 so other Tyr-derived metabolites. The work highlights the significance of 
 upstream primary metabolic regulation for the diversification of specializ
 ed plant metabolism.
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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