Lineage-specific gene radiations underlie the evolution of novel betalain pigmentation in Caryophyllales.


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Authors
Brockington, Samuel F 
Yang, Ya 
Gandia-Herrero, Fernando 
Covshoff, Sarah 
Hibberd, Julian M 
Abstract

Betalain pigments are unique to the Caryophyllales and structurally and biosynthetically distinct from anthocyanins. Two key enzymes within the betalain synthesis pathway have been identified: 4,5-dioxygenase (DODA) that catalyzes the formation of betalamic acid and CYP76AD1, a cytochrome P450 gene that catalyzes the formation of cyclo-DOPA. We performed phylogenetic analyses to reveal the evolutionary history of the DODA and CYP76AD1 lineages and in the context of an ancestral reconstruction of pigment states we explored the evolution of these genes in relation to the complex evolution of pigments in Caryophylalles. Duplications within the CYP76AD1 and DODA lineages arose just before the origin of betalain pigmentation in the core Caryophyllales. The duplications gave rise to DODA-α and CYP76AD1-α isoforms that appear specific to betalain synthesis. Both betalain-specific isoforms were then lost or downregulated in the anthocyanic Molluginaceae and Caryophyllaceae. Our findings suggest a single origin of the betalain synthesis pathway, with neofunctionalization following gene duplications in the CYP76AD1 and DODA lineages. Loss of DODA-α and CYP76AD1-α in anthocyanic taxa suggests that betalain pigmentation has been lost twice in Caryophyllales, and exclusion of betalain pigments from anthocyanic taxa is mediated through gene loss or downregulation. [Correction added after online publication 13 May 2015: in the last two paragraphs of the Summary the gene name CYP761A was changed to CYP76AD1.].

Description
Keywords
Caryophyllales, anthocyanin, betalains, lineage-specific genes, pigmentation, taxonomically restricted genes, Betalains, Biosynthetic Pathways, Caryophyllaceae, Cytochrome P-450 Enzyme System, Evolution, Molecular, Genes, Plant, Likelihood Functions, Molecular Sequence Data, Phylogeny, Pigmentation
Journal Title
New Phytol
Conference Name
Journal ISSN
0028-646X
1469-8137
Volume Title
207
Publisher
Wiley
Sponsorship
Natural Environment Research Council (NE/K009303/1)
S.C. was supported by a grant to IRRI from the Bill and Melinda Gates Foundation and UKAID. This work was supported by a National Science Foundation award (grant numbers DEB 1354048 and DEB 1352907) to S.F.B., M.J.M. and S.A.S., and a NERC Independent Research Fellowship to S.F.B. The 1000 Plants (1KP) initiative, led by G.K.S.W., is funded by the Alberta Ministry of Enterprise and Advanced Education, Alberta Innovates Technology Futures (AITF), Innovates Centre of Research Excellence (iCORE), Musea Ventures and BGI-Shenzhen.