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Carotenoid-based coloration is an essential feature of avian diversity and has important roles in communication and mate choice. The red feathers of birds from phylogenetically diverse orders and families are pigmented with C4-ketocarotenoids produced via the successive action of Cytochrome P450 2 J19 (CYP2J19) and 3-hydroxybutyrate dehydrogenase 1-like (BDH1L) on yellow dietary precursors. Yet, the biochemistry of these enzymes remains incompletely understood. Here we present a series of experiments characterizing the substrates, intermediates, and products of CYP2J19 and BDH1L expressed in heterologous cell culture. We confirm that CYP2J19 preferentially hydroxylates the 4 and 4′ positions of β-ring substrates, but can also hydroxylate the 3 and 3′ positions of C4-ketocarotenoids. We confirm that BDH1L catalyzes the conversion of zeaxanthin to canary xanthophyll B (ε,ε’-carotene-3,3′-dione) a major pigment in plumage of many yellow bird species. These results suggest that the actions of CYP2J19 and/or BDH1L can explain the presence of many metabolically transformed carotenoids in avian tissues.
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Oilseed‐based metabolic engineering of astaxanthin and related ketocarotenoids using a plant‐derived pathway: Lab‐to‐field‐to‐application
Summary Ketocarotenoids, including astaxanthin, are red lipophilic pigments derived from the oxygenation of β‐carotene ionone rings. These carotenoids have exceptional antioxidant capacity and high commercial value as natural pigments, especially for aquaculture feedstocks to confer red flesh colour to salmon and shrimp. Ketocarotenoid biosynthetic pathways occur only in selected bacterial, algal, fungal and plant species, which provide genetic resources for biotechnological ketocarotenoid production. Toward pathway optimization, we developed a transient platform for ketocarotenoid production usingAgrobacteriuminfiltration ofNicotiana benthamianaleaves with plant (Adonis aestivalis) genes, carotenoid β‐ring 4‐dehydrogenase 2 (CBFD2) and carotenoid 4‐hydroxy‐β‐ring 4‐dehydrogenase (HBFD1), or bacterial (Brevundimonas) genes, β‐carotene ketolase (crtW) and β‐carotene hydroxylase (crtZ). In this test system, heterologous expression of the plant‐derived astaxanthin pathway conferred higher astaxanthin production with fewer ketocarotenoid intermediates than the bacterial pathway. We evaluated the plant‐derived pathway for ketocarotenoid production using the oilseed camelina (Camelina sativa) as a production platform. Genes for CBFD2 and HBFD1 and maize phytoene synthase were introduced under the control of seed‐specific promoters. In contrast to prior research with bacterial pathways, our strategy resulted in nearly complete conversion of β‐carotene to ketocarotenoids, including primarily astaxanthin. Tentative identities of other ketocarotenoids were established by chemical evaluation. Seeds from multi‐season US and UK field sites maximally accumulated ~135 μg/g seed weight of ketocarotenoids, including astaxanthin (~47 μg/g seed weight). Although plants had no observable growth reduction, seed size and oil content were reduced in astaxanthin‐producing lines. Oil extracted from ketocarotenoid‐accumulating seeds showed significantly enhanced oxidative stability and was useful for food oleogel applications.
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- Award ID(s):
- 2435264
- PAR ID:
- 10597532
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Plant Biotechnology Journal
- Volume:
- 23
- Issue:
- 8
- ISSN:
- 1467-7644
- Format(s):
- Medium: X Size: p. 3451-3464
- Size(s):
- p. 3451-3464
- Sponsoring Org:
- National Science Foundation
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