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Genes 2018, 9(4), 200; https://doi.org/10.3390/genes9040200

A Possible Trifunctional β-Carotene Synthase Gene Identified in the Draft Genome of Aurantiochytrium sp. Strain KH105

1
Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
2
Marine Genomic Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0945, Japan
3
JST-CREST, Saitama 332-0012, Japan
These authors contributed equally to the work.
*
Authors to whom correspondence should be addressed.
Received: 14 February 2018 / Revised: 27 March 2018 / Accepted: 27 March 2018 / Published: 9 April 2018
(This article belongs to the Special Issue Microbial Metabolic Engineering)
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Abstract

Labyrinthulomycetes have been regarded as a promising industrial source of xanthophylls, including astaxanthin and canthaxanthin, polyunsaturated fatty acids such as docosahexaenoic acid and docosapentaenoic acid, ω-3 oils, and terpenic hydrocarbons, such as sterols and squalene. A Thraustochytrid, Aurantiochytrium sp. KH105 produces carotenoids, including astaxanthin, with strong antioxidant activity. To gain genomic insights into this capacity, we decoded its 97-Mbp genome and characterized genes for enzymes involved in carotenoid biosynthesis. Interestingly, all carotenogenic genes, as well as other eukaryotic genes, appeared duplicated, suggesting that this strain is diploid. In addition, among the five genes involved in the pathway from geranylgeranyl pyrophosphate to astaxanthin, geranylgeranyl phytoene synthase (crtB), phytoene desaturase (crtI) and lycopene cyclase (crtY) were fused into single gene (crtIBY) with no internal stop codons. Functionality of the trifunctional enzyme, CrtIBY, to catalyze the reaction from geranylgeranyl diphosphate to β-carotene was confirmed using a yeast assay system and mass spectrometry. Furthermore, analyses of differential gene expression showed characteristic up-regulation of carotenoid biosynthetic genes during stationary and starvation phases under these culture conditions. This suggests genetic engineering events to promote more efficient production of carotenoids. We also showed an occurrence of crtIBY in other Thraustochytrid species. View Full-Text
Keywords: Aurantiochytrium sp. strain KH105; genome sequencing; carotenoid biosynthesis; trifunctional enzyme gene; CrtIBY Aurantiochytrium sp. strain KH105; genome sequencing; carotenoid biosynthesis; trifunctional enzyme gene; CrtIBY
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Iwasaka, H.; Koyanagi, R.; Satoh, R.; Nagano, A.; Watanabe, K.; Hisata, K.; Satoh, N.; Aki, T. A Possible Trifunctional β-Carotene Synthase Gene Identified in the Draft Genome of Aurantiochytrium sp. Strain KH105. Genes 2018, 9, 200.

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